Ozonation of drinking water may adversely affect the biological stability of the finished water. The study was designed to assess the effect of ozone as a preoxidant on the nutrient status of water treated in a full-scale water treatment plant. The study was conducted over a ten week period with analyses performed on a weekly basis. The Haworth Water Treatment Plant is a direct filtration plant utilizing ozonation, alum and cationic polymer flocculation, flotation-skimming, and dual media (anthracite-sand) filtration. Chlorine is added just prior to the filtration process to maintain a residual in the filter effluent. Chlorine and ammonia are added after filtration to produce a chloramine residual in the finished water. Samples collected were the raw source water, water from the ozone contactor, and the finished product water collected at the entry point of the distribution system. Standard water quality parameters analyzed included total coliform bacteria, heterotrophic place count bacteria, total organic carbon (TOC), pH, turbidity, hardness, alkalinity, specific conductance, sulfate, nitrate and chloride. Biological stability of the water was determined by the assimilable organic carbon (AOC) bioassay using Pseudomonas fluorescens strain P-17 and Spirillum strain NOX, and by the coliform growth response (CGR) bioassay with Enterobacter cloacae and Escherichia coli as the bioassay organisms.

"EPA 600/D-90/228." Microfiche.