What is recycled water?
Recycled water is usually treated wastewater which is further treated to varying qualities that is “fit for purpose” for its intended use. It can then be used for:
- Irrigation of sports grounds, golf courses and public open spaces;
- Industrial processing;
- Groundwater replenishment;
- Toilet flushing / clothes washing / garden watering;
- Environmental benefits (eg: maintaining wetlands);
- Irrigation of food crops;
- Irrigation of non-food crops (eg: trees, woodlots, turf, flowers);
- Construction / dust surpression; and
- firefighting.
Why should we recycle water?
Water recycling is an essential part of maintaining a reliable, sustainable and safe water supply for Western Australia. Increasing the amount of water that is recycled is crucial to managing our precious drinking water resources efficiently and making the most of our wastewater resource that is often 'wasted water'.
Our 50 year plan, Water Forever - Towards Climate Resilience created a portfolio of water options to help make Perth more climate resilient. Working in partnership with the community, by 2060, the Water Corporation intends to:
- Reduce water use by 25%;
- Increase wastewater recycling to 60%; and
- Develop up to 100 gigalitres of new sources.
This will require collaboration between the Water Corporation, State and Local Government, business, industry and the community.
The Water Corporation is involved in approximately 71 water recycling schemes in Western Australia.
While water recycling has been undertaken in regional areas of Western Australia for many years, only 6% of treated wastewater is recycled in the Perth metropolitan area. This is mainly due to the abundant supply of groundwater in Perth. However this is not sustainable in the long term with many groundwater areas in WA reaching the limit of their supply or groundwater levels declining.
Generally, Western Australians are accepting of water recycling with research showing that 90 per cent of Perth residents support recycling treated wastewater for irrigation of recreational areas, industrial or agricultural use.
To achieve the targets set for increasing water recycling, the Water Corporation is exploring a range of options including;
- Increasing water recycling
- groundwater replenishment where high quality recycled water is stored in groundwater for future water supplies;
- beneficial recycling of water to the environment;
- increasing water recycling to existing and new industry;
- dual reticulation recycling schemes for new subdivisions; and
- using recycled water to irrigate public open space.
Water recycling is supported where risks to human or environmental health are carefully managed in accordance with national and State guidelines and local regulation such as Department of Health (DoH), Department of Environment and Conservation (DEC) and Department of Water (DoW).
http://www.watercorporation.com.au/W/water_recycling.cfm
How do they ensure that the water is safe to drink or use?
ReplyDeleteWater recycling systems without purification
ReplyDeleteWater recycling without purification is used in certain agricultural companies (e.g., tree nurseries) and dwellings for applications where potable water is not required (e.g., garden and land irrigation, toilet flushing). It may also be used in dwellings when the greywater (e.g., from rainwater) is already fairly clean to begin with and/or has not been polluted with non-degradable chemicals such as non-natural soaps (thus using natural cleaning products instead). This water system also needs a supply of water to recycle and reuses water as well. It is also not recommended to use water that has been in the greywater filtration system for more than 24 hours or bacteria builds up affecting the water that is being reused. Water purification/decontamination systems then again are used for applications where potable water is required (e.g., to allow drinking, and/or for other domestic tasks as washing, showering).
[edit]Water recycling with purification
For filtering the water to become potable (or near-potable), there are numerous systems based on soft processes. These include natural biological principles such as
mechanical systems (sand filtration, lava filter systems and systems based on UV radiation)
biological systems (plant systems as treatment ponds, constructed wetlands, living walls) and Bio reactors or compact systems as activated sludge systems, biorotors, aerobic and anaerobic biofilters, submerged aerated filters, biorolls[vague] [2]
Finally, "hard", direct processes, such as distillation (evaporation) or mechanical processes such as membrane filtration, (typically ultrafiltration and reverse osmosis, which are capable of treating high volumes of grey water) can create potable, or near-potable water. There seem to be no commercially available "hard" greywater recovery devices suitable for on-site use in the individual household, even though a number of such technologies exist.
In order to purify the potable water adequately, several of these systems are usually combined to work as a whole. Combination of the systems is done in two to three stages, using a primary and a secondary purification. Sometimes a tertiary purification is also added.
Some municipal sewage systems recycle a certain amount of grey and blackwater using a high standard of treatment, providing reclaimed water for irrigation and other uses.
NEWater is the product from a multiple barrier water reclamation process:
The first barrier is the conventional wastewater treatment process whereby the used water is treated in the Water Reclamation Plants.
The second barrier, and first stage of the NEWater production process, uses microfiltration/ultrafiltration to filter out suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts. The filtered water that goes through the membrane contains only dissolved salts and organic molecules.
The third barrier, and second stage of the NEWater production process, utilizes reverse osmosis (RO). In RO, a semi-permeable membrane filters out undesirable contaminants such as bacteria, viruses, heavy metals, nitrates, chlorides, sulfates, disinfection by-products, aromatic hydrocarbons, and pesticides that cannot pass through the membrane. Hence, NEWater is free from viruses and bacteria and contains very low levels of salts and organic matter. At this stage, the water is already of potable quality.
The fourth barrier, and third stage of the NEWater production process, acts as a safety precaution. UV disinfection is used to ensure that all organisms are inactivated and the purity of the product water guaranteed. With the addition of some alkaline chemicals to restore the pH balance, the NEWater is ready for use.
http://en.wikipedia.org/wiki/NEWater#Production
http://en.wikipedia.org/wiki/Sewage_treatment#Process_overview
https://en.wikipedia.org/wiki/Greywater#Systems