The safety of drinking water is one of the most important public health issues in the United States and any society. For most of the 20th century efforts to achieve safety and to meet drinking water quality regulations have focus on the water filtration and treatment. It was felt that with reliable treatment, any deterioration in source water quality could be overcome. Unfortunately, this has proven not to be true. Variations in water quality have undermined the ability of even advanced water treatment plants to consistently and effectively control water quality and treatment and provide safe drinking water. Additionally, some unrecognized contaminants in trace amounts, may pass through the treatment plant. Thus a need for source water quality protection as an additional “barrier” to contamination and an enhancement to water quality.
The rain and snow melt moves through the watershed into streams and rivers and picks up contaminants along the way. As the water travels over the land surface or through the ground on its way to the rivers, it dissolves naturally occurring minerals and vegetation (organic matter) as part of the natural process. The water can also can pick up pesticides, herbicides and other synthetic/volatile organic chemicals from agricultural land, golf courses, or residential and urban lands.
The Washington Suburban Sanitary Commission (WSSC) the water company for Montgomery and Prince Georges Counties in Maryland, obtain their raw water from the Patuxent and Potomac rivers and then treat the water in their Patuxent Water Filtration Plant and Potomac Water Filtration Plant. Potential sources of contamination in the Patuxent Reservoirs watershed include transportation, petroleum pipelines, agriculture, onsite septic systems, developed areas, and minor permitted discharges. Phosphorus runoff from urban/suburban and agricultural land uses is reported by the WSSC to be the primary contaminant of concern for this watershed. Potential sources of contamination in the Potomac River watershed also include runoff from urban and agricultural land uses, and potential spills from highways and petroleum pipelines. Contaminants of particular concern include natural organic matter and disinfection byproduct (DBP) precursors, pathogenic microorganisms (Cryptosporidium, Giardia, fecal coliform), taste and odor-causing compounds, ammonia, sediment/turbidity and algae.
Water drawn from protected areas of the Potomac and Patuxent rivers is treated in the water filtration plants and is continuously and thoroughly tested, before being sent to homes and businesses through the 5,600 miles of distribution pipes in the WSSC system. Continuous monitoring allows WSSC to respond to changing water conditions to maintain water quality. In the filtration plants water is treated first with coagulation and flocculation (to make small particles and microorganisms in the raw source water adhere to each other); sedimentation (to remove most of those particles and microorganisms); filtration (to remove nearly all the remaining particles and microorganisms); chlorination (for disinfection); lime addition (to minimize the potential for dissolving lead solder used in older homes and laterals lines); and fluoridation. Orthophosphate is also added to help minimize lead corrosion and copper pipe pinhole leaks in home plumbing by creating a protective film in pipes.
Cryptosporidium is a microbial pathogen found in surface water throughout the U.S. Cryptosporidium must be ingested to cause disease, and it may be spread through means other than drinking water. Ingestion of Cryptosporidium may cause cryptosporidiosis, an abdominal infection and may even cause death in the vulnerable. The is just completing a 2 year monitoring program for Cryptosporidium as required by the EPA. Though, WSSC has not reported a problem with Cryptosporidium, they have installed UV disinfection at the Potomac Plant to provide an extra barrier of protection against Cryptosporidium.
To ensure that tap water is safe to drink, EPA prescribes regulations, which limit the amount of certain contaminants in water that public water systems provide. The Safe Drinking Water Act regulates almost 90 substance. The quality of the water being produced at WSSC is excellent. It meets or exceeds all United States Environmental Protection Agency (US EPA) standards and requirements. The water quality report release at the end of 2016 covers the sampling done during calendar year 2015. There were no violations of the U.S. EPA’s Safe Drinking Water Act for the and you can view the report at this link.