Oct 27 2008
Background
Grease Traps
Septic Tank
Bacteria Problems
Absorption Trenches
Hints for Using a Septic System
Background
Septic sewerage systems are a biological treatment system for treating waste that utilises the useful bacteria present in the waste itself. The bacteria break the waste down into simpler chemical substances that are readily and safely recycled into the environment. A complete septic sewage system consists of three stages: a grease trap, the septic system and an absorption trench.
Grease Traps
Grease traps are the first stage of an effective septic system. The grease trap captures insoluble greases and fats that are difficult for the septic system to break down. Modern detergents however can keep the fats in suspension causing them to bypass the grease trap and deposit themselves further down the system.
Septic Tank
The septic tank is simply a large concrete or steel tank containing water. Wastewater flows into the tank where low density solids float forming a scum layer and heavy solids drop to the bottom to form a sludge layer. The middle layer is a relatively clear water layer containing, bacteria and chemicals like nitrogen and phosphorous.
As the bacteria breaks down the waste, unpleasant gases are produced. These gases are vented through a vent pipe.
When the septic system is working properly, odours are minimal. Problems can occur with septic systems producing noxious odours or becoming blocked. When either of these occur it is an indication that the septic system is not working as it should. Septic systems are designed around a particular amount of wastewater throughput. Exceeding this quantity of wastewater can cause solids to build up faster than they can be processed. Other problems can be caused by the bacteria not working or working at a low efficiency.
Eventually the accumulation of solid waste in septic system will need to be pumped out. The frequency of pumping will depend on the size of the system and the amount of use it receives but a general rule of thumb is that the system will require pumping every four years. When the system is pumped, the lid of the septic system will need removing and crust of fatty material will need to be removed as well.
Bacteria Problems
Bacteria in septics like an even state with few demand peaks and troughs. The system can be overloaded by excessive amounts of input wastewater or the bacteria can be poisoned by some disinfectants, harsh chemicals and antibiotics. At the other extreme, underuse can also disturb the proper function of a septic system. If a septic system has little or no input wastewater the lack of 'food' for the bacteria can cause it to die and the system will fail.
Absorption Trenches
Absorption trenches or rubble drains take water away from the septic tank. They allow the final bacterial treatment of the wastewater and allow the water to soak away into the surrounding soil. If the absorption trench doesn't work properly the surrounding area may become wet, smelly and unhealthy. A common problem with absorption drains is the build up of grease and fats not removed by the grease trap. These block the trench walls and floor while sealing the surrounding earth, causing a restriction to drainage.
Hints for Using a Septic System
When using a septic sewage system it can be kept performing well by following a few guidelines. These hints include:
- Never use the toilet to dispose of insoluble items like disposable nappies or sanitary pads
- Don't pour fat or grease down the sink or is a sink mounted waste disposal unit to deal with fatty or greasy food scraps
- Avoid the use of disinfectants, bactericides, bleaches, acids, caustics, solvents or other harsh chemicals
- Use septic safe products and biodegradable detergents
- If the septic becomes smelly try boosting the bacteria by 'feeding' it by pouring 20kg of dog biscuits into the septic
- Clean the grease trap regularly
Source: AZoCleantech