Home Sewage Treatment
A Home Sewage Treatment Plant (HSTP) is similar to a Municipal Sewage Treatment Works, except that it is designed to fit in your own back yard. It uses the same proven treatment methods as the larger system to treat all the wastewater that flows from the toilets, baths and sinks. These include coarse filtration, pre-treatment, aeration, settling and disinfection. However, all the water that you use in your house is available to you to recycle and reuse, after it is treated, to irrigate your garden. Most people would not realise that a home has its own HSTP because it is just like living in a home that has mains or Municipal sewer connected and gives you all of the advantages that this service provides.
A septic tank (system) is a method of wastewater treatment that utilises only anaerobic bacteria (bacteria not requiring oxygen to live). The tank has no aeration and treats the wastewater to about 20% of the amount needed to render it harmless to the environment. The remaining 80% of the treatment is provided in the soil. Leach drains or drain lines are laid out into the property and the partially treated water enters these lines and percolates down through the soil, where aerobic bacteria (Bacteria requiring oxygen to live) complete the treatment.
Originally designed to treat only black-water (sewage) using small flush toilet cisterns and narrow throat toilet bowls. This enabled toilets to be brought inside the home but it did not provide treatment to all the sullage (grey) water from the shower, bath, sink, washing machine or dishwasher. This is because it used the treatment principal of low hydraulic loads and high organic loads, giving the slow working anaerobic bacteria a longer time to do their work. The need to treat “all waste” i.e. Black water (sewage) from the toilets and grey-water (sullage) from the sinks, bath, shower etc. causes the basic system to be overloaded with a much higher flow of water.
The basic treatment principal of low hydraulic flows and high organic loading is compromised so the all-waste septic became a high hydraulic flow and (by dilution) a low organic load causing the treatment process to fail. Insufficient time is allowed to the anaerobic bacteria and the leach drains become blocked as solids were flushed out blocking the pores of the soil and stopping the vital second part of the treatment. To try to remedy this failure leach drain areas were expanded and large sand filters were built in the ground to try and obtain a high quality effluent that did not affect the environment.
Septic tanks are vulnerable to poor soil conditions (clay, sand etc.) high water table, clogging of the drain lines, damage to the drain lines by vehicles, animals, trees etc. and neglect by failure to regularly (at least every 3 years, but preferably every year) pumping out the sludge and solids from the tank.
For the sake of the environment, “best practice” is always the default setting. This means that if there is a choice of actions that we can take, we should always choose the one that is best for the environment. In almost all situations the best choice for the environment will be a Secondary Wastewater Treatment System, as it guarantees to purify all the waste discharges in the tank, before it is discharged to the environment (see What is a Septic Tank?).
The currently available Secondary Wastewater Treatment System s purify the water to such a high level that will not cause environmental damage, will not be a danger to humans or animals and will actively assist the environment by recycling all of the water we use in the house to be used again in our gardens. You cannot install a septic tank system in a water catchment area or coastal areas where the effluent can get into estuaries, creeks and rivers and destroy or pollute aquatic life. Many coastal areas have aquaculture or shellfish harvesting, and these have in the past, been rendered unsafe for human consumption by septic tank effluent contaminating the waters. Small blocks of land may not have enough area available after the house, garage, pool, tennis court, paths and driveways are constructed, for the leach drain area necessary for a septic tank system. Even on a large farm, installing a Secondary Wastewater Treatment System will ensure the aquifers, which may be used for stock or drinking and cooking water in the farmhouse, are not polluted by untreated septic effluent reaching them.
A holiday “shack” rather than a holiday “home” may be a suitable site to install a septic system, as there will only be occasional occupancy, probably mains water will not be connected and mains power may also not be available. Premises such as remote Country Fire Authority or Rural Fire Brigade depots which will only have a toilet and hand washing facilities and are not used regularly except perhaps on training weekends, are also likely sites for a septic tank system. Any area where the local Municipality demands that “all waste be treated” should only install a Secondary Wastewater Treatment System due to the breaching of the treatment principals of an All-Waste Septic Tank System in such an application.
An aerobic system is one in which air is used in the operation of the system. It is therefore another name used for a Secondary Wastewater Treatment System.
An activated sludge system is a form of secondary treatment that is used almost exclusively in Municipal or Commercial Sewage treatment systems because of its complex management problems, necessitating full time operation and management of various processes by positive human and mechanical intervention. It is a process for treating sewage and industrial wastewaters using air and a biological floc composed of bacteria and protozoans.
Complex mathematical models are used to design the volume of inputs, the formation of the sludge, removal (wasting) of sludge, the maintenance of a healthy bacteria population and eradication of harmful bacteria such as filamentous bacterium. It is not a system that can be easily scaled down and successfully operated in a domestic situation.
A worm farm, when used in this form (distinct from “worm farms” sold by hardware stores) is a method of sewage treatment that is carried out by the action of worms that live in the sewage treatment plant. The plant is seeded with worms on commissioning and by their action in eating the food sources provided to them, burrowing through the organic matter, produce castings of partially treated matter. Like all aerobic systems, they rely on living organisms to produce the treatment process so they are equally susceptible to mistreatment by overuse of aggressive cleaning compounds etc.
