The Future Of Desalination In The United Arab Emirates and The Technical, Legal Aspect of Desalination - Coursework Example

The technical and legal aspect of desalination I- The different types of techniques of desalination used worldwide In essence, a desalination process is intended to separate saline water into two components: one with law salt concentration and the other with high salt concentration compared to the initial feed water (Bienkowski 2015). The main technologies used for desalination across the globe are categorised into membrane and thermal technology, both of which require energy for the production of fresh water. The membrane and thermal technologies also have their own sub-categories that use different techniques (WaterUse 2011). Table 1: Desalination technologies and their sub-categories Thermal Technologies Thermal technologies rely on heating of saline water before the condensed vapour (distillate) is collected to generate pure water (Krishna, H n.d.). While they are not often used to desalinate brackish water due to their high associated costs, they have found wide application in the desalination of seawater. Thermal technologies are specifically sub-classified into three groups: Multi-Effect Distillation (MED), Vapor Compression Distillation (VCD), and Multi-Stage Flash Distillation (MSF) (Krishna, H n.d.). Multi-Stage Flash Distillation (MSF) Multi-Stage Flash Distillation (MSF) technique entails the application of distillation that relies on a number of chambers, or multi-stage process. Each of the subsequent stage operates at increasingly lower pressures. At the beginning, heating of the feed water takes place under high pressure, before the water is channelled into the first ‘flash chamber,’ for releasing of pressure (Krishna, H n.d.). This causes rapid boiling of water leading to rapid evaporation. A part of the feed undergoes ‘flashing’ at each successive stage, as the pressure in each successive stage is lower compare to the preceding one. Afterwards, the vapour that the flashing generates becomes converted to fresh water after undergoing condensation on heat exchanger tubing found in each successive stage. The MSF plants generate nearly 84% of that capacity in the Middle East (Krishna, H n.d.). Figure 1: Schematic of the desalination process (Munk 2008). Multi-Effect Distillation (MED) Multi-effect distillation technique is designed to takes place using a sequence of vessels. It relies on the principles of condensation and evaporation at minimised pressures. A sequence of evaporator effects generates water at increasingly lower pressure. At the same time, the boiling of water takes place at low temperatures in correspondence with decreasing pressure. In this way, the water vapour found in the first vessel functions as the medium that heats the second, and so on (Krishna n.d.). Three low-temperature MED plants that generate a capacity of 3.5 mgd operate in St. Thomas, U.S. Virgin Islands. Several MED plants are also found in the Middle East and in Caribbean. Membrane Technologies Membrane technologies are classified into two key categories: Reverse Osmosis (RO) and Electrodialysis Reversal (EDR). Electrodialysis Electrodialysis (ED) refers to a voltage-driven membrane process that relies on electrical potential to push salts through a membrane. This in turn generates fresh water. While it was originally intended to desalinate seawater, it is mostly used for desalinating brackish water. The technique operates on principle that much of the salt that dissolves in water is ions, which may be negatively (anions) or positively charged (cations) (Krishna, H n.d.). As like poles repel and unlike poles attract, migration of the ions self-initiates toward the electrodes containing opposite charge. Appropriate membranes are then built for purposes of allowing for selective passage of cations and anions. In the process, the salt in the brackish water gets dilute. On the other hand, concentrated solutions are created at the electrodes. Feed water then penetrates through the cell membranes leading to a continual flow of desalinated water in addition to a steady stream of concentrate. ED units are available in Texas and are mainly used for low-salinity applications, including surface water desalination at Lake Sherman and Granbury (Krishna, H n.d.). Figure 2: Schematic of the ED process (Munk 2008). Reverse Osmosis (RO) The RO process relies on pressure to drive saline water through semi-permeable membranes into a concentrated brine stream and product water stream (Sheeja 2015). It is mainly used for the elimination of Sodium and Chloride. It is primarily applied in the desalination of seawater and brackish water (TDS>1,500 mg/l). Reverse Osmosis (RO) is popularly used in the United States (Ziolkowska 2016). Figure 3: Schematic of the RO desalination process (Munk 2008). II-The energy aspect A- The traditional processes (consideration and criticism ) Desalination energy as osmotic driver When it comes to seawater