Feasibility study of treated sewage irrigation on paddy rice culture

A feasibility study was performed to examine the agronomic application of the treated sewage on paddy rice culture through field experiment. The domestic sewage was treated using a constructed wetland system, a subsurface flow type consisting of sand and macrophyte. The effluent of the wetland system was diluted to maintain the total nitrogen concentration below 25 mg/L and was used as irrigation water. Addition of the treated sewage to the irrigation water showed no adverse effect on the paddy rice culture; in fact some enhancement was noticed in both growth and yield. Irrigation with the treated sewage after the concentration was adjusted accompanied by conventional fertilization showed a better result, with the yield exceeding that of the control where clean water was used, thus suggesting that reuse of the treated sewage as supplemental irrigation water could be a feasible and practical alternative. For a full-scale application, however, further study is recommended on the specific guideline for controlling the major water quality components in the treated sewage.