Multiplex particle refining system to enhance Cryptosporidium recovery for surface water filtration methods

Abstract

Low recovery from large-volume surface water samples strongly limits the feasibility of filtration methods for detecting Cryptosporidium oocysts. Filtration recovery is potentially affected by water particulates under high turbidity conditions. This work reports the Multiplex Particle Refining (MPR) system that employs the novel counter-flow microfiltration for pre-concentrating oocysts in surface water. By use of multiple counter-flow refining units arranged into a cascade-like structure, the MPR system can separate particulates with different sizes from the target oocysts. Concentrating ratio and integrity of the refining filter were thoroughly investigated. Further, protozoan recovery experiments were conducted using 10-L deionized water and surface water spiked with 100 Cryptosporidium parvum oocysts. The MPR has been characterized by recovery rates of 86.4±5.4% and 85.2±6.4% in deionized water and surface water, respectively. Rapid and simple filtration procedure was demonstrated. Employing the refining system prior to five commercially available filters, recovery rates were significantly higher and less variable than those from the filters alone. Moreover, thanks to the capability of the MPR to adjust the number of separation units, the oocyst recovery was consistently above 50% for the US EPA approved Filta-Max and Envirochek HV filter in a wide range of water turbidities. The data presented in this study demonstrate that the MPR can be an effective tool to enhance the efficiency of currently used filtration methods. It has potential as a feasible pre-filter for monitoring source water quality in drinking water supplies.