Use of Biological and Non-Biological Surrogates for EvaluatingCryptosporidiumRemoval by Filtration

Abstract

Water treatment plants are currently facing increasing challenges in monitoring Cryptosporidium in source and treated water because of complex analytical techniques and associated health risks. Surrogates may be easier to analyze than Cryptosporidium, but they must also be reliable and representative of results. Polystyrene Latex (PSL) beads of 2 – 3 µm size have been suggested by researchers as a potential non-biological surrogate for Cryptosporidium as it mimics the size and surface characteristics of the pathogen. Bacillus subtilis (B. subtilis) spores have also been suggested by researchers as a potential biological surrogate for Cryptosporidium because of their resistance to conventional disinfectants and abundance in surface water. Therefore, it is important to examine the surrogacy of PSL beads and B. subtilis spores based on filtration mechanisms. This paper summarizes the results of PSL beads, B. subtilis and Cryptosporidium challenge tests conducted on different package water treatment systems that include bag and cartridge units, membrane and granular media filtration units, and adsorptive systems with charged media. Analytical techniques and the accuracy of surrogate results are discussed and compared for various types of treatment units evaluated at EPA’s Test and Evaluation Facility in Cincinnati, Ohio, and different field locations. NOTICE