OZONE The City of Washington, NC retained EE&T in 1989-90 to conduct a bench- and pilot-scale evaluation of treatment options to reduce color, DBPs, iron, and manganese. The bench testing phase screened the alternatives of air stripping, raw water ozone in combination with chlorine and chloramines, and enhanced coagulation. Subsequent pilot testing investigated ozone as a raw water oxidant, a pre-filter oxidant, and both simultaneously. Testing showed that excellent color removal and DBP control could be achieved by pre-ozonating and using chloramines for disinfection. Prior to a water treatment plant expansion at the 90-mgd A.B. Jewell Water Treatment Plant, EE&T conducted a bench- and pilot-scale treatability study to evaluate existing and future process design parameters. The treatability work included an investigation of the effects of raw water ozonation on color and disinfection byproduct precursors. Applied ozone dosages were varied between 0.3 mg/L and 4 mg/L. GAC filtration was used to enhance organics removals. Testing showed that ozone plus GAC filtration increased removals of disinfection byproduct precursors by 15 percent. EE&T designed, constructed, and operated a 26-gpm pilot plant for the City of Durham, NC to evaluate ozone applied directly in the filter box and ozone applied at the end of the sedimentation basin by baffling the rear portion of the settling ozone. Throughout the study, extensive bench-scale testing of zone was completed to evaluate improvements to coagulation efficiency, coagulant reduction, TOC removal, bacteriologic water quality, and DBP precursor reduction. Particle count analysis of microflocculation in connection with filter performance was conducted. Superior filtered turbidities and DBP control were achieved when ozone was applied above the filter media. Bench- and pilot-scale ozone testing was conducted for the Appomattox River Water Authority (ARWA) in Petersburg, VA in 1987-88. The primary objective of the work was to achieve optimal removal of manganese, while also reducing the formation of disinfection byproducts. Testing was done in conjunction with an evaluation of chlorine, chlorine dioxide, and ozone. Ozone was found to be effective for reducing DBP formation potentials, however, manganese concentrations were not reduced to desired levels.