Ian Pallett reports on a recent Global Watch mission that visited Singapore and Australia to investigate developments in innovative water reuse, recycling and rainwater harvesting technologies. The visit was managed by British Water with funding from the UK Department of Trade and Industry.
Singapore and Australia both have water resource problems with different causes. Singapore receives a considerable quantity of water from Malaysia. Water supply contracts are due for renewal in 2011 and 2061 but costs are proving difficult to agree. Australia is in the grips of a drought which is now in its tenth year and extended periods of rain are not forecasted this year, the recent rains will not have a significant impact as extensive rainfall is needed.
To secure water resources, Singapore has embarked on a programme to review all alternative sources of water, promote more efficient water use, and improve demand management. A government owned utility, the Public Utilities Board (PUB), manages the entire water cycle in Singapore. PUB is promoting water conservation measures through publicity campaigns as part of a sustainable and holistic water resource management strategy.
The programme includes active research and development as well as infrastructure improvements to increase Singapore’s water catchment area. Following successful piloting of innovative technology, including 16-inch diameter reverse osmosis (RO) vessels, four large wastewater treatment plants have been built, providing high quality treated effluent for reuse. These are supplied with wastewater from residential areas via large deep sewers. Secondary treated effluent is further processed by microfiltration (MF), ultrafiltration (UF) and RO membranes, and UV disinfection.
The largest planned indirect potable reuse (IPR) scheme in the world will have 3% of the reclaimed water diverted to public supply reservoirs by 2011. Reclaimed water has been branded “NEWater” and PUB has managed to attain a high level of public confidence in NEWater through an extensive and expensive education and marketing campaign (see Figure 1).
Figure 1
PUB NEWater marketing campaign poster
In Australia, the severe 10-year drought coupled with rising demand for water due to increasing urbanisation have driven resource and supply management strategies. Water supply is a state responsibility often devolved to municipalities, but increasingly state and federal governments are proposing policies designed to develop a coordinated response. Phase 1 of the National Guidelines for Water Recycling covers non-potable uses of treated wastewater and greywater; recent Phase 2 developments give guidance for IPR, managed aquifer recharge and stormwater use.
The Australian Government National Water Commission is responsible for helping to drive water reform and advising the Prime Minister, state and federal governments. It is responsible for managing the implementation of various programmes including the National Water Initiative, a comprehensive intergovernmental (interstate) agreement, aiming to increase the efficiency of Australia’s water use. The scheme is designed to lead to greater certainty for investment and productivity as well as to encourage environmental benefits.
The potential intensity of the drought became apparent when resource estimations were based on the most recent 10 year average rainfall rather than a 100 year average. Some large scale recycling of treated wastewater to industry has been initiated, with technologies similar to those seen in Singapore, but state authorities are developing plans for using recycled treated wastewater in smaller applications and residential areas. Some water suppliers have discounted IPR, others are considering it, but in one referendum the public rejected it. However, in early 2007 the Queensland Premier has recently said there is no alternative in some regions and so he is planning to press ahead with IPR projects.
As well as supplying large industries, recycled water is being used for municipal irrigation. ‘Sewer mining’ is practiced where a convenient main sewer can be tapped and sewage treated using a package plant or reed beds: for an improved public perception of the reclaimed water “sewer mining” has been renamed “water mining”! Greywater recycling combined with rainwater harvesting is also being trialled and many large new developments incorporate dual networks for the supply of potable and recycled treated wastewater. The pipework comes in two distinct colours and cross connections are monitored by comparing meter readings. One region has “water police” to provide guidance to residents. There are examples of in-building recycling of blackwater and rainwater.
Figure 2
Anticipated residential water use in Pimpama Coomera, Gold Coast Water
Australian planning regulations now require the installation of rainwater tanks and plumbing to allow rainwater to be used for external domestic use, toilet flushing and laundry. Use for domestic hot water is being considered but there are some health concerns. Stormwater collection is being trialled using treatment by reed beds or wetlands before the water is used for aquifer recharge, irrigation or by industries such as wool washing.
Figure 3
Covered reed bed for stormwater reclamation
Another problem in Australia is the amount of water used for irrigation.
Typically 50% of the domestic water supply has been used to water gardens and the use for irrigation by agriculture has been extensive. Demand management practices are being introduced leading to restrictions on garden watering.
Useful Links
DTI Global Watch website: www.globalwatchservice.com/
The Global Watch Service has now closed, some of the features of the Global Watch Service are still available via the KTN portals at www.ktnetworks.co.uk
Mission Report: www.environmentalthinking.com/britishwater/36770MR.pdf
NEWater website: www.pub.gov.sg/NEWater
Australian Government National Water Commission website: www.nwc.gov.au
British Water website: www.britishwater.co.uk,
About the Author
Dr Ian Pallett is Technical Director at British Water, Contact via their website.