Biosolids and Bioenergy Management by Florida Water Resources Journal

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News and Features

Education and Training

4 Miami-Dade’s Solution for Achieving Digester Biogas Enhancement and Improved Gravity Concentrator Thickening at the South and Central District Wastewater Treatment Plants— Ernesto Coro, Leo Pou, Manuel Moncholi, Richard Waterous, and Ricardo Colon

10 Sweeney Takes Office as 2019-2020 FWEA President 10 2019-2020 FWEA Board of Directors 11 2019-2020 FWEA Officers, Chairs, and Advisors List 35 Water Professionals Go to the Dogs! 46 So, What’s New? The Proposed Southeast Biosolids Association (SEBA)—Jody Barksdale 47 Bonita Springs Utilities Board Elects New Officers 53 News Beat 54 Correction

13 19 20 21 22 23 27 36 39 50

CEU Challenge FSAWWA Fall Conference Call for Papers FSAWWA Fall Conference Overview FSAWWA Fall Conference Exhibits FSAWWA Fall Conference Poker/Golf Tournament FSAWWA Distribution System Awards Florida Water Resources Conference Sponsor Thank You FWPCOA State Short School TREEO Center Training FWPCOA Training Calendar

Columns 34 C Factor—Mike Darrow 38 FWEA Focus—Michael W. Sweeney 48 FSAWWA Speaking Out—Michael F. Bailey

49 Committee Profile: FWPCOA Systems Operations Committee—Raymond Bordner

Membership Questions FSAWWA: Casey Cumiskey – 407-979-4806 or fsawwa.casey@gmail.com FWEA: Karen Wallace, Executive Manager – 407-574-3318 FWPCOA: Darin Bishop – 561-840-0340

Training Questions FSAWWA: Donna Metherall – 407-979-4805 or fsawwa.donna@gmail.com FWPCOA: Shirley Reaves – 321-383-9690

For Other Information DEP Operator Certification: Ron McCulley – 850-245-7500 FSAWWA: Peggy Guingona – 407-979-4820 Florida Water Resources Conference: 407-363-7751 FWPCOA Operators Helping Operators: John Lang – 772-559-0722, e-mail – oho@fwpcoa.org FWEA: Karen Wallace, Executive Manager – 407-574-3318

Technical Articles 14 Understanding Design Standards and Codes for Biogas Systems—Shayla Allen and Regina Hanson

Departments 51 Classifieds 54 Display Advertiser Index

24 Selecting an Advanced Anaerobic Digestion Configuration and Biogas Management Strategy for the City of Tampa—Kurt Pfeffer, Jacob Porter, Bryan Lisk, Karloren Guzman, Michael Bullard, and Mitch Chiavaroli

40 Overcoming Obstacles with a Difficultto-Handle Sludge: Centrifuge Piloting at Miami’s Central District Wastewater Treatment Plant—Brian Stitt, Terry Goss, Ismael Diaz, and Manuel Moncholi

Websites Florida Water Resources Journal: www.fwrj.com FWPCOA: www.fwpcoa.org FSAWWA: www.fsawwa.org FWEA: www.fwea.org and www.fweauc.org Florida Water Resources Conference: www.fwrc.org Throughout this issue trademark names are used. Rather than place a trademark symbol in every occurrence of a trademarked name, we state we are using the names only in an editorial fashion, and to the benefit of the trademark owner, with no intention of infringement of the trademark. None of the material in this publication necessarily reflects the opinions of the sponsoring organizations. All correspondence received is the property of the Florida Water Resources Journal and is subject to editing. Names are withheld in published letters only for extraordinary reasons. Authors agree to indemnify, defend and hold harmless the Florida Water Resources Journal Inc. (FWRJ), its officers, affiliates, directors, advisors, members, representatives, and agents from any and all losses, expenses, third-party claims, liability, damages and costs (including, but not limited to, attorneys’ fees) arising from authors’ infringement of any intellectual property, copyright or trademark, or other right of any person, as applicable under the laws of the State of Florida.

ON THE COVER: Biogas enhancement and improved thickening at the Miami-Dade South District Wastewater Treatment Plant. For more information, see page 4. (photo: Ricardo Colon)

Volume 70

June 2019

Number 6

Florida Water Resources Journal, USPS 069-770, ISSN 0896-1794, is published monthly by Florida Water Resources Journal, Inc., 1402 Emerald Lakes Drive, Clermont, FL 34711, on behalf of the Florida Water & Pollution Control Operator’s Association, Inc.; Florida Section, American Water Works Association; and the Florida Water Environment Association. Members of all three associations receive the publication as a service of their association; $6 of membership dues support the Journal. Subscriptions are otherwise available within the U.S. for $24 per year. Periodicals postage paid at Clermont, FL and additional offices.

POSTMASTER: send address changes to Florida Water Resources Journal, 1402 Emerald Lakes Drive, Clermont, FL 34711

Florida Water Resources Journal • June 2019

Miami-Dade’s Solution for Achieving Digester Biogas Enhancement and Improved Gravity Concentrator Thickening at the South and Central District Wastewater Treatment Plants Less-than-optimal concentrator sludge solids and corrosion concerns are associated with high gas-phase hydrogen sulfide levels Ernesto Coro, Leo Pou, Manuel Moncholi, Richard Waterous, and Ricardo Colon The Miami-Dade South District Wastewater Treatment Plant (south plant) and Miami-Dade Central District Wastewater Treatment Plant (central plant) have historically generated high levels of anaerobic digester gas-phase hydrogen sulfide (H2S) and less than optimal concentrator (thickener) settling. Anaerobic digester gas-phase H2S levels have historically exceeded 5,000 parts per mil (ppm) at the south plant and 10,000 ppm at the central plant. These high levels of gas-phase H2S contamination have previously been treated by use of a sequential gas cleaning process comprised of an iron sponge system, preceded by a wet scrubber. After the cleaning, the digester gas continues to a cogeneration process. This strategy is unfavorable, as the maintenance and operational costs are high, as is the energy consumption. As a futher complication, gravity concentrators have historically produced thin-settled sludge solids flow to the anaerobic digesters as part of the biosolids treatment process: the more dilute the thickened sludge, the shorter the digester detention times, with less biogas produced. This results in increased solids to dewatering, increased dewatering polymer consumption, and increased solids to disposal. There was therefore a need for a cost-saving technology—with a

Miami-Dade South District Wastewater Treatment Plant (photo: Google Earth)

June 2019 • Florida Water Resources Journal

three-pronged approach—to improve concentrator thickening, odor control, and energy savings. The following is a south plant overview: S Conventional activated sludge process S Average daily plant flow is 100 mil gal per day (mgd) S Two identical treatment trains Continued on page 6

Process Flow Diagram for South Plant

Ferric Sulfate Injection Point in Process and Method of Injection

Gravity Concentrator in Use at Both South District and Central District Plants

Specially Fabricated Polyvinyl Chloride Injection Spool and Static Mixer

Continued from page 4 S Waste activated sludge (WAS) from both plants combined after secondary clarifiers and transferred to gravity concentrators S Plant utilizes four gravity concentrators with three operating prior to the commencement of an evaluation in May 2017; thickeners are 55 in. in diameter with 13-ft sidewalls S 12 anaerobic digesters, with 11 operational prior to trial commencement; six are primary and five are secondary S Digestor gas passes through wet scrubber followed by an iron sponge, then to cogeneration The south plant operating conditions prior to program initiation in May 2017: S Three gravity concentrators in operation S 1000-gal-per-minute (gpm) influent flow to concentrators S 14,000 mg/L typical influent sludge total suspended solids S 8-ft typical sludge blanket level in concentrators S 1.8 to 2 percent typical sludge (underflow) total solids concentration S 5,000 ppm H2S, 62 percent methane for typical digester gas profile

Solution: Ferric Sulfate Technology In May 2017, the addition of ferric sulfate into the common WAS inlet line to the concentrators was begun prior to splitting the separate

June 2019 â&#x20AC;˘ Florida Water Resources Journal

Gravity Thickener Overflow Quality Following Introduction of Ferric Sulfate Feed

concentrators at the south plant. Utilizing a specially designed inline chemical injection ring and static mixer, the introduction of ferric sulfate produced significant improvements in gas quality and gravity concentrator performance. The application point was customized for safe dosing and rapid mixing of the ferric sulfate coagulant to ensure complete dispersion with the WAS line prior to distribution to the concentrators. Preparations are in store for flow pacing of the targeted ferric sulfate feed rates and the WAS flow. The inventory and process monitoring are imbedded into a digitalization platform for web-based application analysis, alerts, and reports. Ferric sulfate is a highly effective coagulant for H2S control, as it combines with dissolved sulfides to form a very stable iron sulfide complex. The robust precipitate is then removed with the biosolids during the digestion process, yielding dramatic reductions in gasphase H2S levels. Anaerobic digester gas-phase H2S levels as low as 25 ppm (and lower) are achievable with ferric sulfate or ferric chloride addition. Additionally, the exceptional coagulating properties associated with ferric sulfate contribute to improved particle (including colloidal) capture rates, resulting in the improvements in concentrator performance (both overflow and underflow) observed at the south and central plants. The following results were observed at the south plant following the implementation of ferric sulfate technology for the gravity thickener/biogas enhancement application: Continued on page 8

Continued from page 6 S Improved concentrator solids settling, stable sludge blankets, and improved operator control. Gravity concentrator sludge blankets have decreased from 8 ft down to 4 or 5 ft, while maintaining good overflow quality. • The concentrator (underflow) sludge solids have increased from 1.8 to 2 percent to 3.5 to 4 percent. • Concentrator capacity/throughput has increased from 300 gpm to as high as 500 gpm. S Digester gas has also been steadily improved. • Anaerobic digester gas-phase H2S levels have dropped from more than 5,000 ppm to as low as 200 ppm. • Methane gas levels increased from 62 to 67 percent. • Bypassing the exisitng wet-scrubber-based gas cleaning systems yields a drier gas. S Requires less chilling. S Reduces energy consumption. S Bypassing iron sponges saves more than $400,000 per year in operating and maintenance costs. S Eliminates sodium hypochorite use for wet scrubber, saving a further $150,000 per year. Following the successful implementation of the program at the south plant, the same application was initiated at the central plant in January 2018. The application point and equipment utilized for dosing ferric sulfate remained as what had been in place at the south plant, the only exception being that separate injection points are in place for the central plant’s two treatment trains (Plant No. 1 and Plant No. 2), as each train utilizes its own bank of gravity thickeners. The results at the central plant have been quite similar to those positive results observed at the south plant, and include: S Improved thickener solids settling, stable and more compact sludge blankets, and improved operator control. S Significant improvement in overflow quality. S WAS belt press (when in use to complement gravity thickeners) throughput increased from 30 to 100 gpm. S Central plant has experienced a dramatic reduction in digester gasphase H2S levels from more than 10,000 ppm to as low as 200 ppm. S Anaerobic digester methane gas levels have increased from 57 to 63 percent.

Measuring Anaerobic Digester Gas Quality at the Miami-Dade South District Wastewater Treatment Plant

Typical Digester Gas Analysis From Miami-Dade Using a Handheld Meter

June 2019 • Florida Water Resources Journal

S The average cogen engine spark plug life has increased from 4 to 200 hours to more than 1,000 hours, saving an estimated $250,000 per year. At both the south and central plants, advanced water treatment (AWT) technical personnel provide continued onsite monitoring to ensure that treatment objectives are maintained. Regular digester gas analysis is performed using a BioGas 5000 handheld gas analyzer.

Conclusions: Multipronged Ferric-Sulfate-Based Technology Implementation The largest implication of the ferric sulfate technology for the concentrators at the south and central plants is the anaerobic digester biogas enhancement, particularly the significant reduction in gasphase H2S levels. Following the H2S mitigation, the methane gas levels at the south plant were observed to increase from 62 to 67 percent, and from 57 to 63 percent at the central plant. The risk of microbialinduced corrosion to the digester infrastructure has also been lowered. The corrosion rates in cogeneration engines were reduced significantly, together with the frequency of engine maintenance and oil changes. Additionally, the performance of the gravity thickeners at each plant has improved, including improved solids settling, stable and more-compact sludge blankets, and improved operator control. Concentrator throughput rates have increased, overflow quality has improved, and at the south plant, underflow total solids have almost increased by 100 percent. As a result of the postive results observed at each plant, a multipronged ferric-sulfate-based technology has been implemented on a full-time basis at the two plants. Ernesto Coro is process engineer–planning and modeling section, and Manuel Moncholi is senior program manager and chief of operations–program management division, with Miami-Dade Water and Sewer Department. Leo Pou is chief plant operator with Miami-Dade South District Wastewater Treatment Plant. Ricardo Colon is an associate for technical sales and service–advanced water treatment, and Richard Waterous is senior account manager–advanced water treatment, with Kemira Chemicals in Bartow. Waterous can be contacted at richard.waterous@kemira.com. S

Ferric Sulfate Storage and Feed System for Central District Plant No. 1

Sweeney Takes Office as 2019-2020 FWEA President

Michael William Sweeney, Ph.D., has begun his term as president of the Florida Water Environment Association (FWEA), following his election at the association’s annual meeting on April 16. Sweeney graduated from Indiana University with a B.S. in public health and environmental science, and subsequently graduated from Purdue University with an M.S. and a Ph.D. in environmental engineering. His graduate work concentrated on water quality modeling and real-time assessment of the nitrification processes in two 150-mgd advanced water reclamation facilities. While pursuing graduate training, Sweeney served the City of Indianapolis as its control systems manager. Subsequently, he went on to serve the Metropolitan Sewer District of Greater Cincinnati and Louisville and Jefferson County Metropolitan Sewer District in technical and executive management positions. In addition to utility management, he worked for EMA Inc. and Woolpert Inc. as a consultant serving utilities and clients throughout North America in various capacities, such as strategic planning and organizational development, and executive coaching, technology planning, and implementation. It was by his consulting experience that he reached central Florida in 2004 working with Orange County Utilities and Toho Water Authority, his future employer. He began his involvement with FWEA in 2006 on the Utility Management Committee, developing the water and wastewater systems

benchmarking survey, followed by the FWEA strategic planning initiative in 2014. In the summer of 2011, he joined Toho Water Authority as deputy executive director based in Kissimmee. Sweeney is involved with most aspects of its management and oversees strategic plan, communications, and asset management programs. Sweeney received the honor of a WEF Fellow in 2018 recognizing professional achievement, stature, and contributions of WEF members to the preservation and enhancement of the global water environment, and prior to that, he received the Ellms Award from the Ohio Water Environment Association recognizing conference activities, civic affairs, and leadership. He has led three WEF committees, including the Utility Management Committee, Literature Review Committee, and Automation and Information Technology Committee, and chaired several specialty conference planning committees, including for the Utility Management Conference in 2006 and 2018. He lives in Kissimmee with his wife of 36 years, Margie, who is a family practice physician. They have two grown children: Patrick, an army captain and Blackhawk pilot; and Kelly, a TV and film set designer and arranger. Aside from utility management, Sweeney is extensively involved with his community serving as immediate past president of the Council on Aging, a major social service nonprofit of Osceola County; past chair of Community Vision, a collaboration of leaders who take on projects that collectively realize the community’s vision; and Rotary International as a past club president. He has also made a dozen trips to Haiti with his wife to help with water sanitation projects and set up and support medical clinics in remote areas. Sweeney enjoys all aspects of the outdoors, including, boating, hiking, camping, motorcycling, and being somewhere in the world he hasn’t been before. S

June 2019 • Florida Water Resources Journal

2019-2020 FWEA Board of Directors

James J. Wallace President Elect

Ron Cavalieri Vice President

Sondra Winter Lee Secretary/Treasurer

Kristiana Dragash Past President

Raynetta Curry Marshall WEF Delegate

Tim Ware WEF Delegate

Jody Barksdale Director at Large

George Cassady Director at Large

2019-2020 FWEA Officers, Chairs, and Advisors Gregory D. Kolb Director at Large

Suzanne Mechler Director at Large

The following officers, directors, committee chairs, chapter chairs, and student chapter advisors began their terms at the beginning of the FWEA annual meeting in April.

