Cost Saving through Optimized Staging of Ozone Gas Addition in Water Treatment Plants

摘要

Metropolitan Water District of Southern California (MWD) is conducting studies to evaluaterndifferent combinations for the addition of ozone gas within the co-current and counter-currentrnchambers in over/under contactors. The purpose of these tests is to evaluate ozone contactingrnstrategies that have the potential to increase overall disinfection credit, stabilize dissolved ozonernresiduals, allow for reduced ozone dosages (while still meeting current disinfection targets),rnreduce ozone operating costs, and potentially decrease both bromate formation and bromaterncontrol costs. Initial results found at two plants indicate that under the water quality andrnoperating conditions found during testing, and utilizing current ozone disinfection calculationrnmethods, ozone gas addition to chambers 1 and 2 generally achieves greater disinfection creditrnthan ozone gas addition to chamber 1 alone. In additional testing, ozone gas addition tornchambers 2 and 3 (and no gas addition in chamber 1) may result in even greater disinfectionrncredit than ozone gas addition to chambers 1 and 2. Limited data indicates that at low tornmoderate water and gas flow rates, ozone gas addition to chamber 2 alone may provide evenrngreater disinfection credit. Given the significant increases in disinfection credit found in somerntests, these optimization studies have the potential to reduce ozone dosages required to meet bothrnUSEPA disinfection requirements and MWD disinfection goals, and possibly result in substantialrncost savings.