호기조, 혐기/무산소조로 구성된 자연친화형 하수처리장의 질소 및 인 제거에 관한 연구
(A) Study on the removal of nitrogen and phosphorus in enviromentally-friendly wastewater treatment facility consisting of aerobic tank and anaerobic/anoxic tank
호기조 혐기 무산소조 하수처리장 질소 인 환경공학 환경보전;
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A pilot-scale constructed wetland with the aerobic tank and anaerobic/anoxic tank connected in series was employed in order to treat 0.6㎥/day raw sewage everyday. Aerobic tank and anaerobic/anoxic tank were filled with sands and gravels which were the main media for the immobilization of microbes. The aerobic tank was kept to be anoxic due to continuous air supply through the natural draft system. The average influent concentrations of BOD5, COD, SS, T-N and T-P were 63.5mg/L, 52.9mg/L, 61.4mg/L, 34.2mg/L and 3.40mg/L, respectively. After being treated at the aerobic tank, more than 85.0% of initial BOD_(5) was removed and the average effluent BOD_(5) concentration from the aerobic tank was 9.5mg/L. The removal efficiency of COD and SS was 80.5% and 95.9%, respectively. Successful biological nitrification could be obtained at the aerobic tank. At the aerobic tank about 33.6% of T-N was removed, and more than 96% of the organic nitrogen and ammonia nitrogen was nitrified successfully into nitrate nitrogen, which is indicative of the successful biological nitrification. Additional removal of BOD_(5) and T-N could be obtained at the anaerobic/anoxic tank of the constructed wetland. About 55.8% of the remaining BOD_(5) was removed at the anaerobic/anoxic tank, and the average effluent BOD_(5) concentration was 4.2mg/L. The removal efficiency of COD and SS at the anaerobic/anoxic tank was 46.6% and 68.0%, and the average concentrations at the final effluent were 5.5mg/L and 0.8mg/L, respectively. The nitrate nitrogen was then finally denitrified with the consumption of remaining BOD_(5) at the anaerobic/anoxic tank. More than 69% of the remaining T-N was denitrified, and the average concentration of T-N at the final effluent was 7.0mg/L. Phosphorus compounds were not only consumed by plants, but also removed through the reaction with cations such as Ca^(2+), Mg^(2+) and Fe^(3+) to form insoluble precipitates. The concentration of total phosphorous(T-P) in the effluent could be maintained below 0.8mg/L regardless of the influent concentrations. The maximum available capacity for nutrient uptake in plants was far less (of the order of 7 %) than the loading rate of nutrients to the constructed wetland.