BOARD OF DIRECTORS

DIRECTOR AT LARGE Gregory D. Kolb, P.E. Jacobs Engineering Group 407-423-0030 Greg.Kolb@jacobs.com

PRESIDENT Michael Sweeney, Ph.D. Toho Water Authority 407-944-5129 msweeney@tohowater.com

Tim Madhanagopal Director at Large

Tyler Semago Director at Large

DIRECTOR AT LARGE Suzanne Mechler, P.E. CDM Smith Inc. 561-571-3800 mechlerse@cdmsmith.com

PRESIDENT ELECT James J. Wallace, P.E. Jacobs 904-636-5432 Jamey.wallace@jacobs.com

DIRECTOR AT LARGE Tim Madhanagopal, P.E., F.WEF, F.NSPE Orange County Utilities 407-254-9785 tim.madhanagopal@ocfl.net

VICE PRESIDENT Ronald R. Cavalieri, P.E., BCEE AECOM Technical Services Inc. 239-278-7996 ronald.cavalieri@aecom.com

Lynn Spivey Director at Large

Alice Varkey Director at Large

DIRECTOR AT LARGE Tyler Semego Carollo Engineers Inc. 813-888-9572 tsmith@carollo.com

SECRETARY/TREASURER Sondra Winter Lee, P.E. City of Tallahassee 850-891-6123 Sondra.Lee@talgov.com

DIRECTOR AT LARGE Lynn Spivey City of Plant City 813-757-9190 lspivey@plantcitygov.com

PAST PRESIDENT Kristiana Dragash, P.E. Carollo Engineers Inc. 941-371-9832 kdragash@carollo.com

Paul Steinbrecher Utility Council President

Kartik Vaith Executive Director of Operations

Bradley Hayes Operations Council Representative

Karen Wallace Executive Manager

WEF DELEGATE Raynetta Curry Marshall, P.E. City of Tallahassee

DIRECTOR AT LARGE Alice Varkey, P.Eng. GHD 904-665-5653 Alice.Varkey@ghd.com

WEF DELEGATE Tim Ware, P.E., CRL Arcadis 813-353-5773 Tim.ware@arcadis.com

UTILITY COUNCIL PRESIDENT Paul Steinbrecher, P.E. JEA 904-665-5653 steipk@jea.com

DIRECTOR AT LARGE Jody Barksdale, P.E., ENV SP Gresham Smith & Partners 813-251-6838 Jody.barksdale@greshamsmith.com

OPERATIONS COUNCIL REPRESENTATIVE Bradley Hayes Woodard & Curran 325-516-4397 bhayes@woodardcurran.com

DIRECTOR AT LARGE George Cassady Hillsborough County Public Utilities Dept. 813-272-5977 cassadyg@hillsboroughcounty.org

Continued on page 12

Florida Water Resources Journal â&#x20AC;¢ June 2019

Continued from page 11 EXECUTIVE DIRECTOR OF OPERATIONS Kartik Vaith, P.E. The Constantine Group 904-562-2185 kvaith@tcgeng.com EXECUTIVE MANAGER Karen Wallace 407-574-3318 admin@fwea.org

COMMITTEE CHAIRS AIR QUALITY Phillip Clark City of Tavares 352-742-6368 PClark@tavares.org AWARDS Damaris Noriega Orange County Utilities 407-254-938 Damaris.noriega@ocfl.net BIOSOLIDS Alexander Kraemer 561-846-0334 alexander@kraemer.com COLLECTION SYSTEMS Jamison Tondreault Kimley-Horn 863-226-6877 jamison.tondreault@kimley-horn.com CONTRACTORS Nathan Hillard Wharton-Smith Inc. 407-402-0120 nhillard@whartonsmith.com EXECUTIVE ADVISORY COUNCIL Greg Chomic Heyward Florida Inc. (407) 628-1880 gchomic@heywardfl.com MANUFATURERS AND REPRESENTATIVES (MARC) Chris Stewart Xylem Water Solutions USA Inc. 239-322-3257 Chris.stewart@xyleminc.com MEMBER RELATIONS Megan Nelson Orange County Utilities 407-254-9927 megan.nelson@ocfl.net

MEMBERSHIP ACTION TEAM Ronald R. Cavalieri, P.E., BCEE AECOM Technical Services Inc. 239-278-7996 ronald.cavalieri@aecom.com OPERATIONS CHALLENGE Chris Fasnacht Water Reclamation Division, OCU 407-254-7724 Chris.Fasnacht@ocfl.net PUBLIC COMMUNICATIONS AND OUTREACH Chuck Olson EAC Consulting Inc. 954-714-2005 colson@eacconsult.com SAFETY COMMITTEE W. Scott Holowasko Gainesville Regional Utilities 352-393-1667 holowaskows@gru.com STUDENTS AND YOUNG PROFESSIONALS David Hernandez Hazen and Sawyer 305-443-4001 dhernandez@hazenandsawyer.com

CHAPTER CHAIRS BIG BEND James H. Peterson IV, P.E. Jim Stidham and Associates Inc. 850-322-8580 jpeterson@jsna.com CENTRAL FLORIDA Jennifer Ribotti, P.E. Tetra Tech 407-480-3934 Jennifer.ribotti@tetratech.com FIRST COAST Jacob Wadkins, P.E. Haskell 904-357-4874 jacob.wadkins@haskell.com MANASOTA Mike Nixon McKim & Creed Inc. 941-379-3404 mnixon@mckimcreed.com SOUTH FLORIDA David Hernandez Hazen and Sawyer 305-443-4001 dhernandez@hazenandsawyer.com

TRAINING AND CONTINUING EDUCATION Kenneth Blanton, P.E. Black & Veatch 407-419-3570 BlantonKM@bv.com

SOUTHEAST Joan Fernandez Arcadis 954-882-9566 joan.i.fernandez@arcadis.com

UTILITY COUNCIL Paul Steinbrecher 904-665-5653 steipk@jea.com

SOUTHWEST Tom Meyers FJ Nugent Co. 239-224-8422 tmeyers@nugentco.com

UTILITY MANAGEMENT Rick Nipper Toho Water Authority 407-944-5071 rnipper@tohowater.com

TREASURE COAST Christine Miranda, P.E. Holtz Consulting Engineers Inc. 561-575-2005

WASTEWATER PROCESS Leslie Samel Mott MacDonald 904-203-1081 Leslie.Samel@mottmac.com WATER RESOURCES, REUSE, AND RESILIENCY (WR3) Nita Naik 813-353-5744 Nita.naik@arcadis.com

June 2019 â&#x20AC;¢ Florida Water Resources Journal

Christine.Miranda@holtzconsulting.com

WEST COAST Matthew Love Wade Trim 813-763-5297 mlove@wadetrim.com

STUDENT CHAPTER ADVISORS FLORIDA ATLANTIC UNIVERSITY Dr. Daniel Meeroff 561-297-2658 dmeeroff@fau.edu FLORIDA INTERNATIONAL UNIVERSITY Dr. Berrin Tansel 305-348-2928 tanselb@fiu.edu UNIVERSITY OF CENTRAL FLORIDA Dr. Anwar Sadmani 407-823-2781 sadmani@ucf.edu UNIVERSITY OF FLORIDA Dr. John Sansalone 352-373-0796 jsansal@ufl.edu UNIVERSITY OF MIAMI Dr. James Englehardt 305-284-5557 jenglehardt@umiami.edu UNIVERSITY OF NORTH FLORIDA Dr. Chris Brown, P.E. 904-620-2811 Christopher.j.brown@unf.edu UNIVERSITY OF SOUTH FLORIDA Dr. Sarina Ergas 813-974-1119 sergas@usf.edu FAMU/FLORIDA STATE UNIVERSITY Dr. Youneng Tang 850-410-6119 ytang2@eng.fsu.edu FLORIDA GULF COAST UNIVERSITY Dr. Simeon Komisar 239-590-1315 skomisar@fgcu.edu

Operators: Take the CEU Challenge!

________________________________________________ SUBSCRIBER NAME (please print)

Members of the Florida Water and Pollution Control Operators Association (FWPCOA) may earn continuing education units through the CEU Challenge! Answer the questions published on this page, based on the technical articles in this month’s issue. Circle the letter of each correct answer. There is only one correct answer to each question! Answer 80 percent of the questions on any article correctly to earn 0.1 CEU for your license. Retests are available. This month’s editorial theme is Biosolids and Bioenergy Management. Look above each set of questions to see if it is for water operators (DW), distribution system operators (DS), or wastewater operators (WW). Mail the completed page (or a photocopy) to: Florida Environmental Professionals Training, P.O. Box 33119, Palm Beach Gardens, Fla. 33420-3119. Enclose $15 for each set of questions you choose to answer (make checks payable to FWPCOA). You MUST be an FWPCOA member before you can submit your answers!

Selecting an Advanced Anaerobic Digestion Configuration and Biogas Management Strategy for the City of Tampa Kurt Pfeffer, Jacob Porter, Bryan Lisk, Karloren Guzman, Michael Bullard, and Mitch Chiavaroli (Article 1: CEU = 0.1 WW02015344 ) 1. Alternative 2 proposed that which of the following be fed directly to the mesophilic digesters? a. Raw fats, oils, and grease stream b. Fully digested thermophilic sludge c. Thickened waste activated sludge d. Primary sludge 2. Separation of acid and gas digestion phases was found to a. improve operational cost. b. improve volatile solids reduction. c. increase retention time requirements. d. produce a drier sludge cake. 3. The bioavailability of soluble organic material within the cell walls of partially treated wastewater treatment residuals is increased by a. thermal hydrolysis. b. aeration. c. acid-phase digestion. d. mesophilic digestion.

Article 1 _______________________________________________ LICENSE NUMBER for Which CEUs Should Be Awarded

Article 2 _______________________________________________ LICENSE NUMBER for Which CEUs Should Be Awarded

Article 3 _______________________________________________ LICENSE NUMBER for Which CEUs Should Be Awarded

If paying by credit card, fax to (561) 625-4858 providing the following information: ___________________________________

__________

(Credit Card Number )

(Exp.Date)

Earn CEUs by answering questions from previous Journal issues! Contact FWPCOA at membership@fwpcoa.org or at 561-840-0340. Articles from past issues can be viewed on the Journal website, www.fwrj.com.

Overcoming Obstacles With a Difficult-to-Handle Sludge: Centrifuge Piloting at Miami’s Central District Wastewater Treatment Plant Brian Stitt, Terry Goss, Ismael Diaz, and Manuel Moncholi (Article 2: CEU = 0.1 WW02015345) 1. Which of the following streams is identified as dilute and difficult to handle? a. Central District waste activated sludge b. North District primary and waste activated sludge c. Central District primary sludge d. Blended North and Central District frac tank sludge 2. Which of the following was not a centrifuge operational parameter that was adjusted for pilot testing? a. Pool depth b. Bowl speed c. Power input d. Differential scroll speed 3. Testing of combined frac tank feed sludge was limited to two to three hours at a time because a. influent flow volume was insufficient. b. neighbors reported odor issues. c. operators had limited time to devote to test protocols. d. of excessive wear on feed pump stator due to grit.

4. As presently operated (baseline conditions), annual average volatile solids destruction is expected to approximate a. 58 percent. b. 60 percent. c. 85 percent. d. 90 percent.

4. Draft dewatering pilot test specifications stated that the active polymer dose should be ___lb per dry ton. a. less than 25 b. 22 to 25 c. 15 to 30 d. 24

5. Thermophilic digestion takes place within which of the following temperature ranges? a. 85 to 95°F b. 95 to 100°F c. 101 to 129°F d. 131 to 140°F

5. Dewatering pilot test results indicate that performance was reduced by 2 to 4 percent total cake solids if ___________ is not used. a. polymer b. ferric chloride c. ferric sulfate d. thermophilic digestion

Understanding Design Standards and Codes for Biogas Systems Shayla Allen and Regina Hanson (Article 3: CEU = 0.1 WW02015346) 1. Solids retention time (SRT) is calculated by the mass of solids into the digester divided by a. digester volume. b. hydraulic throughput rate. c. sludge age. d. mass rate of solids leaving the digester. 2. Most gas utilization equipment requires _________ hydrogen sulfide concentration. a. 50 percent b. less than 100 parts per mil (ppm) c. more than 50 ppm d. zero 3. Which of the following materials is least preferred for biogas piping and tubing systems? a. Cast iron b. Copper c. Plastic d. Stainless steel 4. The most common design standard for biogas management systems is found in a. AWWA Manual M14. b. Florida Administrative Code 62-600. c. USDA Code 366. d. WEF Manual of Practice No. 8. 5. The most common media used for removal of hydrogen sulfide generated by the anaerobic digestion process is a. granular activated carbon. b. struvite. c. biologically activated carbon. d. iron oxide.

Florida Water Resources Journal • June 2019

F W R J

Understanding Design Standards and Codes for Biogas Systems Shayla Allen and Regina Hanson iogas is typically produced during the biological breakdown of organic solids through anaerobic digestion. The gas generated through this process is an energy source that can be captured and utilized, or can be safely burned. It’s a highly moist mixture of gases, consisting of approximately 55 to 70 percent methane, 25 to 35 percent carbon dioxide, and trace amounts of nitrogen and hydrogen sulfide. In the last five years, there has been a rising trend in upgrading municipal wastewater treatment facilities that utilize anaerobic digesters. The main reasons for the upgrade are to fix the inherent issues dealing with a highly corrosive gas and increase a plant’s capacity to handle higher solids loading. The funds for the upgrade usually come from local state revolving funds or through privatization. Priority is usually given when a plant upgrade is necessary in order to comply with state and/or federal environmental regulations. Since biogas is a renewable energy source and has multiple uses, there has been an increase in funding because of the payback potential that biogas reuse offers. Biogas is highly flammable, and to be use-

ful, it needs to be safely captured. Anaerobic digestion is one of the most safe and effective methods of treating biosolids from municipal and industrial wastewater. That being said, it’s important to stay informed on the latest and best practices and design concepts for biogas capture, transmission, and utilization. The most common design standard used is the Water Environment Federation (WEF) Manual of Practice (MOP) No. 8, Design of Water Resource Recovery Facilities. In 2017, WEF published the sixth edition. Chapter 25 on sludge stabilization contains relevant and important information on biogas systems. The 2017 MOP No. 8 edition references ANSI/CSA B149.6-15 Code for digester gas, landfill gas, and biogas generation and utilization from the American National Standards Institute (ANSI). The ANSI/CSA B149.6 was written by the Technical Committee on Digester Gas, Landfill Gas, and Biogas Generation and Utilization, which became an ANSI-approved standard on March 27, 2015, and published in August 2015 by CSA Group, which collaborated on the publication1. The ANSI B149.6 code is more focused and practical in its approach of designing biogas systems.

Shayla Allen is a water resource engineer with ARCADIS U.S. Inc. in Long Island City, N.Y., and Regina Hanson is product marketing manager with Varec Biogas in Huntington Beach, Calif.

Depending on the plant site, there are also localized standards that are available. Some local standards have unique requirements that are not covered in MOP No. 8 that must be taken into consideration when designing at a specific locale. An example of a local or regional standard is the 10 States Standards. The ten member states and provinces that collaborated on the standards are Illinois, New York, Indiana, Ohio, Iowa, Michigan, Pennsylvania, Minnesota, Wisconsin, Missouri, and the Ontario Province in Canada. Chapter 84 covers the safety requirements for biogas systems. A different regional standard is TR-16, Guides for the Design of Wastewater Treatment Works. The member states of TR-16 are Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont. Another handy and focused design standard is the National Fire Protection Association (NFPA) 820, Fire Protection Standard for Wastewater Treatment Facilities. This is especially helpful when determining area classification.

Biogas Production

Figure 1. 95-ft-diameter steel floating covers at the Salt Lake City Water Reclamation Facility.

June 2019 • Florida Water Resources Journal

Biogas production is related to the volatile solids reduction (VSR) during anaerobic digestion. The VSR is typically expressed as a volume of gas produced per unit of mass of volatile solids (VS) destroyed. The VSR rate varies for different organic substances. In a typical anaerobic digester, approximately 13 to 18 ft3 of gas is produced per lb of VSR. For fats, oils, and grease (FOG), the gas produced jumps to 20 to 25 ft3/lb of VS destroyed. Besides the feed stock composition, biogas production is a function of temperature, pH, solids retention time (SRT) and hydraulic retention time (HRT), mixing efficiency, and organic loading rate and frequency.

