Water Week

EWN Publishing

Seawater desalination plants: major direct impacts concern costal sensitivity, high energy demand, intake and outflow structures and effluent issues

Posted by waterweek on 25 September 2007

Desalination infrastructure should proceed only where plants are sited, constructed and operated to minimise adverse environmental impacts, according to the WWF’s Phil Dickie.

Four areas of direct impact outlined: “The major direct impacts are associated with the frequent requirement to site plants in sensitive coastal areas already subject to pressure from urbanisation, their high levels of energy demand, the design and operation of intake and outflow structures and effluent issues with concentrated brines, biocides and chemicals used in cleaning and defouling and corrosion byproducts,” wrote Dickie. “Where possible:

• seawater desalination plants should not be sited in areas where intake or outlet pipes would open into or traverse sensitive marine or coastal environments;

• intakes should be screened to the maximum possible extent with subsurface or beach wells being a preferable technology to open ocean intakes. Care needs to be exercised however that no damage is inflicted on coastal aquifers;

• ‘zero spill’ solutions should be considered the preferable way of treating wastes. Reducing brines to solid or minimal volume form with safe disposal options including former salt mines would minimise a major concern with desalination. In some cases, such wastes would be valuable inputs for the chemical industry. Research into more efficiently and economically concentrating wastes should be a priority; and

• where liquid disposal of concentrated brines is required this should involve adequate dilution, mixing and dispersal, should be restricted to areas of low biological sensitivity and should be subject to adequate monitoring regimes. Disposal at surface level is preferable to seabottom disposal.”

Reference: Phil Dickie, WWF for a living planet, ‘Making Water – Desalination option or distraction for a thirsty world?’, June 2007.

Erisk Net, 23/9/2007

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