The Nemmeli Desalination Plant is a

water desalination Desalination is a process that removes mineral components from saline water. More generally, desalination is the removal of salts and minerals from a substance. One example is soil desalination. This is important for agriculture. It is possible ...

plant at

Nemmeli Nemmeli is an agricultural village in Madukkur Panchayat Union, Pattukkottai taluk of Thanjavur district, Tamil Nadu, India, also known as 28.Nemmeli. Nemmeli village is division of Musugundha Nadu in Chola nadu. It comes under Pattukottai le ...

Chennai Chennai, also known as Madras (List of renamed places in India#Tamil Nadu, its official name until 1996), is the capital city, capital and List of cities in Tamil Nadu by population, largest city of Tamil Nadu, the southernmost states and ...

, on the coast of the

Bay of Bengal The Bay of Bengal is the northeastern part of the Indian Ocean. Geographically it is positioned between the Indian subcontinent and the Mainland Southeast Asia, Indochinese peninsula, located below the Bengal region. Many South Asian and Southe ...

that supplies water to the city of Chennai. Initially the desalination plant experienced operational issues since the beginning and was shut down most of the time as contractor had installed the desalination plant without dissolved air floatation units leading to severe and regular choking of filters. It is located about 35 km south of the city centre, along the

East Coast Road East Coast Road (ECR), combination of SH-49, NH-332A, NH-32, officially known as Mutthamizh Arignar Kalaignar Road, is a two-lane highway (now being partially widened to four lanes from Chennai to Mamallapuram) in Tamil Nadu, India, built alo ...

. Built at a cost of 5,333.8 million, the plant is the second desalination plant in the city after the 100-MLD (million litres per day)

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

Minjur Minjur is a suburb located in the northern outskirts of Chennai, India. It is located in Thiruvallur district in the Indian state of Tamil Nadu. Minjur is called 'Vada Kanchi' meaning North Kanchipuram. The locality has two famous temples for Sh ...

and itself has a capacity to treat 100 million litres of seawater a day. The plant was inaugurated by the then Chief Minister of Tamil Nadu J.Jayalalithaa on 22 February 2010. was built to provide piped water to residents of south Chennai and the newly merged areas.

The plant

The plant, owned by Chennai Metrowater, was constructed by VA Tech Wabag, in consortium with

IDE Technologies IDE Technologies is an Israeli water desalination company.Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

, and Larsen and Toubro (L&T) Limited laid the 65-km-long pipeline from the plant to various parts of the city and built underground sumps en route.

MECON Limited MECON Limited, formerly known as Metallurgical & Engineering Consultants (India) Limited, is a Public Sector Undertakings, central public sector undertaking under the Ministry of Steel (India), Ministry of Steel, Government of India. The compa ...

, a Govt. of India Enterprises, carried out the project management consultancy services for plant construction. The DPR (

detailed project report A project plan, is a series of structured tasks, objectives, and schedule to a complete a desired outcome, according to a project managers designs and purpose. According to the Project Management Body of Knowledge (PMBOK), is: "...a formal, appro ...

), complete design and detailed engineering and bid document was also prepared by MECON Limited. The plant was constructed with a grant obtained from the

central government A central government is the government that is a controlling power over a unitary state. Another distinct but sovereign political entity is a federal government, which may have distinct powers at various levels of government, authorized or deleg ...

. Underground sumps and water distribution stations are located in

Tiruvanmiyur Thiruvanmiyur is a largely residential neighborhood located in the south of Chennai, Tamil Nadu, India. Thiruvanmiyur witnessed a spike in its economy with the construction of Chennai's first dedicated technology office space, the Tidel Park, T ...

Velachery Velachery is a neighborhood of Chennai. It is located in the southern part of the Chennai city sharing borders with Guindy in the north, Taramani in the east, Perungudi in the south-east, Pallikaranai wetland, Pallikaranai in the south, Madipa ...

