APPLICATION OF CHLORINE GAS AS AN OXIDANT IN PACKED TOWER SCRUBBERS

Chlorine gas is used as an oxidant in a two-stage packed tower scrubber system at the Scottsdale Water Campus in Scottsdale, Arizona. An innovative design was developed to avoid the high flow that results when chlorine is injected into the makeup water. The new design addresses the problem by mounting the chlorine injector in a sidestream flow of the recirculation line. In this configuration, chlorine addition is independent of the makeup water and higher solution strength can be obtained. Performance testing confirmed that the new design was successful in providing effective and economical treatment. Two-stage treatment yielded H2S removal efficiencies of 99.7 percent or higher. GC/MS analyses of scrubber stack samples for 43 VOCs, found that all were below 100 ppb. Odor panel results were 6 D/T in the scrubber outlet. An optimization study established that pH and ORP could be lowered to significantly reduce chemical usage yet maintain 99 percent H2S removal. An economic evaluation of Scottsdale's current operational conditions showed savings of 60/day for gaseous chlorine over an aqueous solution.