Temperature The VSR increases as temperature increases (Salsali and Parker, 2007) and the temperature range is dependent on the type of bacteria and staged operation. The most common is a mesophilic digestion where the digester is maintained at a range of 95 to 102°F. A higher temperature range of thermophilic digestion runs at 122 to 135°F. Solids Retention Time and Hydraulic Retention Time The SRT is calculated by the mass of solids going into the digester(s) and the mass rate of the solids leaving the digester(s). The HRT is calculated by the volume of solids in the digester(s) and the volume rate of the solids leaving the digester(s). Optimized retention time (RT) is dependent on the type of bacteria and the temperature. For typical mesophilic digestion, a 15-day retention time achieves Class B biosolids. Mixing Efficiency During digestion, the sludge is mixed, and there are different methods or types of mixing sludge. One example of mixing technology is a linear motion mixer, which uses a single ringshaped disc inside the tank that is driven by a motor in an up-and-down motion, causing oscillating pressure waves in the sludge. Sludge viscosity and revolutions per minute (rpm) for direct mixing affect gas buildup within the sludge. Without adequate mixing, gas within the digester will naturally alleviate; however, this generally results in an enormous release in gas over a short period of time. With adequate mixing, solids will be evenly mixed, allowing the biogas to escape at a consistent rate. Organics Loading Rate and Frequency The VS loading rate is the mass of VS added to the digester(s) each day divided by the working volume of the digester(s); the solids can range between 6 to 8 percent. A typical sustained peak VS loading rate equals .12 - .16 lb VS/ft3/day, while a typical maximum VS loading rate equals .2 lb VS/ft3/day. With effective mixing, biogas is conveyed from the digester. A typical schematic of the biogas piping is shown in Figure 3, which is derived from Chapter 25 of MOP No. 8. After total gas production is calculated with safety factors (peak or future) taken into account, the pipe is sized so that the gas velocity does not exceed 12 ft per second (fps), given the flow rate. The lower velocity helps minimize pressure drop and condensate carryover. Once the pipe size has been established, the related

piping equipment should be the same size as the piping. Due to the corrosive nature of biogas, the material of construction used for piping is stainless steel; the material for equipment is usually low copper aluminum and stainless steel. The gas piping should be laid out to slope to a low point, at a minimum of ¼ to ½ in. per ft of pipe. The slope allows any moisture in the gas to be collected and drained. Water in the pipe, especially in cold-weather application, can freeze and block the pipes; over time, the water will corrode, calcify, and eventually block the piping. The most common culprit in biogas is moisture. Moisture in the pipe is removed through the use of sediment traps on the digester gas take-off line and drip traps at low points in the piping; a drip trap, instead of an isolation valve, allows moisture to collect inside a vessel. The vessel is drained or emptied, but keeps the gas line isolated so that no gas escapes during the draining process. More-enhanced moisture removal includes the use of coalescing filters to remove particulates and a combination of heat exchangers, glycol chillers, and compressors to effectively heat, cool, and reheat the gas to create a dew-point barrier and decreased relative humidity. Another component of biogas that is highly corrosive is hydrogen sulfide (H2S). Most gas utilization equipment, such as an engine generator, requires less than 100 parts per mil (ppm) of H2S. The H2S is usually removed in the gas using a media; it’s required for siloxane removal and the media used is easily degraded with the presence of H2S (e.g., activated carbon). Biogas contains one or more species of siloxane, and when it’s combusted, the silicate

has an abrasive sandy texture that shortens the life span of gas turbines, boilers, or cogens. The most common media used for H2S removal is a form of iron oxide, where it reacts with water to form ferric sulfide. The reaction produces heat, so it’s important to keep the media bed moist to avoid spontaneous combustion when reacting with air during regeneration or disposal. Iron oxide media can be regenerated, and after the first regeneration, the bed life is 75 percent of the initial bed life calculated, given the H2S concentration in the gas. Media effectiveness diminishes over time because it’s determined by the volume available for sulfur conversion. A plant should do frequent sampling of outlet concentration to ensure that the levels of H2S are within the required tolerance Continued on page 16

Figure 2. Linear motion mixer for sludge mixing on a 95-ft-diameter steel floating digester cover at the Salt Lake City Water Reclamation Facility.

Figure 3. Diagram of gas control system2.

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Continued from page 15 of the boiler, gas turbine, or engine. The drawback in using iron oxide is replacement and disposal after the media is spent. Another method of removing H2S in the gas is via a biological process, which is not unlike an anaerobic digester. The sulfur oxidation bacteria thrive and multiply on a packed media inside a closed acid-proof tank. The bacteria require sulfur from the H2S, carbon from the carbon dioxide (CO2), oxygen (O2) from atmospheric air, water and nutrients (nitrogen, phosphorus, and potassium) from the treated effluent, and a temperature between 86 to 130°F. Atmospheric air is injected into the tank and the amount of air required depends on the H2S level in the raw biogas. The volume of methane (CH4) will remain unchanged and the air injection will dilute the relative CH4 content in the clean gas proportionally. A frequency-regulated air blower is used for adjustable air injection. The main part of the O2 is used for oxidation of the H2S to sulfate (SO4), and the O2 in the clean gas will be well below the flammable limits of the gas. The SO4 is discharged with the effluent from the tank and typically measures to 8 percent. The chemical composition of the effluent will depend on the water or treated digester effluent added to the process.

Proper Selection of Safety Equipment Anaerobic digesters should be equipped with a pressure/vacuum relief valve and flame arrester. The valve relieves the digester of an overpressure or vacuum condition and the flame arrester ensures that the flame doesn’t flash back into the digester when vented gases are ignited. The MOP No. 8 recommends redundancy of equipment, which will allow

Figure 4. Iron sponge (wood chips impregnated with rust).

maintenance on one unit, while the other is keeping the digester protected. Flame arresters or flame trap assemblies must be installed within 15 ft of a potential flame source. A flame arrester with a thermal shutoff valve allows gas shutoff so the flame can be quenched in the arrester. Combusting biogas at waste gas burners is the safest method of getting rid of waste biogas when it’s not recovered for use, when there are no storage capabilities, and in an emergency. The type of waste gas burner specified will depend on local air regulations (contact the local U.S. Environmental Protection Agency for any specific emissions criteria).

Design Recommendations for Biogas Systems Since its publication in 2015, ANSI/CSA B149.6-15 provides the most practical and safest design recommendations for biogas systems, and is referenced in WEF MOP No. 8. It takes into account biogas constituents when recommending the type of material of construction; for example, pipe and fittings utilized for biogas piping and tubing systems shall be fabricated from stainless steel, plastic, or copper for specific applications. Cast iron pipe and fittings (including flanges) shall not be used. Components and accessories made of cast iron or cast aluminum (e.g., valves, traps, or flashback [flame] arresters) may be used in the system, but caution should be taken when using cast iron with highly corrosive gases that have significant sulfur, ammonium, or nitrate concentrations that add to the corrosiveness of the gas. All gaskets shall be made of at least 1/8-in.thick neoprene, full-faced, with a hardness of not less than 40 measured on a Shore durometer A scale, or of other material capable of positively resisting the action of the biogas.

Figure 5. Fiberglass-insulated vessel with Iron sponge media at the Sioux City (Iowa) Wastewater Treatment Plant.

June 2019 • Florida Water Resources Journal

All gas piping systems (including bleed vent piping), whether outdoors, inside buildings, or buried, shall be installed having a minimum 2 percent slope. The noteworthy items that impact specification of safety equipment in biogas systems are related to the digester protection. Digester and gas storage tanks, including membrane-type gas holders, should be equipped with redundant safety pressure relief valves. In addition, a secondary pressure relief system for the digester (without flame arrester) is also required to protect the digester gas-holding space. Installing isolation valves on any safety relief devices are a listed prohibited practice. There must be a minimum of two or more digester access holes for covers that are 50 ft or less, or three of more access holes for digesters covers that are 50 ft or greater. At least one of the access holes should be a minimum of 42 in. in diameter. The code also covers the most commonly asked questions when choosing a location for the waste gas burner. Its distance from other structures should be a minimum of 50 ft from the digester perimeter. For open-type flares, the tip should be a minimum of 1 to 5 ft above maintenance ground level. Any open-type stack tip should be a minimum of 25 ft from any other stack tip or exhaust vent. Open-type flares should be installed at a minimum of 25 ft from the property line or road; an enclosed flare can be installed at 10 ft, as long as a safety barrier is installed around it.

Figure 6. BiogasClean biological H2S removal system at the Truckee Meadows Wastewater Treatment Plant in Reno, Nev.

The typical arrangement of a waste gas burner is: S Flame trap assembly within 15 ft with no vent valve on main gas header or pilot line (e.g., explosion relief valve) S Manual shutoff valve upstream of pressure regulator preferably inside a building to protect from cold S Manometer or pressure measurement without power source S Pilot lines equipped with flame check or flame arrestor

10-States Standards: Recommended Standards for Wastewater Facilities The regional standard follows MOP No. 8, but has specific requirements not covered in the manual, and the 2014 edition does not take into account ANSI/CSA B149.6. The 10 States Standards do have some unique requirements that aren’t required in MOP No. 8; for example, float-operated drip traps are not allowed for automatic emptying of the trap or vessel using a float. The drain line is controlled by a needle valve that opens when the float is tripped. There is no means to isolate the “fill” line or its connection to the gas line when the trap or vessel drain is opened. This could result in gas leaking into a confined space when the needle valve doesn’t seal or close properly. Regardless of flow rate, the minimum pipe size is 4 in. in diameter and the pipe should be sized to the 12-fps gas velocity rule. The standard mentions that flares are installed at a minimum of 50 ft from any plant structures, which is a little more difficult to attain, especially in plants with no space to expand. TR-16 Guide for the Design of Wastewater Treatment Works: Chapter 11 Residuals Treatment and Management This is the design standard published by New England Interstate Water Pollution Control Commission; the seven member states are Connecticut, Maine, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont. This standard was modeled after the 2011 MOP edition and requires an update to factor in ANSI/CSA B149.6. Some of the requirements that should be clarified are the flare locations, which can be installed in a building as long as the building is a minimum of 50 ft from the digester perimeter. It also does not allow float-operated drip traps and follows the 12-fps gas velocity guideline.

Figure 7. Redundant pressure/ vacuum relief valve (vent to atmosphere) with flame arrester and safety selector valve.

Figure 8. Flame trap assembly with a thermal shutoff valve and flame arrester combination.

Figure 9. Pressure-reducing valve (PRV)/flame arrester with insulating jacket.

Figure 10. Digester cover with 48-in. manhole cover, redundant PRV/flame arrester with three-way safety selector valve, and secondary pressure relief via the emergency pressure relief manhole cover.

Figure 11. Possible arrangement for waste gas flare stack burners burning digester gas3.

Continued on page 18 Florida Water Resources Journal • June 2019

Continued from page 17 NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities For area classification in a wastewater treatment facility, the best guideline to use is NFPA 820, 2016 edition, which provides tables for specific areas. Biogas falls under Table 6.2.2.(a); for example, a 10-ft horizontal distance from a waste gas flare is class 1, division 1, and a 15-ft horizontal distance from the waste gas flare is class 1, divisions 1 and 2. This makes it easy to determine where to locate the flare control panel, and all components installed inside the 15-ft distance should be supplied as explosionproof.

Conclusions Converting biogas to energy currently dominates the industry’s focus, which makes it important to know how to safely handle biogas production, collection, and transmission. Today there are an influx of plant upgrades that are driven by a plant expansion to allow for increased capacity and loading. There are also projects that use technology that helps to en-

hance biogas production, where in the past, biogas was a nuisance, smelled bad, and was disposed of by burning it as a flare. A clear understanding of design principles will allow wastewater treatment facilities and engineers to excel in creating safer, more-efficient designs, thereby shifting biogas from the sidelines to the forefront of technological progress.

Footnotes 1

ANSI/CSA B149.6 Code for digester gas, landfill gas, and biogas generation and utilization. Technical Committee on Digester Gas, Landfill Gas and Biogas Generation and Utilization; August 2015. Fig. 23.33, ANSI/CSA B149.6 Code for digester gas, landfill gas, and biogas generation and utilization. Technical Committee on Digester Gas, Landfill Gas and Biogas Generation and Utilization; August 2015. Annex B, Fig. B.3, ANSI/CSA B149.6 code for digester gas, landfill gas, and biogas generation and utilization. Technical Committee on Digester Gas, Landfill Gas and Biogas Generation and Utilization; August 2015.

June 2019 • Florida Water Resources Journal

References • WEF Manual of Practice No. 8 (ASCE MOP 76), Design of Water Resource Recovery Facilities. Design of Water Resource Recovery Facilities Task Force of WEF and ASCE/EWRI, sixth edition (2017). • Recommended Standards for Wastewater Facilities: Policies for the Design, Review, and Approval of Plans and Specifications for Wastewater Collection and Treatment Facilities. Wastewater Committee of the Great Lakes-Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers, 2014 edition. • TR-16, Guides for the Design of Wastewater Treatment Works. New England Interstate Water Pollution Control Commission, 2011 edition. • NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities, June 2015. Technical Committee on Wastewater Treatment Plants, American National Standard Institute. S

F W R J

Selecting an Advanced Anaerobic Digestion Configuration and Biogas Management Strategy for the City of Tampa Kurt Pfeffer, Jacob Porter, Bryan Lisk, Karloren Guzman, Michael Bullard, and Mitch Chiavaroli he City of Tampa (city) owns and operates the Howard F. Curren Advanced Wastewater Treatment Plant (plant). The plant is currently permitted for 96 mil gal per day (mgd) average annual daily flow (AADF) and operates with an AADF of approximately 60 mgd. Liquid treatment includes primary clarification, followed by a high-rate activated sludge process. Solids processing consists of secondary sludge gravity thickening, conventional mesophilic anaerobic digestion, belt filter press dewatering, and a rotary drum drying facility. The rotary drum drying facility has not been operated since 2010 due to higher operational costs associated with production of a Class AA pelletized biosolids, as compared to either a Class B dewatered cake land application or dewatered cake landfill disposal. Biogas can fuel boilers for digester heating, with the excess gas flared, or can be routed to a combined heat and power (CHP) system for electrical power generation and digester heating through engine heat recovery. Since much of the facility’s infrastructure is reaching the end of its service life, the city has

programmed comprehensive renewal/replacement upgrades. To that end, the city has commissioned a phased master plan to assess plant condition and performance, identify and evaluate enhanced treatment options, develop conceptual designs of recommended upgrades, and prioritize implementation. A pre-existing process schematic is provided in Figure 1. When the city commissioned a 20-year master plan for the plant to address renewal and replacement of aged facilities, the following treatment process evaluations were also included: 1. Liquid stream alternatives to reduce operational costs, such as methanol use, and improve treatment efficiency. 2. Conversion to advanced digestion processes to maximize solids destruction and biogas production for beneficial reuse. 3. Feasibility of energy and heat recovery from excess digester gas, combined heat and power, and renewable compressed biogas for fueling of the city’s compressed natural gas (CNG) fleet vehicles.

Kurt Pfeffer is associate vice president with Hazen and Sawyer in Boca Raton. Jacob Porter is a senior associate with Hazen and Sawyer in Tampa. Bryan Lisk is a senior associate and Michael Bullard is vice president with Hazen and Sawyer in Raleigh, N.C. Karloren Guzman is a planning engineer with City of Tampa Wastewater Department. Mitch Chiavaroli is director of engineering with McKim and Creed in Clearwater.