desalination, feed water salinity is considered a major energy consumer, as it contains greater amounts of dissolved salts compared to brackish water. The reason for this is because the desalination process has to surmount the osmotic pressure in order to overturn the flow. This in turn forces water to move from the “saltier” the membrane’s feed side to the more “purified” water (See the Figure 2 below). The process requires the use of energy to pump the water. The membrane feed pressure increased with an increase in feed water salinity until a limitation of 1200 psi (82.7 bar), which is appropriate for drinking water, is achieved as shown for a case of seawater that has a salinity of 34,000 mg/L (See Figure 5) (Verg et al. 2011). Figure 4: How temperature affects pumping energy (Verg et al. 2011). Due to the variable nature of salinity across the coastal sides of the United States, the mandatory driving pressure and related energy necessary for producing similar throughput for diverse salinities would as a result vary (Verg et al. 2011). According to Verg et al. (2011), the net driving pressure necessary for generating an equivalent quantity of permeate would increase by nearly “11 psi (0.76 bar) for each 1000 mg/L (1 ppt)” increased change in the salinity of feed water (Verg et al. 2011). The traditional technologies commercially used for desalination in the Middle East and the United States are multistage flash (MSF), reverse osmosis (RO), and multi-effect distillations (MED). While all these technologies demand substantial amounts of thermal in the form of electric energy to run, MED has the highest electricity consumption compared to MSF, while RO has the lowest (Verg et al. 2011). RO’s non-energy operating costs of RO are still higher compared to that of thermal technologies. The desalination technologies require significantly high energy requirements. They also have high negative environmental implication due to their Carbon dioxide emissions and side-products because of the power supply to desalination plants. The energy consumption of the three technologies is demonstrated below. Table 2: Electrical energy use outcomes of desalination process (Verg et al. 2011) These make desalination to be expensive. For instance, 1000 gallons of freshwater from a desalination plant costs average consumers in the United States up to $5. It is also estimated that desalination plants from across the globe consume some 200 million kilowatt-hours daily, while energy costs make up nearly 55% of the total operation and maintenance of the desalination plants (Verg et al. 2011). The RO plants consume some 3-10 kilowatt-hours of energy to generate one cubic meter of freshwater from seawater (Bienkowski 2015). Therefore, the cost of traditional desalination is greatly dominated by energy costs. B - Technological advancement Use of Renewable Energy Desalination using renewable energy sources has a potential to create sustainable means to fresh water generation. Renewable desalination is in most cases (about 62% of the cases) used in the RO process (Verg et al. 2011). The leading energy source used is solar photovoltaics (PV). It is used in nearly 43 percent of the current applications, ahead of solar thermal and wind energy. Combining sources of renewable energy with a desalination technology is central to energy efficiency and environmental conservation. The table below shows a mix of renewable energy sources and desalinisation technology (Meindertsma et al 2010). Figure 5: Combined use of renewable energy and desalination technologies (Verg et al. 2011) Photovoltaic Desalination Photovoltaic (PV) technology can be used with RO or ED desalination technologies, which rely on electricity as the primary input energy. However, its key barrier to PV desalination is the high cost associated with procuring and marinating PV cells and batteries that store electricity (Meindertsma et al 2010). Currently, the biggest solar PV desalination plant in the world that uses nano-membrane technology is in Al Khafji, Saudi Arabia. The first phase of the plant is expected to have a production capacity of about 30,000 m3 /d, which is expected to serve up to 100,000 people in the country. Desalination plants that also use renewable energy are in Abu Dhabi, Morocco, Jordan, Turkey, and Egypt (Meindertsma et al 2010). Figure 6: Schematic of PV and RO desalination plant (Verg et al. 2011) Solar Thermal Desalination Desalination of seawater through MED and MSF by use of solar heat as the primary energy input are potential desalination processes that use renewable energy. Essentially, the desalination plant is made up of two components: distiller and solar heat collector. The process is referred to as an indirect process. An example includes desalination that requires concentrating solar power (CSP) plants (Meindertsma et al. 2010). The CSP plants accumulate solar radiation and in turn offer heat and high-temperature, which generate electricity. Hence, they can be linked to membrane desalination