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Desalination: Our cities can do it, too

Desalination: Our cities can do it, too

Improved and more efficient technology in desalination, and increased volumes may mean better viability for desalination. Sasidhar Chidanamarri writes why, beyond its industrial use, more cities in India can follow the Chennai desalination example, especially as we gear up to reuse water and wastewater.

India is at an exciting stage as far as the market for water and wastewater treatment is concerned. What presents a challenge for the government is that the remarkable economic growth has presented difficulties in sharing water resources among three key sectors: agri­cultural, domestic, and industrial. It is apparent that bal­ancing available water resources to meet the require­ments of all three sectors, recommended in the National Water Policy 2002, as well as in the newly drafted National Water Mission, will be no mean task.


Estimates by the Ministry of Water Resources (MoWR) indicate that by 2050, India's overall water demand will double, growing at a compounded annual growth rate (CAGR) of 1.5 per cent. The industry seg­ment will clock the fastest rate of demand for water, at a CAGR of 4.2 per cent. Population growth with growing disposable incomes and changing lifestyles means that the domestic demand for water is all set to double by 2050. Though these demand estimates appear to be conservative, a recent assessment by the MoWR pegged the industrial water requirement at 120 billion cu m (bcm) by 2025.

High demand for water brings forth the urgent need for effective management and development of water resources using methods like inter-basin water transfers, artificial recharge of aquifers, desalinisation of brackish water, traditional water conservation practices like rain­water harvesting, good maintenance of irrigation sys­t­ems, and promoting efficiency through drip/sprinklers. Desalination can narrow the gap between water demand and supply.

All countries in the Middle East are water-stressed with per capita renewable water resources much below the critical level of 1,000 cu m per day. The Middle East's water issues are naturally caused due to poor rain­fall, resulting in water scarcity and insufficient repl­eni­shment. On the other hand, India's water issues are man-made due to excessive withdrawal of ground and surface water without any regulatory policy, pollutants contaminating the available water resources, and inef­ficient irrigation mechanisms. In both regions, water, a key element in the economic transformation, is facing imminent danger with dwindling resources. It is expected that India's per capita water availability will reduce sha­rply to 1,340 cu m per day by 2025 and further down to 950 cu m per day by 2050. The Middle East was able to successfully tackle the crises by resorting to desa­lination. Today, the Middle East, with about 30 million cu m per day, represents about half of the world's installed cap­acities for desalination. The global desalina­tion capacity is expected to triple by 2020. India's share in the world stands at a mere 450,000-500,000 cu m per day, but the country has potential to garner a much larger share of the global desalination capacity in the next 10 years.

Most large water and wastewater treatment equip­ment manufacturers and turnkey suppliers have strong project management and execution skills. Moreover, local sourcing of components at competitive prices can be managed effectively by local firms. Overseas firms have an edge over Indian firms with respect to niche technologies like desalination, as well as experience in working on large desalination projects globally. Hence, in large municipal desalination projects contracted so far, Indian and overseas firms have formed joint ventures to leverage each other's strengths.


Establishing desalination plants also props up the allied markets, including, but not limited to, high-pres­sure pumps, intake and outlet pipes, transmission and distribution water pipelines, monitoring and control ins­truments, variable frequency drives, membranes, ultra-filtration pre-treatment, and dual-media filters. The foll­owing table gives the count of membrane elements used in various desalination plants. With advancements in technology and use of adequate pre-treatment, the life of reverse osmosis (RO) membrane elements has been enhanced from three years to 5-7 years. The installation of desalination plants are, hence, expected to drive the replacement demand for membrane elements.

If we look at the technology breakdown of the ins­talled desalination capacities across the Middle East, pre­dominating desalination processes like multistage flash distillation (MSF), multi effect distillation (MED) are giving way to reverse osmosis (RO). This shift is particularly evident in Gulf region, where RO technology is expected to eat away the market share of thermal technologies. With the technical adv­ancement and various researches, RO is gaining imp­ortance in the market for its lesser energy consum­ption. It has a much higher yield compared to MSF. This means for the same output, the intake of sea water is only one third in RO systems, hence considerably decre­asing the power and other costs required for pumping sea water to the plant and disposing the spent brine.

New RO/MSF hybrid desalination plants might be implemented in the future. Significant advantages of the hybrid RO/MSF systems include: common, small sea­water intake, optimization of feed water temperature of the RO plant by using cooling water from the heat rejection section of the MSF, extension of the life of the membranes, and low water production cost.

Another key technological trend that can be wit­nessed in the desalination market is the use of renewable solar energy for operating the plant. Realizing that des­alination is a major consumer of energy, the use solar technologies in desalination would lead eventually to a reduction in cost of these technologies. Recently, IBM and Saudi Arabia's national research group have opened a solar powered desalination pilot plant in the city of Al-Khafji.

The use of energy recovery devices (ERDs) and var­iable frequency drives (VFDs) are making the RO des­alination a cost-effective and energy efficient solution. VFDs control the engines joined to high pressure pumps during the membrane separation process where the ene­rgy requirement is high.

