Personal Care Products, Pharmaceuticals, and Hormones Move from Septic Systems to Local Groundwater Completed

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Septic systems are common in areas lacking connection to larger scale municipal sewage treatment such as a sewer. Septic systems consist of holding tank (usually below ground) where raw sewage collects and separates into a sludge (solid) and liquid effluent. The liquid effluent either leaches directly into the surrounding substrate (soil) or goes into a leach field for final treatment by the soil. The liquid effluent from septic systems ultimately discharges to groundwater. Approximately 26 million homes (one-fourth of all homes) in America are served by septic systems and some are connected hydrologically to drinking water sources or lake, stream, or estuarine environments.

Although the major concern with septic systems in the regions studied has been the release of nitrogen to adjacent groundwater and surface water, scientists questioned if other contaminants may also be transported from septic systems. U.S. Geological Survey (USGS) scientists conducted a study at two septic networks in NE and NY during one sampling round in 2011 investigating contaminants in groundwater samples collected downgradient of septic systems. "Downgradient" is the term used for how groundwater flows under the ground, and is a similar term to "downstream" when describing surface water.

In the NE septic network, numerous prescription pharmaceuticals and a floor cleaner were found in the groundwater samples collected downgradient of a septic system from an extended health care facility. In the NY, septic network hormones; detergent degradation products; fragrances; insect repellent; sunscreen additives; a floor cleaner; and pharmaceuticals were found in samples collected downgradient of many small septic systems used seasonally on a densely populated (5 dwellings per acre) portion of a Fire Island beach.

It is not unexpected that pharmaceuticals and other personal care products are present in septic systems, because their use is associated with everyday household activities. Results from this study indicate that contaminants are moving into shallow groundwater near the septic systems. Major factors controlling the types of chemicals moving into the local groundwater include differences in the human populations served by the septic systems, site conditions such as soil permeability, and the properties of the chemicals which dictate if they will adsorb to sediment particles or travel with water. This study found that monitoring for contaminants, such as pharmaceuticals, hormones, and personal care products in areas experiencing high nitrogen levels was important to understanding the breadth of contaminants present in groundwater resources.

The introduction of these contaminants to groundwater systems from septic systems is of concern due to the possibility of downgradient transport to adjacent drinking water supplies, However, many of the contaminants measured don't have established human health guidelines and the concentrations are lower than therapeutic doses in the instance of the pharmaceuticals. The primary concern is for the introduction of the contaminants to surface waters through groundwater inputs which may result in aquatic animal exposure.

This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), the USGS Cooperative Water program and the National Park Service.