units, like in RO or thermal desalination units. In some desert regions like UAE or Saudi Arabia where plenty of solar energy can be collected from high direct solar irradiance, the CSP plants are particularly multi-purpose technology for generation of electricity and desalination of water (Meindertsma et al 2010). According to data from the German Aerospace Centre, choosing between CSP for the MED process and the CSP for the RO process is contingent on feed-water quality. The CSP for MED process tends to be more energy-efficient compared to the CSP for RO process used in the Arabian Gulf as this region has seawater with particularly high salinity level (Verg et al. 2011). Wind Power Desalination The mechanical and electrical power that wind turbine generates is also used in powering desalination plants, particularly for the ED and RO desalination units, as well as in vapour compression (VC) distillation processes, such as in Mechanical Vapor Compression (MVC) (Meindertsma et al. 2010). For instance, when it comes to the MVC, the VC uses the mechanical energy that wind turbine generated directly without a need to convert it into electricity. Generally, desalination that uses wind power is an alternative energy source for desalinating seawater, particularly in the coastal regions experiencing high wind potential (Verg et al. 2011). Geothermal Desalination Geothermal energy also produces heat and electricity, which can be integrated with membrane and thermal desalination technologies to desalinate water. Geothermal energy with low temperatures, such as 90°C, is idyllic for the MED desalination process (Meindertsma et al. 2010). A case in point of geothermal desalination plant is found at Milos Island, Greece, whose system is expected to generate nearly 1,920 m3 /d of water. The desalination plant is made up of a dual system that carries hot water emanating from the geothermal wells used in running a MED desalination unit. The plant is beneficial to the locals as it produces desalinated water at extremely low cost, of about USD 2/m3 as of 2011 (Verg et al. 2011). III- Desalination from a legal point of view From regulatory viewpoint, desalination as a critical source of drinkable or potable water is comparatively new in a majority of countries except for some Gulf countries and the United States. This implies that environmental and health regulations that touch on desalination are yet to be developed (Sellers 2014). United States In the United States, the Environmental Protection Agency (EPA) regulates desalination. The EPA has adamantly stated that water intake structures are key contributors to undesirable environmental implications, as they suck fish into industrial systems, where they are killed by chemicals, physical stress, or heat (Munk 2008). At any rate, the EPA is yet to issue any regulations relating to the disposal of desalination wastes. However, there are a number of existing regulations containing appropriate guidelines. For instance, for disposal of surface water, the Clean Water Act (CWA) is particularly relevant as it oversees disposal of substances into ground or surface water. In particular, section 402 of the CWA requires that any desalination plant that discharges directly into surface or ground waters in the United States must have a National Pollutant Discharge Elimination System (NPDES) obtained from the EPA. The NPDES specifies the permitted levels of pollutant concentrations in the surface or ground waters. The EPA also issues the National Recommended Water Quality Criteria that specify standard values for pollutant concentrations in U.S. waters (Munk 2008). Although the criteria are legally unbinding, they function as guideline for state legislations. Each state in the United States, therefore, uses recommended EPA standards (Munk 2008). UAE In the UAE, desalinated water makes up 80 percent of the total water consumption (Szabo 2011). It is the second largest producer of desalinated water, after Saudi Arabia, in the Middle East and North Africa (MENA) (Business Monitor International 2009). In the UAE, particularly the Abu Dhabi Emirate, which the Business Monitor International (2009) considers to have the highest per capita water consumption rate globally of about 525-600 gallons a day (g/d), desalination is overseen by the Abu Dhabi Water & Electricity Authority (ADWEA), which relies on “Law No (2) of 1998 Concerning the Regulation of the Water and Electricity Sector in the Emirate of Abu Dhabi.” In Abu Dhabi, the Regulation and Supervision Bureau (RSB) for the Water and Electricity Sector also enforces the pertinent laws through licensing. An additional relevant regulation in Abu Dhabi is the Water Quality Regulations, specifically Part 8.1 Drinking water safety plan, which specifies that water suppliers should develop and keep a drinking water safety plan (DWSP) in compliance with the RSB’s standards for drinking water, which encompasses the prospective areas of contamination risks linked to internal and external