Recycled Water and the Harmful Effects on Native Plants

Recycled water is generally referred to as "gray water" because it is no longer fit to drink, but it is much cleaner and easier to reuse than black water, which contains human waste. When used properly, gray water can actually be beneficial to plants.

Possible Negative Impacts

Gray water from bathing, sinks and clothes washers can be used to water plants. Dishwashers generally use chemicals that make the water unusable for this purpose. It is very important to use the gray water within 24 hours; gray water often contains both live pathogens and nutrients, so storing it for long periods can promote the growth of dangerous pathogens. If laundry or dishes are washed with nonbiodegradable chemicals, any product containing bleach or boron, artificial dyes, or excessive salts, the gray water can be harmful to plants and soil structure. Many powdered detergents and some liquid detergents are sodium based, which is harmful to plants.

Using Gray Water Safely

Use only those detergents, laundry products and soaps that are natural and biodegradable. Make sure that laundry detergent in particular does not contain high salts or phosphates, and is pH neutral.

Benefits

At the low concentrations found in bathing and washing water, natural cleaning products can actually contain beneficial plant nutrients, giving gray water some fertilizer-like properties. They use of gray water also reduces the load on municipal water treatment facilities or septic systems, replenishes soil nutrients, encourages plant growth and conserves water.

References

• Australian EPA: Household Greywater Reuse
• Center for the Study of the Built Environment: Graywater Reuse Project