WSSC Safely Adjusts Water Treatment to Reduce Discolored Water in System

Lower Levels of Organic Material in Potomac River Allow for Increase in Chlorine

| News Release



Discolored Water Complaints Dropping: WSSC Cautions Customers
It Will Take Weeks to Fully Resolve

LAUREL, Md. – September 18, 2017: With levels of naturally-occurring organic materials (decayed leaves, river grasses, trees, vegetation) in the Potomac River continuing to decrease, WSSC safely increased chlorine levels Friday morning (9/15) to reduce discolored water caused by an increase in manganese in the finished water. The recent adjustment, coupled with a slight increase in chlorine in early September, brings the chlorine level at WSSC’s Potomac Water Filtration Plant back to where it was in early August.

“I thank our customers for their understanding as we patiently waited for river conditions to change so we could safely increase chlorine levels to address the discoloration,” said WSSC General Manager and CEO Carla A. Reid. “Our number one priority is ensuring public health. In lowering chlorine levels in early August, we chose public safety over this temporary aesthetic issue.”

Following severe weather and storms in July and early August, WSSC water quality experts noticed an increase in organic material and manganese in the river entering WSSC’s Potomac Plant. During the treatment process, WSSC uses chlorine to safely disinfect the water and control manganese levels to make the water clear. On August 8, WSSC lowered chlorine levels to avoid increased levels of a U.S. Environmental Protection Agency (EPA) class of regulated drinking water contaminants known as disinfection byproducts, which are formed when chlorine reacts with organic materials. The lower level of chlorine kept WSSC water below the EPA disinfection byproducts limit but allowed more manganese into finished water – causing the discoloration.

“All water testing results confirm that this is the right time to make this treatment change,” said WSSC’s Director of Production J.C. Langley. “We will closely monitor this situation and continuously test our water to ensure we meet all EPA Safe Drinking Water Act standards – as we have always done for 99 years.”

WSSC increased monitoring and testing of water in the Potomac River and throughout the distribution system since August 8. The following test results support WSSC’s recent treatment changes:

  • Levels of organic material in the Potomac River have decreased
  • Levels of disinfection byproducts in WSSC’s system are well below EPA limits
  • Severe rain/weather events have decreased

Manganese is not a health hazard and is not regulated by the EPA as a drinking water contaminant. EPA considers manganese a secondary contaminant for aesthetic reasons only. The EPA level for manganese, for aesthetic purposes, is 0.05 mg/l. WSSC’s current manganese levels are around 0.01 mg/l to 0.03 mg/l. Although below EPA’s aesthetic level, it can still cause discoloration. With the recent increase in chlorine, WSSC expects manganese levels in the finished water to decrease.

Since August 8, WSSC has received more than 2,200 discolored water complaints from customers in Montgomery and Prince George’s counties. While the number is a sharp increase from a typical month, calls to WSSC have been decreasing over the last two weeks. WSSC typically receives 200 to 300 discolored water complaints each month, primarily caused by broken water mains or other rapid changes to water flow in the distribution system, including when water is used to fight fires.

Customers should continue to report discolored water to WSSC’s Emergency Call Center, which is staffed 24 hours a day. It is important to note some discoloration may continue for several weeks as manganese works its way through WSSC’s extensive water distribution system.

Customer Information:

WSSC’s other treatment plant draws water from two reservoirs along the Patuxent River, which is unaffected by the changes in the Potomac River. Customers receiving their water from the Patuxent Water Filtration Plant are not experiencing this discolored water issue. This includes areas in both Montgomery and Prince George’s counties in/around Laurel.

For more information on discolored water visit our website

For 100 years, WSSC has proudly served the citizens of Prince George’s and Montgomery counties – providing drinking water that has always met strict Safe Drinking Water Act standards and protecting the environment through vital water resource recovery services. Our vision is to be THE world-class water utility, where excellent products and services are always on tap.


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