Effects of Desalination Plants in Abu Dhabi

Effects of Desalination Plants in Abu Dhabi
Introduction
Desalination remains an important process in generating fresh water for human use in Abu Dhabi. Today, as water shortage increases all over the world, desalination provides 5000 million m3 each year, globally. It is a critical process because Abu Dhabi lacks adequate surface water. By processing the salty sea water, desalination provides adequate fresh water to the people of Abu Dhabi. Despite the significant role that the process plays in the economy of Abu Dhabi, concerns are increasing over the potential impacts of desalination on the environment. Desalination affects the environment because it emits harmful chemicals. Furthermore, the process increases the atmospheric temperatures in Abu Dhabi. The implication, therefore, is that desalination requires immediate interventions that will minimize its chemical and temperature effects on the environment. Sustainability of the process is an issue that requires serious attention. However, the responsible authorities must understand how desalination affects the environment. They need information on the chemical emissions of desalination. They also need information about the changes in temperature as a result of desalination. This paper analyzes the chemical and thermal effects of desalination in Abu Dhabi.
Environmental effects of Desalination in Abu Dhabi
The main reason the environmental effects of desalination are a serious problem is that research reveals that the rate of desalination will continue increasing. As many countries turn to desalination, the implication is that the environment will bear more chemical and thermal consequences. In the Asian Gulf region (where Abu Dhabi is), where desalination is the main source of water, the environmental effects will become unbearable if the authorities do not introduce measures to mitigate the problem.
The graph below shows the rates of desalination in the past and how it will increase in the future.

Figure 1: The historical and future projections of desalination
i. Chemical effects of Desalination in Abu Dhabi
Desalination produces greenhouse gases, which have serious negative effects on the marine environment in Abu Dhabi. The process separates fresh water from the saline sea water. The by-products of the purification process green house gases and brine water. Brine water has high concentrations of salt. A schematic diagram shows a general perspective of the process, identifying the inputs and the outputs. The following diagram is a typical schematic diagram for the process.

Figure 2: A schematic diagram showing the process of desalination.
The sustainability report of the Abu Dhabi Water and Electricity Authority shows that brine water, which gets to the marine environment has dangerous chemicals that degrade it. Brine water contains chemicals like magnesium, sodium, sulphur, chlorine, and hydrogen carbonate compounds, among other harmful chemicals. The table below shows the amounts of chemicals that brine water contains. Important to consider is that brine water is a waste product with saturated salts, and that its deposits on the marine environment degrade it.
Chemical in brine water Amount (ppm)
Calcium (Ca) 1350
Magnesium (Mg) 7600
Sodium (Na) Not Reported (NR)
Hydrogen Carbonates (HCO3) 3900
Sulphates (SO4) 3900
Chlorine (Cl) 29000
Table 1: Chemical components of brine water
Gaseous emissions, apart from the chemical compounds in the brine water, also occur during the desalination process. Greenhouse gases, especially the emission of Carbon dioxide (CO2), affect the quality of the atmosphere, and result in global warming. The graph below shows the amount of CO2 emission in Abu Dhabi, between 1996 and 2010. The trends show that the emissions are increasing.
Figure 3: CO2 emissions (in metric tones) in Abu Dhabi between 1996 and 2010.
Over time, there has been a trend of increasing amount of CO2 emissions from the desalination process. The trend is in Abu Dhabi’s plants, and also in desalination plants of other countries, making the effects potential. The forecast above assumes that the environmental authorities in Abu Dhabi will not introduce mitigating measures to reduce CO2 emissions. The forecast also relies on the trend of the increasing rate of desalination, which increases the amount of Carbon dioxide emissions.
The table below shows how CO2 emissions from Abu Dhabi have been increasing in the past.
Year Amount of CO2 emissions (in metric tones)
1996 103
1997 111
1998 116
1999 117
2000 109
2001 118
2002 125
2003 126
2004 132
2005 137.8
2006 141
2007 143
2008 145
2009 153
2010 157
Table 2: Yearly amount of CO2 emissions from Abu Dhabi’s desalination, from 1996 to 2010.
The process of desalination consumes a lot of energy, which is one of the inputs. Due to high energy use in the process, the process pollutes the air by emitting nitrate (NOX) and sulphuric (SO4) gases. The gases, together with the heavy CO2 emissions, make the atmosphere acidic. However, research reveals that the concentration of nitrate gases is decreasing. The reason for the decrease in NOX gases is the upgrading of the technology for desalination. The reduction of SO4 gases depends on the source of energy for the process. The use of natural gas in desalination emits less SO4 than if oil is the source of energy.
The graph below shows how NOX gas emissions have reduced between 2005 and 2010. The decrease in NOX is due to technology improvements of the desalination process.

Figure 4: Reduction in NOX in Abu Dhabi between 2005 and 2010.
The bar graph above implies that as the desalination technology continues improving, the amount of NOX gases reduces. The desalination plants in Abu Dhabi should, therefore, continue to improve their desalination technologies for further reduction of NOX emissions.
Chlorine is a chemical whose role is to prevent biofouling. If biofouling happens, the water that the process produces form hypochlorite and hypobromite compounds. The rate of dosing in the process of desalination is what determines the amount of chlorine in the water. Following discharging during desalination, the concentration of chlorine will drop from the range of 200-500 μg/L to 20-50 μg/L.
The desalination environment also has both ionized and unionized ammonium compounds. Unionized ammonium compounds are extremely toxic to the environment. The occurrence of ionized and unionized ammonia depends on PH. To avoid the risks of ammonia on aquatic life, regulation of ionized and unionized compounds is necessary. Their concentrations must be within the “water quality standards” for them to remain non-hazardous to the environment.
ii. Temperatures
The process of desalination produces a lot of heat, which changes the aquatic temperatures. The rise of sea water temperatures in Abu Dhabi increases during the summer season. Sea water temperature rises to 35oC. Within the vicinity of the desalination plants, there an ambient effect on temperatures, which increase by 7-8oC above the normal temperatures. The rise in temperature levels affects aquatic life. Although some organisms may adapt to slight changes in sea water temperatures, extreme changes to high levels, e.g. 35oC, are unbearable. Most sea water organisms do not survive under such conditions. Since the changes in temperatures also affect the ambient temperatures, desalination causes global warming, considering the cumulative effect that the different desalination plants put on the environment.
Conclusion
Desalination has negative environmental consequences for three main reasons. The process discharges brine water to the environment. It also pollutes the air by omitting harmful gases. Desalination changes the sea water temperatures and the atmospheric temperatures around the plants. Brine water has high salt concentration. Gases such as CO2, NOX, and SO4, are acidic and pollute the environment. It is important for the water authorities in Abu Dhabi to understand the environmental effects of the discharges and emissions from the plants. Research predicts that if the authorities do not make adequate and immediate interventions, the levels of the toxic gases and chemicals will continue rising. Desalination has become the main source of water. As humans continue to rely on desalinated water, the implication is that the negative environmental effects will continue increasing. It is necessary for the water and environmental authorities to introduce measures such as cooling and diluting brine water with sea water; harvesting the brine water; using renewable sources of energy that emit less heat. Also, natural gas is god for desalination. Oil emits more SO4 than natural gas. Adopting more efficient technologies helps to reduce NOX gases.