The Indiana Department of Environmental Management (IDEM) has been imposing total phosphorus (TP) discharge limits on Wastewater Treatment Plants (WWTP) with a design treatment capacity of 1 MGD or above for several years.  The City of Carmel WWTP, in the last NPDES permit renewal, has received a 1 mg/L TP discharge limit in their NPDES permit and the WWTP has to meet the TP discharge limit by end of 2021.

Currently the WWTP is in the process of implementing biological phosphorus removal (Bio-P) with chemical backup.  The Bio-P implementation is scheduled to be completed by end of 2021.   The City is also anticipating that the total nitrogen (TN) monitoring will be required in their next permit renewal with potential for TN discharge limit in the future.  The City would like to conduct a high-level evaluation on implementing Biological Nutrient Removal (BNR) for both phosphorus and nitrogen at their WWTP.

Under the advisement of American Structurepoint, the scope of the proposed project is to conduct a high-level evaluation of the feasibility for implementing BNR at the WWTP, and to evaluate potential modifications that may be needed at the WWTP.  It is anticipated that process modeling will be utilized as part of the evaluation to determine the feasibility of implementing BNR at the WWTP and the treatment process proposed.  The City will provide the data required for the model including physical data for the existing treatment processes (i.e., tank size/capacity, equipment capacity, etc.) and the chemical data from the WWTP’s MROs.