Protecting drinking water supplies from harmful storm water runoff
The power of storm water is apparent when it damages infrastructure and causes destructive flooding. However, it is easy to overlook the way storm water can negatively impact drinking water. When storm water enters a drinking water supply, it can introduce a number of contaminants that may cause severe health problems for those who consume the water. SWS Associate Editor Michael Meyer asked Jon Sigona, president of Perfect Water Technologies, a water filtration and reverse osmosis filter supply company, about how storm water adversely affects drinking water and what can be done to treat that water.
Michael Meyer: In general, how does storm water affect drinking water?
Jon Sigona: Approximately 42 million people in rural and suburban areas use their own private water supplies. Typically, shallow groundwater wells are not covered by the Safe Drinking Water Act and are rarely treated or monitored. Given this fact, there can be cross-contamination from runoff and surface water, as well as contamination by nitrates and pathogens from septic systems.
Meyer: What contaminants are typically found in drinking water that has been altered by storm water?
Sigona: According to a nationwide study, 77 of 127 priority pollutants tested were detected in urban runoff. Principal contaminants found include heavy metals, toxic chemicals, organic compounds, pesticides, herbicides, pathogens, nutrients, sediments, salts and other deicing compounds. Urban runoff is commonly collected in storm sewers and discharged to waterways untreated so that contaminants carried by the storm water are discharged to surface water bodies, which are used as sources of drinking water. In addition, approximately 20% of the U.S. population is served by combined sewer systems (for both sanitary waste and storm water), which, during heavy storm events, allow contaminants from sanitary sewage to discharge directly into waterways that are untreated.
Many of the contaminants referenced above are carcinogenic, while others can lead to reproductive, developmental or other serious health issues if exposed over the long term. Pathogens also can cause illness and can sometimes be fatal, even from just short-term exposure.
Meyer: How can this drinking water be treated?
Sigona: Storm water intrusion into private wells is best addressed by frequent monitoring and testing to identify specific contaminants and quantities present. Based on test results, a combination of commercially available technologies can be applied at the point of entrance with the addition of reverse osmosis systems at drinking water points of use. This can reduce found contaminants to below acceptable or even detectable levels.
Use of cisterns and rainwater harvesting to dilute incoming storm water-compromised sources is an attractive alternative in areas with significant precipitation. Biological filtration may gain favor in very remote surface water applications where reverse contamination into surface water feeds or groundwater is impossible.
Meyer: Are there any measures that can be taken to prevent this contamination?
Sigona: Storm water contamination can be reduced by regulating urban and agricultural storm water drainage and injection wells.
Water retention areas such as greenbelts or rain gardens can be enormously useful in reducing storm water runoff, provided they are designed to filter the water into the ground over a couple of days—otherwise they may produce nuisance odors or dangerous insects.
Additionally, green areas in urban settings can be utilized as a natural filtration mechanism and limit the amount of unbroken, impervious surfaces. Lastly, good citizenship and education to ensure chemicals are handled and disposed of responsibly can have lasting effects.