What is a Tertiary septic system?
The term 'tertiary' refers to a three-stage treatment process. Conventional septic systems usually are a pre-cast
concrete septic tank connected to a leaching bed via distribution pipe and involve a two-stage treatment process.
The initial treatment occurs within the septic tank where solids are separated by gravity and settle to the bottom
while lighter oils and greases rise to the top. Anaerobic bacteria in the tank decompose or 'break-down' solids and
eventually the liquefied solid matters are allowed to pass through to the leaching bed area. Once the liquid sludge or
'effluent' enters the distribution pipe, perforations in the pipe gradually release the effluent into the soil where it
is subjected to further treatment either physically, chemically or biologically.
The third stage (or tertiary stage)
introduces aerobic bacterial action (oxygen) after the septic tank stage but before the effluent is allowed to seep
into the soil. Effluent from the septic tank is aerated (oxygen is added) allowing aerobic bacteria to further break
down the effluent. This added bacterial action usually results in a cleaner, clearer and odourless effluent. As a
result, the area needed to discharge effluent into the surrounding soil is decreased allowing these systems to be
placed in areas where a conventional system would not fit. Also, because of the quality of effluent produced from these
systems, tertiary septic systems can be placed in areas where bedrock and groundwater exist near the surface or on
native soils whose permeability would not adequately accept conventional septic effluent. Check out
www.waterloo-biofilter.com
and
www.ecofloontario.com
for more information regarding tertiary septic systems or contact the Ontario Rural Wastewater Centre for assistance.
