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Queenscliffe Herald Article - March 2007

Greywater Use

By Bob Fuller
Swan Bay Environment Association

With Stage 4 Water Restrictions in place since early December and the likelihood that restrictions will be in place for sometime, it is probably worthwhile refreshing our understanding of why we should be careful about using household wastewater in the garden. Known as 'greywater', the Victorian EPA defines this as all 'non-toilet' wastewater. The sources are the kitchen, bathroom and laundry, and different issues must be considered depending on the source. These issues relate to what might be in the water, and its effect on the plants, soil and our own health.

Authorities and experts usually discourage using wastewater from the kitchen because it may contain high levels of oils and fats. These can accumulate in the soil and make it water repellant, and thus impede water movement through the soil and its uptake by plants. The detergents used in the kitchen to remove these fats from the dishes are also likely to be relatively strong. Greywater from the kitchen can, however, vary greatly and the wastewater from a vegetarian household with a low fat, no salt diet will be quite different to that from a more typical household.

Greywater from the bathroom can come from the shower, bath, spa and hand basin. If the greywater is collected outside the house prior to its entry into the sewerage system, the water will be a real cocktail. The ingredients may not just be those in the soap, shampoo and conditioner, but also the toothpaste, deodorant, mouthwash, sunscreen and cleaning product we use. If the greywater is collected inside the bathroom using bowls and buckets, some of these ingredients can be avoided. However, the wastewater will almost always certainly contain some faecal matter, and therefore should not be used to water vegetables.

In the laundry, wastewater comes from the washing machine and laundry trough. The products we use for washing our clothes tend to be harsher than those that applied directly to our bodies in the bathroom. Many laundry detergents have been tested for the salts and phosphorous levels they contain. Because of the low phosphate levels in our soils, most Australian native plants are sensitive to phosphorous. A good source of independent information about laundry detergents is Lanfax Labs, who have tested and published the sodium and phosphorous levels for about 50 laundry liquids and powders for front and top loading washing machines. The results may be downloaded from the company's website, which can be found at www.lanfaxlabs.com.au. In general, liquids produce lower levels of sodium and phosphorous per wash than powders, if used at the recommended levels. Greywater containing bleaches, nappy wash and water softeners should not be used.

Two books that contain a lot of useful information on greywater and how to use it are "The Water Efficient Garden" by Wendy van Dok and "Waterwise House and Garden" by Allan Windust. The former contains a good A-Z of the ingredients in cleaning products and their effect in the garden. Both books are available through the Geelong Regional Library system. Remember that the quality of the greywater we generate varies greatly. Ultimately, it depends on user behaviour, particularly on the type of household and personal cleaning product we use and in what quantities. These factors will dictate how suitable the wastewater is and whether it can be used with relative safety.


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