From email from the Metropolitan Wastewater Reclamation District (Steve Frank):
As of August 18, the Metro Wastewater Reclamation District stopped using gaseous chlorine brought to its treatment plant via rail car as its disinfecting agent. The District now uses a much safer chemical, sodium hypochlorite, instead.
Sodium hypochlorite is added to the treated water at the Robert W. Hite Treatment Facility (RWHTF) to disinfect it before it is discharged to the South Platte River. Sodium bisulfite is added after the sodium hypochlorite to remove residual chlorine to make the treated water friendlier to fish.
“We are glad to have transitioned away from the gaseous chlorine,” said Director of Operations and Maintenance Steve Rogowski.
“The sodium hypochlorite we now use is much safer, both for our employees and for people who live and work near our treatment facility.”
The District used gaseous chlorine for disinfection from the time the facility was built more than 45 years ago until recently.
From October 1988 to July 2009, liquid sulfur dioxide was used to remove residual chlorine from the effluent, but sodium bisulfite took its place in 2009.
The Metro District is the largest wastewater treatment agency in the Rocky Mountain West. The District’s Robert W. Hite Treatment Facility at 64th and York treats about 140 million gallons of wastewater a day. The service area includes nearly 1.7 million people and encompasses approximately 715 square miles, including Denver, Arvada, Aurora, Brighton, Lakewood, Wheat Ridge, Thornton, and part of Westminster, together with about 40 sanitation and water and sanitation districts in the metropolitan Denver area.
While on their website I ran into their page for the shiny new wastewater treatment plant they’re building on the South Platte River near Brighton. Say hello to the Northern Treatment Plant.
More wastewater coverage here.