Estimation of point source and nonpoint source loadings in the Mahoning River watershed /

Abstract

The goal of this project was to contribute the following components to the Mahoning River Watershed Inventory: evaluation of point source pollutant loading for all waste water treatment plant (WWTP) discharges; statistical summary of in-stream water quality data collected by WWTP's; and comparison of point source and nonpoint source pollutant loadings to the Mahoning River. Pollutant loading calculations were performed using NPDES data for the final effluent from each significant WWTP for the years 2000 and 2001. Means and standard deviations of measured concentrations of several water quality parameters were calculated for 2000 and 2001 separately, and for the two years combined, both upstream and downstream of each WWTP discharge. Pollutant fluxes in the Mahoning River were calculated at Leavittsburg and Lowellville using monthly monitoring data collected by Ohio EPA. These fluxes were considered to represent the sum of point and nonpoint loadings above that station. The nonpoint source loadings were calculated by subtracting the sum of point sources from the total flux for each parameter at each location. The point/nonpoint source pollutant loadings at Leavittsburg were estimated to be: 168/46,914 kg/d for total suspended solids (TSS); 44/115 kg/d for ammonia nitrogen (AN); 386/824 kg/d for nitrite + nitrate nitrogen (NN); and 206/1,864 kg/d for 5-day CBOD. Similarly at Lowellville, point/nonpoint source pollutant loadings were estimated to be: 4,086/67,339 kg/d for TSS; 596/92 kg/d for AN; 2,506/2,339 kg/d for NN and 1,668/6,402 kg/d for 5-day CBOD. Nonpoint source controls would be required to reduce levels ofTSS and CBOD in the Mahoning River.