Removal Characteristics and Mechanism of Cryptosporidium and Giardia from Secondary Effluent in Flocculation Process
污水再生处理絮凝工艺去除病原性原虫的机制分析

Removal of Cryptosporidium and Giardia under different reaction conditions, such as flocculent dosage, pH, temperature, were investigated to study the removal characteristic and mechanism of pathogenic protozoan in a flocculation process. The experimental results showed that after flocculation, there were not good linear relationships between average t potential of colloid in water samples and removal efficiency of the two kinds of microspheres, the surrogates of the pathogenic protozoan, or the residual turbidity (R = 0.49, 0.48, 0.65). But the linear relationship between the removal of the two kinds of microspheres was obvious (R = 0.99), and there were also good exponential relationships between the removal of microspheres and residual turbidity (R = 0.92,0.95). Sweep flocculation appeared to be an important mechanism for protozoan removal under the conditions in this study. The removal efficiency of Giardia was higher than that of Cryptosporidium under same reaction conditions.