AWWA ACE56179

A nine month pilot study simulated raw and settled water ozonation and conventional treatment. The ozone module set-up included six, six-inch diameter plexiglass columns, each roughly 90 inches tall, and was capable of achieving very high ozonation CTs to simulate Cryptosporidium inactivation. Monochloramine, ammonia, and pH adjustment were evaluated for bromate control at various ozone doses, temperatures, and disinfection CTs. Treatability studies were performed on the Trinity River, near Houston, Texas. The Trinity River currently supplies many utilities in the state of Texas. Although raw water bromide levels are only moderate (0.10-0.20 mg/L), ozone doses needed for Cryptosporidium inactivation could easily produce bromate levels above the 10 ug/L MCL. Ozone disinfection CT goals for the project for Cryptosporidium inactivation were established based on previous and separate work conducted by American Water Works Association Research Foundation. For the chloramine evaluations, monochloramine was formed by adding chlorine and ammonia at a 5:1 ratio. Total chlorine residual of 2 mg/L prior to raw or settled water ozonation provided better control than either ammonia addition or pH adjustment prior to ozonation. For example, a total chlorine residual of 2 mg/L consistently produced bromate levels less than 5 ug/L for a range of disinfection CTs and water temperatures. Complete study results for bromate as well as other ozonation byproducts, such as aldehydes, are presented. Includes 11 references, tables, figures.