Thousands of drinking water and wastewater treatment plants, and the railroad lines leading to them, are possible terrorist targets and major accident risks because they use or transport toxic chlorine gas or sulfur dioxide gas. But at least 554 of these plants in 47 states and the District of Columbia have taken themselves out of that bull's-eye since 1999 by converting to safer treatment processes, according to an advocacy organization, the Center for American Progress.
- CAP: "Survey Shows Improved Chemical Security Makes Millions Safer,"  March 2, 2010 (includes a map and chart of all facilities, with their location, former danger zone and exposed population, alternative treatment type now used, and Congressional district); Paul Orum,  202-548-4020.
The technology shifts have made about 40 million people living nearby safer, CAP estimates. The plants, which range from very large to very small, are now using chemicals and processes such as liquid chlorine bleach (sodium hypochlorite), calcium hypochlorite, or ultraviolet light. Sulfur dioxide is used to reduce the free chlorine residual in treated water.
There are concerns beyond terrorism involved in such switches, such as effectiveness for each plant, cost, altered water chemistry at the tap or discharge point, and possible disruption of service during the transition. You can cover how plants of interest to your audience that have already made the switch handled these and other issues.
You can also track down the estimated 2,600 plants that still use the more toxic and hazardous chemicals and see what their future plans are. Operators of these plants are likely following the slowly-unfolding legislation in Congress that is attempting to deal with chemical security at these and other types of facilities. The House passed a bill on Nov. 6, 2009, without a single Republican vote (search  for HR 2868, The Chemical and Water Security Act of 2009).
- OMB Watch: "House Passes Chemical Security Bill,"  Nov. 10, 2009.
The Senate is beginning to have hearings.
- Senate Committee on Homeland Security and Government Affairs hearing, "Chemical Security: Assessing Progress and Charting a Path Forward,"  March 3, 2010.
- Senate Committee on Environment and Public Works, Subcommittee on Superfund, Toxics, and Environmental Health hearing, "Business Perspectives on Reforming U.S. Chemical Safety Laws,"  March 9, 2010.
In addition, legislation expected to be introduced soon by Sen. Frank Lautenberg (D-NJ), chairman of the Senate Subcommittee on Superfund, Toxics, and Environmental Health, may include language addressing use of safer alternatives for chemicals and processes, which could apply to water and wastewater utilities.
For much more information on related legislation, see the TipSheet of July 22, 2009. 
Just before the House passed its bill, the Clorox Co. said on Nov. 2, 2009, that it will phase out its use of chlorine gas at seven large facilities and switch to safer alternatives (in Chicago, Houston, Los Angeles and Fairfield, CA, Forest Park, GA, Tampa, FL, and Aberdeen, MD). This may better protect an estimated 13 million people living near these plants, according to Greenpeace. The conversions are expected to be phased in over about three years, beginning with completion at the first facility in Fairfield, CA, in mid-2010, according to the Bureau of National Affairs.
Greenpeace continues to push Dow Chemical Co. and DuPont to take similar steps, saying that Clorox's actions indicate that such moves make good business sense.
- BNA, "Clorox to Phase Out Chlorine at Its U.S. Production Facilities,"  Dec. 14, 2009.
- Greenpeace, "Safety First: Clorox to Eliminate Chlorine Risks,"  Nov. 2, 2009.