Desalination is the process of removing excess salt and other minerals from water to render it fit for human consumption.

This is easier said then done, for desalination requires use of technologies and machineries. While governments in Spain, the Middle East, and Australia are commissioning big desalination plants to turn seawater into drinking water, there are people who oppose the move, terming it expensive and detrimental to the environment. India has so far installed 175 plants, starting with one at Andaman in 1946. Desalination plants have proved to be an elixir for places like Lakshadweep, Andaman, and some places in Gujarat, Tamil Nadu, and Andhra Pradesh.

Main Technologies“Two basic technologies are used in the desalination plants. They are either thermal based or membrane based,” says M.P. Ramaswamy, Managing Director, SWS&GB Saline Water Specialists. Membrane-based technologies include reverse osmosis (RO) and electro-dialysis (ED), while thermal-based technologies include multistage flash evaporation (MSE), multi-effect distillation (MED), multi-stage flash distillation (MSF), and vapor compression (VC).

Which technology is to be used where depends entirely on local conditions. Both the technologies have proved to be quite popular, with RO accounting for 59 percent of contracted desalination capacity till 2008. It has grown at a rate of 17 percent year-on-year since 1990. RO produces drinking water by forcing seawater against a semi-permeable membrane, producing pure water on one side and concentrated brine on the other. In contrast, MSF process involves both evaporation and condensation split into several stages, which is repeated many times. Seawater is heated and evaporated, and the steam is condensed to produce desalinated water in this process. As the water vapor is being condensed, its latent heat is used to heat incoming seawater. The benefit of MSF is that it can produce large amounts of water at a time.

Ramaswamy says, “Thermal is an age-old technology and is still practiced by people all over the world. It gives you the best water quality.”

With thermal desalination plants, it is possible to get water output of TDS (total dissolved solids) less than 2 ppm (parts per million), important for industrial uses. In case of RO plants TDS count of water produced is normally around 300 ppm. This is acceptable as WHO recommends drinking water to have TDS of 300 to 500 ppm.

“For portable requirements, and for municipality uses, one should opt for RO. For industrial uses, thermal desalination plants should be preferred,” Ramaswamy says.

Economics of desalinationDesalination plants are quite capital intensive. Not only are initial capital investment costs high, but there are considerable investments required for putting up proper water intake systems, whereby seawater is procured and brine is disposed. Operating and maintenance costs need to be borne as well. Thus, project costs depend on a number of factors, namely, type of technology, costs of energy, geographic location, plant capacity, feedwater quality, and cost of water intake from source to desalination plan. According to Tamim Younos of the Virginia Polytechnic Institute and State University, USA, building costs, freight and insurance costs, construction overhead costs like labor, temporary facilities, construction equipment, etc, contingency costs, and owner’s costs also affect the economics of a desalination plant.

Ramaswamy has a method of estimating project costs: “You can take a thumb rule that for 1 MLD (million liters daily; equal to 1,000 cu m per day), costs may come to around Rs 5 to 6 crore for thermal and Rs 4 to 5 crore for RO.”

When it comes to power consumption, a major component in desalination, RO-based plants consume more power. According to Ramaswamy, RO plants consume almost 4 units of electricity for every cubic meter of water. “Thermal plants consume only 0.7 to 1 unit for generating the same amount.”

On an average, for every liter of fresh water produced, desalination plants need around 2.5 L of sea water. The remaining 1.5 L (brine) is dumped back into the sea. “In RO-based plants the reject becomes chemically polluted and this has to be cleaned before dumping back to sea,” Ramaswamy says.

Capital investments for setting up desalination plants may be high, but desalination experts like Ramaswamy and H. Subramaniam, an executive of a water consultancy firm, insist that these are definitely not as high as quoted in developed countries.

Ramaswami says, "I have been doing a lot of exercise on calculating the costs of water realized from desalination plants. My assessment is that the cost of producing water from these plants would be in the order of between 3 paise to 5 paise per liter (Rs. 30 to 50 per cubic meter) – much cheaper than mineral water.”

“We are capable of manufacturing everything in India. When we supply desalination machinery today, we manufacture it here, with only a few components coming from Italy,” he says.

