Teacher background information
What makes up wastewater?
Wastewater comprises of 99.97% water by mass. The remaining 0.03% is organic and inorganic matter either dissolved or suspended in the water. The concentrations of these other components are very small – measured in milligrams per litre of water (mg/L) or parts per million.
How is wastewater treated?
Wastewater is collected every day from households, commercial businesses and industries and is directed to treatment plants. Here the wastewater is treated to an environmentally acceptable standard before being reused or safely discharged back to the environment.
Wastewater treatment is a series of processes that remove the pollutant materials from wastewater such as solids, oil and greases, detergents, nutrients, heavy metals and bacteria. It can be a mix of sewerage and other used water.
The collection, treatment and disposal of wastewater are an integral part of the water cycle that maintains the balance of water in nature.
Wastewater treatment plants
In WA, Water Corporation is responsible for the treatment and disposal of wastewater. Water Corporation operates more than 110 wastewater treatment facilities around the state. The four large metropolitan plants at Beenyup, Subiaco, Woodman Point and Alkimos treat about 80% of our wastewater.
Preventing damage to our wastewater system
There are many household and industrial items that should not enter the wastewater system.
Children’s toys, golf balls, jewellery, scissors, cotton buds and toothbrushes are some of the items that find their way into toilets and inside drains. Disposing of this waste correctly prevents damage to the wastewater system and helps protect the environment.
Many liquids should also not be poured into drains as they can kill the essential bacteria that break down wastewater at the treatment plant. Chemicals such as paints and pesticides, engine oils, solvents, poisons and swimming pool water are harmful to the environment and should be disposed of properly through a licensed hazardous waste contractor or your local council recycling centre.
How to dispose of common household products:
- Cooking fats and oils: pour into a container and place in the bin.
- Chemicals (e.g. paint, pesticides): give to a licensed hazardous wastes contractor or contact your local council.
- Food scraps: place in the bin or compost.
- Newspaper and plastics: recycle – contact your local council for more information.
- Engine oils: take to a local garage or oil recycling centre.
- Unused medicines: return to the pharmacy.
- Nappies, razors, cotton buds, syringes: Wrap and place in the bin.