Quality of Percolate Water After Treatment of a Municipal Wastewater Effluent by a Crop Irrigation System

Abstract

AbstractCrop management effects on the renovation of municipal wastewater effluent were studied in a 6‐year field experiment. A randomized split‐plot block design was used, with corn (Zea mays L.) and forage grasses (reed canarygrass, Phalaris arundinacea L.) as crops and effluent application rates of none, ∼0.05, and ∼0.10 m week−1. Nitrogen, phosphorus, potassium, sodium, and chloride were measured in percolating soil water during 5 years under corn and 3 years under forage grasses to assess the quality of renovated wastewater. Nitrogen concentrations were generally below 10 mg L−1, with total applications ranging between 200 and 970 kg N ha−1 year−1. Nitrogen concentrations also were consistently lower under effluent treatments as compared with fertilized controls and lower under forage crops than under corn. Nitrogen levels increased significantly with increased application rates, especially under corn crops and only occasionally exceeded 10 mg L−1 during early and late season when applications surpassed crop uptake demands. Low P concentrations (< 0.05 mg L−1) in percolate water verified nearly complete removal by the soilcrop system except during the final 2 years under corn when concentrations increased about fivefold to 0.7 mg L−1. Potassium levels suggested a continuing removal from the effluent. Sodium and chloride concentrations began at low levels and increased during the first 1 to 2 years of irrigation until they approached the concentrations of the effluent. These results indicate that high N demand crops such as forage grasses have the potential for better renovation of effluent than corn at high application rates, but at lower rates corn will renovate effluent to acceptable N concentrations.