Even after the successful implementation of demand management strategies to balance rising demand with limited supplies of water, there are regions around the world where water scarcity requires the seeking of alternative water supply sources.
The HAMBURG WATER CYCLE
Hamburg Wasser is developing the HAMBURG WATER CYCLE (HWC), which entails the separation of the material flows of wastewater: blackwater is separated from the greywater, rainwater is collected separately, while separated greywater can be cleaned with minimal energy consumption and either recycled for non-potable household use, or returned back to nature to replenish local waters. The HWC is being implemented in two locations in Hamburg. The Gut Karlshöhe project is a 9-acre environmental theme park created by the Hamburg Climate Protection Foundation for educational purposes. On a larger scale, the HWC will be implemented as part of the Jenfelder Au project, which is a residential area of around 35 acres that will house around 2,000 residents.
Singapore’s NEWater
Singapore’s NEWater process recycles treated used water into ultra-clean, high-grade reclaimed water. In total, five NEWater plants supply up to 40% of the city-state’s current water needs. By 2060, it is projected that NEWater will meet up to 55% of Singapore’s future water demand. NEWater is created from a three-step process involving microfiltration, reverse osmosis, and ultraviolet disinfection. Because of its ultra-clean state, NEWater is used for industrial processes including in wafer fabrication plants.
Melbourne’s City West Water’s Recycled Water Project
In Melbourne, City West Water’s West Wyndham Recycled Water Project aims to deliver high quality, Class A recycled water to housing estates in the Wyndham area, as well as a number of open spaces managed by the Wyndham City Council (Class A recycled water can only be used for toilet flushing, car washing on grassed areas, garden watering, filling water features, providing drinking water for pets, and washing machines). Currently, recycled water – a mix of drinking water and recycled water – is supplied to around 3,750 homes in the area. The aim of the West Wyndham Recycled Water Project is to create a supply of 100 percent recycled water.
City of Tucson’s Rainwater harvesting rebate
Tucson Water in Arizona is providing rebates for qualifying rainwater harvesting systems of up to $2,000 per property. To qualify, applicants must be Tucson Water customers and attend an approved Rainwater Harvesting Incentives Program Workshop that covers topics including what rainwater harvesting is, best methods to conserve potable water by utilising rainwater harvesting systems, and how to develop a rainwater harvesting project plan. There are two types of rebates available to customers: an incentive for single simple/passive rain gardens that direct and retain water in landscapes and another for complex/active rain tanks.
Conclusions
Cities facing acute water scarcity can develop and encourage a variety of alternative water supply sources including greywater systems in new urban developments that recycle water for non-potable household use or to replenish local waters, water recycling facilities that treat water to an ultra-high quality for industrial purposes as well as for household non-potable uses, and rainwater harvesting systems of varying complexity.
