AWWA QTC97085

The occurrence of coliform bacteria in small water distribution systems when none have been detected in the source groundwater has been attributed to regrowth by the coliforms in biofilm on the surfaces of the distribution pipes. As drinking water regulations are more widely applied to smaller utilities, an area of emerging concern is the installation of treatment processes to meet the newly imposed standards. Small systems in frequent violation of total coliform regulations are often required to install disinfection systems. Traditional disinfection technologies used by larger systems are unrealistic for small systems due to the costs and safety issues involved. This paper describes an alternative disinfection option for small system--mixed oxidants. The membraneless mixed oxidant cell described generates a mixed oxidant disinfection solution from a sodium chloride brine and then separates the solutions generated at the anode and the cathode before substantial recombination can occur. The paper also discusses the results of a five phase study undertaken to compare the potential of the mixed oxidants disinfectant system against free chlorine for biocidal efficacy, biofilm/biofouling removal, prevention of biofilm regrowth, relative potential of corrosion and overall costs.