막결합형 A2/O공법을 이용한 양돈폐수 중의 유기물 및 질소제거에 관한 연구

Abstract

국내에서 가동되고 있는 대부분의 축산폐수 공공처리시설에서는 계획유량보다 훨씬 적은 양이 유입되거나 계획농도보다 훨씬 높거나 낮은 농도로 유입되는 등 유입수의 유량과 수질이 불안정하고 적절하게 처리되지 않음으로써 많은 어려움을 겪고 있다. 특히 고농도 축산폐수는 톱밥, 왕겨 등의 수분조절재를 사용하여 퇴비화하거나 저장소에 장기간 저류시킨 후 농지에 살포하고 있으나, 적당한 퇴비화나 액비화 방법이 개발되지 않음으로써 악취, 수질오염 등과 관련한 많은 민원이 제기되고 있다 막 결합형 활성슬러지 공정은 전통적인 활성스러지 공정에 비하여 슬러지의 침전성, 벌킹, 거품현상에 관계없이 고액분리가 가능하고 또한 반응조의 MLSS농도를 높게 유지하여 생물학적 처리능력을 극대화하여 유기물 부하에 쉽게 대처할 수 있는 장점이있다. 본 연구에서는 A2O와 분리막을 결합시킨 MBR(Membrane Bioreactor)을 이용하여 고농도의 유기물과 질소를 함유한 양돈폐수의 처리효율과 MLSS와 반송비에 따른 유기물, 질소 및 인의 제거효율과 공정별 질소의 거동을 조사하고, Free Ammonia(FA) 및 Free Nitrous Acid(FNA)에 의한 질산화 독성을 파악하고자 하였다. Step1, 2, 3에서 각각 반송비를 300%, 300%, 500%로 하였고 MLSS는 3000~4000 mg/L, 6500~8000 mg/L, 6500~8000 mg/L로 유지 하였다. 막의 재질은 Hydrophilized Polysulfone이며, 막의 표면적은 0.1507m3으로 포기조에 침지하여 여과하는 방식을 사용하였다. 제거효율은 각각 SS 99.9%, BOD 98.7%, CODCr 90.2%, T-N 81.2%, NH3-N 90.6%, T-P 64%로 나타났으며, 본 연구에서는 반송비와 MLSS의 증가에 따라 처리효율이 높았으며, Free Ammonia(FA)에 의한 영향은 받으나 Free Nitrous Acid(FNA)에 의한 질산화 독성없었다.|Because stock raising wastewater is containing organic matter and nitrogen of high concentration, there is much difficultys in general biological system. Specially, nitrogen ingredient can cause wealth effect evil if is flowed in rivers. Most of public livestock wastewater disposal facilities operated in Korea have many difficulties in treating wastewater because of unstable quantity and quality of inflow water such as too small quantity of inflow and too high or too low concentration than planned. In particular, high?concentration livestock wastewater is mixed with bulking agents such as sawdust and rice hulls for composting or impounded in a reservoir for a long time and scattered at farms but, because there is no adequate method of turning it into compost or liquid fertilizer, many public complaints are raised related to bad odors and water contamination. Different from traditional activated sludge processes, the process of membrane coupled activated sludge system can separate solid from liquid regardless of the precipitation, bulking and bubbling of sludge. In addition, it maintains the high concentration of MLSS in the reactor and, as a consequence, maximizes the capacity of biological treatment and copes with the load of organic matters efficiently. The present study purposed to investigate the efficiency of MBR (membrane bioreactor) that coupled A2O with membrane in treating swine wastewater that contains high?concentration organic matters and nitrogen, the efficiency of removing organic matters, nitrogen and phosphorus according to MLSS and recycle ratio, and the behavior of nitrogen by process, and to examine the toxicity of nitrification by free ammonia (FA) and free nitrous acid (FNA). Recycle ratios at step1, 2 and 3 were 300%, 300% and 500% respectively, and MLSS was maintained at 3,000～4,000 mg/L, 6,500～8,000 mg/L and 6,500～8,000 mg/L respectively. The material of the membrane was hydrophilized polysulfone and the surface area of the membrane was 0.1507m3. The membrane was soaked in an aeration tank and filtered. Removal efficiency was 99.9% for SS, 98.7% for BOD, 90.2% for CODCr, 81.2% for T-N, 90.6% for NH3-N and 64% for T-P. In this research, treatment efficiency increased along with the increase of recycle ratio and MLSS. In addition, there was influence by free ammonia (FA) but no toxicity of nitrification by free nitrous acid (FNA).