Potential Environmental Impacts Table 6-1 from the EPA Design Manual for Onsite Wastewater Treatment and Disposal Systems is provided on the following page which shows typical concentrations of key parameters for effluent from residential septic tanks. A thorough site evaluation must be conducted in order to determine the appropriate level of pretreatment prior to final onsite subsurface disposal. Septic tanks can only provide for primary levels of treatment. Thus, some type of further treatment will need to be provided for if the soil and subsurface conditions at the site are such than ground or surface water may be adversely impacted by applying typical septic tank effluent. Energy Consumption Septic tanks do not require power consumption.
Wastewater drains by gravity from the house to the tank.
Costs Costs for septic tanks depend upon a variety of factors including subsurface site conditions, location of and access to the site, and the type of tank. Aesthetic Considerations Septic tanks are buried below grade, and usually do not have significant visual impacts on the site. State and Local Acceptance Septic tanks are the most frequently used pretreatment unit for the final onsite treatment and disposal of residential wastewater. Small Flows newsletter, Volume 9, No. 3, Summer 1995, National Small Flows Clearinghouse, West Virginia University, Morgantown, West Virginia. 5. All values are for raw residential wastewater, and not effluent from septic tanks.