factors affecting production, transmission, and distribution of water (Parmigiani 2015). IV- Environmental impact of water desalination In spite of the many huge benefits of desalination, including accounting for 5000 million m3 of the global water production, it has significant negative effects on the environment (Dawoud & Mulla 2012). Seawater desalination plants would typically accept feed water from a variety of sources, even as open seawater intakes are more prevalent. When the open intakes are used, it leads to a loss of aquatic organisms, which run into intake screens or are absorbed into plants with source. Constructing intake structures and piping leads to initial disruption of the seabed. This leads to re-suspension of pollutants in the water column. Once installed, the structures interfere with water exchange and transportation of sediments, which function as artificial reefs for organisms (Dawoud & Mulla 2012). Desalination processes generate massive quantities of brine water that have high temperatures and are made up of residues of cleaning and pre-treatment chemicals. Additionally, high salt concentration gets discharged to the sea, which leads to higher levels of seawater salinity (Al-Mutaz 2010). As seawater is less dense than brine, it sinks into the bottom of the sea and, therefore, potentially damages the ecosystem. It also interferes with the marine life, as sea plants and animals that cannot survive in highly saline waters become eliminated. In the Gulf, the ambient seawater salinity was originally nearly 45 ppm, although the desalination plants increased the level to averagely 10 ppm above the ambient condition. The adverse environmental conditions also fend off marine life (Dawoud & Mulla 2012). Desalination also increases seawater temperatures. In the Gulf countries, a majority of the desalination plant are integrated with a power plant where the water temperature of the power plants effluents raises the seawater temperatures of the ambient water (Al-Mutaz 2010). During hot season, ambient seawater temperature is estimated to reach about 35 °C while the power and desalination plants lead to increased temperatures by nearly 8 °C beyond the ambient conditions. While a majority of organisms have a potential to adapt to small temperature deviations, and may in most instances put up with extreme conditions momentarily, continual exposure to adverse conditions are fatal for aquatic life, and contribute to long-term alterations species composition. The adverse environmental conditions may as well repel marine life (Younos 2005). Desalination also causes greenhouse gas (ghg) emission. In the Gulf countries, water desalination is considered to be an energy-intensive process that uses non-renewable fossil fuels. A major concern is its potential impacts on climate change. The non-renewable fossil fuels emit carbon dioxide, which is a major contributor to climate change (Dawoud & Mulla 2012). References Al-Mutaz, I 2010, "Environmental Impact Of Seawater Desalination Plants," Environmental Impact of Seawater Desalination Plants, vol 3, pp.1-10 Bienkowski, B 2015, "Desalination is an expensive energy hog, but improvements are on the way," PRI, 24 Aug 2016, Business Monitor International 2009, “Part of BMI's Industry Report & Forecasts Series," United Arab Emirates Water Report Q1 2010 Dawoud, M & Mulla, M 2012, "Environmental Impacts of Seawater Desalination: Arabian Gulf Case Study," International Journal of Environment and Sustainability, Vol. 1 No. 3, pp. 22‐37 IRENA 2011, Water Desalination Using Renewable Energy, viewed 24 Aug 2016, Krishna, H n.d., Introduction to Desalination Technologies, viewed 24 Aug 2016, Meindertsma, W, Sark, W & Lipchin, C 2010, "Renewable energy fueled desalination in Israel," Desalination and Water Treatment, vol 13, pp.450-463 Munk, F 2008, Ecological and economic analysis of seawater desalination plants, viewed 24 Aug 2016, Parmigiani, L 2015, "Water and Energy in the GCC: Securing Scarce Water in Oil-Rich Countries," IFRI Centre Energie Sellers, J 2014, Desalination policy in a multilevel regulatory state, viewed 24 Aug 2016, Sheeja, P 2015, "Advance Technologies In The Process Of Desalination," World Journal Of Pharmacy And Pharmaceutical Sciences, vol 4 no 2, pp.875-886 Szabo, S 2011, "The Water Challenge in the UAE," Dubai School of Government Policy Brief no. 2, viewed 24 Aug 2016, Verg, H, Ilian, I & Tannock, Q 2011, Patent Landscape Report on Desalination Technologies and the Use of Alternative Energies for Desalination, World Intellectual Property Organization (WIPO), viewed 24 Aug 2016, WaterUse 2011, "Seawater Desalination Power Consumption," WaterUse White Paper, November 2011 Younos, T 2005, "Environmental Issues of Desalination," Journal Of Contemporary Water Research & Education, Iss 132, pp.11-18 Ziolkowska, J 2016, "Desalination leaders in the global market – current trends and future perspectives," Water Science & Technology: Water Supply, vol 16 no 3, pp.563-568 Read More

