Desalination maybe no Cinderella-solution

Desalination of seawater, which removes dissolved minerals from the water, seems to be presented as the universal answer to a fast-expanding global water crisis. It offers massive investment potential for some companies and short-term relief for some South African communities. Serious environmental risks that could rival the Acid Mine Drainage monster are however also starting to emerge.

Furthermore, it will be a very costly exercise to ensure that there are no negative environmental ‘spills’ or ‘by-products’ of desalination. An expert report earlier this year stated that “until recently no-one worried too much about the environmental impact of desalination, but it has become a major consideration in places such as Australia, California and Spain.”

Reports of negative environmental and other impacts are also increasingly emanating from Israel and the Arab world

A leading international expert recently warned “desalination projects require proper environmental impact assessments (EIA’s) in South Africa before they are constructed.  I have personally witnessed the negative environmental impacts of seawater desalination plants in Abu Dhabi and Dubai in the United Arab Emirates”.

There is a global water crisis, with the World Bank now reporting that 80 countries are facing ‘water shortages that threaten the health of their citizens and economies’.

Southern Cape

Desalination has been in the news in the Southern Cape recently because of plans to delay a desalination plant in Mossel Bay. That while desalination has served as a lifeline to Sedgefield since December and also in the Southern Cape, where a severe drought is being experienced.

At one stage there was talk that the supply of water to the PetroSA plant at Mossel Bay would have to be interrupted to ensure security of supply to the citizens of the local municipality. This could have had devastating economic consequences for the company and the region.

PetroSA is investing R80-million on the plant’s construction, with the balance of the R200-million total capital expenditure to be funded by the municipality.

In March 2010, Knysna’s municipal officials pledged their support for a desalination plant in Sedgefield and said that the purification of seawater offered a long-term and environmentally friendly solution to the ongoing drought problems.

Officials expressed the belief that a number of the technological innovations employed in the Sedgefield operation are considered groundbreaking, resulting in a saving of up to 40% in  the electrical energy required to run the plant.

Alarming and disturbing research

But since March 2010 there has been more research and more alarming and disturbing revelations.

The common misconception that the brine stream byproduct of desalination is ‘just salt’ has been challenged by warnings of heavy metals and industrial chemicals in the discharge.

Leading desalination expert Sabine Lattemann, of the Institute for Chemistry and Biology of the Marine Environment at the University of Oldenburg in Germany, has chaired a World Health Organisation committee charged with creating guidelines for the environmental impact assessment studies of desalination plants.

She said the content of the brine stream includes chlorine and heavy metals.

Chlorine is added to the desalination-plant feed water to prevent bio-fouling on heat exchanger surfaces.

In a recent comprehensive study on the environmental impact of desalination, Prof Mutaz Qutob, assistant professor in the department of applied earth and environmental studies at Al-Quds University in Jerusalem confirmed Lattermann’s stance on chlorine.

He warned that desalination plants have the potential to adversely affect the environment in many ways. The location of a desalination plant should be chosen carefully to minimise the effect on habitats around the plant.

Professor Qutob said the effluent in the waste is a heavily concentrated brine solution. After the brine solution is discharged it has the potential to kill marine organisms.

Although the brine solution contains natural ingredients of the seawater, because of its unnatural concentration it may cause damage to marine population near the outlet.

Other concerns are the chemicals from pre-treatments and from periodical cleaning of the membranes can harm the habitat. One example is the use of chlorine, which is used to clean pipes and to pre-treat the water. These chemicals must be treated before they are released to the ocean.

Environmental impact assessments have historically

considered concentrated discharge to be the major environmental concern with desalination plants.

Recent overseas research has, however, now suggested that the greatest single ecological problem associated with desalination plants that use seawater is that organisms living in the vicinity of the desalination plant are sucked into its equipment.

Cost factor

The cost of desalinated water has also risen sharply despite continued efficiency gains in the process, according to a new report entitled “Desalination Market 2010: Global Forecast and Analysis”.

Christopher Gasson, editor of the report says: “Until recently no-one worried too much about the environmental impact of desalination but it has become a major consideration in places such as Australia, California and Spain.

He says: “In Australia, in particular, the need for complex fish-friendly intakes and low-impact brine-disposal systems has pushed up the price of desalinated water.” (For full report click here)

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