Desalination – is it the answer?

– Seetha Gopalakrishnan

Population growth estimates suggest that India will be supporting over 1.5 billion inhabitants by 2050 if the present growth rate of 1.9 per cent a year continues. From 710 billion cubic metres (BCM) in 2010, the demand for water is expected to surge to 1,180 BCM in 2050 as the Planning Commission has predicted a 2.5-time increase in domestic and industrial consumption.

With conventional surface water sources drying up or disappearing over time and borewells getting deeper by the year, sourcing and supplying water have become uphill tasks for corporations and panchayats across urban and rural areas. It is at such a time that seawater desalination is emerging as one of the top alternatives. But the most important question is, is it a viable one?

Desalination technology has grown and matured by leaps and bounds over the years. Seawater Reverse Osmosis (SWRO) technology, developed by American scientists in the 1950s, was a game changer of sorts.

According to the International Desalination Association (IDA), there are around 18,500 desalination plants in 150 countries, benefitting as many as 300 million people. Nearly half of Israel’s water is manufactured and many countries, especially in the arid regions of North Africa and West Asia, find desalination a relatively cheaper option compared to other alternatives.

Among the early adopters of this technology, Tamil Nadu currently boasts of two functional desalination plants churning out 200 million litres of water per day (MLD) to quench its capital’s thirst. The two 100 MLD plants, one in Minjur and the other in Nemmeli, installed after a government decision in 2003-04, now contribute close to one-third of the city’s total water supply.

Sustained governmental support has enabled Tamil Nadu to contribute 24 per cent of the total desalinated water in India, making it the second best in the country after Gujarat.

The Minjur Desalination Plant, India’s largest, was set up in Kaattupalli, just north of Chennai, in 2010. Ever since, the plant has been supplying 100 MLD water to households in Ennore, Manali, Tiruvottriyur, Tondiarpet and Madhavaram. The second plant came up at Nemmeli, about 35 km south of Chennai on the East Coast Road. Functional since 2013, the plant supplies 100 million litres of drinking water a day mainly to the city’s southern suburbs, including Sholinganallur, Neelankarai, Thoraipakkam, Tiruvanmiyur, Velachery, Taramani, Adyar and Besant Nagar.

While the water demand for the Chennai urban agglomeration is projected at 1,560 MLD in 2019, the actual water supply hovers around 840 MLD. To fill this demand gap of 720 MLD, the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) has proposed setting up additional units of 150 MLD and 400 MLD as part of its phased expansion in Nemmeli and will come up in Perur, very close to the existing facility.

A staunch opponent of desalination, especially in “a rain-rich location like Chennai”, Professor S. Janakarajan of the Madras Institute of Development Studies terms desalination as an utterly “lazy option”. “Seawater desalination was conceived as an option for providing potable water in rain-starved countries, like those in West Asia. Chennai’s average annual rainfall is well over 1,200 mm. Where is the need to go in for such an environmentally damaging and costly exercise? It should ideally be the absolute last resort, which, in this case, it is not,” he says.

For every 100 MLD of potable water generated by the desalination plant in Minjur, the treatment unit draws in 237 MLD of seawater. Post-treatment, the briny reject is let out into the sea, around 650 m away from the shore. While it is said that a similar reject-discharge arrangement is in place at Nemmeli, reality appears otherwise.

Back in 2013, a fact-finding team looked into allegations of environment and human rights violations arising out of the construction and operation of the Nemmeli plant. The report recorded villager’s accusations of the desalination plant eroding the coastline and endangering their livelihoods in addition to turning the groundwater salty.

From the time the plant commenced operations in 2013, villagers have complained of brine reject from the plant being let out directly onto the beach and not 650 m into the sea as mentioned in the environmental clearance granted by the Ministry of Environment, Forests and Climate Change (MoEFCC). Pipelines carrying the reject water were later buried under the sand but poor maintenance led to clogging, as a result of which pools of brine reject stagnated along the beach stretch. Even as recently as December 2016, the Chennai-based Coastal Resource Centre has documented evidences of hyper-saline reject being dumped right on the beach. The situation has not changed since; concentrated brine reject continues to be let out on the beach till date.

Ecologist Sultan Ismail says that the brine reject has an impact on marine life. He explains, “There are some species of fish which feed, breed and spend the better part of their early life along the coast. If the hypersaline reject is let out close to the coast, the probability of these organisms being affected is high. Fish species, such as sardines, mackerels and anchovies, feed on planktons along the coast. When the plankton population decreases due to hypersalinity, it affects the health of fish up the food chain which in turn affects fish diversity as well as density.” High-pressure motors used to draw in water also bring in marine life forms of varying sizes despite nets placed to avoid relatively larger organisms. Fish fry and crabs get crushed and killed in the process.

Loss of income and marine resources is alleged by fishermen in and around Nemmeli. Santhosh, a fisherman from Sulerikattu Kuppam, recalls that 6-7 years ago fishing was “lucrative almost throughout the year. Prawns and fish were abundant and we didn’t have to venture very far. But that is not the case today. Near-shore navigation and the use of periya valai (shore seines) have become problematic ever since boulders were dumped into the sea for the laying of the plant’s pipelines.”

The plant has also depleted the area’s freshwater sources. During its construction, groundwater was pumped out continuously to sink deep foundations. This resulted in rapid depletion of the available underground sweet water, which eventually got replaced with intruding salt water from the sea. The area’s drinking water supply has been affected. A fact-finding team has noted that the CMWSSB violated coastal regulation zone notifications of 1991 and 2011 by pumping out fresh water from a CRZ area in addition to irreparably damaging the beach front.

“Our land and livelihoods have been compromised so that people in the city don’t go without water. We don’t get a drop of drinking water from the plant,” complains Santhosh.

The MoEFCC’s Expert Appraisal Committee (EAC) which met in January 2017 questioned the need for setting up two additional desalination plants within a distance of 600 metres in addition to bringing up the significant issue of beach erosion which has plagued Nemmeli since the first plant was inaugurated in 2013. The EAC has deferred the project for want of information and has called for fresh studies to understand the impact of shoreline change in the area. It has also sought recommendations of the Tamil Nadu Coastal Zone Management Authority (TNCZMA) in connection with certain relevant provisions of the CRZ notification 2011.

Janakarajan insists that our aim should be to conserve water received during the monsoon months instead of resorting to options like desalination after letting fresh water run wastefully into the sea. “Desalination is extremely unfriendly to the environment, contributes to coastal ecological degradation in addition to being ridiculously expensive,” he says.

Brine concentrate and effluent management are huge concerns the world over. Despite advancements made at developing “zero liquid discharge” technologies, where the brine concentrate is converted into solids fit to be disposed at landfills, the costs remain prohibitive.

In spite of their heavy reliance on desalination, countries like Israel have invested heavily in securing their water sources and recycling used water. For example, Israel treats close to 85 per cent of its wastewater which it then uses for irrigation, gardening and industrial purposes. Another crucial element is strengthening water supply infrastructure to prevent losses arising from transit leakages. Even officials at the Israeli Water Authority recognise that efforts at strengthening infrastructure and recycling wastewater should precede desalination.

Options such as sewage and greywater recycling should be taken up in earnest to ease civic bodie’s water supply burden. Increased focus should be laid on caring for water bodies; cascading tanks should be desilted and rejuvenated on a priority basis to save every drop of water before spending precious time and resources on extravagant options such as desalination.
(Courtesy: Indiawaterportal.org)

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