Let’s be clear about wastewater

Bird's eye view of a water treatment plant

Time to take a closer look at the murky world of wastewater

When you receive your water account, it is natural to focus on “water use”, meaning the water coming out of the tap. But just looking at how much water you have consumed, doesn’t take into account the cost and difficulty of removing, treating, as well as safely disposing of wastewater. When your water goes down the plughole the hard work begins.

The treatment and delivery of wastewater is important for our natural environment and for reuse.  It is one of the services you pay for when you receive your water bill.  Just like your drinking water, your wastewater is a valuable resource.

What is wastewater?

Wastewater, also known as ‘blackwater’, is the used water and sewage that goes down sinks, toilets and outside drains. It is potentially harmful for the environment and needs to be treated and disposed of correctly. This comprehensive process involves pumping the wastewater from your home, removing sludge (organic matter), removing scum (grease, oils, plastic, soaps), killing harmful bacteria that pose health risks, and finally disposing of the wastewater residuals.

How is wastewater treated?

All treatment plants are a bit different, however, generally the process involves three stages in the treatment as follows:

Stage One

The first stage includes screening out items such as toys and larger objects.  The water is left still, allowing some of the sludge to settle and be removed, leaving mostly water.

Stage Two

The second stage uses nature to clean the water, often in big lagoons. Sunlight and natural micro-organisms will process almost everything that needs to be treated if you leave it long enough. The water is allowed to settle again and more sludge is taken out so it is quite clean now. All the sludge taken out is broken down using natural bacteria and used as fertiliser.

Stage Three

The third stage is optional and used for final disinfection or to remove something like excessive nitrogen. Sunlight will eventually clean the water but ultra-violet treatment or chlorine is quicker if a lot of water is being treated.

How does it affect you?

In many parts of Australia, over 50% of the cost of managing water is related to sewerage and is reflected in your bill. Nearly all indoor water use is pumped to a wastewater plant; imagine the substantial cost in maintaining pipes, pumping waste and running treatment plants for 22 million Australians every day.

Is wastewater safe?

All wastewater is tested to make sure it meets safety standards when it leaves the treatment plant. In saying this, you should be careful when using recycled water as generally, it is not used for drinking.

What happens to wastewater?

Most wastewater is returned to rivers and the sea but is sometimes reused for agriculture and industrial uses.

How can you help?


– Dispose of cooking oils and food scraps in the bin, rather than the sink

– Dispose of plastic bags appropriately, recycle them where possible


– Do not flush cotton buds, unused pharmaceuticals, medicines, condoms and sanitary items down the sink


– Use local, designated facilities to recycle engine oils, fuels and unused chemicals

– Do not put cigarette butts down the drain

Filthy waterway

Just think where all of that rubbish we consume ends up.

These items can either block the pipes, requiring expensive repairs, or make wastewater treatment much more difficult and potentially damaging our natural environment.

Do you know a clever way to help the treatment of wastewater, or maybe even some handy tips on how to help stop excessive wastewater going down the sink? If so, let us know and help others become more environmentally conscious.