This white paper focuses on impacts of major desalination projects and their mitigation and investigation by environmental impact assessment. It also gives an overview of the existing seawater desalination capacities and projects by countries, a summary of important environmental concerns of desalination, new ways in which the impacts of desalination on the environment can be modified and several factors like socio economic impacts driving the demand for water desalination process. Desalination is extensively used in the Gulf Cooperation Council regions as the main source for fresh water supply for a domestic sector because of the scarcity of renewable natural freshwater resources.<
This white paper focuses on impacts of major desalination projects and their mitigation and investigation by environmental impact assessment. It also gives an overview of the existing seawater desalination capacities and projects by countries, a summary of important environmental concerns of desalination, new ways in which the impacts of desalination on the environment can be modified and several factors like socio economic impacts driving the demand for water desalination process. Desalination is extensively used in the Gulf Cooperation Council regions as the main source for fresh water supply for a domestic sector because of the scarcity of renewable natural freshwater resources.
Many Middle East countries have established desalination plants like Egypt. Many of the desalination plants are joined with the power plants with the production of power. The overall seawater desalination capacity is around more than 5500 Mn m3/year that means little less than half of global production. The main manufacturers in the Gulf region are Saudi Arabia, Oman, Kuwait and the United Arab Emirates. The overall capacity of desalination in GCC countries has augmented from more than 3500 Mn m3/year to about 5500 Mn m3/year.
As desalination of seawater providing a range socio-economic, human health and environmental advantages by offering an unlimited, continuous supply of good quality drinking water instead of impairing natural freshwater ecosystems and the concerns raised up because of the potential negative impacts. They are mainly accredited to the chemical discharges that may damage coastal water quality and hamper the marine life and the emissions of air pollutant endorsed to increase the energy demand. To avoid a disruptive and unsustainable growth of coastal areas, desalination activity should be combined into management plans regulating the use of water resources and the technology of desalination on a regional scale. In contrast, the probable environmental impacts of desalination projects are required to be evaluated where adverse effects alleviated as far as possible and remaining concerns composed against the impacts of other water supply and the options of water management, to protect the sustainable use of technology.
Several effects on marine environment arising from the operation of power and the desalination plant from the repetitive discharge of effluents. Water effluents are causing the localized rise in the temperature of sea water, can directly hamper the organisms in a discharge area. Augmented temperature affects the processes of water quality and leads to reducing the concentration of dissolved oxygen. In addition, desalination plants surge the salinity in the receiving water. The substances focusing on the water quality standards and issues for ecological assessment are:
Even though the technological advances have occasioned in the development of a high and newly efficient process of desalination, little enhancements have reported in handling and the management of by-product waste of desalination plants known as reject brine. The management or disposal of desalination brine signifies several environmental challenges to most plants and is becoming more expensive. Reject brine mostly comprises the variable concentrations of various chemicals like inorganic salts and anti-scale additives that are negatively impacting groundwater and soil. Reject brine is the most concentrated water in the last phase of desalination process that is mostly discharged as wastewater.
Assessment of Environmental Impacts
There are several environmental impacts of the desalination process in GCC regions equivalent to other industries. Though there are effects that are more precise to desalination plants like entrainment and impingement of marine organisms because of the intake of seawater, emissions of Green House Gases because of the substantial energy demand of fossil fuel and discharge of brine water to a marine environment. Based on the sources, a list of the probable environmental impacts of desalination on the environment are as follows:
Consumption of seawater
Seawater desalination plants receive feed water from various sources but open the option of seawater intakes. Utilization of open intakes results in the losses of aquatic organisms on colliding with intake screen are drawn into a plant with the source water. The production of intake structure and piping creates and primary disturbance of seabed that results in the suspension of nutrients, sediments or pollutants in the water column. After the installation, structures are affecting the water exchange and transport of sediment that acts as artificial reefs for organisms may inhibit with shipping routes or the uses of maritime.
Salinity of marine water
All the processes of desalination are producing huge quantities of brine water that may be surged in temperature containing residues of pretreatment and cleaning of chemicals, their reaction products and corrosion of heavy metals. High concentration of salt is discharged to sea with the help of desalination plants outfall leading to the increased level of salinity of ambient seawater. The chemical pretreatment and cleaning are essential in many of the desalination plants including the treatment against corrosion, foaming, scaling and bio fueling in thermal plants and in contrast of bio fueling, suspended solids and scale deposits in membrane plants. The impacts of a desalination plant on the marine environment depend on the physic-chemical properties of reject streams and hydrographical and biological features of the receiving environment.
Temperature of Marine Water
In all the regions of GCC many of the desalination plant is integrated with the power plant where the water temperature of the effluents of power plants will be high and increase the temperature of seawater in the vicinity of the plant. The ambient seawater temperature is more than 36°C on average and power and desalination plants cause an upsurge in the level of temperature in its vicinity by around more than 7 to 8°C over the ambient condition. Many organisms can accept the minor deviations from the conditions of temperature and optimal salinity and may tolerate huge situations, but not the continuous exposure to disapproving conditions. The continuous discharge of reject streams with a level of temperature and high salinity can be harmful to marine life and can make the long-lasting change in the composition of species and great quantity in discharge site.
For analyzing the environmental impact, a risk assessment matrix is utilized. The environmental risk matrix is the product of two factors known as the severity of effect and probability of occurrence.
Discharge of Brine Water
The common practice in dealing with a large amount of brine is to discharge it back into the sea, where it can result in a long run, in harmful effects on aquatic life and the quality of seawater present for desalination in an area. Even though technological development has resulted in the advances of high and new effective desalination process, fewer enhancements reported in the handling and management of by-product waste of desalination plants. Management or disposal of desalination brine is representing the environmental challenges to plants and is becoming expensive. For avoiding the impacts from high salinity, desalination plant can be diluted previously with seawater or power plant cooling water. For evading the impact of high temperature, outfall should accomplish maximum heat dissipation from the waste stream to the atmosphere earlier to entering the water body and extreme dilution following discharge.
Use of Energy
Use of energy is the main cost factor in the desalination industry and been reduced by the technological inventions like the use of energy recovery equipment or flexible frequency pumps in RO plants. In addition, the potential for renewable energy use is to be investigated for minimizing the impacts on climate and air quality. This may be in the form of renewable energy fueling desalination technologies or the compensating measures like installation and usage of renewable energy in other localities for other activities.
In the process of desalination, the Environmental Impact Assessment is very important. A standard EIA procedure for minimizing and evaluating the effects of desalination projects is not accessible. The current concept of EIAs is underpinned by reference material and the methodological approach specific for desalination projects to facilitate the implementation of EIAs for the desalination projects. This includes the basic information on the impacts of desalination activity for conducting the monitoring activities for investigating the environmental impacts of the project and assessing the monitoring data and the decision-making tool for harmonizing benefits and impacts of desalination and options of water supply against each other.