Methodology The preliminary evaluation of digestion and biogas recovery options consisted of identifying potential options, quantifying solids production projections, preliminary sizing of unit processes, developing mass balance calculations, preliminary facility layouts, and calculating comparative life cycle costs for each option. Solids treatment options that were evaluated included: S Upgraded conventional mesophilic anaerobic digestion (MAD) S Conversion to temperature-phased anaerobic digestion (TPAD) S Conversion to acid-gas mesophilic digestion (AGMD) S Addition of thermal hydrolysis pretreatment (THP) to upgraded MAD (THP+MAD) Biogas energy recovery options included: S Direct digester heating by hot water boilers and heat exchangers, with flaring of excess gas. S Replacement of the aged combined CHP system, including heat recovery, to produce electrical energy and capture thermal energy. S Use as renewable natural gas (RNG) to replace the CNG currently purchased for the city’s solids waste and bus vehicle fleets.

Figure 1. Pre-Existing Process Schematic

June 2019 • Florida Water Resources Journal

Digestion and biogas recovery options were evaluated for two liquids process scenarios: 1. Optimize the existing high-rate activated sludge process (low solids retention time [SRT], greater sludge production, higher volatile content, and higher gas yield). 2. Convert to a parallel Modified Ludzack-Ettinger (MLE) process (higher SRT, lower sludge production, lower volatile content, and lower gas yield).

Table 1. Projected Plant Anaerobic Digester Long-Term Organic Loads

Results: Advanced Digestion Alternatives Quantify Solids Production A GPS-XÂŽ process model was developed to predict treatment performance and solids production for both liquid stream alternatives. Table 1 summarizes the projected longterm organic loading to the digesters for the selected liquid stream alternative (Alternative 1: Optimize existing high-rate activated sludge process). Table 2 presents GPS-X process modeling results of predicted digestion performance based on the sludge production rates and longterm biological nutrient removal (BNR) process changes. Under these baseline conditions, annual average volatile solids destruction is expected to approximate 58 percent. Alternative 1: Baseline Maintain/Upgrade Mesophilic Anaerobic Digestion Process In the baseline condition, existing digesters would continue to operate in a conventional mesophilic mode, with operating temperatures of 95 to 100Ë&#x161;F. Smaller digesters 1 through 4 were constructed in the 1950s, digester 5 was constructed in the 1970s, and larger digesters 6 and 7 were constructed in the 1980s. Structural analysis of the oldest digesters indicates that concrete tanks can be reused in planned upgrades. A mechanical equipment condition assessment concluded that most digester covers, and all pumping, mixing, heating, and gas handling equipment, should be replaced. Alternative 2: Conversion to TemperaturePhased Anaerobic Digestion This alternative evaluates converting the conventional mesophilic anaerobic digestion process into a TPAD configuration, which consists of thermophilic digestion (131 to 140oF), followed in series by mesophilic digestion (95 to 100oF). In temperature-phased mode, thickened waste activated sludge (TWAS), plus primary sludge (PS), would be fed to the thermophilic digesters, and partially digested sludge from the

Table 2. Projected Plant Anaerobic Digester Performance

Table 3. Anaerobic Digester Volatile Solids Reduction Parameters

Table 4. Minimum Hydraulic Retention Time for Temperature-Phased Anaerobic Digestion (Days)

Continued on page 26 Florida Water Resources Journal â&#x20AC;˘ June 2019

Figure 2. Solids Process Schematic: Temperature-Phased Anaerobic Digestion

Figure 3. Site Plan: Proposed Temperature-Phased Anaerobic Digestion Facilities

Table 5. Anaerobic Digester Volatile Solids Reduction Parameters

Table 6. Minimum Hydraulic Retention Time for Acid-Gas-Phased Anaerobic Digestion (Days)

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Continued from page 25 thermophilic digesters would be transferred to the mesophilic digesters. A raw fats, oils, and grease (FOG) stream would be routed directly to the second-phase mesophilic digesters. When implemented in other facilities, temperaturephased operation has increased the degradable fraction of volatile solids and has also increased digestion reaction rates. Table 3 summarizes the differences in volatile solids reduction between mesophilic and thermophilic anaerobic digesters. These parameters indicate that thermophilic conditions promote faster and morecomplete degradation than mesophilic conditions, resulting in an increase in both volatile solids reduction and digester gas production. The minimum digester HRT required for temperature-phased operation is presented in Table 4. Based on these HRT criteria, a minimum of two operating thermophilic digesters and six existing operating mesophilic digesters would be required to meet future organic loading conditions (80-mgd sludge production). In addition to the eight operating digesters, a standby digester would be required for â&#x20AC;&#x153;N+1â&#x20AC;? reliability; therefore, conversion to a TPAD configuration would require a total of nine digesters, including the seven existing digesters and construction of two new thermophilic digesters (minimum total volume of 6.1 mil gal). Key design criteria for the new thermophilic digesters include: S Cast-in-place concrete construction (to meet structural and temperature insulation criteria) S Fixed digester covers (for odor control) S Gas mixing systems (similar to existing digesters) A new thermophilic digestion process equipment building would also be constructed to house thermophilic-to-mesophilic transfer pumps, heated sludge recirculation pumps, heat exchanger units, and a sludge heat recovery system. The proposed TPAD facilities are shown in Figures 2 and 3. For maximum-month loading conditions, with one of the two thermophilic digesters out of service, thermophilic residence time meets the minimum recommended HRT of five days. Similarly, with one of the largest mesophilic digesters out of service, mesophilic residence time meets the minimum recommended HRT of 10 days. A sludge heat recovery system (sludge-tosludge heat exchangers) would be provided in the thermophilic digester control building to transfer (recover) excess heat from the therContinued on page 28

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Continued from page 26 mophilic sludge to “preheat” TWAS+PS feed to the thermophilic digesters and cool thermophilic sludge before it enters the secondstage mesophilic digesters. For the temperature-phased anaerobic digestion alternative, the necessary improvements, in addition to those included for the baseline digestion facilities, include: S Two new temperature-phased digesters 8 and 9, including gas-holding covers, gas safety equipment, mixing systems, electrical, and instrumentation and control (I&C). S One new digester building D, including thermophilic sludge transfer pumps, heat exchanger equipment, heating pumps, waste gas burners, gas safety equipment, piping (sludge, gas, water and fuel), electrical, and I&C.

Alternative 3: Conversion to Acid-GasPhased Anaerobic Digestion This section evaluates converting the conventional mesophilic anaerobic digestion process into an acid-gas-phased anaerobic digestion (AGMD) configuration, which consists of acid-phase digestion, where shorter detention times favor the proliferation of acidogenic organisms that produce volatile fatty acids, while suppressing methanogenic growth (pH remains in the weakly acidic range of 5 to 6). This is followed in series by gas-phase digestion, where longer detention times allow the methanogenic organisms to grow. In the acid-gas-phased mode of operation, TWAS+PS would be fed to the acid-phase digester, where partially digested sludge from the acid-phase digester would be transferred to the gas-phase digesters; a raw FOG stream would be

Figure 4. Solids Process Schematic: Acid-Gas Mesophilic Digestion

Figure 5. Site Plan: Proposed Acid-Gas Mesophilic Digestion Facilities

June 2019 • Florida Water Resources Journal

routed directly to the gas-phase mesophilic digesters. When implemented in other facilities, acid-gas-phased operation has increased the degradable fraction of volatile solids and has also increased digestion reaction rates. Table 5 summarizes the differences between mesophilic and acid-gas-phased anaerobic digesters. The two-phase acid-gas digestion process was developed to provide ideal growth conditions for acid- and gas-producing organisms. Separation of acid and gas phases was found to improve volatile solids reduction, while reducing retention time requirements. The minimum digester HRT required for acid-gas-phased operation is presented in Table 6. Based on these HRT criteria, a minimum of one operating acid-phase digester and five existing operating mesophilic digesters would be required to meet future organic loading conditions (80-mgd sludge production). A standby digester would be required for “N+1” reliability. Digesters 1 and 2 would be configured to operate as either an acid or a gas reactor. The size of the smaller existing digesters is ideal for use as acid reactors to meet the short two-day HRT; therefore, conversion to an AGMD configuration would not require additional digesters, but rehabilitation of the seven existing digesters. The proposed AGMD facilities are shown in Figures 4 and 5. Alternative 4: Addition of Thermal Hydrolysis Pretreatment to Baseline Digestion This section evaluates the addition of THP to the conventional mesophilic anaerobic digestion process configuration. The THP could be added prior to anaerobic digestion at the plant. The process would significantly increase volatile solids reduction across the digesters, reduce postdigested sludge mass, and improve postdigested sludge dewaterability, resulting in much lower hauling costs. Because THP reduces WAS viscosity, it’s expected that the anaerobic digesters could be operated with a feed concentration of 8 to 10 percent TS. Increasing the digester feed sludge concentration could potentially allow anaerobic digestion to be consolidated to three mesophilic digesters. Thermal hydrolysis pretreatment facilities proposed under this scenario would be preceded by a new sludge screenings process to remove small trash and debris, and a new predewatering process to concentrate the feed sludge. The predewatering facility would consist of centrifuges, cake pumps, and polymer storage and feed facilities. Thermal hydrolysis processes generally expose partially dewatered biological wastewater Continued on page 30

Table 7. Thermal Hydrolysis System Design Criteria

Table 8. Anaerobic Digester Volatile Solids Reduction Parameters

Table 9. Predicted Performance for Advanced Digestion Alternatives

Continued from page 28 treatment residuals to a combination of high temperature and high pressure for a fixed time period, such that the cellular wall structure in the residuals is fractured and soluble organic material contained within the cells is made bioavailable as a substrate in downstream digestion unit treatment processes. There are several THP system providers. The CAMBI® thermal hydrolysis process has the largest installation base and was assumed for this evaluation. The CAMBI system proposed was based on the design criteria summarized in Table 7. When implemented in other facilities, the addition of thermal hydrolysis pretreatment has increased the degradable fraction of volatile solids and has also increased digestion reaction rates. Table 8 summarizes the differences between mesophilic and THP anaerobic digestion facilities. Based on the HRT criteria, a minimum of two existing operating mesophilic digesters would be required to meet future organic loading conditions (80-mgd sludge production). In addition to the operating digesters, a standby digester would be required for “N+1” reliability; therefore, conversion to an THP configuration would not require additional digesters, but instead, rehabilitation of three existing digesters (5, 6, and 7) and construction of new thermal hydrolysis pretreatment and predewatering facilities. Proposed THP facilities are shown in Figures 6 and 7. Table 9 compares predicted performance for each of the four digestion alternatives. Table 10 compares net present value of capital and annual operation and maintenance (O&M) costs for each of the four digestion alternatives. Table 11 presents a matrix developed jointly by the city and its engineer, with weighting of decision factors and scoring for each alternative. The scoring system is based on a scale of 1 to 10, with 10 being the most-preferred option. The life cycle operational costs include all energy usage. Alternatives 2 (TPAD) and 4 (THP) were the lowest ranked and were removed from further consideration. Alternatives 3 (acid-gas) and 1 (baseline upgrades) had the highest and very similar scores of 7.4 and 7.5, respectively. As a result, either option is a good fit for the city. The acid-gas alternative was chosen and the design will allow for an alternate operational mode in conventional mesophilic mode.

Results: Biogas Recovery Alternatives Figure 6. Solids Process Schematic: Thermal Hydrolysis Pretreatment

June 2019 • Florida Water Resources Journal

Biogas Production Desktop modeling estimated the biogas

production by first calculating theoretical secondary and primary sludge production prior to digestion, which was then calibrated to fit the existing sludge supervisory control and data acquisition (SCADA) data from 2015 monthly averages. Biogas production was then estimated by using the modeled sludge production, historical sludge characteristics from 2015 (monthly averages), and industry standard gas production rates to generate a low and high estimated range of digester gas biogas production, which is expected to increase ~1 percent per year. Figure 8 shows the expected annual digester gas production for the liquid and biosolids alternatives. Alternative 1 represents optimizing the existing liquid stream, and alternatives 2a and 2b represent different parallel liquid feed options. The liquid stream treatment alternatives were found to have the largest impact on biogas production; the biosolids treatment alternatives did not have a large impact on the biogas production. From Figure 2 it’s clear that optimizing the existing liquid stream produces the most biogas, which can be utilized in the most beneficial way possible. This biogas production relationship was similar for the other biosolids alternatives evaluated (TPAD+acid-gas, and T+P+Mesophilic). The following biogas utilization alternatives were identified and evaluated: S Alternative 0 – Flare all Biogas. Alternative 0 assumes that all biogas is flared and natural gas is purchased to provide digester heating. The purpose of evaluating this alternative is to establish a “zero resource recovery” baseline to compare the revenue generation of the other biogas utilization alternatives. S Alternative 1 – Biogas to Boilers. This alternative makes beneficial utilization of the biogas by fueling the existing boilers to provide digester heating. All unused biogas would be flared. This alternative eliminates the capital costs and O&M costs associated with biogasfueled engines. S Alternative 2 – CHP. This alternative explores technologies and strategies that utilize digester gas to produce electric energy to offset purchased and thermal energy that can be recovered for digester heating. The electric energy is used to offset the purchased utility power at the current retail rate. Thermal energy is recovered from the exhaust and engine cooling system to provide the digester/building heating demands. It was assumed that the benefits gained from offsetting the purchased electric energy under the retail rate would be from the energy usage component of the total utility bill, only to account for the loss of demand offset

Figure 7. Site Plan: Proposed Thermal Hydrolysis Pretreatment Facilities

Table 10. Net Present Costs for Advanced Digestion Alternatives

Table 11. Digestion Alternatives Decision Matrix

from CHP system downtime. It was determined the annual average electric energy offset benefit would be approximately $0.07/kilowatt hour (kWh) for the CHP alternative. • Alternative 2a – Refurbish Existing Engines. Refurbish the existing five 500-kW Waukesha CHP engines for reuse in lieu of purchasing new engines. • Alternative 2b – New CHP System Engines and Building. Remove the existing Wauke-

sha engines and heat recovery equipment and install new engines furnished with engine jacket heat recovery in a new building. • Alternative 2c – New CHP System Engines in Existing Building. Remove the existing Waukesha engines and heat recovery equipment and install new engines furnished with engine jacket heat recovery in the existing building. • Alternative 3 – Biogas to RNG for Vehicle Continued on page 32

Florida Water Resources Journal • June 2019

Figure 8. Mesophilic Biosolids Treatment Digester Gas Production

Figure 9. Net Revenue Annualized Cost/Benefit

Figure 10. Annualized Net Revenue Cost/Benefit

June 2019 • Florida Water Resources Journal

Continued from page 31 Fueling. Recover and condition/compress biogas to be used in the city’s CNG-capable vehicles. For this alternative, digester gas is treated (or “upgraded”) to natural-gaspipeline quality (RNG) and will be used as a transportation fuel to gain the benefit from the renewable identification number (RIN) commodity market. For the purposes of this alternative, it’s assumed that all biogas will be treated to natural-gaspipeline quality standards and injected into the natural gas pipeline. The CNG will be “wheeled” through the TECO Energy (Tampa) natural gas pipeline network out to a wide network of customers, including the city’s CNG fueling stations. Between the city’s existing 60 refuse trucks and 60 CNG busses from the Hillsborough Area Regional Transit Authority (HART), it’s anticipated that approximately 1.1 mil gasoline gal equivalents (GGE) of RNG per year will be consumed, which is the majority of RNG produced. The biogas utilization feasibility evaluations were performed using Hazen’s energy balance and analysis tool (EBAT), which models the complex relationship of energy production, demands, and costs to provide accurate long-term cost/benefit assessments for multiple biogas utilization alternatives. The EBAT model was used to generate a 20year life cycle cost/benefit analysis (LCA) for each of the biosolids and liquid stream alternatives and the impact on the biogas production and utilization alternatives. The 20-year LCA incorporates capital cost debt service, energy savings, and O&M costs to calculate the true 20-year life cycle cost/benefit for each alternative. The EBAT model also calculates 20-year life cycle costs for current market conditions, as well as high and low market conditions, so that the full range of economic outcomes for the biogas utilization alternatives can be understood. The EBAT model calculates all costs/revenues for the year incurred (nominal dollars) over the 20-year life cycle. To simplify the costs and be consistent with previous studies, the revenue and cost data are shown as “annualized,” which represent the net present value of the 20-year lifecycle costs expressed in present-day dollars over a 20-year amortization period. Using the biogas production information, the EBAT model was used to calculate the annualized net revenue cost/benefit for CHP (with new engines) and RNG. Figure 9 summarizes the annualized net revenue cost/benefit for all evaluated treatment alternatives for both the

CHP (with new engines) and RNG biogas utilization alternatives. In addition to producing more biogas, as shown previously, Figure 9 clearly shows that optimizing the existing liquid stream treatment has the potential to produce the most revenue for the plant. The city selected the existing liquid stream treatment alternative and the acid-gas biosolids treatment alternative. The combination of these alternatives is expected to produce ~3 percent more biogas. Figure 10 shows the annualized net operating cost for all alternatives. The study results show that alternatives 2 (CHP) and 3 (vehicle fueling/RNG) are the only two alternatives with a positive annualized net operating cost and could produce revenue for the plant. As shown in Figure 10, the RNG alternative could produce greater revenue than the CHP alternative under the market conditions at the time of this report. Itâ&#x20AC;&#x2122;s important to note that the RNG alternative can have a higher revenue potential and may have a higher level of volatility due to the uncertainly on the long-term health of the RIN market.

