Barnstable County PPCP Studies

Onsite Septic Systems for the Removal of Selected Micro-Constituents and Contaminants of Emerging Concern

UMass Research Team: Dave Reckhow, Varun Srinivasan, Soon-Mi Kim

The goal of the most recent portion of this study was to determine the capability of shallow soils-based onsite septic system technology to remove selected contaminants of emerging concern (CEC). In particular, we provided assistance to monitor the performance of drip dispersal technology. This employs ½ inch tubing equipped with small orifice emitters that “drip” filtered septic tank effluent to the soil along the length of the distribution tube. The pipe is usually six to ten inches below the surface. The broader distribution of effluent in small doses onto the soil interface near the plant root zone was theorized to enhance treatment for a variety of traditionally-observed contaminants such as fecal indicators, biochemical oxygen demand, total suspended solids and others.

In July 2010, seven test cells containing drip dispersal piping were constructed side-by-side at the Massachusetts Alternative Septic System Test Center (MASSTC). Each cell was 30 feet in length and five feet wide. Four emitter lines with emitters located at 24-inch intervals were laid in parallel within each cell. All test cells were underdrained to collect the wastewater as it percolated through the underlying soil. Three of the seven cells were supplied with only septic tank effluent, three cells were additionally equipped with the ability to introduce air at selected intervals, and finally, one cell was equipped with drip tubing but no supply of wastewater or air. This cell was used as a control to determine rainfall amounts potentially contributing to the dilution of compounds. The performance of these installations for removal of CECs has been assessed by annual sampling on the following dates; November 9, 2010, October 11, 2011 and July 15, 2012.

The overall PI on this project is George Heufelder of the Barnstable County Department of Public Health and Environment. The work is supported by the Massachusetts Department of Environmental Protection, Bureau of Resource Protection and The US Environmental Protection Agency, Region 1.

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