Tuesday, 7 July 2009

Septic Tanks versus Sewage Treatment Plants

Septic Tanks used to be the only method for sewage treatment in rural areas. Thankfully, things have changed.

Differences between septic tanks and sewage treatment plants
Septic tanks do not really treat the sewage but split it into liquid effluent and solids, which are removed once a year by a tanker. The traditional septic tanks as shown above, were built in brick, block or concrete. They had a large surface area in contact with the air, so some aerobic digestion took place, as in a sewage treatment plant. However, the modern fibreglass 'onion' shaped septic tanks have very little surface area interface between the air and the effluent and the effluent which comes out is often more polluting than that which goes in. The liquid part of the septic tank effluent is highly polluting and is NOT allowed to be discharged to any watercourse, or find its way into a watercourse as it strips the oxygen out of the water and kills all life in it.
Septic tank effluent also kills all earthworms, beetles, etc. which live in or near the soil of the soakaway.
Because of these factors, septic tanks are generally no longer an ecologically acceptable solution for sewage treatment in rural areas.

Vortex 6 person sewage treatment plant
A sewage treatment plant treats sewage by providing an environment in which aerobic (oxygen-breathing) bacteria are cultured. These bacteria digest the biological matter in the sewage. Because the bacteria are aerobic, they need free access to oxygen, usually via an air pump or compressor.
Most sewage treatment plants still settle out the solids first in a primary settlement tank for regular emptying by tanker, and simply treat the organic matter in the liquid part of the sewage. FilterPod sewage treatment plants remove over 97% of all the pollutants in sewage effluent whilst requiring no electricity at all. They also have a 2 year emptying interval, unlike the annual emptying required by a septic tank.

The main differences are shown in the table below:-

                                                  Septic Tank                                                FilterPod
Removes the Pollutants                NO                                                             YES
Noxious smells                            YES                                                             NO
Regular Emptying                       YES                                                              NO
Pollution Risk to Water               YES                                                             NO
Kills Earthworms and soil fauna YES                                                             NO
Requires Electricity                      NO                                                              NO

Stricter guidelines on the design of soakaways will mean that even fewer successful septic tank treatment installations are likely in the future.

Think very carefully before installing a septic tank as future legislation could mean that the septic effluent is no longer clean enough to be discharged, even to ground.

If you have an existing septic tank and would like to upgrade it to a full sewage treatment plant which can discharge into a watercourse, then a FilterPod sewage treatment plant is the ideal solution. Please click on:-
Septic Tank Conversion