Electrodialysis (ED) refers to a voltage-driven membrane process that relies on the electrical potential to push salts through a membrane. This in turn generates fresh water. While it was originally intended to desalinate seawater, it is mostly used for desalinating brackish water. The technique operates on the principle that much of the salt that dissolves in water is ions, which may be negatively (anions) or positively charged (cations) (Krishna, H n.d.). As poles repel and unlike poles attract, migration of the ions self-initiates toward the electrodes containing the opposite charge. Appropriate membranes are then built to allow for the selective passage of cations and anions. In the process, the salt in the brackish water gets dilute. On the other hand, concentrated solutions are created at the electrodes. Feedwater then penetrates through the cell membranes leading to a continual flow of desalinated water in addition to a steady stream of concentrate. ED units are available in Texas and are mainly used for low-salinity applications, including surface water desalination at Lake Sherman and Granbury (Krishna, H n.d.).

The RO process relies on pressure to drive saline water through semi-permeable membranes into a concentrated brine stream and product water stream (Sheeja 2015). It is mainly used for the elimination of Sodium and Chloride. It is primarily applied in the desalination of seawater and brackish water (TDS>1,500 mg/l). Reverse Osmosis (RO) is popularly used in the United States (Ziolkowska 2016).

When it comes to seawater desalination, feedwater salinity is considered a major energy consumer, as it contains greater amounts of dissolved salts compared to brackish water. The reason for this is because the desalination process has to surmount the osmotic pressure to overturn the flow. This in turn forces water to move from the “saltier” membrane’s feed side to the more “purified” water (See Figure 2 below).

The process requires the use of energy to pump the water. The membrane feed pressure increased with an increase in feed water salinity until a limitation of 1200 psi (82.7 bar), which is appropriate for drinking water, is achieved as shown for a case of seawater that has a salinity of 34,000 mg/L (See Figure 5) (Verg et al. 2011).

Due to the variable nature of salinity across the coastal sides of the United States, the mandatory driving pressure and related energy necessary for producing similar throughput for diverse salinities would as a result vary (Verg et al. 2011). According to Verg et al. (2011), the net driving pressure necessary for generating an equivalent quantity of permeate would increase by nearly “11 psi (0.76 bar) for each 1000 mg/L (1 ppt)” increased change in the salinity of feed water (Verg et al. 2011).

The traditional technologies commercially used for desalination in the Middle East and the United States are multistage flash (MSF), reverse osmosis (RO), and multi-effect distillations (MED). While all these technologies demand substantial amounts of thermal in the form of electric energy to run, MED has the highest electricity consumption compared to MSF, while RO has the lowest (Verg et al. 2011). RO’s non-energy operating costs RO are still higher compared to that of thermal technologies. The desalination technologies require significantly high energy requirements. They also have high negative environmental implications due to their Carbon dioxide emissions and side-products because of the power supply to desalination plants. The energy consumption of the three technologies is demonstrated below.

These make desalination to be expensive. For instance, 1000 gallons of fresh water from a desalination plant costs average consumers in the United States up to $5. It is also estimated that desalination plants from across the globe consume some 200 million kilowatt-hours daily, while energy costs make up nearly 55% of the total operation and maintenance of the desalination plants (Verg et al. 2011). The RO plants consume some 3-10 kilowatt-hours of energy to generate one cubic meter of fresh water from seawater (Bienkowski 2015). Therefore, the cost of traditional desalination is greatly dominated by energy costs.

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