Rusty Tate is a Senior Process Engineer in Garver’s Water Design Center with over 15 years of experience in water and wastewater treatment planning and design. He has a BS in Biological Engineering and a MS in Environmental Engineering both from the University of Arkansas. He is a registered professional engineer as well as a licensed water treatment and wastewater treatment operator.

Over the past several years, municipal utilities that own and operate wastewater treatment facilities have kept a close eye on upcoming regulatory changes that could drive future nutrient removal projects at their facility. However, in the case of one municipal utility, the driver was industrial water reuse. This particular utility owns and operates a wastewater treatment plants (WWTP) with the majority of the treated effluent being conveyed to an industrial user for cooling water. The industrial user has historically used this water for cooling and then discharged via spray irrigation on farm land. However in recent years, the regulatory agency has put the industrial user on notice that phosphorus (<1 mg/L) and nitrate (<5 mg/L) limits should be expected for the land application discharge.

The industrial user operates a lime softening wastewater treatment plant to treat water utilized at the facility but current operation does not have the ability to remove nitrate and can only remove phosphorus through chemical addition. The purpose of this evaluation was to determine the feasibility of implementing full scale BNR at the municipal WWTP as compared to a new treatment facility at the industrial site.

Three different nutrient removal alternatives were evaluated for the municipal WWTP. These included the MLE process with chemical addition, the A2O process, and denitrifying filters. Hydromantis GPS-x process modeling software was used to confirm the treatment capacity of the plant as currently designed and determine the feasibility of converting to nutrient removal. A detailed influent sampling protocol was implemented to collect the necessary data for proper influent characterization. Once the influent was characterized and the simulated plant performance was calibrated to field data, the model was used to evaluate the different nutrient removal alternatives and define the treatment capacity of the new biological process and any new treatment improvements necessary. After the different process alternatives design criteria had been identified, conceptual capital cost estimates as well as life cycle cost estimates were completed for each alternative. The industry determined it was best to provide funding to improve the municipal WWTP. The MLE alternative was the recommended alternative and design started in early 2019 to convert the conventional activated sludge WWTP to a BNR WWTP.

This presentation will give a general overview on the need for BNR at this WWTP. The data from the special sampling period will be shown with a discussion of the influent characterization and its importance in evaluating nutrient removal alternatives. The results of the modeling efforts will be presented along with capital and life cycle costs for each alternative as well as operating data from the WWTP after start-up.