earticle

영어

A sewage treatment plant built with water plants and gravels in an open field has been operated for 3 years with a daily average flow of 50 m3. The quality of treated water was regularly analysed and the economic assesment of the process has been investigated. Seasonal performance of the plant has been investigated with emphasis on treatment efficiency, shock loading responses, effects of sewage evaporation rate, effects of high and low ambient temperature, long term shutdown and start-up. Analyses of sewage indicated that the quality and quantity of the sewage generated in farming and fishing villages depend mainly on the life pattern of the residents. A sewage treatment plant with mechanical equipments may have high operating costs and low treatment efficiency to treat this type of sewage.However, the sewage treatment plant suggested in this study employs natural purification processes and has showed stable long term treatment efficiency even with shock loading and ambient temperature variation. Treatment of phosphorus with mechanical processes may need high operating costs but the suggested processes using water plants and gravels removes phosphorus in natural ways resulting in high removal efficiency and low costs. The natural sewage treatment plant showed good efficiency for all year around to meet the discharge guide-lines of drinking water protection area with respect to BOD, COD, TN. TP and SS. The high treatment efficiency may be due to the action of microorganisms living attached on the surface of the gravels. However, the water plants showed limited treatment performance.