The demand for drinkable water is ever on the increase and several cities and towns across the globe are struggling to meet the water requirements of its citizens. Chennai is a burgeoning metropolis with an unfulfilled requirement of safe drinking water, and that makes a multitude of projects the need of the hour. To provide a solution to the problem, IVRCL came up with a prestigious project of commissioning a desalination plant near Chennai that converts sea water into safe potable water. This prestigious project adds another feather in IVRCL’s cap and the company furthered its plunge into engi-visioning a new world.
Water is an essential source for life and good health. A lack of water to meet daily needs is a reality today in most parts of our country and in several parts of the world. Globally the problem is getting worse as cities and populations grow and the need for water increases in households.
We all know that 99 % of the water available in the world is salt-water. What better solution than to convert salt-water to drinkable water?
IVRCL along with Chennai Water Desalination Plant Limited, commissioned seawater desalination project by reverse osmosis process to get potable water as per IS10500:1991. Today 2.5 million residents of this city get potable drinking water from the 100 Million Litres per Day desalination plant.
The Minjur Desalination Plant is a reverse osmosis, water desalination plant at Katupalli village, a northern suburb of Chennai, India, on the coast of the Bay of Bengal that supplies water to the city of Chennai. Built on a 60-acre site, it is the largest desalination plant in India.
The project has been nominated as one of the highly commendable Desalination Deals of the year 2007 at The Global Water Intelligence Conference in Barcelona, Spain.
Having conceptualized, built and operated our own 100 MLD desalination plant – first in the country - at Chennai for the last several years, which is incidentally India’s largest plant, we are in a good position to take up the challenge of converting sea water to potable water for coastal areas of India.
Drinking water scarcity is higher in coastal regions in comparison with the interior parts of India; in coastal areas, the groundwater is saline and not suitable for drinking. Therefore, desalination of sea water becomes an ideal solution to bridge the widening gap between growing water needs of urban population and scarcity in supply in major coastal cities in India. Extending supply from dams or transporting through tankers has been proven costlier than water supplied by desalination. Continuous efforts to amend the desalination technology have brought down the cost of desalination technique, thereby reducing the per liter cost of water.
It is the process of removing salt and other impurities from water and rendering it fit for human consumption. Seawater has a high percentage of salt whereas pure drinkable water should ideally contain less than 10 ppm of salt.
Osmosis is a natural phenomenon, without which life would be made impossible. Osmotic processes enable plants to absorb nutrients from the ground. Our kidneys purify the blood in our bodies by means of osmosis.
Although osmosis has been discovered and studied as early as 1850, it has taken us until 1960 to be able to apply the process for water desalination. We can explain the term “reverse osmosis” as follows:
To desalinate water, we must create a flow through a membrane, causing the water to leave the salty side of the membrane, flowing into the unsalted side. To achieve this, pressure must be created upon the water column on the salt side of the membrane; firstly, to remove the natural osmotic pressure and secondly, to create extra pressure on the water column, in order to push the water through the membrane. For the desalination of seawater, the pressure must be about 50-60 bars.
Project Name: 100 MLD Seawater Desalination Plant
Project Location: Kattupalli Village, Ponneri Taluk, Minjur
Project Cost: Rs. 550
Crores Owner: M/s Chennai Water Desalination Ltd (CWDL).
A Special Purpose Vehicle formed by M/s IVRCL LTD.
Client: Chennai Metropolitan Water Supply & Sewerage Board (CMWSSB)
Project Type: Design Build Own Operate & Transfer basis (DBOOT)
Operation & Maintenance Period: 25 years from the date of Commerical Operations Date (COD)
Process: Seawater is desalinated by Reverse osmosis process to get potable water as per IS 10500: 1991 & as specified in the Agreement BWPA between CMWSSB & CWDL.
For getting 100 MLD of Potable water, about 237MLD of seawater is drawn through HDPE pipes by gravity intake from the Intake structures located at a distance of about 589m from the shore at a depth of 9m. the Seawater drawn is pretreated by screening, coagulation & flocculation, sand filters, anthracite filters, chemical dosing to make the seawater suitable for feeding to Reverse osmosis system and the treated water from reverse osmosis system is post treated with lime to meet the requirements of IS 10500:1991 .The reject from the RO system brine will be disposed off through outfall pipes at a distance of 650m from the shore. The distance between the intake & outfall system is kept as 698 m as per the requirements under Ministry of Environment & Forests. The treated water will be metered before delivering into the Product water tank which is located in the battery limits of the plant. The energy from the brine in the reverse osmosis process is recovered through the Energy Recovery System and fed back to the Reverse osmosis membranes through booster pumps. This is the main advantage in our system which substantially reduces energy cost of the plant.
CWDL has undertaken the following studies for the project.
1. Marine Environmental Impact Assessment studies
2. Delineation of LTL and HTL and CRZ- Coastal Regulation Zone
3. Marine geophysical investigations
4. Mathematical Modeling study on the dispersion of saline reject disposed in the sea
5. Water Quality Geotechnical Investigations studies to assess the properties of the soil
Geotechnical Investigations studies to assess the properties of the soil
In addition to the above studies, Rapid impact Assessment of high saline effluent from the proposed Desalintiaon plant at Minjur on the Coastal marine life and fishery was also conducted by Central Marine Fisheries Research Institute, Kochi as per the instructions of Ministry of Environment & Forests, New Delhi for getting CRZ clearance for setting up of 100 MLD Sea Water Desalination Plant at the proposed location.
We look at Water Projects as a humbling experience as they contribute and effect directly or indirectly the quality of life of the people of our country very significantly and will continue to do that in future as well. ‘Sea water desalination plant’ is a project where our engineering expertise triumphed, and we took pride in adding another jewel to India’s crown.