Seventy percent of the earth’s surface is covered by water but unfortunately over 97% of it is too salty for human consumption and only a fraction of the remainder is easily accessible.
Seventy percent of the earth’s surface is covered by water but unfortunately over 97% of it is too salty for human consumption and only a fraction of the remainder is easily accessible.
Climate change, droughts, overpopulation and increasing industrial demands are severely depleting our available supplies of fresh water, making the proper allocation of water critical to our survival.
According to the United Nations, more than 1 billion people live in areas where water is scarce and that number could increase to 1.8 billion by 2025. Since over 90% of the worlds fresh water is located in Antarctica – making access difficult – finding cost effective ways to desalinate water becomes a pressing issue.
President John Kennedy observed, nearly 50 years ago: “If we could ever competitively—at a cheap rate—get fresh water from salt water that would be in the long-range interest of humanity and would really dwarf any other scientific accomplishment.”
Desalination or desalinisation refers to any of several processes that remove excess salt and other minerals from water. Water is desalinated in order to be converted to fresh water suitable for human consumption or irrigation. In addition to seawater, desalination can be applied to brackish water, river water, wastewater, and even treated water from municipal supplies.
Large-scale desalination typically uses extremely large amounts of energy as well as specialised, expensive infrastructure, making it very costly compared to the use of fresh water from rivers or groundwater.
The large energy reserves of many Middle Eastern countries, along with their relative water scarcity, have led to the extensive construction of desalination plants in this region. By mid-2007, Middle Eastern desalination accounted for close to 75% of total world capacity.
The world’s largest desalination plant is Jebel Ali Desalination Plant (phase 2) in the United Arab Emirates, which uses multi-stage flash distillation and is capable of producing 300 million cubic meters of water per year. Desalination technology itself has evolved substantially, making it significantly cheaper, more reliable, less energy-intensive and more environmentally friendly than it was just a few decades ago. Further exploration in this field promises even more efficiency.
Water shortage is an especially urgent matter in certain regions of the world, especially African countries.
Algeria is an example of a country that has used desalination effectively to alleviate its water shortage problems. Algeria has significant indigenous energy resources and started investing in desalination plants during the 60s.
It has been especially involved in desalination for industrial use – mainly in connection with the development of oil and gas projects – for many years. Through investment and forward planning, Algeria is on the forefront of desalination, compared to many other countries in the region where the issue of water shortage is often handled quite differently, using methods that only ensure water in the short term.
Bacteria can be used to turn ‘dirty’ salt water ínto drinkable water, as well as to generate electricity, according to new research from scientists at Pennsylvania State University and Tsinghua University.
Among the millions of microbes in a cup of water from a pond or other natural source, some of the bacteria naturally produce electrons and protons inside their cells and transport them outside themselves These microbial bial fuel cells have been used in the past to produce electricity or store it as hydrogen or methane gas, The researchers found that water can be desalinated by modifying the electricity generated by these bacteria.
However microbial fuel cells, whether they desalinate water, generate electricity or create hydrogen, methane or other gases, are limited to small-scale laboratory devices.
It has been proposed that desalination can be the solution to the global problem of water shortage and can guarantee water supply for the long term. However, it must be highlighted that desalination alone cannot deliver the promise of improved water supply and that establishing desalination plants is not as easy as 1-2-3.
The ability to make the best use of desalination is subject to a series of wider water-sector-related conditions.
Factors such as weak water utilities, politically determined low water tariffs, high water losses and poor sector policies affect how wisely desalinated water is used and put desalination plants at the risk of falling into disrepair. There are thus many factors to take into account apart from the desalination plants themselves.
Andrea Firth is the editor of The Sustainable Water Resource e-Journal (http://www.waterresource.co.za).
