Wastewater is generated in various areas of the home and disappears from mind once it goes down the sink or toilet. Wastewater treatment and disposal is an important household service along with things like electricity and potable water. Most people prefer not to think about sewage at all, so it’s not often talked about.
Home wastewater comes from your kitchen, bathroom, laundry, and toilet. Most of this wastewater is known as grey water or sullage, while wastewater from your toilet is known as black water or sewage. Waste streams are mixed in the drainage system and are treated together.
If you are in a city or town, your municipal connection will take all of your wastewater to the municipal Sewage Treatment Plant (STP) for treatment and disposal. Many properties in regional and remote areas or new satellite communities don’t have access to this service. Instead, they have an onsite sewage treatment system that manages their wastewater stream within the property boundaries. Normally tucked away in the garden, these systems can be a mystery to many people but provide an important service.
History of Australian household sewage management
Aussie folklore is packed with references to the dunny. The good old loo, thunder box, or out-house often sat at the bottom of the garden with its resident population of redbacks. The out-house primarily contained a long drop toilet or can. The long drop was a hole that slowly filled and required occasional relocation of the out-house, while the can was taken away and emptied.
Progress came with the advent of the flushing toilet and the septic tank. Septic tanks have been the mainstay of onsite wastewater for many years. They are still the system of choice in some locations. Septic tanks treat wastewater to a “primary” or basic level before it is disposed of in trenches beneath the ground. They rely on a natural anaerobic (without oxygen) process to treat the wastewater.
Modern treatment methods and regulations
Along with many advancements and improvements in modern life, wastewater treatment has advanced too. Often called a Home Sewage Treatment Plant or HSTP, modern systems treat to a much higher and safer level than a septic tank. They combine the old anaerobic treatment with a complimentary aerobic (with oxygen) treatment. This treatment relies on millions of microbes and bacteria breaking down the organic matter. This treatment process works the same way as many natural processes. The systems are designed to make the perfect habitat for the microbes to work at their best. Strange honeycomb balls or “media” provide massive surface areas for the bacteria to live on and thrive.
These modern systems can also be called an Aerated Wastewater Treatment System (AWTS) or Aerobic Treatment Unit (ATU). Aerated refers to the air that is pumped through one of the chambers in the system for the aerobic part of the process. The microbes in the system really are the key to the whole process. They are one of the reasons we need to take care of what goes down our sinks and toilets.
These different levels and methods of treatment are used in different circumstance. Sometimes primary treatment via a septic tank is enough. At other times, secondary treatment is needed with further filtration supplied by the method of disposal. The choice of system type is dependent on government regulations, the environment, the area available and the size of the dwelling.
The last step in the treatment chain
Once the wastewater has been treated, it needs to be disposed of onsite. It is this need for disposal that has seen the rise in HSTPs and the demise of the septic tank. There are many criteria that dictate the treatment level and disposal method of the treated water. These include property size, soil type, proximity to waterways, and terrain. Councils often stipulate an STP to take care of our homes and the environment.
The treated water is released via a disposal area or Land Application Area (LAA). The two main types of LAA are irrigation and ETA beds. Irrigation is often called Sub-Surface Irrigation (SSI) or Sub-surface Drip Irrigation (SDI). As the name suggests, this is an irrigation network beneath the soil and is great for keeping your lawn green. ETA beds (evapotranspiration absorption beds) are a type of trench system located deeper beneath the ground. These are used in more challenging locations and also for the primary treated water from septic tanks. If you live in a flood zone or on a confined lot, you may even need something called a Wisconsin mound. This is a built up, engineered sand mound that provides effluent disposal above the normal ground level.
These methods of effluent disposal also provide the final step of filtration through the soil and grass to ensure there are no contaminants released back into your property.
Local councils have different acronyms for home wastewater systems, but two common ones are OSSM and OSMS. OSSM stands for Onsite Sewage Management and OSMS is Onsite Sewage Management System. These terms encompass both HSTPs and septic tanks. You will also see OSSM designers mentioned. They do not design the actual systems but assess your property as a whole. They design the LAA and produce a Wastewater Report or an Effluent Management Report specific to your project. You submit this report to your local council with any new or upgraded OSSM installation.
One of the most important things to be careful of with home wastewater systems, is what you put down your sinks and toilets. Toilets should only ever receive the 3 Ps; poo, pee, and paper. Anything else, including so called “flushable” wipes, need to go in the bin. Natural and environmentally friendly cleaning and washing products are important to use. These make life easier for the beneficial microbes and reduce the chance of harmful chemicals contaminating the soil of your garden.
To take the next step in installing your new HSTP, or for more information, please contact the team at True Water.