When choosing which type of system to use, certain factors must be considered so that the
system selected will best serve the individual's needs:
- Type of soil on the property
- Topography (lay of the land)
- Lot size; available property for the installation
- Surrounding features - wells (both yours and the neighbors'), water lines,
property lines, driveways, etc.
Aerobic System: An aeration unit also works independent of soil absorption. This type of
system uses aerobic (with oxygen) bacteria to break down the solids rather than the anaerobic-
type bacteria found in septic tanks. Specifically approved units are allowed to discharge to
farm tiles, river, etc.
Buried Sand Filter: A buried sand filter is composed of alternate layers of rock, pea gravel,
and filter media (a type of sand) which biologically and physically filter the septic tank
discharge. The filtered liquid can then be discharged to a suitable site. This system does not
use the soil to absorb the discharge from the tank.
Recirculating Sand Filter: A recirculating sand filter consists of an open filter bed and a
pumping chamber following the septic tank. The liquid from the pumping tank is recirculated
several times before discharging to a suitable location.
Sub-Surface Seepage System: The most common private sewage system installed
nationwide is the septic tank followed by a subsurface seepage system. Since this system
depends on the absorption properties of the soil, it must be installed in soils which drain well
and are not affected by a seasonal high water table. To determine the suitability of the soil, a
percolation test must be conducted prior to installing the system. Once the test results are
known, it can be determined if a field will function properly and if so, how much field is
necessary. If your percolation tests do not pass, then one of the following types of alternative
systems must be considered.
Waste Stabilation Pond / Lagoon: An oxidation pond or lagoon operates naturally using
sunlight and wind movement to aerobically decompose sewage. The tight clay soils which
prevent seepage fields from working properly are needed for this system to help retain the
water long enough for good treatment. These ponds also discharge to the ground surface.
If you have any questions concerning this guide or if you wish to apply for a permit to install
one of the above private sewage disposal systems, please feel free to contact:
Marion County Health Department
Division of Environmental Health
118 Cross Creek Boulevard
Salem, Illinois 62881