Table 12. Biogas Recovery Options

Conclusions For digestion, conversion to AGMD results in the lowest life cycle cost, primarily because the existing smaller digesters 1 and 2 can be repurposed as acid-phase reactors to avoid the need for new tanks, while increasing biogas for energy recovery. The TPAD and THP+MAD options also improve biogas production, but would require significant additional capital infrastructure, resulting in reduce economic attractiveness. For biogas recovery, cost benefits from energy production make CHP and RNG options more financially attractive than the base op-

tion of a digester heating and flaring excess biogas. Table 12 summarizes preliminary findings/conclusions for the biogas recovery options. Itâ&#x20AC;&#x2122;s recommended that the RNG alternative be investigated further with TECO Energy and that the following next steps be taken: S Initiate a detailed utility pipeline assessment with TECO. This will determine if there is a nearby injection point for the plant or if a pipeline extension would be required. S If the first step is viable, an interconnection capacity study can be initiated to determine if there is capacity in the pipeline for the additional natural gas. S

Florida Water Resources Journal â&#x20AC;˘ June 2019

C FACTOR

Workforce Sustainability: Now and for the Future Mike Darrow President, FWPCOA

’m glad to be here communicating again with you. Well, another successful conference is over. I had the opportunity to attend the Florida Water Resources Conference (FWRC) in Tampa that was held in April. I personally like to learn what’s up in our industry and network with folks who attend this excellent conference. It’s always a good overview of our profession. It was sure good to talk with many of you who were there and find out what’s on your mind.

As always, there were many things going on at the conference. My congratulations go to the award winners who were announced at the two lunches. I enjoyed watching the Operations Challenge competition—those folks can sure cut some pipe and install a lateral connection fast! I attended several of the fine technical sessions and workshops and learned what other utilities and companies are doing to meet their challenges. I visited many vendor booths and saw new technology first hand in the exhibit hall. I also attended the FWPCOA Operators Showcase, led by Tom King and Scott Anaheim. We discussed the topics of emergency responder status, water reuse and future operator licensing, long-term water sustainability, and developing the youth in our profession. These are all very good topics for our operators association to be acting on.

June 2019 • Florida Water Resources Journal

Sustainability in Our Workforce Sustainability is a challenge for us all. I have talked with many operators, mechanics, coordinators, and maintenance technicians out there and one thing is clear to me: A wealth of knowledge and experience is leaving our utilities as these folks (and others) retire and leave the workforce. I have met many good young people in our industry who are working and learning to be their best, and wanting to achieve a good career; however, I feel that many more of them are needed for the future if we hope to sustain (and exceed) the level of service our customers expect. We talk a lot about the young professionals (YPs) in the industry, but we need more professional development for young operators (YOs), including those folks out of high school, technical school, or college programs, who are needed to replace us—right now and in the future. Today, water distribution and collection system operators, advanced certified treatment operators, instrumentation and control (I&C) and supervisory control and data acquisition (SCADA) technicians, lift station electricians, pump mechanics, and utility managers are in high demand and are needed across the state. These are all skilled craft positions needing new workers to match the knowledge and expertise of some of the old operators (OOs!) I know who have already left or will be gone soon. For a long time, development in these professions has been done with in-house programs and by using associations like FWPCOA. Now

we must take it a bit further and all work together for this new challenge of developing a sustainable program of replacing ourselves in our skilled crafts.

Mentoring for the Future Many more mentorship programs in our profession are needed. We must mentor our new professionals looking for training, experience, advancement, and increased responsibilities. Leading the next generation to work in our profession is greatly needed if we’re to replace ourselves and our experience levels. When I started my career (and actually, throughout my career), I met many folks who helped me out technically and professionally. This is done by teaching the skills, experiences, practices, ideas, and consistent work ethic that are needed to do our jobs more efficiently and effectively. Giving new people exposure to the many disciplines and practices in the industry is crucial. The FWPCOA is built on this principle. Many seasoned professionals are actively training the next generation, but much more is needed. I’m proud to be a small part of that. We are involved in this core fundamental of replacing ourselves at FWPCOA. Experience is taught in our courses—both onsite and online—to new operators by current professionals who actually are performing the work. Recruiting the youth of Florida to an operator, technical, or mechanical job has its complications. Competing with the IT game and YouTube-type professions is difficult. The outdoor hands-on work we do is beyond the concept of many young people. To attract new folks to this profession, outreach and an interesting technical curriculum are needed for middle- and high-school students to learn about our industry. It’s incredible to realize that many kids have no idea that this industry exists! We need to show how science, engineering, environmental issues, biology, physics, public heath, and mechanical skills are blended together to form the operators, coordinators, and technicians of the future. We must partner with high schools and technical schools to help them set up their programs, and partner with the students as they learn about our trade and get actual experience working in the field. Utilities must also look to opening trainee and or apprenticeship positions in all of these areas to fill the needs for the future. I had the opportunity to attend a workshop at FWRC for workforce apprenticeships

and I learned a lot from the discussion. At the workshop were utility employees from around the state, and representatives from the University of Florida Training, Research, and Education for Environmental Occupations (TREEO) Center, FSAWWA, and FWPCOA, discussing how they present these issues to their students and workers and how this workforce development and sustainability challenge could move forward. As I see it, this is the beginning of a joint partnership among all water industry workers and organizations for the progression of this important issue. Your help is needed for us to move forward, so get involved when and where to can.

Emergency Responder Status Under its Publicity Committee, FWPCOA is working on emergency responder status recognition for our working professionals. We respond in emergencies and keep the water flowing in all directions and where it’s supposed to go (and not go). Protecting public health and welfare by providing safe drinking water, collecting and treating wastewater to protect Florida’s environment, and preventing sanitary sewer overflows is as important as the work that our brave police officers and firefighters do. Like them, we’re required to stay on duty and work overtime under dangerous conditions as we repair the systems until water and wastewater are back to normal operation. We train for natural and manmade disasters and we have emergency response plans that are required by law. Many of you worked long and hard during our recent storm events, as you’ve done in many years past. We’re looking for this recognition now, which I believe will help us recruit young people to our industry and advance our profession. The FWPCOA is looking for support from you on its quest for emergency responder status for water and wastewater utility workers. Our Publicity Committee is working with representatives in Tallahassee to help get this going, and by working with Florida’s legislators, we can get this recognition. If you have a story of an emergency response situation (that either you or another worker or a team experienced), we would love to hear from you. Please send any letters of support or examples of response situations to me at president@fwpcoa.org, or to Phil Donovan, our Publicity Committee chair, at publicity@fwpcoa.org. Remember to keep mentoring each other—and go with the flow! S

Water Professionals Go to the Dogs! Two recently retired Florida water utility professionals, Mike Cliburn, formerly of AECOM, and Brian Wheeler, a former TOHO Water Authority employee (along with Brian’s dog Nick), participated in the Southeastern Guide Dogs Walkathon on April 13 at Cranes Roost in Altamonte Springs. Every winter and spring highly trained guide dogs are matched with visually impaired people for a family- and dog-friendly walkathon fundraiser in up to seven locations throughout Florida. Those locations have included Bradenton, Fort Myers, Orlando, Sarasota, Tampa, St. Petersburg, and The Villages. The events include music, food, games, shopping, and other familyfriendly activities. Cliburn is the organizer of this annual fundraising event and trains the guide dogs, and Wheeler is also involved in the dog-training program. Both report they are very happy in retirement and have found useful endeavors like this that keep them busy and involved. S

Mike Cliburn (left) and Brian Wheeler participate in the walkathon. (photo: Jim Peters)

Florida Water Resources Journal • June 2019

Florida Water & Pollution Control Operators Association

FWPCOA STATE SHORT SCHOOL August 12 – 16, 2019 Indian River State College - Main Campus – FORT PIERCE –

COURSES Backflow Prevention Assembly Tester ..........................$375/$405

Stormwater Management C, B & A...............................$325/$325

Backflow Prevention Assembly Repairer ......................$275/$305

Utility Customer Relations I, II & III................................$325/$325

Backflow Tester Recertification ......................................$85/$115

Utilities Maintenance III & II ..........................................$325/$325

Basic Electrical and Instrumentation ............................$225/$255

Wastewater Collection System Operator C, B & A ......$325/$325

Facility Management Module I......................................$275/$305

Water Distribution System Operator Level 3, 2 & 1............$325/$325

Reclaimed Water Distribution C, B & A ........................$325/$325 (Abbreviated Course) ................................................$125/$155

Wastewater Process Control ........................................$225/$255 Wastewater Troubleshooting ........................................$225/$255

For further information on the school, including course registration forms and hotels, visit: http://www.fwpcoa.org/FallStateShortSchool

SCHEDULE CHECK-IN: August 11, 2019 1:00 p.m. to 3:00 p.m. CLASSES: Monday – Thursday........8:00 a.m. to 4:30 p.m. Friday........8:00 a.m. to noon

FREE AWARDS LUNCHEON P Wednesday, August 14, 11:30 a.m. P

For more information call the

FWPCOA Training Office 321-383-9690 36

June 2019 • Florida Water Resources Journal

Florida Water Resources Journal â&#x20AC;¢ June 2019

FWEA FOCUS

Get Ready for a Successful 2019-2020! Michael W. Sweeney, Ph.D. President, FWEA t’s truly an honor and privilege to serve as your president and contribute to the Florida Water Resources Journal. The magazine’s quality and presentation are highly regarded among all of the WEF member associations, and being able to write a monthly column is an exceptional opportunity. Allow me to begin with outlining changes to your board of directors. The changes are minor by comparison to last year’s efforts, but intend to build on what our past president Kristiana Dragash started. We have eight very capable directors at large (DALs) this year, with the only change being the addition of DAL Alice Varkey, P.Eng., succeeding Lindsay Marten-Ellis, who is pursuing an exciting new business venture. Varkey will be assisting the Manasota Chapter, Southwest Chapter, Manufacturers and Representatives Committee (MARC), and our strategic planning efforts. The dedication remains to further promote opportunities for students in our eight student chapters and involve young professionals (YPs) in our leadership and acAlice Varkey tivities. Supporting and growing the Student Design Competition and what it provides in the way of real-life experience also continues to be a focus. We cannot forget that students and YPs are the future of FWEA and our mission, and we must attract and retain our fair share of the best and brightest! Serving on the board of directors provides a broad view of this venerable 78year-old association. The beginning of the year brings the opportunity to build on its strong foundation. At this year’s Florida

Water Resources Conference (FWRC) in Tampa, I outlined several areas to pursue that are of strategic importance to FWEA and its members. Here, I have organized and aligned them with the four goals of our strategic plan:

Professional Development Continue the effort of professional development to recognize and promote, through a new certification process, the competencies of our operators and system support professionals in three functional areas that are not currently licensed: maintenance mechanics, supervisory control and data acquisition (SCADA) systems support, and electrical power systems support. We started this effort last year and want to continue the momentum to culminate into a certificate of achievement that is based on experience and demonstrated knowledge through an examination. I hope that we can launch at least one of the three this year and continue to pursue the other two. Perhaps in the future there could be a license for each, but earning a certificate of achievement serves as a step toward recognizing competency, reinforcing effective and safe practices, and enabling an upward progression of careers.

choices for communities as their feasibility is being further explored. Our members need to become more aware of the future professional opportunities, and also be a “force multiplier” in sharing information and helping to promote fact-based discussion. The FWEA needs to continue to be a growing part of this “One Water” reality.

Strong Organization Our 2015-2020 strategic plan has provided essential guidance and direction and it’s time to begin the process of updating it. To make it a holistic and informative process, we will offer a means for our membership at large to provide input as our board reviews it. We have a solid plan now, but it’s a best practice to review and refine it periodically.

Public Awareness Our website is a storehouse of information, and even in the world of social media, it stands as a go-to place for further information that members and the public can draw from. Many feel it’s time to review and determine how we can make the platform more timely, interactive, and convenient to update.

Sound Public Policy By coordinating with the FWEA Utility Council and other partners, we need to prepare to put sound policy into practice by informing our members about the development of potable reuse. We produce millions of gallons per day of reclaimed water that provides irrigation, cooling water, and water supply recharge across Florida. Now, indirect and direct potable reuse are gradually emerging as additional water reuse

June 2019 • Florida Water Resources Journal

I look forward to working with you on these pursuits and I am very grateful for this opportunity to serve you. As Isaac Newton once said, “If I have seen further it is by standing on the shoulders of giants.” It’s important that we remember where we came from and find new ways to accomplish our mission, ensure sustainability, and provide opportunities to develop and prepare the next generation. S

Florida Water Resources Journal â&#x20AC;¢ June 2019

F W R J

Overcoming Obstacles with a Difficult-to-Handle Sludge: Centrifuge Piloting at Miami’s Central District Wastewater Treatment Plant Brian Stitt, Terry Goss, Ismael Diaz, and Manuel Moncholi s part of the consent decree project for Miami-Dade’s Central District Wastewater Treatment Plant (CDWWTP), the program management and construction management (PMCM) team conducted pilot testing of centrifuge thickening prior to anaerobic digestion and centrifuge dewatering postanaerobic digestion. The pilot dewatering testing used digested biosolids from the digester, receiving mechanically thickened biosolids at high solids input concentration after steady state operation was achieved. The pilot testing established performance criteria used for the design-build documents and associated process performance guarantee. The CDWWTP, located on Virginia Key, is the oldest existing sewer treatment plant operated by the Miami-Dade Water and Sewer Department and was originally constructed in 1956. The CDWWTP is a high-purity oxygen-activated sludge secondary treatment facility with a permitted capacity of 143 mil gal per day (mgd) or 22,555 cu meters per hour (m3/h). The plant has two separate liquid processing streams: Plant 1 was rated at 60-mgd average daily flow (ADF)

(9,464 m3/h) and Plant 2 was rated at 83-mgd ADF (13,091 m3/h). The CDWWTP produces only waste activated sludge (WAS). The WAS is mixed with polymer in the piping and sent to eight 55-ft-diameter (16.8meter) gravity thickeners with a 13-ft (4-meter) side-water depth. Both Plant 1 and Plant 2 contain four gravity thickeners, which thicken the solids to 2 to 4 percent total solids (TS) before being stabilized in twenty-four 105-ft-diameter (32-meter) anaerobic digesters, each with a nominal operating volume of 1.5 mil gal (MG) (5,700 cu meters) that are operated under two-stage mesophilic conditions. The digesters are currently being upgraded from primary-secondary to single-stage operation. Plant 1 consists of two digester clusters, each with four digesters, and Plant 2 consists of four digester clusters, each with four digesters. The digested biosolids are further dewatered using Alfa Laval DS 706 centrifuges that achieve greater than 25 percent TS. The sludge fed to the centrifuges is currently conditioned using a dry-polymer-type system. Ferric sulfate is also added to the dewatering feed, primarily for struvite control.

Brian Stitt is senior project manager with AECOM Water in Miami, and Terry Goss is biosolids practice leader with AECOM Water in Morrisville, N.C. Ismael Diaz is project manager with GHD in Miami. Manuel Moncholi is division chief and senior program manager with Miami-Dade Water and Sewer Department.

