EFFLUENT MANAGEMENT FLEXIBILITY THROUGH NUTRIENT REMOVAL

The City of Carson City (City) Wastewater Reclamation Plant (WRP) is facing several effluent management challenges, which include increased effluent nitrogen concentrations, seepage from its reclaimed water storage reservoir, and increased influent flow due to growth. The City desires an economical solution that will allow it to continue its 100 percent reuse program as well as protect the public health and environment.The City approached the problem by working with the Nevada Department of Environmental Protection (NDEP), the public and private consultants to define viable WRP and reuse improvement alternatives.The solution to the problem entails incorporating biological nutrient removal (BNR) aeration basins into the secondary treatment process coupled with additional reuse sites. The BNR process coupled with disinfection improvements will produce a WRP effluent with values of 10 mg/L total nitrogen and 0.10 mg/L total phosphorus suitable for Category A reuse. The improved effluent water quality will also reduce reservoir seepage and eliminate the need for a new reservoir liner as well as reduce nutrient loading to reuse sites. The effluent may also be suitable for seasonal discharge to the Carson River. Both the WRP and reuse system improvements will be implemented over the 20 years to distribute capital costs ahead of the pace of flow increases.