Process Page—Babcock Ranch A Community With a Focus on Sustainability—Al Mitrovic

Greetings from the FWEA Wastewater Process Committee! This month’s column will highlight the Babcock Ranch Water Reclamation Facility, which won the 2022 Earle B. Phelps Award in the advanced secondary category for facilities with a design capacity of less than 3 million gallons per day.

Babcock Ranch: A Community With a Focus on Sustainability

Al Mitrovic

The Florida Water Environment Association (FWEA) proudly recognizes the Babcock Ranch Water Reclamation Facility (WRF) as the winner of the 2022 Earle B. Phelps Award in the advanced secondary treatment category. This award is presented annually to wastewater treatment plants that demonstrate exceptional effluent quality throughout the year and maintain the highest removal of major pollutioncausing constituents. The WRF is noted for its consistency in providing a high-quality effluent, as well as its dedication to green energy practices and sustainability.

The WRF has been the recipient of multiple awards, including: S The 2018 First-Place Safety Award Class C

from FWEA for the plant’s excellent safety programs. S The 2018 Plant Operations Excellence

Award from the Florida Department of Environmental Protection (FDEP) for the plant’s excellence in operation, maintenance, innovative treatment, waste reduction, pollution prevention, recycling, and other special achievements. S The 2018 David B. Lee Award from the

Florida Water and Pollution Control

Operators Association (FWPCOA) for the leadership and operational effectiveness of Nathaniel Mastroeni, utility operations manager. S The 2019 David W. York Award for Reuse

System of the Year presented by the FWEA

Water Resources, Reuse, and Resiliency

Committee for the plant’s commitment to developing, using, and maintaining exemplary reuse programs. S The 2019 Earle B. Phelps Award in the advanced secondary wastewater treatment category awarded by FWEA to recognize the facility for its removal of major pollution-causing constituents prior to effluent discharge to receiving waters.

These awards are a testament to the district for its dedication and commitment in protecting local water resources and the environment.

Figure 1. The Florida Power and Light Babcock Ranch Solar Energy Center.

The Community

The town of Babcock Ranch is located northeast of Fort Myers and has a footprint of approximately 18,000 acres. Under the current master plan, it’s designed to accommodate 19,500 residences and has an engaging downtown with commercial and retail space, numerous green spaces, lakes, and nature trails. Ultimately, it will be home to approximately 50,000 residents.

The WRF and reclaimed system is operated by MSKP Town and Country Utility (TCU) with the objective of providing water utility services to the new Babcock Ranch Continued on page 36

Figure 3. Membrane bioreactor tank.

Figure 4. Membrane bioreactor permeate pumps. Continued from page 34 community. The WRF was commissioned into service April 2017 and the entire town, including the WRF, operates on solar power. The Florida Power and Light Babcock Ranch Solar Energy Center (Figure 1) opened as the largest solar-plus storage project operating in the United States and has a generating capacity of 150 megawatts (MW), with 10 MW of battery storage.

Babcock Ranch has been designed to incorporate the most sustainable green technology practicable to meet the growing demands of its innovative community. Drinking water is obtained from the sandstone aquifer and is filtered using nanofiltration (NF). The NF concentrate is recycled by blending with the WRF effluent and is stored as reclaimed water. All irrigation throughout the community uses this water to irrigate the town and provide fire protection.

Facility Overview

The WRF is permitted for an annual average daily flow (AADF) capacity of 0.375 million gallons per day (mgd) and can handle peak daily flows up to 1 mgd. All the equipment maintains Class 1 reliability, which includes onsite backup power generation in the event of a power outage. The treatment system is a fourstage Bardenpho process; a flow diagram is shown in Figure 2. Reclaimed water is sent to a nondischarging lake that is directly connected to a G-II aquifer. The lake will serve as storage for a future slow-rate, public access reclaimed water irrigation system.

The TCU utilizes its own computerized maintenance management system using Excel, where every piece of equipment is tracked according to the operation and maintenance manuals. Utility personnel update these spreadsheets on a weekly basis to ensure that all assets are properly maintained.

Process Description

The 0.375-mgd WRF was originally designed with sequencing batch reactors that have since been repurposed for a four-stage Bardenpho nutrient removal process, followed by membrane filtration. For mechanical screening at the headworks, TCU selected 2-millimiter stainless steel drum screens. All mechanical equipment operates in a duty/standby configuration and allows for Class 1 reliability.