The CDWWTP also receives primary sludge and WAS from the North District Wastewater Treatment Plant (NDWWTP). The sludge transfer building at NDWWTP houses four sludge transfer pumps with variable speed drives. The pumps are used to pump sludge through two 16-in. force mains, which are parallel for about 10 mi before they join at an interconnection. From the interconnection, sludge can be directed to the sewage collection system of CDWWTP (Force Main 2) or to an extension of one 16-in. force main that continues another 6 mi, where it then discharges to the gravity sludge thickeners located at Plant 2 of CDWWTP (Force Main 1). The sludge from NDWWTP contains an exorbitant amount of rags, plastics, and grit, which have historically been problematic for CDWWTP sludge thickening operations. Screening of NDWWTP sludges will be implemented to remedy this operational challenge. The CDWWTP is replacing the existing gravity thickeners with new centrifuge thickeners that are expected to improve the performance and increase the capacity in the existing digestion complex. The existing dewatering centrifuges are also near the end of their useful service life and the design includes replacing the system with a new centrifuge dewatering complex.

Pilot Study Overview and Objectives Figure 1. Site Plan Showing Centrifuge Pilot Installation at Central District Wastewater Treatment Plant on Virginia Key

June 2019 • Florida Water Resources Journal

To better establish performance criteria for the new thickening and dewatering centrifuges, a five-

month centrifuge thickening, digestion, and centrifuge dewatering pilot study was conducted at CDWWTP from May to September 2016. The pilot study was set up to simulate future thickening, digestion, and dewatering operating conditions to establish thickening and dewatering performance criteria. Figure 1 shows a plan view layout of the site and identifies the locations for the centrifuge thickening and dewatering pilot trailers; Figure 2 provides photos of the pilot testing trailers provided by Centrisys, which were selected after a competitive bidding process. The PMCM team oversaw the piloting effort with outstanding support from the CDWWTP operations and maintenance staff. Periodic samples collected throughout the pilot operation were all analyzed for TS. The PMCM team regularly monitored the volatile solids (VS) content of the thickened sludge fed to the digester and digested biosolids samples, the digested biosolids pH was measured, and the centrate samples were also analyzed for total suspended solids (TSS). College interns from Florida International University and University of Miami were trained to perform the sampling and laboratory analysis throughout the duration of the pilot-testing period.

Figure 2. Photos of Pilot Equipment: Thickening (left) and Dewatering (right)

Figure 3. Thickening Polymer Injection Point

Thickening Pilot Testing The thickening pilot operation was based on feeding three different sludges to the pilot centrifuge thickener: S CDWWTP: WAS-only S NDWWTP: Primary and WAS S CDWWTP: WAS + NDWWTP Primary and WAS The purpose of the thickening pilot operation was to determine the optimum polymer design conditions and performance of the centrifuge thickening. The overall target for the centrifuge thickening performance, as stated in the basis of design and specifications, was to thicken the WAS to 5.5 percent TS, while maintaining greater than 95 percent solids recovery. Determining the necessary polymer dose to achieve this performance is also important. Parameters that were adjusted for the centrifuge thickening included the pool depth, bowl speed, and differential scroll speed. Thickening Pilot Setup Thickening in the pilot unit was tested without polymer, with emulsion polymer, and with dry polymer. The pilot unit was set up to allow injection of polymer at two locations, as illustrated in Figure 3, either directly into the bowl of the unit (internal injection) or in the sludge feed line upstream of the centrifuge inlet (external injection). Polymer flow was measured during each sampling

event using a calibration column located on the pilot trailer. The emulsion polymer used for testing was PRAESTOL® K144-L, a cationic, high-molecularweight emulsion polymer. Two different dry polymers were also tested, including the dry polymer currently used in CDWWTP’s gravity concentrators (SNF Polydyne Clarifloc SE-1138) and the dry polymer currently used in CDWWTP’s dewatering centrifuges (SNF Polydyne Clarifloc SE-1141). Thickening Pilot Testing: Central District Wastewater Treatment Plant Waste Activated Sludge For the CDWWTP WAS-only thickening operation, the system was set up and operated with emulsion polymer, with dry polymer, and without polymer. Polymer curve tests were conducted by maintaining a constant volumetric throughput of sludge feed to the centrifuge, while changing the polymer dose. With the exception of changing the polymer dose, all other parameters on the centrifuge remained the same for each polymer curve test. After generating the polymer curves, the unit was operated for several days at a constant flow rate, with optimized settings to test the stability of operation throughout the course of a day. The testing showed that the centrifuge, operating on CDWWTP WAS-only, could reliably thicken the WAS from 0.9 to 1.3 percent TS to 5 to

6 percent TS, and achieve greater than 95 percent solids recovery. Testing was conducted using both dry and emulsion polymers. The dry polymer required 3 to 4 pounds per dry ton (lb/DT) or 1.5 to 2 grams per dry kilogram (g/kg) active dosing, compared to 0.6 to 3 lb/DT (0.3 to 1.5 g/kg), based on the emulsion. It was also possible to thicken the sludge to 5 to 6 percent TS without the use of polymer, but this reduced hydraulic throughput by about 25 percent to allow solids recoveries to remain above 95 percent. Examples of the polymer curve data and extended operation data that were collected are provided in Figure 4. Thickening Pilot Testing: North District Wastewater Treatment Plant Primary and Waste Activated Sludge When pilot operation initially began in May 2016, the 6-mi, 16-in. line from the interceptor that allowed NDWWTP sludge to be fed to CDWWTP gravity thickeners was out of service, so pilot testing of NDWWTP sludge could not begin until it was brought back into service. In addition, the amount of debris and grit in the sludge from NDWWTP, which has historically been problematic for CDWWTP operations, was exacerbated during the piloting period since the primary sludge degritters at NDWWTP were out of service for a replacement. Continued on page 42

Florida Water Resources Journal • June 2019

Figure 4. Dry Polymer Curve and Extended Operation Data: Central District Wastewater Treatment Plant, Waste Activated Sludge-Only

Figure 5. Central District Wastewater Treatment Plant Screens for North District Wastewater Treatment Plant Sludge

Figure 6. Central District Wastewater Treatment Plant and North District Wastewater Treatment Plant Blend Tank

June 2019 • Florida Water Resources Journal

Continued from page 41 In order to provide a solution to minimize the impact of rags and grit for an interim period before the consent decree projects were to be implemented, water and sewer department operations personnel installed two Lakeside Raptor® Screens, shown in Figure 5 on the receiving pipe for NDWWTP sludge. The unit contains a screening system and an aerated grit chamber that provides removal of both rags and grit to a dumpster. The NDWWTP sludge from the screens was directed to one of CDWWTP’s gravity concentrators. Testing of NDWWTP sludge started at the end of June 2016, and testing ultimately continued through mid-September 2016. During the testing period, daily plant records for NDWWTP sludge production and transfer operations were provided to the PMCM team, which included information of flow to Force Main 1 and the solids concentration. The preliminary design for the NDWWTP sludge concentration was 0.75 percent TS average, with a range from 0.5 to 1 percent TS, but the data collected showed that the NDWWTP concentration was typically less than 0.5 percent TS. Initial testing was conducted mostly on NDWWTP primary sludge, since a large proportion of the WAS was directed to Force Main 2 to the influent of CDWWTP due to limitation in the piping. On Aug. 29, 2016, after some piping modifications were made, all NDWWTP sludge began going through Force Main 1, and this mode of operation remained throughout the duration of the pilot that concluded on Sept. 15, 2016. The combination of thin sludge and the high proportion of primary sludge made thickening in the pilot centrifuge very difficult. Although the CDWWTP WAS-only sludge was easily able to thicken in the pilot centrifuge, the NDWWTP primary sludge and WAS, which was more dilute, was difficult to handle and thicken reliably. After testing the NDWWTP primary sludge and WAS alone using multiple parameters, stable operation could not be maintained. Initial attempts to blend NDWWTP primary and WAS with CDWWTP WAS using an in-pipe blending system were also unsuccessful. Because of the difficulties with the NDWWTP primary and WAS operation, a separate frac tank and recirculation pump was rented to allow a buffer for the NDWWTP primary and WAS, and for better control of blending the CDWWTP WAS and NDWWTP primary and WAS. When the NDWWTP sludge was blended with CDWWTP sludge in the blend tank (shown in Figure 6), stable operation could be maintained in the centrifuge, and greater than 5.5 percent TSthickened sludge, with greater than 95 percent solids recovery, could be achieved. The dry polymer required 1.5 to 3 lb/DT (0.75 to 1.5 g/kg) ac-

Figure 7. Central District Wastewater Treatment Plant and North District Wastewater Treatment Plant Polymer Curve and Extended Operating Testing Data

tive dosing, compared to 2 to 3 lb/DT (1 to 1.5 g/kg), based on the emulsion. The testing showed that including a blend tank to mix the CDWWTP and NDWWTP sludge would be important for future operation to be successful. Example data collected for thickening the CDWWTP and NDWWTP sludge blend are provided in Figure 7. The setup used during the pilot had several limitations with regard to capacity, tank mixing, and flow metering that should not be issues in a full-scale system. Because of the limitations, there were some variations noted for day-to-day operation. In addition, during the time of testing, the feed pump on the pilot centrifuge was wearing out and close to failure due to excessive wear on the stator from grit. Because of these issues, it was not possible to conduct an extended operation run for more than two to three hours at a time.

Continuous Thickening Pilot Operation Centrifuge-thickened sludge was fed to Plant 2, cluster 1, digester 3 (the test digester) to simulate future high-rate single-stage mesophilic anaerobic digestion conditions and to increase the solids content of the digested biosolids for the dewatering pilot operations. Near-continuous operation began in mid-June and the team maintained continuous operation through mid-August, but performance testing on CDWWTP and/or NDWWTP sludge continued to be conducted during normal workday hours, with operation switching to CDWWTP WAS-only for overnight and weekend operations. A manifold was set up to allow switching between the NDWWTP and CDWWTP sludges and was also used initially to blend them. Mechanical problems with the unit, specifically the thickened cake pump, limited the throughput and the operation time. The stator in the thickened sludge pump had to be replaced several times throughout the duration of the pilot. For the stable period (shown in Figure 8), the thickened solids content to the digester averaged

Figure 8. Continuous Thickening Operation

6.3 percent TS (with a 2.3 lb/DT [1.15 g/kg] active polymer dose) and the volatile solids content of the raw sludge being fed to the digester averaged 86 percent VS/TS. The solids content in the test digester was increased to approximately 2.8 to 3 percent TS. For comparison, the rest of the digesters operating at CDWWTP were being fed gravitythickened sludge at approximately 3.8 percent TS, with a volatile solids content of 83 percent VS/TS; the other operational digesters operated at an average of 2.2 percent TS. The volatile solids reduction (VSR) estimations during this period ranged from 50 to greater than 70 percent, while the digester was approaching a steady state.

Dewatering Pilot Testing The purpose of the dewatering pilot operation was to determine the optimal design conditions and performance of the dewatering centrifuge using the thickened biosolids fed from the test digester. The overall target for the centrifuge dewatering performance as stated in the basis of design specifications was to dewater the thickened digested biosolids to greater than 24 percent TS, while maintaining greater than 95 percent solids recovery. The necessary polymer dose to achieve this performance is also important to determine (and the draft specifications indicate) that an active polymer dose should be less than 25 lb/DT. Metcalf and Eddyâ&#x20AC;&#x2122;s Wastewater Engineering Treatment and Reuse (5th edition) lists 22 to 25

percent TS expected for anaerobically digested WAS and primary sludge, where the polymer consumption is expected to be 15 to 30 lb/DT active polymer dose, and solids recoveries are expected to be 95 percent or greater. The CDWWTP currently doses ferric sulfate at a rate of 1.9 gal per 1000 gal of sludge ahead of the centrifuges for struvite control. This practice is planned to continue in future operations, so a temporary ferric dosing system was also included with the pilot. Dewatering Pilot Testing: Setup For the dewatering pilot, the system was set up and tested with both emulsion and dry polymer, as well as ferric sulfate conditioning, which is similar to the current CDWWTP dewatering operation. The majority of the testing was conducted using the plantâ&#x20AC;&#x2122;s dry polymer, which is more representative of the future design; however, some limited testing was also conducted using emulsion polymer to provide a comparison. The initial dewatering operation was dedicated to optimizing the machine for the site-specific operation. Adjustable parameters included the pool depth, bowl speed, and differential scroll speed. The pool depth was adjusted manually through adjustment of the outlet weir plate and throughout all of the dewatering operation. The system was operated with the B weir plate, which corresponds to the second-deepest pool depth. For most of the dewatering operation, the centrifuge Continued on page 44

Florida Water Resources Journal â&#x20AC;˘ June 2019

Figure 9. Central District Wastewater Treatment Plant Dewatering Polymer Curve Testing With and Without Ferric Sulfate (data, left; photo of cake, right)

Continued from page 43 also operated at the highest bowl speed of 3,350 revolutions per minute (rpm). It was also found that injecting polymer directly into the feed tube was the best injection point, compared to other polymer injection locations tested. Initial testing started with emulation polymers on Aug. 11, 2016. Three cationic, high-molecularweight emulsion polymers were tested in order to determine the top polymer type for further testing. The emulsion polymers were able to achieve 21 to 26 percent TS, with greater than 95 percent solids recovery, but required higher polymer doses than were listed in the specifications (>30 lb/DT [15 g/kg]). Since the emulsion polymer dosing requirements were high compared to the specification requirements, and the basis of design is for a dry polymer, only limited further testing was conducted using emulsion polymer. The dry polymer used for all of the dewatering testing was Polydyne Clarifloc C-SE-1141, which is currently used for CDWWTP dewatering centrifuges. This dry polymer testing used for the duration of the pilot was optimized to start performance testing on Aug. 17, 2016. Dewatering Pilot Testing: Polymer Curve Testing Polymer curve tests were conducted by maintaining a constant volumetric throughput of digested biosolids feed to the centrifuge, while changing the polymer dose to measure the impact.

With the exception of changing the polymer dose, most of the other parameters on the centrifuge remained the same for each polymer curve test. Poymer curve tests were conducted primarily on dry polymer with feed tube polymer injection. Testing was mostly done with ferric sulfate dosing, but testing without it was also done as a comparison; the data for this comparison are shown in Figure 9. The cake solids ranged from 23.5 to 26.3 percent TS with the addition of ferric sulfate; without the addition, the cake solids were 3 to 4 percent points lower, ranging from 21 to 24 percent TS. The difference in solids content was visibly noticeable, as can be seen in Figure 9. Without the addition of ferric sulfate, the solids recovery was also noticeably worse than the operation with ferric sulfate. Dewatering Pilot Testing: Extended Operation Results In addition to polymer curve tests, the dewatering centrifuge was operated for two days at a constant flow rate to test the stability of operation throughout the course of a day. Two tests were conducted at 80 gal per minute (gpm) (18.2 m3/h) using dry polymer. Throughout the course of the test, it was desired to maintain constant settings; however, periodic adjustments were made based on visual observations of both the dewatered solids concentration and the centrate quality. The pilot field staff collected samples during these trials approximately once every 30

Figure 10. Extended Operation Using Dry Polymer

June 2019 â&#x20AC;˘ Florida Water Resources Journal

minutes to one hour, depending on the total duration of the particular test. One extended run using dry polymer is shown in Figure 10. Performance during this run was stable, with dewatered cake solids averaging 25 percent TS and solids recoveries averaging over 98 percent for all samples collected. The feed during this run was consistent, averaging 3 percent TS. The differential speed was held at 3 rpm during the five hours of operation and the power consumption averaged about 0.19 kW (kilowatt)/gpm (0.83 kW/[m3/hr]). The polymer concentration during this run averaged 0.8 percent and the active polymer dose averaged 25.8 lb/DT (12.9 g/kg). The results of the dewatering pilot indicate that the centrifuge dewatering unit will be able to achieve a total cake solids of >24 percent TS and solids recovery requirements of >95 percent. The testing showed that >24 percent TS cake could be achieved with 25 lb/DT (12.5 g/kg) active dosing of dry polymer and a ferric sulfate dose equal to 1.9 gal ferric sulfate per 1,000 gal of sludge. Testing conducted without the use of ferric sulfate conditioning showed that the dewatering performance was reduced by 2 to 4 percent TS in cake solids and that the solids recovery percentages were lower. The centrifuge could achieve 26 to 28 percent TS with emulsion polymer, but the polymer dosages are higher and almost double than the desired maximum of 25 lb/DT (12.5 g/kg) active.

