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

RAINWATER HARVESTING : A SUSTAINABLE WATER SUPPLY

RAINWATER HARVESTING: A SUSTAINABLE WATER SUPPLY

TASMANIAN RAIN is rainwater captured on the pristine north west coast of the island of Tasmania, Australia. The water is collected just minutes of where the World Meteorological Organization records the world’s purest air.

The rain has traveled eastward via air currents over Antarctica and 10,000 miles of ocean. As a result, TASMANIAN RAIN contains only 17 parts per million of dissolved solids.

TASMANIAN RAIN is collected by a custom-designed catchment facility, and never touches the ground. http:www.tasmanianrain.com

The above website was very exciting to me as I graduated from University of Tasmania; but of course during the 70’s, environmental issues were just emerging and of not much interest to the community. However there were Environmentalist groups in Tasmania then, who were opposing the construction of Dams for Hydroelectric power which was the main source of electrical supply for the island.

The website was discovered while I was researching material for a talk I gave to the Institution of Engineers at the recent Colloquium on the sustainable water supply; aka Rainwater Harvesting (RWH).

RWH is an age old technique involving capturing or trapping the rainwater on the roofs or some other surface before it touches the ground and storing it for reuse. It has been practiced in arid and semi -arid regions and in roman villas, Indian old cities and in Balinese temples.

Presently, RWH is gaining recognition as a sustainable means of water supply.

This is a result of the paradigm shift in concept of municipal water supply. When cities grow with ever increasing demand for municipal water, it has been traditional to seek new water catchments, construct dams with large water surfaces, build long interstate water pipelines and construct treatment plants.

All the above causes damage to the environment. Biodiversity is affected; treatment consumes chemicals and produces toxic wastes not to discount the CO2 emissions during the construction and operational process.

“The sustainable method of water supply is to capture the rainwater at source where it falls, store and utilized it there.”

From a typical breakdown of water use in a Malaysian home, the water used for toilet flushing (30%), clothes washing (13%), outdoor (7%), and cleaning (8%) amounting 58% of household water consumption in Malaysia, can be replaced by rainwater harvesting. (Baharuddin A., 2007)

The Malaysian government has recognized that RWH contribute towards national water conservation. It has made a commitment to revise the Guidelines for Installing a Rainwater Collection and Utilization System, in the Ninth Malaysia Plan; ref: item 18.50, Chap 18, of Ninth Malaysia Plan 2006-2010

In 2003, a shopping complex in Petaling Jaya has successfully installed a RWH system and reported a savings of 30% of its monthly water bill.

JPS and NAHRIM has installed and studied RWH in a double storey link house, Mosque and the JPS headquarters building. NAHRIM reported a savings of 34% of the household water consumption and a stored rainwater quality equivalent to Malaysian National WQI Index of Class IIA; ie suitable for recreation and body contact.

Sumida City, Japan has promoted RWH and to date 300 tanks have been installed in the city, whilst it was reported that 750 private and public buildings in Tokyo have installed RWH systems.

At Changi Airport, rainfall from the runways and the surrounding green areas is diverted to two impounding reservoirs. The water is used primarily for non-potable functions such fire-fighting drills and toilet flushing. Such collected and treated water accounts for 28 to 33% of the total water used

In a project at Belss-Luedecke-Strasse,Berlin, rainwater from all roof areas (7,000 m2) is transferred into a an underground cistern together with the runoff from streets, parking spaces and pathways and the water is used for toilet flushing and garden watering.

In St. Thomas, US Virgin Islands, a rainwater utilisation system is a mandatory requirement for a residential building permit. In Bermuda RWH systems are regulated by a Public Health Act which requires that catchments be whitewashed by white latex paint; catchments, tanks, gutters, pipes, vents, and screens must be kept in good repair. Roofs are repainted every two to three years and storage tanks must be cleaned at least once every six years.

In Australia, states are giving rebates and subsidies for installations of RWH systems in an effort to reduce the consumption of municipal water supply. In fact from the following table 36% of households in South Australia are using RWH as the source of potable water supply.

Malaysian Scenario:

In Malaysia, the government shall promote the use of RWH by not only issuing regulations but need to look into financial incentives, rebates and subsidies to encourage the installations of RWH systems.

RWH is sustainable and shall be a part of the water supply system in Malaysia.

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Note: The author is a member of the International Rainwater Catchment Systems Association (IRCSA) which aims to promote and advance rainwater catchment systems technology with respect to planning, development, management, science, technology, research and education worldwide; It was founded in August 1989. Biannual international conference has been held since 1989 with the last in Sydney 2007.

The 14th International Rainwater Cistern Systems Conference will be held in Malaysia in 2009.

Check out the following websites related to RWH; http://www.ircsa.org/ ; http://www.irha-h2o.org/; http://www.arcsa.org/; ; www.skywater.jp/ ; http://www.eng.warwick.ac.uk/dtu/rwh/index.html;

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