Process Page: A Visit to the Polk County Utilities Sun Ray Wastewater Treatment

Greetings from the FWEA Wastewater Process Committee! This month’s column will highlight the Polk County Utilities Sun Ray Wastewater Treatment Facility, which won the 2021 Earle B. Phelps Award in the secondary category for facilities with a design capacity of less than 3 mgd.

A Visit to the Polk County Utilities Sun Ray Wastewater Treatment Facility: Challenging Influent, Excellent Results

Bartt C. Booz

The Sun Ray Wastewater Treatment Facility (WWTF) was recognized in 2021 by the Florida Water Environment Federation (FWEA) as the winner of the Earle B. Phelps Award in the secondary treatment category for its impressive effluent quality and consistency. The award is presented annually to wastewater treatment plants that demonstrate exceptional secondary treatment throughout the year and maintain the highest removal of major pollutioncausing constituents, including total nitrogen.

The WWTF has been the recipient of the award in 2019, 2020, and again in 2021. The consistency of the plant’s performance, and the awards it has received, are a testament to Polk County (county) and its dedication and commitment to protecting water resources and the environment.

Facility Overview

The WWTF is a 1-miliion-gallon-per-day (mgd), annual average daily flow (AADF), Type I, two-stage, packaged, extended aeration domestic facility, consisting of three parallel treatment trains that were originally constructed in 1997 and upgraded in 2012. The county identified the need for the 2012 plant expansion due to the growth and waste loadings from the county’s South County Jail, which provides the majority of the flow to the WWTF. Influent wastewater, which currently averages approximately 0.385 mgd, enters the plant through a master influent pump station. This pumps up to an elevated headworks, where an automatic bar screen removes influent screenings. Flow is split between three trains: Trains 1 and 2 consist of two anoxic tanks, two aeration tanks, three secondary clarifiers, four chlorine contact chambers, and two aerobic digesters; and Train 3 consists of a pre-anoxic basin, anoxic/aeration basin, clarifier, digester/holding tank, and chlorine contact basin (one each). Multistage centrifugal blowers provide aeration to the activated sludge process. Sodium hypochlorite is used to provide basic disinfection through an effluent flow-paced control system. Waste sludge is thickened in the digesters to 1.5 to 2 percent through aeration and decanting. The facility also includes a concrete pad for a mobile centrifuge dewatering unit and piping to convey centrate to the main influent pump station. Sludge is dewatered to 18 to 20 percent solids before being hauled to the county’s north central landfill for disposal.

Following disinfection, effluent from the chlorine contact basins flows to an effluent splitter box and an effluent pump station wet well, where flow is distributed to one of three rapid infiltration basins (RIBs); one RIB is onsite at the plant, and the other two are remote. The onsite RIB is a four-cell, 4.02-acre parcel with a capacity of 0.098 mgd. The offsite RIBs include the Prine RIB, with a 0.650-mgd capacity, and the Hopson Road RIB, with a capacity of 0.350 mgd.

Table 1 summarizes the typical plant loadings and effluent quality from January to December 2021.

Polk County Utilities (PCU) uses a computerized maintenance management system (CMMS), called Hach JobCal, to automatically generate preventive maintenance work orders and document corrective work that has been completed. This program is used by the operations team, trades helpers, mechanics, and electricians. The storage of information allows for easy access by all stakeholders. Preventive maintenance is Continued on page 6

Activated sludge packaged ring plant, March 2022. Headworks and activated sludge process tank, March 2022.

Continued from page 4 set up as recurring events based on parameters dictated by the JobCal users.

Operational Challenges and Dedicated Staff

Those who are familiar with treating prison wastewater understand that the loadings can be highly variable. In addition, you never know what is going to come down the pipe. The South County Jail has an inline grinder onsite to provide preliminary processing; however, it’s not uncommon to see prison jumpsuits, thousands of candy wrappers, and other debris hitting the WWTF in slug loadings.

While the influent screen catches a lot of the material, the county staff is often busy dipping the activated sludge tanks to keep the material from impacting downstream processes and effluent quality. The facility currently has one level A operator, one level B operator, and two level C operators responsible for the plant.

The PCU operations staff is comprised of Todd Potter (south region supervisor), Doug Lasseter, William Altman, and Andrew Martin. Doug has been operating the plant for over 26 years. The dedication and commitment to safety, education, and quality of the WWTF operations, maintenance, and electrical/instrumentation staff resulted in the WWTF consistently producing exceptional effluent quality, exceeding all regulatory requirements, and earning the 2021 Earle B. Phelps Award for secondary treatment. This is a muchdeserved win by PCU’s dedicated team!

Bartt C. Booz, P.E., is senior project manager with Wright-Pierce in Maitland. S

A process flow diagram of the plant.

Annual Average Influent Annual Average Effluent Number of Occurrences Out of Compliance

Table 1. Plant Loadings and Effluent Quality

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

TN (mg/L)

TP (mg/L) TKN (mg/L)

NH3 (mg/L)

140 245 0.04 N/A N/A 37 3.8 37 25.7

2.0 0.7 2.92 <1 N/A 2.92 2.53 0.62 0.23

0 0 0 0 0 0 0 0 0