Volatile Organic Compounds in Small Community Wastewater Disposal Systems Using Soil Absorption

The objectives of this study were:

1. To complete a literature review of the potential sources and presence of VOCs in on-site wastewater disposal,
2. To identify VOCs in the septic tank effluent, septage and the groundwater at sites using septic tank soil absorption systems,
3. To estimate potential loadings of VOCs to the environment from small community septic tank soil absorption systems.

In the first phase of this study, the concentrations of VOCs were quantified for effluent from six septic tanks from septic tank soil absorption systems (STSAS). Five of the systems investigated were small community STSAS ranging in age up to eight years. The sixth system analyzed was a mobile home park. Three samples were collected over a four month period from the dosing chamber or siphon chamber at each site during phase 1.

The second phase of the investigation involved the installation of groundwater monitoring wells at four of the small community sites. The assumption was that if VOCs were present in the septic tank effluent as had been demonstrated, VOCs could migrate and be discharged to groundwater. In addition, four STE samples were collected at the six sites from phase 1. During phase 2, four groundwater samples were also collected from four of the sites. Septage samples were also collected at two of the small community sites which used a central septic tank.