The footprint of the desalination processes on the environment

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 *Corresponding author. Submitted to the EuroMed 2002 conference on Desalination Strategies in South Mediterranean Countries: Cooperation between Mediterranean Countries of Europe and the Southern Rim of the Mediterranean. Sponsored by the European Desalination Society and Alexandria University Desalination Studies and Technology Center, Sharm El Sheikh, Egypt, May 4–6, 2002. 0011-9164/02/$– See front matter © 2002 Elsevier Science B.V. All rights reserved

The processes of desalination as a source for potable water are about to become more widespread. Our duty as citizens and as planners is to be aware of the environmental aspects related to the various processes and in each case to consider the environmental costs as well as the requirements and the financial costs. In a paper, which deals with the problems caused by processes of desalination, it is also important to address the numerous advantages, both direct and indirect, of adding desalinated water to the existing water system. The main purpose of seawater desalination is to offset present or future deficits in potable water, by producing water of good quality at a reasonable price. However, the amounts and the quality of the produced water highlight several additional environmental advantages. These advantages are dependent on the intended point of use of the desalinated water as well as on the volume and quality ratio between this water and the rest of the water in the water supply system. The added environmental advantages of the use of desalinated water are: a. Improvement in quality and sanitation — by adding to the general water supply water that is free of pollutants, carcinogenic materials, organic materials, viruses as well as of offending colors, tastes and scents. b. Softening of the water — the advantages to the average household from the softening of water include prevention of clogging of water pipes, prevention of scale formation in boilers and kettles, improvements in laundry and dish-washing efficiencies, etc. The advantages to the industry include savings on water softening expenses, economizing the use of anti scaling materials, etc. The softening of water also reduces the need for detergents and this reduced usage would improve the quality of sewage water. c. Advantages to the agriculture and the environment — the use of treated wastewaters which contain high concentrations of dissolved salts, sodium, chloride and boron, harms agricultural growth and especially harms sensitive crops. This use damages the soil, interferes with proper drainage, causes the accumulation of salts in the substrata, and even damages the underlying groundwater. It has been observed that salination has already damaged the aquifer and a large number of wells have already been shut down. Any damage to the soil, to the crops and to the groundwater brings with it further damage to the environment and to the economy. The Israeli quality requirements of the product water from desalination specify an upper limit of 0.4 mg/l for boron, so that the product water is bound to be low in salinity, and thus the concentrations of chloride and sodium would be 10–100 mg/l. In addition, there is the potential for a decrease in the amount of salts that are now being added to urban sewage due to the softening of industrial and domestic water. Thus desalination is expected to reduce the salinity of treated wastewater, with all the related implications, including the ability to make intensive use of treated wastewater in various agricultural applications and even as potable water. The only way to insure the preservation of natural water systems is by the addition of artificially produced water for domestic and industrial use. A balanced environmental evaluation of the processes of desalination will take into account the extent to which the population requires the water, the ability to allocate water for agricultural, industrial and nature preservation needs, as well as the need for drinking water. A balanced environmental evaluation of the processes of desalination will take into account the level of sensitivity of the corresponding environment, both marine and terrestrial, to the environmental impacts of the desalination plant, and the costs of minimizing these impacts. A balanced environmental evaluation of the desalination processes will take into account the economical and environmental costs of the various technologies for acquiring water, such as (deep) drillings, recycling, use of brackish water, etc. Taking into account the various environmental aspects, there is an apparent advantage to the use of reverse osmosis processes over the use of evaporation processes [9,37–38]. By employing intelligent planning and the appropriate technologies, it is possible to minimize the adverse effects of seawater desalination plants on the environment. The environmental awareness of the planners, the designers, the decision-makers and the public during the early stages of planning and construction, will enable the construction of environmentally friendly plants.