As much as 50% of the water we use in the home goes down the drain. It’s discharged as wastewater to the sewer or onsite wastewater system, or to the stormwater drain. It is important to realise that many of the chemicals we add to this water affect wastewater treatment and recycling, and can harm the environment.

Furthermore, water discharged to stormwater (from the roof, drains, gutters and backyard gully-traps) often enters local creeks and waterways, without any treatment at all.

Many of the chemicals of concern originate in the bathroom, kitchen and laundry. They are found in laundry detergents, dishwashing detergents, and other cleaning agents such as bleach and carpet cleaners. Other potentially harmful chemicals include medicines, herbicides, pesticides, paints, motor oil and pool chemicals.

At the individual household level, it may seem that the quantities being discharged are insignificant. However, the cumulative impacts from whole suburbs can be significant.

Some of the harmful characteristics present in household wastewater include:

• Phosphorous
• Nitrogen
• Salts
• pH levels
• Greases and oils
• Bleaches
• Corrosive chemicals.
  

• When buying detergent, read the side of the pack for information on the environmental benefits of the product.
• Some detergents have the symbol ‘NP’ marked on their packaging. This means that the product contains little or no phosphorous, which is beneficial. Detergents containing phosphorous may be labelled ‘P’.
• Choose products that have been endorsed by environmental groups or consumer groups for their environmental features.
• Use detergents sparingly- we often add much more than is necessary.
• Ask your local water retailer or local council where you can safely dispose of used oil, paints and chemicals (for example through household chemical collection days).
• Always use a strainer on your kitchen sink.
• Remove food from plates before washing, and use a compost or worm farm to dispose of them.
• Explore the links below for recipes on safe and organic cleaning solutions.
  

When using an on-site wastewater system such as a greywater system or septic tank, both the quality of the wastewater, and how it is used has to be addressed. The chemicals mentioned earlier can have damaging effects on soils, plants and animals, groundwater and local waterways.

There are various ways to reduce harmful chemicals in greywater that is used on the garden. These include:

• Use the cleanest greywater as a priority.
• Use liquid detergents rather than powders. Powders have about 10-20 times more sodium salts in them than liquid detergents.
• Avoid using greywater that you know contains chemicals such as acid, bleach, drain-cleaner, dye or disinfectant.
• Filter kitchen water to remove fats and oils before use.
• Don’t use water that has been used to clean work clothes or equipment that may be covered in harmful chemicals such as paint.
• Allow water to cool before it’s used in the garden.
• Use a trough connected to the sewer, instead of the greywater system, to dispose of harmful chemicals.
• Consider having you soil tested regularly for pH, salinity, conductivity and chemical levels. This will tell you the suitability of the soil to absorb greywater, as well as allowing you to monitor the ongoing effects of the greywater on the soil environment and plants.
• Trial greywater use on a small section of the garden, to see what effect it has on the soil and the plants.