Study On The Optimization And Application Of Cryptosporidium Giardia Detection Method

Issue regarding Cryptosporidium and Giardia has nowadays become an international concern and arose widespread attention. Drinking water containing oocysts or cysts can cause severe gastrointestinal infections, and even death. In recent years, as Chinese people's lifestyle changes, more and more people are drinking unboiled water directly, Cryptosporidium and Giardia in drinking water has become a serious health threat.EPA1623 method is currently one of the most mature and authorative methods detecting Cryptosporidium and Giardia. However, this approach is limited in its usage for its high cost and low recovery rate. So this study did research on the basis of EPA1623, worked out the optimization method suited to China's national conditions and applied this optimization method to detect Cryptosporidium and Giardia in raw water and process water in water supply plant within Shanghai.In order to establish an effective method for detecting Cryptosporidium and Giardia, this study analysed the three main steps constituting EPA1623 detection methods, namely, concentration and separation, immunomagnetic separation (IMS) and immunofluorescence assay. After carrying out step by step research and analysis, we reached the conclusion that concentration and separation is the main factor affecting the recovery and put forward an optimized process. The key technologies of the process are two replacements, namely domestic filter capsule + ultrasonic elution replacing Envirochek filter capsule and membrane filtration + ultrasonic seperation replacing centrifuge enrichment. The optimized ultrasonic frequency is 60KHZ, ultrasonic duration is 15 minutes and the water temperature is 40°C.Compared with EPA1623, the optimizd method using domestic filter capsule + ultrosonic elution + membrane filtration + ultrasonic separation + IMS + FA can increase the low limit of recovery rate from 20% to 50~60%, halve test cost and reduce one-off investment in equipment by 30%.On this basis, we applied optimization method to detect Cryptosporidium and Giardia in raw water, finished water, water through sedimentation, water through filtration in a water treatment plant. The results showed that Cryptosporidium and Giardia existed in Shanghai raw water and the density of Giardia maintained at 0 ~ 5 / 10L, the density of Cryptosporidium maintained at 0 ~ 3 / 10L. No Cryptosporidium and Giardia were found in water plant effluent, water through sedimentation and water through filtration, which means that in the water treatment process, coagulation and sedimentation have great effect on the removal of Cryptosporidium and Giardia.