Case Studies

Challenge – Sustaining a water starved city:

India is the second most populated country in the world. With one of the highest rates of urbanization, we are no stranger to the water crisis. It sustains 18 percent of the world’s population but on the contrary has access to only 4 percent of the total usable water sources of the Earth.

Due to the lack of alternatives the country is majorly dependent on the surface water sources. But these are unevenly distributed across its states. Such conditions give rise to certain geo-political water disputes which further aggravate the water crisis and threaten the per capita availability of water.

The city of Chennai in Southern India was also facing similar issues. It has been historically dependent on surface water sources to sustain its drinking water needs. Since the city receives irregular rainfall, the replenishment of such water bodies was highly uncertain. At times when these reservoirs were running at a fraction of their capacities the residents had to resort to the use of ground water which had a negative impact on the water table of the city, thus causing sea water ingression.

The situation put enormous pressure on the government think tank and advisory committees to come up with a solution that would not only curb the prevalent water crisis but ensure water sustainability for future generations as well.

The solution:

Chennai being a coastal city is blessed with an abundant coastline, hence the city sought an answer to the water crisis in the form of large scale sea water desalination. There were certain challenges in the form of high power requirement to run such desalination plants and to build a plant which can treat sea water with varying salinity.

The situation called for technology experts who were commercially competitive as well, thus entrusting VA Tech WABAG with the responsibility.

Embodiment of the solution – The 110 MLD Nemilli Desalination Plant

In order to tackle the growing water stress, a 100 MLD (Million Litres per day) desalination Plant was envisaged along the coast of the Chennai City at Nemmeli

VA Tech WABAG was given the responsibility to design, build and operate this mega project, first of its kind for India.

The plant is equipped with the most advanced technology in the field of desalination. The entire process starts with the inflow of sea water through gravity flow in a 1 Kilometre pipeline embedded at the sea floor at a depth of 10 metres. The inlet water from the sea is pre treated with a state of the art pre treatment technology – Lamella Clarifier. The Lamella Clarirfier not only efficiently removes high amount of suspended solids in the incoming water but its compact size also reduces the footprint of the entire facility. The process water then flows through the disc filters to the Ultra-Filtration units.

Post the Ultra-Filtration, the water is treated by a single pass SWRO system which enables the removal of dissolved solids. A significant reduction in the salinity from around 35000 ppm to less than 500 ppm is achieved in this stage, which is the process core of the project.

The plant ensures production of the highest quality of desalinated water coupled with a process that optimizes power consumption. This is enabled by the use of high end pressure exchanging mechanism which uses the residual pressure of the reject from the RO membranes, thus boosting the pressure of sea water feed to the RO system.

The plant ensures production of the highest quality of desalinated water coupled with a process that optimizes power consumption. This is enabled by the use of high end pressure exchanging mechanism which uses the residual pressure of the reject from the RO membranes, thus boosting the pressure of sea water feed to the RO system.

The treatment cycle is complete with the remineralization of the process water with Carbon Dioxide and Lime in order to make the desalinated water fit for human consumption.

This project is a testament to the feasibility of desalination as an alternative coupled with WABAG’s process know how to optimize the lifecycle cost at INR 35 for every thousand litres of desalinated water produced.

In 2016 the plant’s capacity was further enhanced by 10 MLD with an innovative process retrofit and optimization by VA Tech WABAG’s water professionals. This was a welcome step for a city which was experiencing a dry spell that year.

Awards and accolades:

The Nemmeli plant today supplies water to over a million south Chennaites, thus projecting an alternative, sustainable and viable technological solution for water security which has been a challenge for decades.

Being the largest desalination plant in India to be executed on Design Build Operate basis, recognitions for this project have been global in stature. Success of this project reinforced the recognition given by Global Water Intelligence ranking WABAG among the top 10 desalination companies globally.

The plant was awarded with the Dun and Bradstreet Infra Awards in 2016. Another feather in WABAG’s cap was the International Engineers Institution’s Industry Excellence Award in 2016 that complimented the technology employed to make the project feasible and sustainable.

Present Status and the future of Desalination:

The Nemmeli desalination plant has satisfactorily helped bridge the water demand- supply gap (desalination caters to 25% of daily water supply in Chennai).This proves that advanced technology can provide solutions to one of humanity’s most critical problems – the scarcity of drinkable water.

Seeing this the Government of India has also acknowledged the sustainability promised by desalination especially along the coastal cities of India.

The recent announcements of two new desalination plants – a 150 MLD Plant and 400 MLD plant at Chennai are a few welcome measures promoting desalination as a reliable source to safeguard our country’s water security.