4 Types Of Home Sewage Treatment Systems Explained

in Stage
See how the old-fashioned septic tank compares with mechanically aerated systems, sand filters and the wet composting toilet.

They all treat sewage and do greywater recycling in the backyard...yet they are all so different. Understand 4 different ways the effluent society comes clean

Tanks Septic

Septic tanks have several chambers, where 3 main processes take place:

Stage 1: The heavier, solid particles settle to the bottom of the tank forming a sludge layer

Stage 2: Lighter materials, such as fat, grease and paper, float to the surface forming a scum layer

Stage 3: Some of the solids are broken down by anaerobic bacteria. However, the sludge does accumulate and needs to be pumped out periodically.

The treated sewage is then disposed of in trenches, which can fail when excessive amounts of solids escape. Some councils no longer allow septic tanks due to their high failure rate. They do not do grey water recycling.

The Biolytix BioPod

The BioPod is a wet composting toilet - an ecosystem in a tank. It is engineered to treat wastewater and for greywater recycling in the same way that nature does, and for nature to do the work.

Stage 1: As the wastewater enters the tank, the solids and liquids are separated from each other immediately. The macro-organisms in the tank, such as worms, quickly move in and convert the solid waste into humus.

Stage 2: The organisms live in this humus, naturally aerating it as they create kilometres of meandering tunnels. The wastewater trickles through these tunnels, and is cleansed in the process.

Stage 3: The effluent is now treated. A tiny fish tank air pump keeps the treated water at the bottom of the tank aerated (this uses 90% less energy than mechanically aerated systems).

Aerated Waste Water Treatment Systems (AWTS)

Also known as aerated septic tanks.

Stage 1: The Septic Stage - This is identical to that which occurs in a septic tank (described above) and consequently shares many of the inherent problems

Stage 2: Mechanically Aerated Treatment - a large aerator pumps air into the wastewater up to 16 hours per day. This is to keep the aerobic bacteria alive so that it can break down the solids. It uses up to 10kWh per day.

Stage 3: Final settlement: the waste water settles prior to being pumped for irrigation

The pump/s in an AWTS require a continuous power supply. The complexity and wear and tear of the system (multiple pumps, multiple chambers/tanks/filters) makes it more vulnerable.

Sand filters

Sandfilters generally have two main treatment stages:

Stage 1: is a septic system and consequently shares the same septic problems.

Stage 2: The wastewater then flows to a large 30 square metre sandfilter in the garden. Here it is treated by a microbiological culture.
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Jenny Allen has 1 articles online

This article is written b y Jenny Allen, author of the coffee table book Smart Permaculture Design has appeared on many gardening shows, including ABC Gardening Australia.

Jenny also works for Biolytix Water, for more information please visit: http://www.biolytix.com.au

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4 Types Of Home Sewage Treatment Systems Explained

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This article was published on 2010/10/22