정수처리 과정에서 Cryptosporidium과 유사한 특성을 가지고 있는 C. tracer를 이용하여 공정별 제거효율을 조사하였다. PACI(Poly aluminium chloride, $Al_2O_3$(10%)) 주입량이 10 mg/L일 때 C. tracer는 97.16%로 가장 높은 제거율을 보였으며, 탁도 제거율과 SS 제거율이 높을수록 C. tracer 응집 효율이 높았다. 원수의 pH가 높을수록 C. tracer 제거율이 증가 하였으며 응집 침전 후의 유출수 탁도와 C. tracer 제거율과의 상관성이 $R^2=0.9506$로 높게 나타나 응집 침전 후의 유출수 탁도로 Cryptosporidium 제거 효율을 평가할 수 있음을 알 수 있었다. 또한 여과 실험에서는 유입 탁도에 따른 C. tracer 제거율은 $94.00{sim}95.83%$ 범위였으며 유출수 탁도와 C. tracer 제거율과의 상관성은 $R^2=0.8704$였다. 최적 응집 조건 하에서 여과수 탁도가 양호할 경우, 예상되는 Cryptosporidium의 제거율은 응집 침전의 경우 1.55 log(97.16%), 급속모래여과의 경우 1.38 log(95.83%), 응집 침전+급속모래여과의 경우 2.31 log(99.51%)로 나타났다.
In this study, removal efficiencies of treatment processes with C. tracer which is similar to the characteristics of Cryptosporidium were investigated. The highest removal efficiency of C. tracer was 97.16% when the input dose of PACI(Poly aluminium chloride, $Al_2O_3$(10%)) was 10 mg/L. The higher turbidity and SS removal efficiencies were, the more C. tracer cohesion efficiency increased. Also when pH of the raw water was high, removal efficiency of C. tracer increased. As the correlationship($R^2$) between effluent turbidity after coagulation-precipitation and removal efficiency of C. tracer was 0.9506, removal efficiency of Cryptosporidium could be evaluated by effluent turbidity after coagulation-precipitation. Also the range of C. tracer removal efficiency by sand filtration was $94.00{sim}95.83%$ and the correlationship($R^2$) between effluent turbidity after filtration and removal efficiency of C. tracer was 0.8704. Therefore, when filtration-effluent turbidity is good under the optimized coagulation condition, removal efficiencies of Cryptosporidium by coagulation-precipitation, sand rapid filtration and sand rapid filtration after coagulation-precipitation are estimated as 1.55 log(97.16%), 1.38 log(95.83%) and 2.31 log(99.51%) respectively.