This has reduced the costs considerably in India vis-à-vis developed countries. Ramaswamy, says, "Today we can handle projects of any size, as we have the support from my collaborators."

Market sizeMarket share of desalination in the overall water market, estimated at US$ 400 billion, is a miniscule 0.1 percent. According to the International Desalination Association (IDA), the global desalination market is expected to grow to US$ 95 billion through 2005 to 2015. According to a report by Global Water Intelligence (GWI), the worldwide desalination industry is expected to grow 140 percent over the next decade, with US$ 25 billion in capital investment by 2010 and US$ 56 billion by 2015.

A report by GWI also says that in the Middle East (ME), where water availability is less than 20 percent of the world average, the desalination industry has grown into an annual market of US$ 8 billion since 2004. The report predicts that total capital expenditure on wastewater will grow from US$5.3 billion in 2009 to US$13.3 billion in 2016 in ME.

While countries like the US, Spain, and the Gulf countries have been able to build mega plants, poor countries in Asia, Africa, and South America have inadequate resources to do so. But the need for water is such a basic one that they will be forced to invest in technologies either on their own or by arranging funds from financial institutions. Failing this, wars and civil wars cannot be ruled out, as many have predicted. Clashes over water has taken place in India as well, and that too in a city like Mumbai. Other probable sources of sourcing fresh water, namely, surface water and ground water, are not sufficient to quench the water needs of the ever-growing population. Desalination is thus destined to grow.

Indian scenarioAround 22.5 crore people in India do not have access to safe drinking water. Requirement of freshwater in India for domestic consumption, agriculture, and industrial purposes every year is close to 900 billion cu m. What India gets at the maximum is 500 to 600 billion cu m of water. The deficit is not just there in the arid landlocked states of Rajasthan, Chhattisgarh, and Madhya Pradesh, but even in the coastal states of Tamil Nadu, Gujarat, Andhra Pradesh, and Maharashtra. Desalination can be a perfect solution for water problems in these coastal states. But this is talked about only after a drought, cyclone or flood.

Setting up desalination plants will also prove less time consuming than any irrigation or drinking water projects involving rivers, which have to bear huge opportunity costs of displacing population from one place to another. Desalination plants at three or four places can be interconnected in a state like Tamil Nadu to form a water grid, which should be connected to the existing municipal water supply network, as Ramaswamy points out. He says dependence on rivers like the Cauvery or Rewati will end forever with this. “This is feasible in the very budget of Tamil Nadu itself,” he adds.

Bhabha Atomic Research Centre (BARC) set up a 1.8 million-liters-a-day capacity desalination plant at Kalpakkam in Tamil Nadu in 2008 and is set to comission a MSF-based plant there itself. BARC has set up several desalination plants in rural Rajasthan, Andhra Pradesh and Gujarat, producing 30,000 L a day. It has licensed its technology to as many as seven industries. IVRCL, IL&FS, Mahindra and Reliance are other companies that have set up desalination plants. Foreign players like Israel Desalination Enterprises Technologies (IDE) and GE are also setting up such plants in India.

Calculations reveal that on an average the production cost from brackish water plants come to Rs 10 to15 for every cubic meter, and from seawater comes to Rs 40 to 50 per cubic meter. The production cost of desalted water from effluents comes to Rs 15 to 50 per cubic meter depending upon the TDS load. This translates to a household expenditure of Rs 300 to 400 per month on drinking water, which a family is anyway bearing in cities like Chennai, Bangalore, Hyderabad, and Mumbai.

SummaryThe cost of setting up desalination plants is still on the higher side. In areas that are arid and close to the sea, setting up such plants will definitely cost less compared to other alternatives. This is why it is used as a main source of drinking water through municipal supply in several parts of the world, including many pockets in India. Desalination technologies are also being increasingly used to soften mildly brackish water.

Industries in India should first be discouraged from procuring water from the municipality. Shore-based power projects, like the one being built by the Tatas in Mundra, Gujarat, should be compelled to build their own desalination plants. This has been the prevalent norm all over the Middle East.

“People and government will have to ultimately adopt desalination as the way forward,” Ramaswamy concludes confidently.