  Location of Witsand Solar Desalination Plant | |
 | |
| Desalination plant | |
|---|---|
| Location | Witsand, Hessequa Municipality, Western Cape Province |
| Coordinates | 34°23′48″S20°50′51″E / 34.39667°S 20.84750°E |
| Estimated output | 100,000 liters (100 m3) of water daily |
| Cost | ZAR:8.6 million (US$650,000) [1] |
| Technology | Sedimentation, Reverse osmosis, Chlorination |
| Operation date | October 2018 (Expected) |
Witsand Solar Desalination Plant (WSDP) is a water purification project under construction in South Africa. [2] [3]
The water treatment facility is under construction in the seaside town of Witsand, in Hessequa Local Municipality, in the Western Cape Province, at the mouth of the Breede River. [2] This is approximately 305 kilometres (190 mi), by road, south-east of Cape Town, the nearest large city. [4]
The town of Witsand is a tourist attraction, with a low-season population of approximately 300 people. During the tourist high-season, the population swells to over 3,000 people, leading to freshwater scarcity in the town. To address that scarcity, the government of the Western Cape and the French government, decided to jointly develop and fund he Witsand water purification project. [2]
The WSDP is the first desalination plant in South Africa, that uses solar energy to power its processes. Its new technology applications, allow for the elimination of storage batteries in the design. [3] The plant's new Osmosun technology, involves the use of a specialized "intelligent" membrane that is able to continue delivering reverse osmosis, even when the sun goes behind a cloud, thus reducing the amount of solar energy delivered. The energy delivered would increase again when the clouds moved away. That ability to "soften" the variability in the energy delivered, preserves the reverse osmosis membrane. At night, when there is no sun, the design allows the plant to switch to conventional grid-electricity and continue working all through the darkness, until the sun rises the next morning. [2]
The budgeted cost of the plant is ZAR:8.6 million (approx. US$650,000), to be shared equally between the governments of the Western Cape and that of France. [1] The unit cost of the purified water at this plant is between ZAR:7 to ZAR:8 (US$0.52 to US$0.60) for every 1,000 liters (220 imp gal; 264 U.S. gal). In comparison, the temporary diesel-fueled desalination plant at Strandfontein, in Cape Town, produces potable water at ZAR:35 to ZAR:40 (US$2.62 to US$3.00) for every 1,000 liters. If this project is a success, it might be reproduced in other parts of the country, where drought is a problem. [2]
In order to generate enough solar energy for its internal processes, the plant needs 3.5 hectares (8.6 acres) to accommodate the requisite solar panels. This requirement for large areas to install solar panels, may restrict the project's reproducibility in crowded cities like Cape Town. [2]
Desalination is a process that takes away mineral components from saline water. More generally, desalination is the removal of salts and minerals from a target substance, as in soil desalination, which is an issue for agriculture. Saltwater is desalinated to produce water suitable for human consumption or irrigation. The by-product of the desalination process is brine. Desalination is used on many seagoing ships and submarines. Most of the modern interest in desalination is focused on cost-effective provision of fresh water for human use. Along with recycled wastewater, it is one of the few rainfall-independent water resources.
Forward osmosis (FO) is an osmotic process that, like reverse osmosis (RO), uses a semi-permeable membrane to effect separation of water from dissolved solutes. The driving force for this separation is an osmotic pressure gradient, such that a "draw" solution of high concentration, is used to induce a net flow of water through the membrane into the draw solution, thus effectively separating the feed water from its solutes. In contrast, the reverse osmosis process uses hydraulic pressure as the driving force for separation, which serves to counteract the osmotic pressure gradient that would otherwise favor water flux from the permeate to the feed. Hence significantly more energy is required for reverse osmosis compared to forward osmosis.
Water reclamation is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include: urban reuse, agricultural reuse (irrigation), environmental reuse, industrial reuse, planned potable reuse, and de facto wastewater reuse. For example, reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater. Reused water may also be directed toward fulfilling certain needs in residences, businesses, and industry, and could even be treated to reach drinking water standards. The injection of reclaimed water into the water supply distribution system is known as direct potable reuse. However, drinking reclaimed water is not a typical practice. Treated municipal wastewater reuse for irrigation is a long-established practice, especially in arid countries. Reusing wastewater as part of sustainable water management allows water to remain as an alternative water source for human activities. This can reduce scarcity and alleviate pressures on groundwater and other natural water bodies.
Solar desalination is a desalination technique powered by solar energy. The two common methods are direct (thermal) and indirect (photovoltaic).
An atmospheric water generator (AWG), is a device that extracts water from humid ambient air, producing potable water. Water vapor in the air can be extracted either by condensation - cooling the air below its dew point, exposing the air to desiccants, using membranes that only pass water vapor, collecting fog, or pressurizing the air. AWGs are useful where potable water is difficult to obtain, because water is always present in ambient air.
Osmotic power, salinity gradient power or blue energy is the energy available from the difference in the salt concentration between seawater and river water. Two practical methods for this are reverse electrodialysis (RED) and pressure retarded osmosis (PRO). Both processes rely on osmosis with membranes. The key waste product is brackish water. This byproduct is the result of natural forces that are being harnessed: the flow of fresh water into seas that are made up of salt water.
