Disinfection Efficacy Studies wWith Electrochemically Generated Mixed Oxidants in the Development of CT vValues for Drinking Water PathogensEPA Grant Number: U915410
Title: Disinfection Efficacy Studies wWith Electrochemically Generated Mixed Oxidants in the Development of CT vValues for Drinking Water Pathogens
Investigators: Wilson, Sacoby M.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1998 through January 1, 1999
Project Amount: $66,682
RFA: STAR Graduate Fellowships (1998) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objective of this research project is to perform laboratory studies to develop disinfectant concentration and contact time (CT) data for disinfections by mixed oxidants (MIOX) in demand-free water on Cryptosporidium parvum oocysts, bacteriophage MS2, Coxsackievirus B5, and hepatitis A virus in buffered, oxidant demand-free water at pH 6, 8, and 10, and 5°C.
The use of mixed oxidants (MIOX) as an alternative method of drinking water disinfections has been shown as more effective in destroying harmful waterborne microbes than chlorination. The mixed oxidant solution is generated by the electrolysis of a solution of sodium chloride. The electrolysis converts the brine solution to a mixture of oxidants (free chlorine, chlorine dioxide, hydrogen peroxide, ozone, and other short-lived oxidants). This technology was developed over several decades ago (liquid and gas-phase generators), yet the chemical components of the mixture and the efficacy of the pathogen reduction, have not been adequately examined.
Known quantities of purified test microbes are added to batch volumes of buffered, oxidant demand -free water at the target pH that contains the test mixed oxidant MIOX at the target concentrations (2-3 and 5 mg/lL as free -available chlorine). At various times after the microbe addition (3, 10, 30, 100, and 300 minutes), aliquots of the reaction mixture are sampled, the disinfectant is neutralized, and the sample is plated to enumerate the remaining concentration of infectious microbes through various proven plaque and cell culture infectivity assay techniques. Disinfectant concentration in the reaction mixture also is also measured periodically. Control samples include vessels containing all reaction components except the disinfectant (to monitor microbe stability) and other vessels containing all reaction components except microbes (to monitor disinfect stability). Microbial reductions are calculated for each particular time endpoint, and the time for a specified degree of inactivation is estimated by linear regression analysis. This data is used to calculate the CT values.