Effluent from the swing zone flows into one of the two 17,000-gallon membrane bioreactor (MBR) tanks (Figure 3) with the SUEZ leap-high, leap-low MBR system at

Figure 6. Aeration blowers.

cBOD (mg/L) TSS (mg/L) Fecal (CFU) Turbidity (NTU)

TN (mg/L)

Annual Average Influent 353.9 251.9 N/A N/A 56.4 Annual Average Effluent 2.3 0.6 1 0.3 2.19 % Removal 99.3% 99.4% - - 95.4% Number of Occurrences Out of Compliance 0 0 0 0 0

the heart of the facility. The system utilizes ZeeWeed ultrafiltration membranes, which provide a barrier that prevents the passage of solids and produces a low-turbidity effluent, allowing the water to be returned to the environment or reused for irrigation and fire suppression.

Filtrate from the MBR is pumped by the permeate pumps (Figure 4) into the back pulsation tank, which provides the flow required for carrying out periodic maintenance and recovery cleaning of the membranes. The flow is then diverted into the chlorine contact tanks (Figure 5), with a total capacity of 52,000 gallons. Two peristaltic pumps are used for disinfection. The chlorine contact tanks are designed to provide highlevel disinfection, with a contact time of 25 minutes at peak-hour flows of 3 mgd. Disinfection is provided by a 12.5 percent sodium hypochlorite solution with a 30-day storage capacity.

The disinfected effluent discharges by gravity over a weir and combines in a pump station wet well. Effluent meeting the criteria for use as public access reclaimed water is blended with NF concentrate from the water treatment plant (WTP) and is transferred by gravity to a 160-acre lake. This water is also used for irrigation and fire suppression. Any reject effluent is diverted to a million-gallon reject substandard tank, where it’s pumped to the head of the plant for additional treatment.

Additionally, the facility has an aerated biosolids holding tank, with two sludge drying beds for disposal of waste sludge.

Instrumentation and Monitoring

The instrumentation and plant monitoring system consists of dissolved oxygen (DO) probes placed at each of the aeration basins and swing zones. The DO levels are achieved with variable frequency drive blowers (Figure 6) that shut off once the desired oxygen concentration is reached. Probes measuring total suspended solids (TSS) are placed at the common return activated sludge (RAS) splitter box/membrane Continued on page 38

Figure 7. From left are Myles Adrian, Taran Brown, and Jason Bailey, members of the plant operation staff.

Continued from page 37 tank inlet piping, allowing for TSS monitoring of what is entering and leaving the membrane tank.

Continuous trending and monitoring of the transmembrane pressures on the ultrafiltration process provide the staff with an indication of system performance. The staff also regularly samples and monitors mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids (MLVSS) concentrations, time to filter testing (indicating permeability conditions of the solids), and nitrate and ammonia. Monitoring these parameters allows for excellent control of the treatment process, yielding an annual average effluent total nitrogen of 2.19 mg/L.

Table 1 summarizes the typical plant loadings and effluent quality.

Sustainability Goals

Babcock Ranch is entirely solar-powered and has an overall objective to build one of the most sustainable communities in the U.S. This ambitious goal is reflected in the city’s master planning, which incorporates green technology wherever possible.

Aside from genuine care for the operation of the facility, the TCU staff members have an overall vision for the sustainability of the wastewater infrastructure of Babcock Ranch as a whole, which is inspiring to see. Describing themselves as a “symbiotic community,” they ensure that every drop of both reclaimed water and concentrate from the WTP has been reused since day one.

Plant Staff

The TCU, which runs the WRF, has a deep commitment to providing employees with a safe and healthful workplace (Figures 7, 8, and 9). This includes providing them with personal protective equipment and regular safety classes. All equipment at the facility is labeled to be easily identifiable.

Using quality assurance/quality control (QA/QC) training, each team member is given the task of researching and composing operation and maintenance standards of practice that are reviewed with the management team. This creates a sense of ownership when it comes to learning.

The utility also shows a strong dedication to the onboarding of new employees. New hires go through a training phase, where the utility management team assigns each one to shadow an experienced plant operator. Training typically lasts for 18 months, and the trainees have an opportunity to learn routine tasks from senior operators and field crew.

Conclusion

The WRF is powered by the sun and consistently succeeds in providing highquality effluent that meets advanced secondary criteria. The facility is noted for its dedication to green energy practices and its contributions to one of the most sustainable communities in the U.S. The beneficial use of reclaimed water has reduced the domestic residential daily water usage at Babcock Ranch from a state average of 85 gallons per capita (based on the 2010 report, “Estimated Public Supply Water Use and per Capita Use in Florida by County”).

The FWEA Wastewater Process Committee is proud to highlight the accomplishments of this facility!

Al Mitrovic, P.E., is a professional engineer with Wade Trim in Tampa. S