Risks and Concerns About Seawater Desalination

All the time we talk about advantages of the desalination, let also discuss about risks and concern about seawater desalination.

1 Answer

1. Hi Priyanka: As any other water supply alternative, seawater desalination has two main types of risks - environmental and human health related. Environmental risks mainly relate to the intake of marine organisms with the source seawater used for desalination and the discharge of high-salinity concentrate separated from the produced fresh water. Injury or distruction of aquatic organisms due to intake of source water for produciton of fresh water is not unique to desalination - collecting water from rivers or lakes to produce drinking water carries similar impacts. Such impacts are typically minimized or completely avoided by appplying latest intake technology and using subusrface wells for source water collection. Impacts casued by discharge of saline concetrate into the receiving water body are unique to desalination. The main impact on marine life is by osmosis - the extraction of water an other liquids from the bodies of marine organisms which causes them to dehydrate and ultimately to die if exposed to such conditions for a long time - ususally day or so. The good news is that most marine orgnaisms are osmoregulators - i.e., nature have equipped them with mechanisms to regulate their osmotic pressure and adopt to the changes of the outside osmotic pressure - similar to the mechanisms our bodies have to regulate our blood pressure to the changes in athospheric pressure arround us. Not all marine organisms are borh with osmoregulatory ability as not all terestrial organisms are borh to walk from the first moment they are born. Therefore, discharging concetrate in the spowining areas for marine orgnaisms has to be avoided. Most adult organisms can ultimately avoid or adopt to elevated salinities - so as long as the location of concetrate discharge is selected appropriately and the concentrate is dilluted quickly down to within 10 % of ambient water salinity, the impact on aquatic life from concetrate discharge can be minimized and practically avoided. In the past, our understanding of the mechnisms of environmetal impacts were limited and some desalination dicharges have caused environmental damage. However, the sicence and technology in this field has evolved to the point where we can build environmentally safe desalination facilities. Human health impacts are mainly related to the lack of some minerals in desalinated water such as calcium and mangesium. At present most desalination plants worldwide add calcium to the desalinated water to avoid this impact. The debate about the need to add magensium is ongoing. You can read the publicatons on this topic in the desalination group library. Nikolay Voutchkov Water Globe Cosulting