Computational modeling of wastewater land application treatment systems to determine strategies to improve carbon and nitrogen removal

Abstract

Land application of domestic and food processing wastewater is used due to its low cost, energy use, and maintenance. Design procedures are generally based on empirical relationships that may not account for critical site and waste-specific conditions. A mathematical model was utilized to simulate the complexity of wastewater land application. Multiple scenarios were run to determine system performance as measured by chemical oxygen demand (COD) and the nitrification/denitrification process. The modeling results showed that COD and nitrification occurred within the first 15.4 cm of a sandy loam soil. Increasing the dosing frequency slightly reduced the COD effluent concentration. Complete denitrification does not occur in a typical land application wastewater treatment system. In a domestic wastewater land application system, up to 32% of nitrate can be removed by increasing the dosing frequency and providing more organic carbon. In a food processing wastewater land application system, up to 56% of nitrate can be removed by increasing the dosing frequency and hydraulic and organic loadings. HYDRUS CW2D modeling is a valuable design tool to simulate multiple operation strategies and predict carbon degradation, nitrification, and denitrification. The model result can provide operational strategies to maximize the treatment while minimizing environmental impacts.