The homeowner is required to clean any sediment from inside the distribution pit, wearing protective gloves and bury 200mm below ground. Because the treatment method only partly removes the pollutants, the water pumped from the system must be discharged at least 200mm below ground in a trench system (Victorian EPA Requirement), identical to the requirements throughout Australia for Septic Tank Systems. Usually they will service only one toilet and may be used where mains water or electricity are not available.
A sand filter is an additional treatment process fitted to a Septic Tank outlet to process the partially treated effluent from the Septic Tank. Because the All-Waste Septic Tank (see What is a Septic Tank?) is incapable of reducing the pollution level in the sewage and sullage (influent) that discharges into it from the home, to a level that is safe to humans and the environment, a sand filter is constructed behind the septic tank to receive all the still heavily polluted water (effluent). It usually consists of up to 20 cubic metres of the correct type and grade of sand, which is placed in an excavation, usually sealed by an impervious plastic liner, that may be 2 metres wide, 10 metres long and 1 metre deep.
The effluent is fed into slotted plastic pipes laid flat in the top sand of the filter, where it percolates down through the sand media and is collected by a slotted pipe set in the base sand. It then either flows into a pump-out chamber or gravitates into absorption lines. Aerobic bacteria proliferate in the open, air filled lattice of the sand media and extract from the water as it passes, their nutrient food, which is the polluting matter. The correct grading and placement of the sand, placement of the distribution and under-drains etc. can greatly affect the successful operation and operating life of the Septic Tank Sand Filter System. Because the sand acts as a mechanical filter for non-treatable matter, the septic tank must be pumped regularly to ensure the sand media does not become blocked by solids flushed out of the septic tank.
The sand media cannot be backwashed or cleaned and must be removed and replaced by fresh sand at the end of the life of the sand media. In poorly designed or constructed systems, failure can occur in as little as 3 years or less. Effluent from the system can be used in the same way as effluent from HSTP. Annual maintenance costs are usually considerably less than a HSTP. However, sand replacement costs when they inevitably occur, usually cost approximately as much as the installation cost of the complete system some 9 or 10 years before.
The need to dig out the sand with a machine, load it into trucks, remove it to a noxious disposal site and bring back in several truckloads of fresh sand usually causes mild to severe damage to the now established property. Minimal homeowner intervention in the operation of the system is an advantage to uncaring homeowners.
The best system will mean different things to different people. Whenever we interact with suppliers, our opinion of the product we have purchased is very often coloured by the tone of the dealings we have had with them.
At the extreme end, most of us would not buy a product from someone we couldn’t deal with or relate to, or who treated us poorly, unless there was no alternate supplier or equivalent product available (think Telstra, the Banks etc). Some will always think that the cheapest is the best, others the dearest is always the best. Often we buy a product and feel good about the transaction, but when we use it, we are disappointed. We were either oversold on what the product was going to do or how good it was or worse, it actually does not do what the salesman claimed. The same is equally true in selecting a system to treat your sewage and sullage.
You are entering into a long term commitment with the supplier and manufacturer and if you were not happy in the beginning, you are unlikely to become happier as time passes. Small problems will be magnified out of proportion, nothing will be right and you will wish you had purchased another product. So think carefully as you decide: are you dealing with an ethical supplier, do they listen to you, do they make you feel confident in their knowledge and abilities, have they given you a fair price for what they are doing for you, will you be happy to see them or their employees over the many years that the Secondary Wastewater Treatment System will service your Home?
If you can answer YES to all these points, then the plant you have chosen is the best – for you.
We think that Taylex will “tick all the boxes” for you but if you disagree, please tell us why.
In almost all circumstances the truthful answer is “YES”. A Secondary Wastewater Treatment System will consistently treat all the water we have polluted and downgraded from A1 Potable water to sewage by our use in the home, bringing it back to a higher grade water, still not potable, but to a standard that will not pollute the environment, be a hazard to ourselves, our family, companion pets, neighbours or the environment. A septic tank cannot guarantee to do this because we can’t control the environment into which the partially treated effluent from the septic tank is discharged.
We cannot be sure that the septic tank effluent does not pollute the aquifer below the leach drain or absorption area. We cannot control heavy rain percolating into the leach drains and overflowing out into our backyard, the creek or the neighbour’s property. We can’t guarantee that a visitor will not drive over the leach drains, crushing and blocking them. We don’t see the final effluent, so we don’t know what it is really like. For holiday “shacks” as distinct from a holiday home where we have everything just the same as at our home, a septic tank may be the system of choice because we may not be there very often, there may be no power available with very little water usage.
The environmental benefit of a Secondary Wastewater Treatment System includes the major advantage of being able to use twice the water we have paid for or the precious water we have harvested ourselves from our roof, once in our home, then in our garden.
Both the Taylex concrete and polymer wastewater treatment systems are six- stage aerated wastewater treatment systems that exceed the national standards and are certified in all Australian states and territories. So why have both options available if they essentially do the same thing?
Our concrete ABS Systems are suited to 90% of all domestic installations. Taylex Polymer Tanks are designed to accommodate site conditions where it is not possible to crane in a concrete treatment system e.g. steep terrain. Our unique polymer mould cleverly uses ‘Sandwich closed-cell foam polymer’ to mould the compartment walls in one piece. There are no joins or glued-in compartments and all partitions extend to the lid of the tank, so you can enjoy the same peace of mind as if you had a Taylex concrete system.