Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/867173
18 In Site September 2017 Water. desalination + reuse crISIS SolutIonS cape town sought quick, affordable and flexible solutions • information on small, medium and large solutions is sought • project cost of ZAr 15 billion ($1.1 billion) identified in earlier feasibility study considered a barrier • flexible, mobile, and temporary solutions are preferable to a mega plant project Can desalination help to solve Cape Town's water crisis? The city's RfI in June aimed to "gauge interest in partnerships to install and operate temporary plants at various locations along Cape Town's shoreline and inland, and to inject water cape town authorities deploy two-pronged approach to water crisis • Request for information on temporary desal solutions in June • Three-stage tendering process outlined in August • Residents urged to limit use to 87 litres a day the city of cape town in South Africa's Western cape province is in the grip of its worst drought in the 103 years since records began in 1904. Since 2014, the volume of water in the city's six major dams has dropped precipitously, leading to concern that water supplies are in danger of running dry before the end of this year. the Western cape authorities declared the entire province a disaster zone in May, in part to hasten approvals for water projects. A few weeks later, the city's Water & Sanitation department put out a request for information (rfI) on possible temporary desalination options. the call- out sought ideas on "reverse osmosis or similar" solutions to augment water supplies by between 100,000 m3/d and 500,000 m3/d, by treating seawater, surface water, or runoff. In August, executive mayor Patricia de lille outlined a "portfolio response" to the crisis based on the work of the water resilience task team. the city began to procure and commission augmentation schemes for up to 500,000 m3/d of non-surface water. A second part of the response was to introduce water use restrictions for businesses and individuals. A special campaign, think Water, encourages residents to assess their water consumption using an online calculator, and aims to reduce usage to 87 litres per person a day. However, the city's collective usage target of 500,000 m3/d has continued not to be met, and authorities are stepping up their enforcement activities. collective usage was 632,000 m3/d in the week to 7 August 2017. Rainfall continues at well below long-term average levels for the second winter in a row. Water in the city's dams rose slightly during August owing to the water saving initiatives. into the distribution network". It focused on temporary solutions, "whether modular, containerised, or mounted on a barge or other sea vessel," for three sizes of project: small, less than 5,000 m3/d; medium, at 5,000 to 30,000 m3/d; and large, between 30,000 and 50,000 m3/d. The city wanted fast, emergency-type solutions from numerous vendors to which there is no significant commitment to purchasing water over the long-term. The approach reflects a sensitivity around price. Back in 2015, Cape Town completed a feasibility study on a 450,000 m3/d desalination plant near Koeberg, on the coast north of the city. The estimated cost of such a project was pegged at ZAR 15 billion ($1.1 billion), comprising ZAR 9.2 billion for the first phase of 150,000 m3/d, and ZAR 5.7 billion to expand up to 450,000 m3/d — before planning and design costs. "They went to market and got a quote on a plant of ZAR 15 billion. That's outrageously priced, no plant is that expensive. That kind of price would scare anyone off," says Tom Callaghan, head of group business development at water technologists GrahamTek. GrahamTek, based in South Africa, which installed its first reverse osmosis (RO) desalination unit using the 16-inch membrane developed by founder William Graham in Power Seraya, Singapore, in 2007, now has a global footprint with core businesses particularly in the Middle East and Asia. In June, GrahamTek brought out a special report in response to Western Cape's water crisis, 'White paper for the deployment of emergency and disaster relief desalination plants for the city of Cape Town'. In it, the desalination company suggested that "a complex array of solution alternatives" are required by Western Cape Province to meet its water needs, and it detailed a flexible system of potential alternative configurations of installations that GrahamTek could provide. GrahamTek argued that the proposed solutions represented an "augmented, non-conflicting and temporary disaster relief solution that could be converted into a long-term infrastructure asset." The solutions met the requirements of the province's disaster relief decision framework, and consider the future picture, including the potential impacts later down the line of decisions made today. The headline of the proposal was to install 100,000 m3/d of temporary, containerised RO capacity within an expedited timeframe, and simultaneously to kick off long-term desalination plant projects raising total desal capacity to 450,000 m3/d. The aim, says Callaghan, was to show how desalination could be used to augment the city's water supplies to up to about 33 per cent of total supply. "Our proposal is that desal should never be a 100 per cent solution. It should be maybe a quarter or a third of the water supply. You need base water supply augmentation, which desalination can provide," he says. The paper proposed installing mobile units at four port locations: Cape Town, Hout Bay, Simons Town, and Gordons Bay; as well as developing