How sustainable can desalination be?

Abstract

Population growth, climate change and urbanization are the main challenges to meet the water demand for the next decades. The global gap between sustainable water supply and water demand is expected to grow above 2,700 km³ by 2030, equivalent to 40% of total water demand. Desalination is an established method to make fresh water—mostly as a last resort. Its contribution to water supply is minor on a global scale. In some regions, though, it is difficult to imagine a sufficient water supply without desalination. But is this technical fix sustainable? In its main part, this paper sheds light on the major issues that call the sustainability of desalination into question. Examination of a number of criteria indicates that the energy demand for desalination is by far the most important issue. Further relevant impacts are wastewater discharges, waste disposal and visual impact. In retrospect, it is noted that energy demand has already shaped today’s desalination market, since energy-efficient membrane-based desalination technology has gained market share compared with the more energy-intensive thermal desalination technologies. This development has been supported by a substantial decrease in the specific energy demand of seawater reverse osmosis (SWRO) plants. As a result, state-of-the-art SWRO plants require approximately 3–5 kWh/m³ compared to some 10 kWh/m³ or more two or three decades ago. But almost all desalination plants are powered by fossil energy resources. Hence, using renewable energy (RE) resources instead would be a big step forward towards sustainability. Case studies prepared for three projects in the MENA region demonstrate that selecting RE sources for a desalination plant is economically feasible when compared to non-subsidized fossil fuel. This paper is based on our viewpoint as engineering consultants. It is a summary of studies, reports and surveys conducted on this issue by us in past years. It is intended to give an idea of the options that are available today to make seawater desalination sustainable.

Keywords:

• Sustainability
• Energy demand
• Carbon footprint
• Renewable energy sources
• MENA case studies
• Water production costs

Notes

Presented at the International Conference on Desalination for the Environment, Clean Water and Energy, European Desalination Society, April 23–26, 2012, Barcelona, Spain

¹It is correct, that the MED requires less electrical power. However, to get the full picture, you have to consider the electrical power that could have been generated when expanding the heating steam, which is required by the MED process, in a steam turbine. This “equivalent power” can be determined to be at minimum corresponding to 4.3 kWh/m³. It is obvious, that he sum of the electrical power actually required and the equivalent electrical power exceeds the electrical power demand of a SWRO process.

²GCC stands for Cooperation Council for the Arab States of the Gulf. The GCC Countries are: United Arab Emirates, The Kingdom of Bahrain, The Kingdom Of Saudi Arabia, The Sultanate of Oman, Qatar and Kuwait.