What options do I have with wastewater treatment?
Wastewater is the effluent from a household that comes from toilets, the kitchen sink, the laundry and all water flowing out of the bathrooms from basins, showers and baths. If a sewer system is not available for your property, then this effluent has to be treated and kept on-site. On-site wastewater systems are typically either a septic tank system or a secondary treatment system (STS), formerly called an aerobic treatment unit (ATU) in WA. In many parts of Australia an STS/ATU is called an Aerated Wastewater Treatment System (AWTS).
What is aerobic / aerated wastewater treatment?
Aerobic treatment occurs when wastewater is subject to air (oxygen) which enables particular bacteria and other microscopic organisms to survive and digest waste material. Most of the micro-organisms involved in wastewater treatment are bacteria, but fungi and protozoans are also important in digesting household wastewater. You can also find viruses and helminth worms in wastewater. An aerated wastewater treatment system (AWTS or Secondary Treatment System - STS in WA) is a tank system where various processes (both aerobic and anaerobic) occur, breaking down household wastewater into small particles and reducing nutrients, and the resulting treated effluent is then used for irrigation purposes.
What micro-organisms are used in sewage treatment? What role does bacteria play in sewage treatment?
There are many different types of micro-organisms that digest wastewater. Most of these are bacteria that can live in different conditions in the water. Some prefer low oxygen (anaerobic) while others need oxygen (aerobic) to survive. Some bacteria convert various substances from one form to another, and many have specific roles to play in changing organic compounds into simpler substances. Besides bacteria, single celled animals (protozoans) also help to digest waste material and they also eat bacteria.
What is a septic tank system?
A septic tank system comprises one or two large tanks and a disposal system. The overall capacity of the tanks is typically anywhere from 3250 to 4000 L. The primary tank (or chamber) is where gross solids are held. These are broken down by bacteria in anaerobic conditions. i.e without oxygen. As new wastewater enters the system, effluent is displaced and flows into the secondary tank or chamber. This is often called a sedimentation chamber. Again, bacteria continue to break down small waste particles in anaerobic conditions. Finally, wastewater flows into a disposal system which could be leach drains, conventional beds, special soakwells or other approved soil-based systems.
What is anaerobic treatment?
Anaerobic treatment occurs when wastewater is treated in little or no air (oxygen). Many types of bacteria can live in low oxygen conditions and they derive their energy from the waste particles in wastewater. When they digest our wastes various gases may be produced, such as methane, hydrogen sulphide, carbon dioxide and many other gaseous organic compounds.
How long does the aerobic system last for?
As long as the aerobic treatment unit is serviced and maintained, it should last indefinitely. There are many systems already twenty years old and still performing well. Pumps and blowers will eventually need replacing and the chambers need periodic pumping out to remove accumulated scum and sludge.