Waste Water Recycling - Making the Most of a Precious Resource

Points covered:

• What is waste water?
• What is waste water recycling?
• What are the benefits of waste water recycling?

Words to know:

• STORMWATER - rainwater runoff
• POTABLE WATER - drinkable water

Much of the water we use ends up as waste water. Waste water is produced when we use showers, toilets and machinery in our homes, shops, offices and factories. It is also be produced by polluted stormwater from urban and agricultural areas.

Of the 1,600 million litres of potable water used in Sydney every day, only a quarter is consumed for uses such as drinking and watering gardens. The remaining three quarters is discharged into our rivers and oceans via the sewerage system.

However, it is possible to collect and reuse waste water in our homes, offices, factories and farms as it can be treated to the standards required for agriculture, industry and even drinking. Waste water can be redirected prior to treatment, such as when shower water is directly re-used for flushing toilets, or after treatment, such as when treated sewage effluent is used for irrigating golf courses and orchards.

The main benefits of recycling waste water are:

• that lesser quantities of potable water are used for purposes other than drinking. This lowers water supply costs, as potable water is expensive and limited, treatment costs and the need to build more dams.
• that stormwater and sewage discharges are reduced, lowering the stress on streams, sewerage systems and stormwater systems during wet weather.
• that waste water used for irrigation undergoes natural treatment lowering the nutrient loads in waterways and reducing the pollution load in our rivers and oceans.

However, there are financial, environmental and health considerations involved in recycling waste water. In certain circumstances, re-use systems can be expensive, for example installation of pipework for recycling systems between homes and sewage treatment plants in existing suburbs. Furthermore, recycled water systems must be well managed and must treat waste water to a sufficient standard to ensure there are no health and pollution risks. But the benefits often outweigh the costs and risks: appropriate waste water recycling systems can help both our environment and our economy.

Kendall Banfield & Geoff Milne
Institute for Sustainable Futures
University of Technology, Sydney