| System Description.
A septic tank system
uses natural processes to treat and dispose of the wastewater
generated in your home. It typically consists of a septic tank
and a drainfield, or soil absorption field. The septic tank provides
the first step in treatment. As wastewater flows into the tank,
the heavier solids settle to the bottom to form a sludge layer,
and the lighter solids, greases, and oils float to the top to
form a scum layer. The liquid wastewater (effluent) from the
tank flows into gravel-filled trenches in a typical drainfield
where it is distributed via perforated pipes and then treated
by the natural soil system. The diagram below shows the components
of a typical septic system.
System Operation.
The septic tank provides some biological treatment
of the sludge and scum layers that accumulate there. The majority
of treatment occurs in the drainfield where the effluent enters
the soil and is treated as it percolates to the groundwater.
The soil acts as a biological and physical filter to remove harmful
substances, including disease-causing bacteria and viruses, toxic
organics and other undesirable wastewater constituents remaining
in the effluent.
Outlet filters or baffles are located in the tank and are designed
to prevent the sludge and scum from flowing into the drainfield.
If the tank is not pumped regularly to remove the accumulated
solids, the tank will fill with sludge and the solids will be
washed out into the drainfield, or clog the outlet filter. If
solids reach the drainfield or clog the outlet filter, they will
quickly clog the soil and eventually lead to system failure. |