Conclusions The CDWWTP WAS-only thickening testing showed that the centrifuge, operating on CDWWTP WAS-only, could reliably produce solids at 5 to 6 percent TS and achieve greater than 95 percent solids recovery. Testing was conducted using both dry and emulsion polymers. The dry polymer required 3 to 4 lb/DT (1.5 to 2 g/kg) active dosing, compared to 0.6 to 3 lb/DT (0.3 to 1.5 g/kg), based on the emulsion. It was also possible to thicken the sludge to 5 to 6 percent TS without the use of polymer, but this reduced hydraulic throughput by about 25 percent to allow the solids recoveries to remain above 95 percent.

Although CDWWTP WAS-only sludge was easily able to thicken in the pilot centrifuge, NDWWTP primary sludge and WAS, which was more dilute, was difficult to handle. After testing NDWWTP primary sludge and WAS alone, stable operation could not be maintained. Initial attempts to blend NDWWTP primary and WAS with CDWWTP WAS using an in-pipe blending system were also unsuccessful. Because of the difficulties with NDWWTP primary and WAS operation, a separate tank was rented to allow a buffer NDWWTP primary and WAS, and for better control of blending the CDWWTP WAS and NDWWTP primary and WAS. When NDWWTP sludge was blended with CDWWTP sludge in the blend tank, stable operation could be maintained in the centrifuge, and greater than 5.5 percent TS thickened sludge, with greater than 95 percent solids recovery, could be achieved. The dry polymer required 1.5 to 3 lb/DT (0.75 to 1.5 g/kg) active dosing, compared to 2 to 3 lb/DT (1 to 1.5 g/kg), based on the emulsion. The testing showed that including a blend tank to mix the CDWWTP and NDWWTP sludge is important for future operation to be successful. Near-continuous operation began in midJune and the team maintained continuous oper-

ation through mid-August, but mechanical problems with the unit, specifically the thickened cake pump, limited the throughput and the operation time. For the stable period, the thickened solids content to the digester averaged 6.3 percent TS (with a 2.3 lb/DT [1.15 g/kg] active polymer dose) and the volatile solids content of the raw sludge being fed to the digester averaged 86 percent VS/TS. The solids content in the test digester was increased to approximately 2.8 to 3 percent TS. For comparison, the rest of the digesters operating at CDWWTP were being fed gravitythickened sludge at about 3.8 percent TS, with a volatile solids content of 83 percent VS/TS and the other operational digesters operating at an average of 2.2 percent TS. The VSR estimations during this period ranged from 50 to greater than 70 percent, while the digester was approaching a steady state. Overall, the pilot testing was used to set the necessary performance criteria for a designbuild package. The testing also showed the importance of including a blend tank to be able to successfully manage and thicken the primary and WAS from NDWWTP. The pilot results highlight the importance of piloting to determine operational difficulties and to refine design performance criteria.

Acknowledgments The team thanks all of the plant staff at CDWWTP, especially Francois Saint-Phard and David Hall, for their outstanding support during this pilot testing. The team also thanks the staff members from Centrisys for their commitment to making the testing a success. We also thank the undergraduate student interns (Gabriela Aramayo and Alejandro Cepero, at Florida International University; and Kate Ireland, at University of Miami) who helped make this project possible by monitoring pilot operations, collecting samples, and running numerous laboratory tests.

References • S-888 - CDWWTP SLUDGE THICKENING & DEWATERING BLDG CD 2.12, 2.13, 2.16, Specification Section 46 71 36 – CENTRIFUGES, MWH, Jan. 20, 2016. • American Public Health Association, American Water Works Association, Water Environment Federation, Standard Methods for the Examination of Water and Wastewater, 20th edition, 1999. • Metcalf & Eddy (2013). Wastewater EngineerS ing Treatment and Reuse, 5th edition.

Florida Water Resources Journal • June 2019

So, What’s New? The Proposed Southeast Biosolids Association (SEBA) Why is a regional biosolids association needed? Jody Barksdale Biosolids issues continue to be a huge challenge in Florida and throughout the United States. Do you wish you had help in monitoring the activities surrounding biosolids in Florida, the Southeast, and nationally in one common forum? Many of your colleagues have decided that it’s time to form the Southeast Biosolids Association (SEBA). The new association would advocate sound science, as well as sustainable use and management of biosolids, while tracking biosolids issues and topics in Florida, Georgia, South Carolina, and North Carolina. The new association would support biosolids beneficial reuse, public outreach, and lobbying efforts in the same way that Mid-Atlantic Biosolids Association (MABA), (Northeast Biosolids & Residuals Association (NEBRA), and Northwest Biosolids currently do. As many of us are aware, recycling and reuse of biosolids continue to be challenged by the public and media, despite decades of testing, research, and successful experience. This year there have been at least two legislative bills introduced in Florida related to biosolids management that include proposed restrictions on land application. One proposed bill sought to ban the land application of Class B biosolids based on an arbitrary seasonal high

groundwater table. This “knee-jerk” reaction is not based on appropriate hydrogeology, evidence of impact due to land application, or the existing rules. Proposed bills like these appear to have the goal of eventually eliminating Class B biosolids land application in Florida and, quite frankly, are very short-sighted and must be examined thoroughly before enactment. The financial implications of these proposed bills would be extremely burdensome on utilities and their ratepayers. It’s obvious that wastewater and subsequent biosolids production are not going away, and will only become more of an issue, especially as our state continues to grow. Due to the ongoing concerns regarding biosolids in Florida, the Florida Department of Environmental Protection (FDEP) recently formed a Biosolids Technical Advisory Committee (TAC) to better understand biosolids reuse, processing technologies, and the potential risks related to Class B land application. The TAC, which includes stakeholders and members from environmental groups, the agricultural industry, utilities, consultants, and academia, made several recommendations: S Review of permitting related to nutrients and water body impairment. S Hydrogeological reviews related to land application of biosolids.

S Land application practices, including increased inspection. S Water quality monitoring and additional protocols to detect nutrient migration. S Establishment of criteria for risks at sites related to land application. S Nutrient management and more research on runoff. S Promotion of innovative technology, including pilot projects related to beneficial end-use projects. While Florida is definitely feeling the pressure, several southeastern cities, such as Charlotte, N.C.; Atlanta, Ga.(and surrounding counties); and Greenville, S.C., as well as other areas in the Southeast, continue to face a multitude of challenges with biosolids. These challenges include increased regulatory constraints, financial issues, and public scrutiny that are often based on misinformation. The lack of public understanding and acceptance needs to be addressed with more accurate information and education. The Water Environment Federation (WEF) and various state organizations are addressing education and outreach on biosolids issues, but more needs to be done. For these reasons, regional biosolids associations and state biosolids committees advocate on behalf of the wastewater industry to address biosolids topics and keep our industry and the public informed. These independent groups of expert professionals accomplish the following: S Promote and advance research, as well as management best practices. S Provide members with industry communications and accurate information. S Give critical feedback to regulators and politicians. Other states and regions throughout the U.S. have committees and organizations that maintain webpages and/or sponsor biosolids training, seminars, and/or conferences, including: S Florida Water Environment Association (FWEA) Biosolids Committee S Indiana Water Environment Association (IWEA) Biosolids Committee S Michigan Biosolids Team - WEA of Michigan

June 2019 • Florida Water Resources Journal

S New England Water Environment Association (NEWEA) Residuals Management Committee S New York Water Environment Association (NYWEA) Residuals and Biosolids Committee S North Carolina AWWA-WEA Resource, Recovery, and Reuse Committee S Water Environment Association of Ontario (WEAO) Biosolids Committee S Rocky Mountain Water Environment Association (RMWEA) Biosolids Committee S Water Environment Association of Texas (WEAT) Biosolids Committee Nationwide wastewater and biosolids groups include: S National Biosolids Partnership S WEF S Water Environment Research Foundation S National Association of Clean Water Agencies (NACWA) S U. S. Environmental Protection Agency (EPA) Biosolids Program A dedicated regional biosolids director would be named to SEBA to coordinate and provide a common platform at local and state levels for biosolids information and management, thereby organizing and consolidating information. The organization would coordinate with existing biosolids associations and committees at the state and national level to provide cohesive and accurate information on biosolids rules and legislation. Parties interested in establishing SEBA have already contacted other regional groups, such as NEBRA and MABA, and have received their full support. We also have reached out to FWEA and its Utility Council, and the groups are excited to see this move forward. Additionally, private industry leaders, such as NEFCO, Denali, and Syangro, are interested in SEBA and will continue to track its progress. As the management of biosolids continues to see increased challenges, organizations like SEBA will provide our industry with information and tools to ensure that wastewater treatment facilities are meeting the needs of the public and all stakeholders. As an independent regional organization, SEBA can assimilate critical information and communicate future trends and technological advances, while focusing on the specific interests and needs of the Southeast. When several professional organizations, municipalities, and private companies contribute knowledge and share information, an association such as SEBA will allow us to be better prepared to face the inevitable challenges that lay ahead. There will be more to come regarding SEBA, so please stay tuned! Jody Barksdale, P.E., ENV SP, is senior vice president with Gresham Smith in Tampa. S

Bonita Springs Utilities Board Elects New Officers The board of directors of Bonita Springs Utilities Inc. (BSU) has elected its latest slate of officers: S Brian Farrar - president S Vincent J. Marchesani - vice president S Paul J. Attwood â&#x20AC;&#x201C; secretary S Mike Malloy (reelected treasurer for a third term) Brian Farrar joined the board in 2016 and is president/managing member of BCF Management Group LLC. He recently started his second term as commissioner of the Lee County Mosquito Control and Hyacinth District, where he serves as the secretary/treasurer. Farrar is also vice chair of the CREW Land and Water Trust board of directors. A Bonita Springs resident since 2006, Vincent J. Marchesani is a retired vice president of corporate health, safety, and environmental affairs with global chemical company Basell. An active member of the City of Bonita Springs technical advisory board, he has also served as chair of the VillageWalk of Bonita Springs Safety Committee. A board member since 2001, Paul J. Attwood serves on the board of directors for the Imperial River Conservancy. He is a past president of the Everglades Geolog-

Brian Farrar

Vincent J. Marchesani

ical Society and is retired from the oil and gas regulatory section of the Florida Department of Environmental Protection. Mike Malloy has served on the board since 2012. In 2017, he retired as a vice president of customer service with Mach Energy and formed Gulf Coast Utilities Management, providing financial and technical services to businesses focused on cost reduction. A Bonita Springs resident since 2003, he has 40 years of experience in the utility industry and held management positions with various utility companies. The BSU members elect nine directors to the board to govern the utility. The other board members are Robert Bachman, Ben Nelson, Frank Liles, Robert H. Sharkey, and James Strecansky. A not-for-profit water and wastewater utility, BSU was founded by local citizens in 1970. The member-owned utility provides service in the City of Bonita Springs, the Village of Estero, and unincorporated South Lee County. The utility is recognized as an industry leader with awards from the American Water Works Association, Florida Department of Environmental Protection, and Florida Water and Pollution Control Operators Association. S

Paul J. Attwood

Mike Malloy

Florida Water Resources Journal â&#x20AC;˘ June 2019

FSAWWA SPEAKING OUT

FSAWWA’S Outstanding Awardees at FWRC Michael F. Bailey, P.E. Chair, FSAWWA

s the Florida Section AWWA chair, one of my greatest pleasures is presenting awards to outstanding utilities and water industry employees across the state who are out there doing their jobs 24 hours a day, seven days a week. Oftentimes, the mindset in our business is that “no news is good news” and we feel like we’re doing a good job if we don’t get too many phone calls or see our company name in the news. Although that can be true sometimes, I think we all can agree that it’s important to take the opportunity to promote our industry and recognize individuals and entities that go above and beyond in providing the water-related services that are so critical for a healthy society. The Florida Water Resources Conference (FWRC) provides an excellent opportunity to provide this recognition, and this year was no exception. So, without further ado, please allow me to present to you the outstanding awardees and contest winners from this year’s event!

Top Ops Competition Well, you probably guessed it—Palm Coast's public works/utility division has done it again and its Water Buoys team won the Top Ops state championship this year. Palm Coast’s winning record is nothing short of amazing! Questions in this fast-paced, game-show-type competition cover a broad range of operational topics, including basic science, hydrology, water distribution, public health and sanitation, plant maintenance, safety, and process control. The annual contest recognizes and promotes excellence in all aspects of water operations, giving operators the opportunity to showcase their knowledge and talents. The Water Buoys will now have the opportunity to compete for top national honors in June during ACE19 in Denver. Congratulations to the Water Buoys—we’ll be cheering for you!

“Best of the Best” Drinking Water Contest Talquin Electric Cooperative/Meadows

Regional Water System won the statewide “Best of the Best” Drinking Water Contest on April 16 at the conference. Four taste-test judges chose Talquin from 12 regional winners to earn the title as Florida’s best, and they will now go on to the national competition to be held in Denver at ACE19. Talquin, which provides water and wastewater services from Florida’s Gulf Coast to the Florida state line (including portions of Tallahassee and the surrounding areas), won the Region I competition earlier this year. Judges for the statewide contest were yours truly; Kim Kowalski, incoming FSAWWA chair; Rick Harmon, Florida Water Resources Journal editor; and Brian McClure, Bay News 9 award-winning meteorologist. Good luck Talquin, and we’ll be cheering for you in Denver, too!

Outstanding Water Treatment Plant This award is presented to the top water treatment plant in the state in each plant classification: A, B, and C. Entries are judged by the FSAWWA Awards Committee based on various categories, such as regulatory compliance, process control, safety, and emergency preparedness. All of the plants submitted wonderful brochures highlighting their plants. The pride they take in their facilities is obvious. Class A: Peace River Manasota Regional Water Treatment Facility The Peace River Manasota Water Treatment Plant uses a conventional surface water treatment process that consists of coagulation, flocculation, sedimentation, disinfection, and filtration. The source of the water is surface water from the Peace River that is stored in two reservoirs totaling 6.5 billion gallons of storage, and the plant averages 27.5 million gallons per day (mgd). I was very proud to present this award to the Peace River Manasota Regional Water Authority at their annual barbeque on May 10 (I was also thrilled to consume mass quantities of barbeque!). Class B: City of Tarpon Springs Alternate Water Supply Facility The Tarpons Springs Water Treatment Plant treats brackish groundwater from 16 wells, which is directed to 5-micon filters, and then treated by reverse osmosis (RO). Sulfuric

June 2019 • Florida Water Resources Journal

acid and antiscalant are added as pretreatment ahead of the RO trains. Chlorine is added for disinfection, as is carbon dioxide, to lower the pH prior to the addition of lime and caustic for hardness and alkalinity. Finally, a corrosion inhibitor and fluoride are added prior to distribution. The average daily flow is 2.5 mgd. Class C: City of Plant City Utilities The City of Plant City operates four drinking water treatment plants, with a groundwater extraction well at each. All of the plants have chlorination, fluoridation, corrosion control, and a 4-log virus removal certification. A storage tank is associated with each plant and the distribution system is looped for water quality and reliability. Most Improved Water Treatment Plant, Class A: Palm Beach County – Treatment Plant No. 3 Palm Beach County’s Treatment Plant No. 3 underwent several improvements during the past 12 months and certainly earned the most improved award. Improvements included heaters added to the membrane cleaning system, a new permeate flushing system, coating of the clearwells with a polyethylene lining, a new degasification tower, a second sand strainer, and replacing 10 trains of membrane elements with a new hybrid system that lowered operating pressures by 20 pounds per square inch (psi) and increased permeate production. These folks have been busy! Most Improved Water Treatment Plant, Class C: City of Leesburg Plantation Water Treatment Plant Leesburg’s Plantation Water Treatment Plant earned this year’s most improved award due to the construction of a new treatment facility that incorporates a new high-service pump building, new motor control room, new sodium hypochlorite disinfection system, and a new emergency generator. Additionally, Leesburg rehabilitated its raw water wells and built a new raw water main to the treatment plant. The city is very proud of its new facility!

