Performance of an ecological treatment system at three strengths of dairy wastewater loading

Ecological treatment systems, which rely on renewable resources, have successfully treated municipal and industrial effluents with reduced costs compared to conventional methods, but their capacity to treat dairy wastewater is unknown. In order for ecological treatment systems to be practical for agriculture they must be able to treat a significant portion of a dairy's daily wastewater production. In this study, the impact of three strengths of dairy wastewater on effluent water quality was assessed. Three ratios of wastewater and city water—(1) one part wastewater:three parts city water, (2) one part wastewater:one part city water, and (3) two parts wastewater:one part city water—were each pumped into an ecological treatment system. Influent and effluent water samples were analyzed for PO4-P, TP, TN, NH4-N, NO3-N, total suspended solids (TSS), and carbonaceous biochemical oxygen demand (CBOD5). Influent dairy wastewater volumetric loading rates were much greater than those of municipal wastewater. Regardless of influent wastewater strength, concentrations of all measured variables were significantly reduced between the influent and effluent of the ecological treatment system. At the lowest wastewater strength, PO4-P was reduced 39%, TN 83%, and NH4-N 89%, while at the highest wastewater strength, PO4-P was reduced 41%, TN 79%, and NH4-N 70%. Increased wastewater strength required greater aerobic treatment volume to reduce concentrations of NH4-N and CBOD5.