Chlorine kills bacteria in sewage but creates environmental headaches, writes Wired reporter

• Ever since the advent of modern plumbing, people have embraced a practice of flush and forget.
• Unfortunately, public works employees and clean-water advocates rarely enjoy such a luxury, and recent debate has focused on the final step in sewage processing, chlorine disinfection, which is no longer the foregone conclusion it once was.
• Chlorine disinfection kills pathogenic bacteria so people swimming or fishing near treatment plants' discharge locations don't contract cholera, E. coli infection, Legionnaires' disease or other illnesses.
• The practice is still widespread, and chlorine remains the most widely used disinfectant at 16,000 wastewater treatment plants nationwide, according to John Millett, a spokesman for the U.S. Environmental Protection Agency.
• However, the toxicity of chlorine that kills harmful bacteria also hurts other life.
• And while the EPA says treatment plants must dechlorinate before spewing out treated wastewater, that effluent is not pure.
• "The chemical process might cause more problems in the environment than if you didn't do it at all," said Tom Franza, assistant general manager of wastewater enterprise for the San Francisco Public Utilities Commission, or SFPUC.
• In 1988, SFPUC successfully petitioned the San Francisco Bay Regional Water Quality Control Board to eliminate requirements to disinfect water released from a pipe four miles offshore.
• SFPUC conducted a study with the EPA and the National Oceanic and Atmospheric Administration that tracked effluent currents and demonstrated that the bacteria died quickly in the cold, salty water and that the stream never made it shoreward, where surfers or bathers might get sick.
• In the short term, some municipalities such as San Francisco have succeeded in reducing their chemical use by improving chemical-delivery methods and developing more sensitive instruments to take measurements, according to Arleen Navarret, regulatory manager for SFPUC Wastewater Enterprise.