GREY WATER REUSE : SUSTAINABLE WATER RESOURCE

GREY WATER REUSE: SUSTAINABILITY
There are many colors of water. Bluewater from aquifiers, rivers and lakes. Greenwater is soil moisture. Blackwater is from toilets, kitchen sinks and dishwashers. Greywater (GW) is wastewater from baths, showers, hand basins and washing machines.

GW is a sustainable water resource and may be reused in an appropriate manner for garden watering directly without treatment

The reuse of GW shall reduce the water demand on municipality water supply and reduce the pressure in seeking new catchment areas for traditional water supply from dams. In a Malaysian home, typically up to 50% of the discharged water is considered greywater suitable for reuse.

Australia and some US states have issued guidelines on the reuse of graywater in the gardens. In Victoria, Australia, rebates of $500 is given for GW system that must be installed by a licensed “Green Plumber”.

GW contains bacteria, protozoa, viruses and parasites. It also contains grease, fats, oils, detergents, food, hair and chemicals. However the public health risk associate with onsite reuse of domestic greywater are considered low, as the source of the contamination is from the immediate family. Other sources of transfer of pathogens among the immediate family members would be considered as higher risks. (Greywater-Canberra Fact sheet No: 7).

The contaminants in GW can usually be processed by the soil and plants, and some of the nutrients are also beneficial to plant growth. However some salts (sodium and potassium) present in laundry detergents may cause soil degradation.
GW from baths and showers are less polluted than from basins due to the high volumes used. Concern of urine discharge in baths and showers are considered low due to the fact that urine is sterile and germs have low chance of transmission and survival in the soil.

Some Do’s and Don’ts are:

1. The greywater shall be used for irrigation only at the place of generation


2. Vegetable or Food crops shall be the types that do not touch the ground. Suitable plants are tomatoes, chilies, ladies fingers, brinjals, and cucumbers. Unsuitable are spinach, carrots, and cabbages.


3. Use low phosphorus detergents in the unit
   
4. Greywater should be diverted to the garden by a below ground seepage pipe to reduce human exposure to the water and aerosols.


5. A diversion system that will automatically divert the greywater to the sewer if the greywater system blocks or malfunctions shall be installed.


6. Greywater shall not be discharged into watercourse but into a public sewer.


7. Ensure excess greywater is diverted to the sewer.


8. During wet periods, the greywater shall be diverted into the sewer system.


9. Stop using greywater if you smell odours and your plants do not appear to be healthy


10. Use only in soil which has a watertable more than 2metres below.


11. Wash your hands after gardening in greywater irrigated areas


12. Use less fertiliser when irrigating with greywater


13. Ensure greywater does not contaminate any source of drinking water: extreme care must be taken to ensure there is no cross-connection between the greywater re-use system and the drinking water supply

Don't

1. Never water vegetable gardens if the crop is to be eaten raw


2. Never use greywater that has faecal contamination, for example, wastewater used to wash nappies


3. Never store untreated greywater for more than 24 hours


4. Never allow greywater to flow beyond your property boundary or enter stormwater systems


5. Do not use kitchen wastewater (including dishwashers) - it contains highly concentrated food wastes and chemicals that are not readily broken down by soil organisms


6. Do not allow greywater to pool or stagnate as this will attract insects and rodents, which may transmit disease.
   
   

Irrigation system Buffer Tank and Distribution Pipes

Vegetable Beds and Crops