There
are many different types of bacteria
that occur naturally in a septic system.
Those present in the septic tank help
to process waste and organic matter.
This is the first stage of waste treatment.
Liquid that has been partially treated
in the tank is called effluent. Effluent
entering the drain field is then treated
while passing through the biomat.
The
biomat is a naturally occurring tar-like
substance that forms on the bottoms
and sides of the drain field trenches.
It is made up of living anaerobic
(existing without oxygen) bacteria,
which feed on organic matter in the
effluent. As the biomat matures it
grows thicker, slowing down the flow
of effluent to the surrounding soil.
As the effluent passes through the
biomat pathogenic organisms and viruses
are removed. On the outside of the
trench, beyond the biomat where the
soil is not saturated, are living
colonies of aerobic (existing with
oxygen) bacteria. These aerobic bacteria
colonies feed on the excess biomat
as it matures, they keep it from becoming
so thick that wastewater will no longer
pass through.
When soil floods aerobic
bacteria colonies will die off and
no longer keep the biomat in check.
The biomat will grow too thick and
drainage will stop. Further, as these
colonies die off they leave behind
sulfides, which over time will clog
soil passages stopping the flow of
water.
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