Use of Shallow Reservoir and Flooded Organic Soil Systems for Waste Water Treatment: Nitrogen and Phosphorus Transformations

Abstract

AbstractUse of a shallow reservoir (with a marly clay loam bottom) and flooded organic soil (Histosol) for inorganic N and PO4‐P removal from waste water (agricultural drainage effluent) was evaluated under simulated conditions. The results show that the shallow reservoirs and flooded organic soils could be effectively used for NH4‐N and NO3‐N removal from the waste waters. Aerating the floodwater resulted in rapid removal of NH4‐N as a result of nitrification and NH3 volatilization. Creating an anaerobic condition in the water column resulted in slower removal of NH4‐N due to volatilization. Nitrate N removal was more rapid under anoxic water column conditions than with aerobic water column conditions. Rapid nitrification resulted in the initial increase in NO3‐N levels in the water column. Aerating the water column with CO2 free air resulted in rapid losses of NH4‐N through volatilization. Aerating the water column with the air containing CO2 resulted in a greater loss of NH4‐N through nitrification than volatilization. A shorter residence time (1–6 days) of waste water over a soil column was required for effective removal of NH4‐N, and a longer residence time of 12–24 days was required for effective removal of NO3‐N from the water. For reservoir soil, about 70 and 76% of the floodwater P was removed under aerobic and anaerobic water column conditions, respectively. For flooded organic soil, 51% of the aerobic floodwater P was removed after 2 days of incubation, followed by an increase in soluble P concentration of the overlying water, whereas about 64% of the anaerobic floodwater P was removed during a 29‐day incubation.