Therefore, accurate control of pumps and custo­mi­sation of the operating point based on the sea water characteristics is pivotal to enhance energy efficiency of the desalination plant. Reducing electrical consumption in RO plants has been the prime focus lately. Energy recovery devices are aimed at reducing electrical con­su­mption by recovering pressure energy from the membrane reject stream and returning it to the process. Broadly, these ERDs can reduce the electricity consumption by as much as 40-60 per cent.


Over time, industries in the coastal belt will be nu­dged to adopt desalination plant for their process water requirements, aided by the technological advancements in membrane water treatment processing especially in aspects such as more efficient energy recovery devices, improved pre-treatment, large diameter RO technology, and improved membrane properties.  
However, cost is one of the major barriers in adoption of this technology in the municipal segment where many of the urban local bodies, barring a few, are cash starved. Project cost inv­olved in constructing and setting up a RO desalination is almost 20 times more than that in a conventional drinking water plant. The operating exp­enses (Opex) are also significantly higher for a des­alination plant. Technology will further reduce the Capex for desalina­tion plants. For example, in the last two decades, due to technological developments and mass commercialisation of RO water treatment process around the world, the price of an RO membrane element dropped from $850-950 per piece in 1980s to $500-550 per piece now.


Full (100 per cent) foreign direct investment is allo­wed by the government under automatic approval for water plants. There is exemption on all items of mach­inery, including instruments, apparatus and appli­ances, auxiliary equipment, and their component parts requi­red to set up water supply plants, including a plant for desalination, demineralisation, or purification of water. Recently, the government has been planning to offer tax breaks to industrial users for saving water.

A policy such as this is long overdue in India. It could boost the market for recycle and reuse technologies like membrane bio-reactors and desalination, as the ulti­mate goal is to reduce dependence on fragile and dwin­dling ground water and surface water resources. If one looks at the water usage patterns globally, developed nations are diverting up to 60 per cent of the water towards industrial usage.

On the other hand, developing nations such as India are utilising 80 per cent of water towards agri­cultural productivity. This proportion is soon going to reverse with industries guzzling more water; this mirrors the water usage pattern of developed countries. Hence, tech­nologies and solutions like recycle and reuse of was­te­water (both domestic sewage and industrial effluent) and tapping means to desalinate the perennial sea water should be effectively implemented under the new National Water Mission. In fact, the government can also contemplate issuing tradable certificates, akin to car­bon emission reduction credits, so that industries sav­ing water can sell their certificates to industries con­suming more water.

The National Water Mission aims at ensuring inte­grated water resource management and increasing water usage efficiency. The mission also seeks to ensure that a considerable share of urban water demand is met through recycling of sewage, and that the water consumption req­uirement in coastal cities is met through desalination technology. To have maximum impact, the government has identified guidelines to develop robust Public-Private Partnerships (PPP) and offered monetary incentives to states and urban local bodies. The success of the PPP model in desalination has already been established with the commissioning of 100,000 cu m per day des­alination plant at Minjur in Chennai. Chennai Water Desalination Limited, a consortium of IVRCL and Befesa, had enga­ged in Design, Build, Own, Operate, and Transfer (DBOOT), while Chennai's municipal water authority had entered a bulk water purchase agreement. Quintessentially, this model can serve as a template, wherein public and private parties can further work tog­ether constructively to offer win-win solutions to citiz­ens, government bodies, and private sector participants.

Gujarat has been the vanguard of the desalination market. Several industries have taken desalinisation of sea and brackish water as the means of industrial process water. Lately, an RO desalination plant with capacity of 25,000 cu m per day has been contracted at Tata Ultra Mega Power Plant (UMPP) in Mundra, Gujarat. In the municipal segment, Chennai has commissioned its first 100 million litre per day (MLD) desalination plant, while the construction work is in progress for the second 100 MLD plant in Nemmeli. Meanwhile, Chennai has already chalked out plans for its third 100 MLD plant in the Kancheepuram district, for which the initial detailed project report is being prepared. Mumbai is also con­tem­plating setting up a desalination plant to meet the bur­geoning water needs of its citizens.

Rampant release of effluents and over-extraction has contaminated the sources of ground and surface fresh water. Inter-state water conflicts, irregular monsoons due to climate changes, and satiating the water needs of industrial, agriculture, and domestic sectors have blown the water issue into a mega problem. Despite being an energy-intensive process, the use of energy recovery dev­ices (ERDs) and variable frequency drives (VFDs), and capturing solar energy to run the plants would eventually transform desalination into a cost-effective and energy-efficient solution. Moreover, the developer or the con­cessionaire can also avail carbon credits, which can low­er the operating expenses over a period of 20-30 years. On the whole, private sector participation and joint ventures are helping this sector to grow faster. Reduced plant costs, best practices brought about by overseas fir­ms, and government push will further advance the gro­wth of the Indian desalination market.

The author is Industry Manager, Environment and Building Technologies Practice, Frost & Sullivan, South Asia, Middle East and North Africa.


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