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What is Grey Water? Grey Water is the water generated from the use of the shower, bathtub, hand sink, laundry, kitchen sink, and dishwasher. Is Grey Water different from wastewater? Yes. Household wastewater, also known as sewage, is composed of two distinct sources: - “Black Water” is wastewater contaminated by feces or urine, and includes wastewater arising from toilet, urinal, or bidet. - “Grey Water” is the remaining wastewater coming from the laundry, bathroom and kitchen. Why should I reuse Grey Water? Grey Water is a significant water resource, provided it is managed in an environmentally responsible manner, and public health and the health of the household are protected. By capturing Grey Water and using it in an appropriate manner as an alternative to your water supply, you can reduce your water consumption. Your water bill will reflect this reduction in water use and there will also be positive environmental outcomes. Is it safe to reuse Grey Water ? Yes, if used in an appropriate way. Grey Water can contain disease-causing microorganisms such as bacteria, protozoa, viruses and parasites. It may also contain fats, oils, detergents, soaps, salt, nutrients, food and hair derived from household and personal cleaning activities. These constituents can pose both health and environmental risks. However, the public health risks associated with onsite reuse of domestic Grey Water are considered low, as the source of the contamination would be from the immediate family. Other sources of transfer of pathogens around the immediate family are considered a higher risk, such as direct contact or sharing of food and utensils. Similarly, the risk of environmental damage from the careful use of Grey Water is low. How can I reduce the risks associated with Grey Water reuse? The following measures will reduce the health and environmental risks associated with the use of Grey Water; · do not use sprinklers to distribute Grey Water; · use subsurface irrigation systems; · do not spray Grey Water directly onto food plants; · do not put Grey Water on lawns where children are likely to play; · do not irrigate with Grey Water during periods of wet weather; · do not allow Grey Water to enter the storm water system; · make sure Grey Water does not create a nuisance, for example through odours or ponding. Do I need a plumber? If your Grey Water system requires connection to the sewage system, i.e. to the pipes below your sinks, shower or bath, a licensed plumber must do this work. If you intend to intercept Grey Water before it enters the sewage system, i.e. before it enters the drain hole of a sink, you can do this yourself. This may be a simple setup in which you bucket water from a sink, or direct the water from your washing machine to your garden. Can Grey Water from all parts of the house be reused? Kitchen Kitchen wastewater could be heavily polluted with food particles, oils, fats, and other wastes. It can also contain high concentrations of microorganisms. It is often polluted with detergents and cleaning agents, particularly those from dishwashers, which are very alkaline and may be harmful to soils and plants by altering their characteristics in the long term. For these reasons kitchen Grey Water is not recommended for use. Bathroom Chemical constituents of bathroom Grey Water include soap, shampoo, hair dyes, toothpaste and cleaning chemicals. Grey Water from hand basins is more polluted than bath or shower Grey Water, but is much lower in volume. Some of these contaminants act as plant nutrients and can be beneficial in the garden, but others can adversely affect plants or soil structure. Concern is often expressed about people urinating in showers and baths and the associated health aspects of using Grey Water in the garden. However, urine in a healthy person is sterile. While some bladder infections may pass microorganisms in urine, the potential for these organisms to survive and cause infection is considered remote. Grey Water from the bathroom is suitable for reuse. Laundry Grey Water from the laundry improves in quality from wash water to first rinse water to second rinse water. Bacterial loads in laundry Grey Water are not usually high, except when diapers are washed. Chemical contaminants of the wash cycle water are soap, salt, sediment and organic material. If used for garden watering, the wash cycle water can damage plants and soils and create bad odours. Rinse water contains a much lower pollutant load and the use of this water poses a much lower threat to the environment and to the public health. Domestic pets, which are washed in the laundry tub, can be a further source of contamination for Grey Water. Grey Water from the laundry, particularly rinse water is suitable for reuse.
Can I store Grey Water on my property before I use it? It is recommended that untreated Grey Water is not stored for more than 24 hours. When the immediate reuse of Grey Water is not practical, for instance during periods of wet weather, Grey Water should be directed to the sewer system. What is a Grey Water treatment system? A treatment system will remove the bacterial load and chemical pollutants from Grey Water so that it can be stored. However, satisfactory treatment tends to be neither simple nor cheap. Treatment processes can include filtering, settling of solids, anaerobic or aerobic digestion, chemical removal of pollutants, and disinfection. My neighbour is reusing Grey Water, is my property still safe? Appropriate reuse of Grey Water is not considered a health threat to neighbouring properties. What are the environmental risks associated with reusing Grey Water? Soil or plants can process many of the contaminants in Grey Water if the system is not overloaded, including organic material, nutrients, salt and sediment. Nutrients can even be beneficial in moderate concentrations, for example, on lawns but not on native plants. Some Grey Water contaminants are not capable of being treated or degraded in the soil. Principal among these is salt, which can comprise up to 30 % of some laundry detergents and can cause soil degredation. How much Grey Water do households generate? The amount of Grey Water generated by a household will vary greatly depending on the number of occupants, their age, and their water usage patterns. As a general rule of thumb, the average detached household generates approximately 110,000 litres of Grey Water per year from the bathroom and laundry. This is equivalent to 300 litres of water per day. How can I improve Grey Water quality by using different types of soaps, detergents etc.? The choice of cleaning products can reduce the environmental impact of Grey Water. Common washing powders contain sodium salts as bulking agents that produces a saline (salty) Grey Water. Some detergents and powder cleansers contain boron that can be toxic to plants in high concentration. It is recommended that for clothes washing you select products low in sodium: either liquid concentrates or powdered products that use potassium salts. There are websites that list the sodium content of a range of laundry products.
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