Meritorious Drinking Water Treatment Plant Operator of the Year: Douglas Heistand Doug Heistand has been an integral part of Hillsborough County Public Utilities De-

FWRJ COMMITTEE PROFILE This column highlights a committee, division, council, or other volunteer group of FSAWWA, FWEA, and FWPCOA.

Systems Operators Committee (originally known as the Collection and Distribution Committee) Affiliation: FWPCOA Current chair: Raymond Bordner water resources department, water distribution division, City of St. Petersburg (retired) Year group was formed: 1981 Scope of work: By the direction of the FWPCOA board of directors and in conjunction with the association’s Education Committee and its training coordinator, the responsibility of the System Operators Committee is to organize, schedule, and/or approve classes referred to as “short schools” for the purpose of voluntary certification of wastewater collection system operators level C, B, and A; reclaimed water distribution system operators - level C, B, and A; and Florida Department of Environmental Protection requirements for

water distribution system operators - level 3, 2, and 1. The committee will determine the criteria of the short school training courses and schedule the speakers and instructors for them. The committee is responsible for the review and approval of applications for the voluntary certification exams and the course completion exams for water distribution systems and is responsible for the administration and proctoring of the exams. The short schools are held twice each year: the fall school in August and the spring school in March/April. They are held at Indian River State College in Ft. Pierce. The schools provide 30 contact hours, with four-day training classes Monday through Thursday and the exams administered on Friday. Recent accomplishments: The most recent short school was held the week of March 18-22, 2019. There were 194 in attendance, with 193 exams administered.

The fall short school is scheduled for the week of August 12-16, 2019. Current projects: The committee is working on revisions to all the exams to coincide with recent editions to the California State University office of water programs manuals that are used as the texts. Future work: The committee continues to work with the FWPCOA Online Institute for the online training courses. The committee is also in the process of setting up the courses and instructors for the fall short school in August. Group members: • Glenn Whitcomb - City of Deltona Utilities • David Pachucki - Pinellas County Utilities (retired) • Jeff Elder - City of Deltona Utilities • Milton Skipper - wastewater collection, Jacksonville Electric Authority (retired) S

partment throughout his career as a water plant operator, where he started in 2008 at the Lithia Water Treatment Plant as an operator trainee. In 2009, he transferred to the new central water treatment plant to assist with the commissioning of that facility, while simultaneously studying, testing for, and obtaining his water plant operator A license. Doug continues to be a mentor to all the employees he has coached, and understands that the most valuable part of an organization is its people. We are proud to acknowledge and reward Doug as one of the best at what he does in his profession.

So there you have it—well-deserved recognition for several of our industry’s best and brightest. Congratulations to you all and, for those of you taking it on to the competitions at ACE19, we wish you the best of luck! S Florida Water Resources Journal • June 2019

FWPCOA TRAINING CALENDAR SCHEDULE YOUR CLASS TODAY! June 3-6 ......Water Distribution Level 3 ..........................Osteen..................$225/255 3-6 ......Reclaimed Water Distribution C, B ............St. Petersburg ........$225/255 ......Stormwater A ................................................St. Petersburg ........$225/255 ......Utility Maintenance Level III........................St. Petersburg ........$225/255 ......Wastewater Collection A ............................St. Petersburg ........$225/255 ......Water Distribution 3, 2, 1 ..........................St. Petersburg ........$225/255 ......Water Treatment Plant Operator ..............St. Petersburg ........$225/255 10-14 ......Stormwater C, B............................................St. Petersburg ........$225/255 ......Utility Maintenance Level II ........................St. Petersburg ........$225/255 ......Wastewater Collection C, B ........................St. Petersburg ........$225/255 ......Wastewater Treatment Plant Operator ....St. Petersburg ........$225/255 10-24 ......Reclaimed Water Distribution** ................Broward County ....$225/255 ......Wastewater Collection C** ..........................Broward County ....$225/255 ......Water Distribution 3, 2** ............................Broward County ....$225/255 17-20 ......Backflow Tester ............................................Osteen..................$375/405 24-27 ......Backflow Tester* ..........................................St. Petersburg ........$375/405 28 ......Backflow Tester Recerts***..........................Osteen..................$85/115

July 8-12 15-17 15-19 22-26 26

......Reclaimed Water Field Site Inspector ......Osteen..................$350/380 ......Backflow Repair ..........................................St. Petersburg ........$275/305 ......Wastewater Collection B ............................Osteen..................$225/255 ......Wastewater Collection B ............................Pembroke Pines ....$225/255 ......Backflow Tester Recerts*** ........................Osteen..................$85/115

Course registration forms are available at http://www.fwpcoa.org/forms.asp. For additional information on these courses or other training programs offered by the FWPCOA, please contact the FW&PCOA Training Office at (321) 383-9690 or training@fwpcoa.org. * Backflow recertification is also available the last day of Backflow Tester or Backflow Repair Classes with the exception of Deltona ** Evening classes *** any retest given also

You are required to have your own calculator at state short schools and most other courses.

CLASSIFIEDS CLASSIFIED ADVERTISING RATES - Classified ads are $20 per line for a 60 character line (including spaces and punctuation), $60 minimum. The price includes publication in both the magazine and our Web site. Short positions wanted ads are run one time for no charge and are subject to editing. ads@fwrj.com

POSITIONS AVAILABLE WATER AND WASTEWATER TREATMENT PLANT OPERATORS Reiss Engineering delivers highly technical water and wastewater planning, design, and construction management services for public agencies throughout Florida. Reiss Engineering is seeking top-notch talent to join our team!

U.S. Water Services Corporation is now accepting applications for state certified water and wastewater treatment plant operators. All applicants must hold at least minimum “C” operator’s certificate. Background check and drug screen required. –Apply at http://www.uswatercorp.com/careers or to obtain further information call (866) 753-8292. EOE/m/f/v/d

Available Positions Include: Business Development Leader – Tampa Area Client Services Manager Water Process Discipline Leader Senior Water/Wastewater Project Manager Wastewater Process Senior Engineer Project Engineer (Multiple Openings, 0-15 yrs. exp.) To view position details and submit your resume: www.reisseng.com

MAINTENANCE TECHNICIANS U.S. Water Services Corporation is now accepting applications for maintenance technicians in the water and wastewater industry. All applicants must have 1+ years experience in performing mechanical, electrical, and/or pluming abilities and a valid DL. Background check and drug screen required. -Apply at http://www.uswatercorp.com/careers or to obtain further information call (866) 753-8292. EOE/m/f/v/d

Career Opportunity for Chief Engineer Toho Water Authority is the largest provider of water, wastewater and reclaimed water services in Osceola County. The purpose of this position is to provide engineering and project management services from initial planning through budgeting, design, and construction. Minimum qualifications required include a Bachelor’s Degree from an ABET accredited university in the field of Chemical, Civil or Environmental Engineering and a State of Florida Professional Engineer License. TWA offers a competitive benefit and compensation package. Applicants must submit a complete online application for employment consideration. To learn more about TWA and to apply, please visit www.tohowater.com. This position is eligible for relocation assistance!

Utilities Foreman (Water & Storm Water) $49,348 - $69,436/yr.

Utilities Treatment Plant Operator II $49,348 - $69,436/yr.

Utilities Treatment Plant Operator I/Trainee $42,628 - $66,130/yr.

Utilities System Operator II & III $40,598 - $57,127 / $42,628 - $66,130/yr. Apply Online At: http://pompanobeachfl.gov Open until filled.

Florida Water Resources Journal • June 2019

Career Opportunity Operator A, B, and C for Wastewater Treatment Plant Toho Water Authority This is your opportunity to work for the largest provider of water, wastewater, and reclaimed water services in Osceola County. A fastgrowing organization, Toho Water Authority is expanding to approximately 100,000 customers in Kissimmee, Poinciana and unincorporated areas of Osceola County. You can be assured there will be no shortage of interesting and challenging projects on the horizon! As an Operator, you will be expected, among other specific job duties, to have the ability to do the following: Maintain compliance and operations of Wastewater Treatment Plants; Conduct facility inspections, perform maintenance on equipment, and ensure normal operations; Evaluate water systems; and Fulfill recordkeeping, documentation, and reporting requirements. Candidates are required to hold the following certifications: Class “A”, “B or C” Wastewater Operators License, and Valid Class E Florida Driver’s License. Toho Water Authority offers a highly competitive compensation package, including tuition reimbursement, on site employee clinic, generous paid leave time, and retirement 401a match. If you are a driven professional, highly organized, and looking for a career opportunity at a growing Water Authority, then visit the TWA webpage today and learn how you can join our team! Visit www.tohowater.com to review the full job description and submit an employment application for consideration.

Water Distribution Lead Operator City of Clearwater Government is hiring now for a Water Distribution Lead Operator! Salary: $ 37,027 - $57,716 Annually Qualified candidates must have a Water Distribution Level II Operator’s license. APPLICATIONS SHOULD BE FILED ONLINE AT: http://www.myclearwater.com MINIMUM QUALIFICATIONS: Possession of a state of Florida Water Distribution level II license and CDL Class “A” driver’s license is required. APPLICATIONS SHOULD http://www.myclearwater.com

FILED

ONLINE

MINIMUM QUALIFICATIONS: Possession of a state of Florida Water Distribution level II license and CDL Class “A” driver’s license is required.

The City of Edgewater is accepting applications for the following positions. Water Plant Operator “C” or higher Wastewater Plant Operator “C” or higher $35,172 - $52,977 (“C” pay scale) Cross Connection/Reclaimed Water Inspector $27,589 - $43,680 Apply online at http://www.cityofedgewater.org Open until filled

Plant Operator Peninsula Engineering is hiring a Water/Wastewater Plant Operator for a long-term client project in rural Collier County. Must have FDEP Class “C” dual licensure (or higher). Highly competitive benefit and compensation package. Position requires a valid driver license, background check/drug screen. Send resume or inquiries to HR@barroncollier.com EOE/DFWP

Miccosukee Tribe of Indians Water Plant Operator Full-time, day shift, ability to work flexible schedule & holidays as necessary. Performs work involving operation and maintenance of small water plant utility. Operator must possess a “C” License from State of Florida or equivalent. Must have a valid Florida Drivers License. Clean Criminal Background. Email resume to: crystalm@miccosukeetribe.com or fax (305) 894- 2350. Work Location is 20 Miles west of Krome Ave on Tamiami Trail, Miami. Salary range $20.19/hr to $25.00/hr depending on qualifications and licensure

June 2019 • Florida Water Resources Journal

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The City of Fort Lauderdale Public Works Department is hiring dynamic and goal-driven employees to join our team. WATER OPERATIONS SUPERVISOR $59,179.20 - $91,719.27 Annually SURVEYING SUPERVISOR $53,299.49 - $82,634.38 Annually Utilities Service Representative-Locators $38,971.20 - $60,410.33 Annually Industrial Electrician $48,014.12 - $74,440.98 Water Facilities Manager $72,912.68 - $113,009.35 Annually PROJECT MANAGER I-Airport Construction $59,179.20 - $91,719.27 Annually Visit the City website at www.fortlauderdale.gov/jobs to apply today. For more information, send an email to Cynthia Lamar at CLamar@fortlauderdale.gov.

The Coral Springs Improvement District – A GREAT place to further your career and enhance your life! CSID offers… • Salary levels are at the top of the industry • Health Insurance that is unmatched when compared to like sized Districts • Promotions from within for qualified employees • Continuing education courses to develop your skills and further your growth • Retirement plans where an employee can earn 18% of their salary by contributing toward their future The Coral Springs Improvement District is seeking qualified employees in the following fields: Water Plant Operator Applicants must have a valid Class C or higher Drinking water license and experience in Reverse Osmosis/Nano Filtration treatment processes preferred however not required. Position requirements include knowledge of methods, tools and materials used in the controlling, servicing, and minor repairs of all related R.O. water treatment facilities machinery and equipment. Minimum starting salary - $45,000. Salary to commensurate relative to level of experience in this field. Benefits: Excellent benefits which include health, life, disability, dental, vison and a retirement plan which includes a 6% non-contributory defined benefit and matching 457b plan with a 100% match up to 6%. EOE. All positions require a valid Florida Drivers license, high school diploma or GED equivalent and must pass a pre-employment drug screen test Salaries for the above position based on level of licensing and years of experience. Applications may be obtained by visiting our website at www.csidfl.org/resources/employment.html and fax resume to 954753-6328, attention Jan Zilmer, Director of Human Resources.

News Beat Tina Nixon, P.E., BCEE, joins the Tampa office of Stantec, with 28 years of extensive design, management, construction, and commissioning experience in civil, mechanical, and environmental engineering. She has considerable experience in many types of pumping system projects, responsible for the process mechanical design of several large flood control pumping facilities, reuse/reclaimed water facilities, odor control systems, solid waste facilities, biosolids projects, and sewer rehabilitation efforts throughout the U.S. She has worked with multiple municipalities across the country; federal clients, such as the U.S. Army Corps of Engineers; water management districts; Tampa Bay Water; and international clients. Her capabilities also include conceptualization, management, and development of computer hydraulic models and analysis of sanitary sewer overflows, water distribution, and reclaimed water transmission. Nixon holds bachelor and master degrees in civil engineering from the University of South Florida.

CITY OF WINTER GARDEN – POSITIONS AVAILABLE The City of Winter Garden is currently accepting applications for the following positions: EXPERIENCED & TRAINEES/LABORERS - Collection Field Tech – I, II, & III - Distribution Field Tech – I, II, & III - Public Service Worker II - Stormwater Please visit our website at www.cwgdn.com for complete job descriptions and to apply. Applications may be submitted online, in person or faxed to 407-877-2795.

LOOKING FOR A JOB? The FWPCOA Job Placement Committee Can Help! Contact Joan E. Stokes at 407-293-9465 or fax 407-293-9943 for more information.

Florida Water Resources Journal • June 2019

Correction January 2016

Editorial Calendar January ....Wastewater Treatment February ....Water Supply; Alternative Sources March ........Energy Efficiency; Environmental Stewardship April ..........Conservation and Reuse; Florida Water Resources Conference May............Operations and Utilities Management June ..........Biosolids Management and Bioenergy Production July............Stormwater Management; Emerging Technologies; FWRC Review August ......Disinfection; Water Quality September Emerging Issues; Water Resources Management October ......New Facilities, Expansions, and Upgrades November ..Water Treatment December..Distribution and Collection

In the article, “Lake City Treatment Wetland: Water Quality Performance and Operation,” which appeared in the April 2019 issue, page 10 had the incorrect Figure 4 and Figure 5. The correct figures are shown below. The magazine regrets the error.

Figure 4. Phosphorus Inflow Concentrations

Technical articles are usually scheduled several months in advance and are due 60 days before the issue month (for example, January 1 for the March issue). The closing date for display ad and directory card reservations, notices, announcements, upcoming events, and everything else including classified ads, is 30 days before the issue month (for example, September 1 for the October issue). For further information on submittal requirements, guidelines for writers, advertising rates and conditions, and ad dimensions, as well as the most recent notices, announcements, and classified advertisements, go to www.fwrj.com or call 352-241-6006.

June 2019 • Florida Water Resources Journal

Figure 5. Nitrogen and Phosphorus Inflow and Outflow Concentrations

Display Advertiser Index ACIPIO ............................................................33 AECOM............................................................45 Blue Planet ....................................................55 CEU Challenge ................................................13 Data Flow Systems ........................................18 FSAWWA Fall Conference Call for Papers ....19 FSAWWA Fall Conference Exhibits ................21 FSAWWA Fall Conference Overview ..............20 FSAWWA Fall Conference Poker/Golf ............22 FSAWWA Fall Conference Water Distribution System Awards ......................23 FWPCOA State Short School ..........................36

FWPCOA Training Calendar............................50 FWRC Sponsor Thank You..............................27 Grundfos ..........................................................9 Heyward ........................................................49 Hudson Pump & Equipment ..........................37 Hydro International ..........................................5 Infosense........................................................53 J&S Valve........................................................29 Lakeside Equipment ........................................7 Stacon ..............................................................2 UF Treeo..........................................................39 Xylem..............................................................56