Nemelli desalination plant to quench thirst of 15 lakh people

Chennai:

Chief Minister J Jayalalithaa on Friday inaugurated Nemelli desalination plant that will give the city additional 100 million litres per day (MLD) of drinking water to quench the thirst of 15 lakh people in south Chennai.

The Rs 871.24 crore plant built by V A Tech Wabag Limited in consortium with IDE Technologies in Israel is set up on an extent of 40.05 acre of land belonging to Alavandar Trust on East Coast Road at about 35 km from Chennai city in Nemmeli and Krishnan Karanai Villages in Chengalpattu taluk in Kancheepuram district. The land has been given on a lease to Metro water for a period of 30 years.

Speaking during the occasion Municipal Administration and Water Supply Department secretary K Phanindra Reddy and Metro Water managing director B Chandra Mohan said that 265 MLD of raw water from sea will be drawn by gravity by laying 1600 mm pipes for a length of 1000 metre and after undergoing reverse osmosis, 100 MLD desalinated water would be produced. After the sea water is converted to drinking water the brine would be released into the sea through a 650 metre long pipeline.

Reddy said the desalination plant would quench the thirst of 15 lakh people. He said the water would be supplied to residents in Velachery, Palipattu, Tiruvamiyur and IT corridor. The water will be supplied through the pumping stations at Nemelli, Akarai, Tiruvanmiyur and Velachery.

Metro Water engineers said the water would be supplied to the city from next month. Right now we are flushing the pipes after which the water would be supplied.

Interestingly, the Nemelli plant is more sophisticated than the Minjur desalination plant. “Minjur desalination plant was built on a conventional system while Nemelli is built using latest technologies like ultra filtration membrane and reverse osmosis membrane. The technology is such that it removes even the bacteria,” said a metro water engineer.

Metro Water said that operation and maintenance of the plant willl be done by VA Tech Wabag for seven years. It is believed VA Tech Wabag will be earning a revenue of Rs 70 crore a year due to this contract. Metro Water said even the cost of producing the drinking water in Nemmeli is cheaper than Minjur.

The government is currently buying 90 MLD of water a day from the Minjur desalination plant at an average cost of Rs 48.66 per KL (4.8 paise per litre of water) per day that includes water capacity charges (the cost for the facilities they have provided) as well as water variables (cost of treatment, manpower and chemicals. Metro water believes the cost of water in Nemelli would be Rs 21 per kilolitre.

How will Chennai Benefit from Nemelli

--    The desalination plant is expected to quench the thirst of 15 lakh south Chennaites

---    The water would be supplied to residents in Velachery, Palipattu, Tiruvamiyur and IT corridor

---    The cost incurred to produce one kilolitre of water from Nemelli is Rs 21 which is much lesser than Minjur desalination plant (Rs 48.66)

---    The opening of Nemelli plan is crucial following Veeranam lake, which supplements the water supply to city, nearly drying up

---   Cuurently, the city is dependent on four reservoirs – Poondi, Cholavaram, Red Hills and Chembarambakam which has nearly 4 TMC ft of water

---   Currently, the city supplies 830 mld of water a day

---    Metro water is also preparing to build a third 200 MLD desalination plant which could be scalable to 400 MLD

---   Currently, the city has secured supply of 200 MLD of water from two desalination plants

Salient features of desalination plant at Nemmeli

1. Nemelli plan will treat 265 million litres a day raw water to produce 100 mld of drinking water

2. The Nemmeli plant will treat Sea water total dissolved solids (TDS) which ranges from 36,200 to 41000 parts per million (PPM) to 500 PPM

3.  For drawing sea water 1600 mm dia High Density Poly Ethylene (HDPE)  pipes are laid below the sea bed for a length of 1100 metre

4.  For discharging brine into sea, 1200mm dia HDPE pipes are laid below the sea bed for a length of 600 metres

5. Pre-treatment is done by means of back washable disc filters (30 sets) followed by ultra filtration (UF) membrane

6.  Sea water intake pumphouse has four pumps of 630 horse power each. b) Two pumps will be working and two on stand-by

7. Desalting is done by using reverse osmosis (RO) membrane

8.  Post-treatment using carbonation and re-mineralisation system