Employing large regional sewage systems in rural areas and smaller communities can lead to the loss of open space and can create local environmental concerns. Often, the conventional septic tank/leach field has been the only option. Below are some alternative systems that can work for residential projects in these areas.
- Septic Tank & Mound System: Effluent is pumped into a gravel bed or trenches on top of a bed of sand. Sandy soil carefully placed above the plowed ground surface treats the effluent before it moves into the natural soil. The system extends on-site system use in areas with high groundwater, high bedrock, or tighter clay soils. This type of system requires regular inspection of the pumps and controls and flushing of the distribution network.
- Evaporation & Absorption Bed: Effluent from a septic tank or aerobic tank flows into gravel trenches or chambers in a mound of sandy soil. Less permeable soil placed at the surface of the mound helps shed rain from the system. Trees that grow around the system and plants on top of the system pull liquid from the sand and transpire the water into the air. Some effluent may seep into the soil. This system can only be considered in a climate where evaporation consistently exceeds rainfall.
- Sand Filters: Open or buried beds of sand may receive single or repeated applications of effluent, which passes through the media and drains from the gravel and pipe network below the filter. Effluent may be discharged to the environment directly or into a soil absorption or land treatment system. Disinfection often precedes discharge into a stream or land irrigation. Certain types of filters can significantly reduce nitrogen and may be used in areas where soil absorption is not possible. This system requires inspection and periodic maintenance and surface discharge requires management.
This is just a sample of alternatives to conventional sewer or septic systems. For more information on these and other alternative systems, contact the National Small Flows Clearinghouse at (800) 624-8301.