The footprint of the desalination processes on the environment

Abstract

Processes of desalination of seawater are intended to reduce the deficits in potable water both at present and in the future. Water desalination processes offer various environmental benefits (related to sanitation, water softening, quality of sewage effluents), but the process is also accompanied by adverse environmental effects. These effects can be minimized by the appropriate planning. Most of the effects anticipated would then affect the local environment in the vicinity of the desalination plants. Desalination may have an impact on five domains: the use of the land, the groundwater, the marine environment, noise pollution, and finally the intensified use of energy. The impact on land use is caused by the use of the coastal land for the purpose of building factories, thus converting the coastal area into an industrial zone instead of an area of tourism and recreation. The impact on groundwater mainly occurs if pipelines carrying seawater or brine are laid above an aquifer. It also occurs in the case of feed drilling. In such cases the aquifer may be damaged either by infiltration of saline water or by disturbances of the water table. The impact on the marine environment takes place mainly in the vicinity of the concentrated brine discharge pipe. Even though the concentrated brine contains natural marine ingredients, its high specific weight causes it to sink to the sea floor without prior mixing. In addition, chemicals, which are administered to the water in the pre-treatment stages of the desalination process, may harm the marine life in the vicinity of the pipe's outlet. The actual placement of the discharge pipe may also damage sensitive marine communities. Noise pollution: A desalination plant, which is based on reverse osmosis technology, requires high-pressure pumps, which generate noise. Therefore the plant must be located at a suitable distance from population centers. Technological means may be employed in order to minimize noise intensities. A desalination plant may also affect the environment indirectly, such as via the intensified use of energy by the plant. This increased use of energy results in an increased production of electricity by the respective power station, which in turn results in increased air pollution, pollution by coal dust, thermal pollution, etc. The severity of these effects differs in different areas according to: a) the hydrogeological nature of the marine body (bathymetry, depth, tides, waves, currents); b) the biological sensitivity of the marine habitat; c) the type of desalination plant, its size, the required secondary structures and infrastructure. Environmental awareness and preliminary planning can minimize the adverse effects of the desalination process on the environment.