, Kelambakkam, and Akkarai. The pumping stations at Nemmeli, Akarai, Tiruvanmiyur and Velachery have a combined capacity of 1,375 HP. The process technology involves marine sea water intake system and pre-treatment system consisting of

disc filter A disc filter is a type of water filter used primarily in irrigation, similar to a screen filter, except that the filter cartridge is made of a number of plastic discs stacked on top of each other like a pile of poker chips. Each disc is cover ...

s followed by

ultra filtration Ultra may refer to: Science and technology * Ultra (cryptography), the codename for cryptographic intelligence obtained from signal traffic in World War II * Adobe Ultra, a vector-keying application * Sun Ultra series, a brand of computer work ...

(UF). A 1,050-metre-long pipeline with a diameter of 1,600 mm (

HDPE High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or " polythene" when used for HDPE pipes. With a high strength-to-density ratio ...

) has been sunk at a depth of about 14.1 m in the sea side and 5.5 m in the shore side, capable of drawing nearly 265 MLD of seawater by means of

gravity In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force b ...

. Another 750-metre-long pipeline with a diameter of 1,200 mm discharges waste water from the plant. Disc filters and ultra-filtration membranes that remove sediment and finer sand particles from the raw seawater were imported from

Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...

, while additional

reverse osmosis Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane, semi-permeable membrane to separate water molecules from other substances. RO applies pressure to overcome osmotic pressure that favors even distribu ...

membranes were imported from

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. The pipeline, varying in diameter from 500 mm to 700 mm, runs for a distance of 64.371 km, and bridges have been constructed above the pipelines in areas such as Kelambakkam, Muttukadu, and

Kovalam Kovalam is a beach and seaside resort in the city of Thiruvananthapuram in Kerala, India. Kovalam is located southeast of the city center. The beaches around Kovalam are popular vacation destinations for both domestic and international travelle ...

. Although 40.5 acres of land was allotted for the plant, only 20 acres were required as fewer treatment units were built at the site. This is because the plant uses a compact and faster treatment process compared to the conventional filtration system used in the Minjur desalination plant.

Operations

The desalination plant experienced problems in the beginning and was shut down most of the time as contractor proposed the design without dissolved air floatation leading to severe and regular choking of filters. The plant treats the seawater by means of several units, including those containing disc filters and ultra filtration membranes, to remove the suspended solids in the seawater. Then the water is sent to the final stage of the treatment process through reverse osmosis membranes before distribution, which reduces the total dissolved solids in seawater from about 40,000 parts per million (ppm) to 300 ppm, thus making it potable. In the first phase of its operation, about 50 MLD of treated water is expected to be transmitted due to plant downtime, with the amount getting stepped up gradually after contactor addressed faulty pre treatment design. In December 2013, the plant reached its full capacity generation of 100 MLD. As of 2019, the plant produces 93 MLD on an average, catering to 1 million residents in South Chennai.

Cost

The production cost of treated water at the plant has been calculated approximately as 36 per kilolitre of water.

Expansion

A second desalination plant at the Nemmeli premises, and the third in the city, with a capacity of 150 MLD at a cost of 12,593.8 million is under construction on the 10.50-acre plot of vacant land near the existing plant. Planned in 2013, it will employ the reverse osmosis process as the current one, but with additional components in the pre-treatment process including dissolved air flotation and ultra filtration to prevent particles such as sea algae from hindering the purification process as it happened in Nemmeli Phase 1. The treated water will be distributed via a 49-km-long pipeline, serving about 900,000 people in southern areas of the city including Alandur, Sholinganallur, Medavakkam, Nanmangalam, Kovilambakkam, and St. Thomas Mount. The project is partly funded by KfW, the German Development Bank. The production cost for treated water is estimated to be 42 per kiloliter as against 36 per kiloliter in the first Nemmeli plant. A 1-km pipeline will be laid in the sea at a depth of 10 meters to draw seawater. A 750-meter-long pipeline will discharge the waste water.

References

External links