Design Guide for Community Water Systems - The Water, Sanitation ...

utilized, shall be 1.0 milligrams per liter at distant points in thedistribution system.4.4.3 Testing equipment.Chlorine residual test equipment shall meet the requirements established in10 CSR 60-5.010 and shall be capable of measuring residuals to the nearest0.2 milligram per liter. All treatment plants serving a population greater than3,300 shall be equipped with recording chlorine analyzers monitoring waterentering the distribution system.4.4.4 Other Disinfecting Agents.Although disinfecting agents other than chlorine are available, each hasusually demonstrated shortcomings when applied to a public water supply.Proposals for use of disinfecting agents other than chlorine, including ozonedisinfectant, must be approved by the department prior to preparation of finalplans and specifications.4.4.5. Ozone Disinfectant.4.4.5.1. Bench scale studies.Prior to the use of ozone for primary disinfectant, bench scalestudies must be conducted for ground water sources and full scalepilot studies must be conducted for surface water and groundwater under the influence of surface water sources.4.4.5.2. Chief operators.Chief operators for water systems treating water with ozone musthave the appropriate operator certification level required by theoperator certification rules in 10 CSR 60-14.4.4.5.3. Disinfectant residual.Systems utilizing ozone for the primary disinfectant must providefor maintaining a residual of chlorine or chloramine in thedistribution system.4.4.6. Disinfection Byproduct and Precurser Removal and ControlDisinfection byproducts are formed when disinfectants reacts with naturallyoccurring organic substances. These organic substances, called "precursors,"are a complex and variable mixture of compounds. Formation of disinfectionbyproducts is dependent on such factors as amount and type of disinfectantused, temperature, concentration and type of precursor, pH, and contact time.Aug. 29, 2003Page 68