Effectiveness of Wastewater Land Application: Monitoring and Modelin

Wastewater land application has been used for decades because of its low cost, energy use, and maintenance requirements, compared to a conventional wastewater treatment system. The performance of treatment depends on the hydraulic and organic wastewater loadings, soil characteristics, and soil conditions. Understanding the complexity of soil is important. The aerobic or anaerobic condition of the soil may result in nitrate leaching and metal mobilization into groundwater, respectively. Currently, design criteria are generally based on empirical relationships, which do not adequately consider site and waste-specific conditions. Because organic and hydraulic loadings are generally fixed based on production, dosing is the only operational parameter that can be adjusted to enhance treatment for site-specific conditions. In this study, an evaluation of domestic and food processing wastewaters land application systems were performed including examining their benefits, effectiveness, and techniques for modeling. Monitoring strategies at the demonstration site showed the viability of using land application to treat food processing wastewater and helps in making an operation decision. The HYDRUS Constructed Wetland 2D (CW2D) model was successfully calibrated and validated using data from laboratory experiments. The modeling results showed that most of the COD removal in a domestic wastewater land application system occurs within a 30.5 cm (1 ft) depth for a sandy loam soil. Increasing the dosing frequency was effective in slightly reducing the COD effluent concentration. An increase in nitrate removal by changing dosing frequency while providing sufficient carbon was found to be possible.