Inactivation of Cryptosporidium parvum Oocysts and other WaterborneMicrobes by Oxidants Generated Electrochemically from Sodium Chloridefrom Portable Pen and Bench Scale Systems

摘要

The electrochemical generation of oxidants from NaCl has been used to produce freechlorine for many years. Recent studies suggest that under certain conditions, this electrolysisreaction produces other oxidants besides free chlorine, resulting in an oxidant mixturecapable of inactivating microbes not inactivated by free chlorine. In this study we describethe results for microbial inactivation of the chlorine-resistant protozoan parasiteCryptosporidium parvum and other test microbes by mixed oxidants generated from twoelectrochemical cells quite different in their size. One cell is in the form of a small "pen"intended to disinfect personal drinking water supplies and the larger one is a bench scale unitused as a model for systems made to disinfect municipal drinking water supplies. Testmicrobes seeded into oxidant demand-free, buffered water at pH 7 and either 5 or 25°C weredosed with 2.5 or 5 mg/L of oxidants generated from the two cells. Aliquots were taken at 1,10, 30, and 90 minutes to assay the infectivity of Cryptosporidium parvum oocysts,Clostridium perfringens spores, Klebsiella terrigena, E. coli, hepatitis A virus (HAV) andcoliphage MS2. Inactivation was expressed as log10 reductions of microbe infectivity.Oxidants generated from the cells produced extensive (>4 log_(10)) inactivation of test bacteria,bacterial spores, and viruses within 1 to 10 minutes. The inactivation of C. parvum oocystsby 10 minutes ranged from 0 to >3.0 log_(10), depending on the cell, experimental conditionsand experiment. The results of these studies demonstrate that optimally designed andoperated electrochemical cells generate oxidants from NaCl that extensively and rapidlyinactivate C. parvum oocysts as well as bacterial spores, bacteria and viruses in water.However, the inactivation of C. parvum oocysts by electrochemical oxidants is somewhatunpredictable, perhaps due to variability in the concentrations of the actively microbiocidalchemical species.