Water Journal : Water Journal September 2012-1
feature article water SEPTEMBER 2012 49 Recycled water, reclaimed water, reused water, NEWater, treated effluent, treated sewage, highly purified recycled water and potable reuse water are words commonly used by community leaders, water planners, technologists and the public to describe water that was once raw sewage, wastewater or an effluent to be managed or disposed of at the earliest opportunity. To keep things in line with the latest research into public acceptance of water recycling, the term drinking water reuse (DWR) has been adopted to describe the water management practice of converting used water such as wastewater or raw sewage into drinking water. For non-potable uses the terms water reuse or recycled water are used interchangeably to describe water reuse that does not include drinking. Global Developments From the late 1960s we have seen many new water recycling developments and upgrades to existing DWR projects in the global arena. Namibia was a pioneer in producing drinking water from wastewater or used water sources. Its first DWR plant opened in 1968 with a capacity of 4800kL per day and was refurbished in 2002 to produce water for agricultural irrigation, while a new state-of-the-art treatment plant was commissioned to produce 21,000kL per day for drinking water use (Cyclifer, 2012). Namwater currently has a number of tenders open for equipment upgrades and policy development across several of its sites (Namwater, 2012). Most recently a large groundwater aquifer was discovered under Namibia that could potentially take some of the focus off DWR for the time being should it be more economical (Department for International Development, 2012). Texas in the US, like Namibia, has a longstanding water reuse program. The San Antonio Water System holds the reputation for the largest water reuse treatment process in the United States and is a key player in reducing withdrawals from the surrounding groundwater systems in the desert state. Similarly, recycled water from Dallas gets pumped into the Trinity River, supplementing the flow of the river and replenishing the water that was removed, which ultimately supplies the city of Houston. This effectively creates a chain of water use and reuse within this catchment. The higher the quality of water reintroduced after the Dallas outlet, the less processing that is required for the Houston treatment facility downstream -- not to mention maintenance of river health to support many aquatic species and recreational activities. Arizona has a different approach to encouraging water recycling and, ultimately, DWR. After almost 30 years of supplying greywater for non-drinking uses an initiative established by the City of Tucson and supported by the Federal Government, which commenced in 2007 and has subsequently ceased, provided financial incentives for both new home owners and builders to install rainwater and greywater systems in all new homes that were built during this period. Providing an incentive of 25 per cent, up to US$1000 tax rebates for home owners and US$200 per install for contractors, as well as education on the safe uses and sources of recycled water, helped to re-brand recycled water for another generation of citizens. Being a desert community, Tucson Water supplies private residences with a recycled water supply, thus reducing the demand for groundwater for services such as irrigation. It has been reported that enough water has been saved to support 60,000 families every year (City of Tucson, 2012). Other incentives include a more affordable price for recycled water than for drinking water; this is achievable by using revenue from the drinking water service to fund the recycled water system. Big Spring, which is being built by the Colorado River Municipal Water District, is another facility that is designed to reduce the demand from groundwater sources. The purpose is to process the wastewater downstream of the treatment plant by passing it through a series of membranes and disinfection processes before it goes directly into water supply pipelines. From here the water is blended with water coming into existing water supply reservoirs and then passed to a conventional water treatment plant to become drinking water. The water supplies Permian Basin Cities, such as Odessa, with about 8,000kL of water per day, about one-eighteenth of the overall supply (Galbraith, 2012). Effectively, this system is practicing direct DWR without the customary intermediate buffer or environmental storage seen in other DWR projects such as NEWater, Singapore or Orange County, US. Water Reuse Practice and Projects: An Overseas Perspective For decades water shortages have seen governments and organisations around the globe look for ways to reuse water for both potable and non-potable purposes. Increasingly a lack of water security and new technology are opening up opportunities for safe, effective ways to augment existing water supplies. John Poon, Principal Technologist with CH2M HILL Australia, prepared this overview. A recycled water scheme in Riyadh could make 800,000kL of water per day available to the city.
Water Journal November 2012-1
Water Journal August 2012