A very interesting piece on experience of Chennai with desalinating seawater. Needless to say, we need a holistic policy to do these things:
The Minjur Desalination Plant, India’s largest, was set up in the village of Kattupalli along the northern fringes of Chennai city in 2010. Ever since, the plant has been supplying 100 MLD water to households in the northern suburbs of Ennore, Manali, Tiruvottiyur, Tondiarpet and Madhavaram. The second desalination plant came up at Nemmeli, about 35 km south of Chennai city along the East Coast Road. Functional since 2013, the plant supplies 100 million litres of drinking water per day mainly to the city’s southern suburbs including Sholinganallur, Neelangarai, Thoraipakkam, Thiruvanmiyur, Velachery, Taramani, Adyar and Besant Nagar.
While the water demand for the Chennai city and its urban agglomeration is projected at 1560 MLD for the year 2019, the actual water supply hovers around 840 MLD, leaving a supply-demand gap of 720 MLD. To fill this void, the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) has proposed the setting up of additional units of 150 MLD and 400 MLD as part of its phased expansion in Nemmeli. Both these plans will come up at Perur in Nemmeli village, very close to the existing facility.
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 650m away from the shore. While documents suggest that a similar reject-discharge arrangement is in place at Nemmeli, reality appears otherwise.
From the time the plant commenced operations in 2013, villagers complained of brine reject from the plant being let out directly onto the beach and not 650m 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 got stagnated along the beach stretch. Even as recently as December 2016, 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.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 villagers’ accusations of the desalination plant eroding the coastline and endangering their livelihoods in addition to turning the groundwater salty.
Ecologist Sultan Ismail explains that the brine reject tends to create a sort of niche microhabitat with higher levels of salinity around areas where they are let out. This microhabitat creates a localised imbalance as it may not house organisms which are otherwise found in the adjoining waters, resulting in a lower organism diversity in the area. Government bodies set out to study such imbalances claim that the ocean is too big for such a small niche to actually be a troublesome entity.
But the impact on marine life can be better understood by identifying where the reject water is being let out. “There are some species of fish which feed, breed and spend most 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 rather prominent. 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 fishes up the food chain which in turn affects fish diversity as well as density,” adds Ismail. In addition, high-pressure motors used to draw in water also brings 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.
You intervene somewhere and it leads to problems elsewhere. Water is by far the biggest issue which will hit India (and other water irresponsible countries) like nothing else has hit us. It is such a pity when you go around old sections of cities/towns where you see how conscious we were with respect to water. We have done away with all these methods and principles in the name of modernism only to stare at a water crisis which will disrupt everything.