비용편익분석을 통한 슬러지 처리공정 개선에 관한 연구

Abstract

Cost-Benefit analysis was performed for optimization of sewage sludge treatment process in Public Owned Treatment Works (POTWs). The sludge treatment efficiencies were evaluated by thickening type(gravity and centrifugal), dewatering procedure (after thickening and after digestion) and dewatering type(belt press and screw decanter). Economical efficiency was evaluated by B/C ratio based on Cost-Benefit Analysis(CBA) for four types of sludge treatment processes. Regarding thickening type, the centrifugal thickening was more beneficial than gravity thickening in terms of solid recovery and sludge thickening rate. Results showed that after digestion type consumed 1.8 times as small as after thickening type. The digestion rate and the sludge reduction rate were 42.4% and 39.7%, respectively. Results showed that the screw decanter type was more effective as dewatering type because the moisture content of dewatering cake was 79.1%. However,the amount of dewatering chemicals was 1.3 times for large scale POTWs and 2.8 times for small scale POTWs. The result of CBA showed that the B/C ratios of centrifugal thickening and centrifugal thickening after digestion were 3.0 and 2.45, respectively. Therefore, these types were applicable to the sludge treatment in the aspect of cost benefit.