A reverse osmosis plant is a manufacturing plant where the process of reverse osmosis takes place. Reverse osmosis is a common process to purify or desalinate contaminated water by forcing water through a membrane. Water produced by reverse osmosis may be used for a variety of purposes, including desalination, wastewater treatment, concentration of contaminants, and the reclamation of dissolved minerals. An average modern reverse osmosis plant needs six kilowatt-hours of electricity to desalinate one cubic metre of water. The process also results in an amount of salty briny waste. The challenge for these plants is to find ways to reduce energy consumption, use sustainable energy sources, improve the process of desalination and to innovate in the area of waste management to deal with the waste. Self-contained water treatment plants using reverse osmosis, called reverse osmosis water purification units, are normally used in a military context.
A solar-powered desalination unit produces potable water from saline water through direct or indirect methods of desalination powered by sunlight. Solar energy is the most promising renewable energy source due to its ability to drive the more popular thermal desalination systems directly through solar collectors and to drive physical and chemical desalination systems indirectly through photovoltaic cells.
The Perth Seawater Desalination Plant, located in Naval Base, south of Perth, Western Australia, turns seawater from Cockburn Sound into nearly 140 megalitres of drinking water per day, supplying the Perth metropolitan area.
The Victorian Desalination Plant is a water desalination plant in Dalyston, on the Bass Coast in southern Victoria, Australia. The project was announced by Premier Steve Bracks in June 2007, at the height of the millennium drought when Melbourne's water storage levels dropped to 28.4%, a drop of more than 20% from the previous year. Increased winter-spring rains after mid-2007 took water storage levels above 40%, but it was not until 2011 that storages returned to pre-2006 levels.
Reverse osmosis (RO) is a water purification process that uses a semi-permeable membrane to separate water molecules from other substances. RO applies pressure to overcome osmotic pressure that favors even distributions. RO can remove dissolved or suspended chemical species as well as biological substances, and is used in industrial processes and the production of potable water. RO retains the solute on the pressurized side of the membrane and the purified solvent passes to the other side. It relies on the relative sizes of the various molecules to decide what passes through. "Selective" membranes reject large molecules, while accepting smaller molecules.
The Adelaide Desalination plant (ADP), formerly known as the Port Stanvac Desalination Plant, is a sea water reverse osmosis desalination plant located in Lonsdale, South Australia which has the capacity to provide the city of Adelaide with up to 50% of its drinking water needs.
Australia is the driest habitable continent on Earth and its installed desalination capacity has been increasing. Until a few decades ago, Australia met its demands for water by drawing freshwater from dams and water catchments. As a result of the water supply crisis during the severe 1997–2009 drought, state governments began building desalination plants that purify seawater using reverse osmosis technology. Approximately one percent of the world's drinkable water originates from desalination plants.
The Minjur Desalination Plant is a reverse osmosis, water desalination plant at Kattupalli village, a northern suburb of Chennai, India, on the coast of the Bay of Bengal that supplies water to the city of Chennai. Built on a 60-acre site, it is the largest desalination plant in India. Construction works were carried out by the Indian company IVRCL and the Spanish company Abengoa, under the direction of the Project Manager Fernando Portillo Vallés and the Construction Manager Juan Ignacio Jiménez-Velasco, who returned to Europe after the inauguration of the plant to work on renewable energy projects. Originally scheduled to be operational by January 2009, the work on the plant was delayed due to Cyclone Nisha in October 2008, which damaged a portion of the completed marine works and destroyed the cofferdam meant for the installation of transition pipes. The trial runs were completed in June 2010 and the plant was opened in July 2010. Water from the plant will be utilised chiefly for industrial purposes such as the Ennore Port and North Chennai Thermal Power Station. However, during droughts, water from the plant will be supplied to the public, serving an estimated population of 1,000,000.
Witsand, Western Cape, South Africa, is a small coastal town, situated on the banks of the Breede River estuary. Witsand is home to 4 kilometers of clean, sandy beaches, surrounded by a magnificent variety of Cape Fynbos species and the Breede River. The town is known as the Whale Nursery of South Africa due to the high concentration of whales in the bay between June and November. Witsand is an authentic water-sport and adventure destination with kite-surfing, surfing, standup paddle boarding and fishing as top visitor experiences. The town is located within the Hessequa region, which is branded as The Explorer's Garden Route.
There are approximately 16,000 operational desalination plants, located across 177 countries, which generate an estimated 95 million m3/day of fresh water. Micro desalination plants operate near almost every natural gas or fracking facility in the United States. Furthermore, micro desalination facilities exist in textile, leather, food industries, etc.
The Erongo Desalination Plant, also known as the Orano Desalination Plant, is a sea water desalination plant in Namibia. The facility was constructed between 2008 and 2010 by Orano Mining Namibia, which at the time was known as Areva Resources Namibia. The desalination plant was established to supply water to Orano’s Trekkopje Uranium Mine. At the time this plant was commissioned, it was the largest reverse osmosis desalination plant in Southern Africa.
The Bethanie Desalination Plant, also Bethany Desalination Plant, is a brackish water desalination plant in the settlement of Bethanie, in Namibia. The facility is owned and was developed by the Namibia Water Corporation (NamWater). The potable water produced by this plant, whose capacity production is 487 cubic meters (487,000 L) per day, is expected to supply the town of Bethanie until 2037.
Robert L. McGinnis is an American scientist, technology entrepreneur, and inventor who has founded a number of technology companies including Prometheus Fuels, Mattershift and Oasys Water.
Water scarcity in the United States is an increasing problem and it's estimated that more than 50% of the Continental U.S. has experienced drought conditions since 2000.
