A temporary solution to the discolored water South Pasadena residents have been experiencing in their homes since January may be implemented as soon as the first week of July, South Pasadena officials said earlier this week. Known as breakpoint chlorination, the treatment works by injecting enough chlorine into a water supply to make chlorine the supply’s primary disinfectant. Public Works staff plan to apply the treatment to Metropolitan Water District (MWD) surface water they believe is causing the discoloration.
The city began to use MWD water after the state passed a new regulation in late 2017 lowering the acceptable amount of the industrial solvent 1,2,3–Trichloropropane (1,2,3–TCP) in drinking water to 5 parts per trillion. South Pasadena’s ground water supply exceeds that maximum contaminant level (MCL). To meet the new MCL set by that regulation, South Pasadena introduced a large amount of MWD water into its system. The MWD uses chloramine, instead of chlorine, as its primary disinfectant.
Public Works Department staff believe the high level of chloramine in the MWD water supply can be corrosive when interacting with galvanized pipes. That corrosion, according to staff, is causing iron to discolor residents’ water.
Breakpoint chlorination will induce a chemical reaction in the MWD water that will rid it of chloramine. The city expects the treatment, which will take place at Wilson Reservoir, to cost around $20,000.
“The City still has to give a monitoring and operation plan to the state Department of Drinking Water (DDW),” John Pope, South Pasadena’s public information officer, said Wednesday. “Once that is delivered and we get the green light from the state, staff will implement the solution.”
The project will be performed by city staff under the direction of the DDW, Pope said. Results may be slightly delayed, he added.
“There may be some lag time (between the injection of chlorine into the water and residents experiencing clean water),” Pope said. “It can take a little while for pipes to adjust. It took a bit of time for brown water to appear in homes after MWD water was introduced, so we are expecting the same to happen in reverse.”
Under the direction of Kristine Courdy, Public Works is also making progress on a temporary wellhead treatment solution to be put in place in mid-August that would eliminate the city’s need for MWD water altogether. The plan calls for four wellhead filtration systems, 8-9 foot tall tanks that would remove 1,2,3–TCP from the city’s ground water, to be installed at Wilson Reservoir. Four is the minimum number of tanks needed to filtrate the city’s water supply.
Sometime in December, four more tanks would be installed to allow for maintenance and service long-term.
The cost of the temporary wellhead treatment option will be discussed at the June 20 Council meeting.