Desalination of seawater

Desalination technology is hailed as a positive answer to worldwide water shortages, and is being developed and encouraged in areas that are close to oceans but lacking in freshwater supplies. However, desalination is not a fail-safe process and carries with it many environmental repercussions.

Desalination of seawater

Desalination of seawater

Desalination of Pacific Ocean Water 2. If seawater desalination is replacing the use of over-pumped coastal or inland groundwater aquifers, or is eliminating further stress on environmentally sensitive estuary and river habitats, then the higher costs of this water supply alternative would also be offset by its environmental benefits.

Similarly, seawater desalination provides additional benefits in the time of drought where traditional water supplies may not be reliable and their scarcity may increase their otherwise relatively low costs.

Energy use Salt separation from seawater requires a significant amount of energy to overcome the naturally occurring osmotic pressure exerted on the reverse osmosis membranes.

Desalination of seawater

This in turns makes seawater desalination several times more energy intensive than conventional treatment of fresh Desalination of seawater resources. Table 1 presents the energy use associated with various water supply alternatives.

The table does not incorporate the costs associated with raw water treatment Desalination of seawater product water delivery. For example, a number of water agencies and municipalities in San Diego County, Los Angeles County and Orange County in Southern California, have to import and convey a portion of their untreated source water at an additional energy expenditure of 1.

When this energy use for conveyance of source water is added to the energy needed for water treatment, the total power demand for production of fresh water from imported sources in some cases i.

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Often the opponents of seawater desalination in California argue that the energy used for desalination would create a significant negative impact on the energy use in the state. According to a report prepared recently by the California Energy Commissionthe current power demand of the water sector in California including both water and wastewater conveyance and treatment totals 13, MWh.

Assuming a conservative unit energy use for seawater desalination of 2. Seawater intakes A number of the seawater desalination projects under consideration in California and Florida are proposed to be collocated with power generation plants which currently use seawater for production of electricity.

Under the collocation configuration the desalination plant does not have a separate intake and discharge to the ocean and both the desalination plant intake and desalination plant discharge are connected to the exiting power plant discharge outfall or canal.

Figure 1 depicts a general schematic of the configuration of collocated desalination plant intake and discharge. Collocation yields a number of benefits mainly because it avoids construction and permits for new intake and concentrate discharge facilities, and because of the energy cost savings associated with the desalination of warmer source water.

However, collocation has been considered undesirable by some environmental groups due to the potential loss of marine organisms caused by the impingement of marine organisms against the screens of the power plant intake and their entrainment inside the power plant conveyance and cooling system and subsequently inside the desalination plant.

The actual significance of the loss of marine organisms due to once-through cooling as compared to other beneficial uses of the ocean, such as commercial and recreational fishing, has been a subject of debate and a flurry of recent federal and state regulations.

Based on recently introduced regulatory requirements, the 21 once-through cooling plants along the California coast are required to prepare comprehensive plans for discontinuation of their use of open intakes and switching to air-cooling towers or to water close-circulation cooling towers in order to reduce impingement and entrainment of marine organisms.

Opponents of collocated seawater desalination plants have often presented the argument that if the power plant changes its cooling system in the future, seawater desalination under collocated configuration at the particular location would no longer be available.

However, this argument is unfounded in reality, because most collocated desalination facilities have already executed long-term agreements with their power plant hosts to reserve the right to use their outfall and intake systems and equipment even if the power plant no longer needs them in the future.

Even if the host power plants abandon once-through cooling in the future, the desalination projects will still retain the main cost-benefits of collocation — avoidance of the need to construct a new intake and outfall. Recent studies of wedge-wire screens in Santa Cruz, California indicate that this type of open intake may prove to be a viable alternative for dramatic reduction in impingement and entrainment of marine organisms.

Wedge-wire screens are passive intake systems, which operate on the principle of achieving very low approach velocities at the screening media see Figure 2. Wedge-wire screens installed with small slot 1 to 5 mm openings reduce impingement and entrainment and are an EPA approved technology for compliance with the US EPA b Phase II rule provided the following conditions exist: This cross high flow velocity allows organisms that would otherwise be impinged on the wedge-wire intake to be carried away with the flow.

Some wedge-wire screen systems are air burst back-flush systems, which direct a charge of compressed air to each screen unit to blow off debris and impinged organisms back into the water body where they would be carried away from the screen unit by the ambient cross flow currents.Desalination Sea Water RO (SWRO) designed to handle a feed TDS of up to 42, ppm maximum.

An industrial-sized reverse osmosis (RO) system to covert sea water into drinking quality with PLC-based controller, Duplex SS Pumps. Designed and manufactured in USA.5/5(25). Perspective of the Water Shortage Problem (WSP) in Libya: The Sea Water Desalination River (SWDR) of Libya to Resolve the Water Shortage Problem (WSP) with Fresh Water Resources Feb 14, by Abdulmonem Elhassadi.

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Previous Page 1 2 3 6 Next Page. Today, desalination plants are used to convert sea water to drinking water on ships and in many arid regions of the world, and to treat water in other areas that is .

desalination - the removal of salt (especially from sea water) desalinisation, desalinization chemical action, chemical change, chemical process - (chemistry) any process determined by the atomic and molecular composition and structure of the substances involved.

Water desalination processes separate dissolved salts and other minerals from water. Feedwater sources may include brackish, seawater, wells, surface (rivers . Desalination of seawater to water suitable for human consumption or agricultural uses is a vital operation. Desalination is a process that removes minerals from seawater.

Desalination is the process of removing salt, especially from sea water so that it can be used for drinking or watering crops.

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