Water and sanitation: Follow one offering through the chain
Utilities and treatment firms supplying clean water and handling wastewater and sludge
Follow one offering through the chain
A litre of Chennai's desalinated water
Follow seawater at Perur from intake pipe to a south Chennai tap, and the sewage that comes back.
Lakes that fill only with monsoon
1,246 MLDChennai's piped supply, September 2026Chennai's traditional supply comes from reservoir lakes filled by monsoon rain and managed by state agencies. The four main lakes yield only 500 to 800 million litres a day (MLD), depending on rainfall, against demand of about 1,200 MLD (2021). In September 2026 Metro Water supplied about 1,246 MLD, of which 1,035 MLD was surface water and 154 MLD desalinated.1,7
Constraint Rainfall sets the yield: the lakes give 500 to 800 MLD, so a failed monsoon leaves Chennai far short of 1,200 MLD demand (2021). H₂O WaterCem CementSt SteelH2O Water cycleConstruction and infrastructureMembranes that hold back the salt
3.5-4.5typical kWh per cubic metre, seawater ROAt Perur, south of the city, seawater passes through lamella clarifiers, dissolved-air flotation and dual-media filters, then is forced at high pressure through spiral-wound reverse-osmosis membranes whose thin polyamide skin lets water through and holds salt back. Pumping is the main running cost: seawater RO plants typically use about 3.5 to 4.5 kWh per cubic metre (2020 review).2,4
Constraint Power and imports: typically 3.5 to 4.5 kWh per cubic metre, and most RO elements come from a handful of foreign membrane makers. Amn Specialty amines and ethanolaminesPTFE Fluoropolymers (PTFE, PVDF)PSF Polyester fibreEPX Epoxy resinsMot Electric motors and drivesPlastic and rubber productsElectrical equipmentPlastic under the sea, mains under streets
59 kmtransmission mains for the Perur plantTwo seawater intake pipes and a brine outfall of HDPE run along the seabed, and these offshore works were complete by mid-2026. On land, 59 km of large-diameter transmission mains carry the product water into the southern network; 37.13 km of that pipe had been supplied by July 2026, and laying it through built-up roads sets the pace.3
Constraint Laying large mains through dense streets, not the plant itself, is the critical path; about 63% of the pipe had arrived by July 2026 (calculated). HDPE High-density polyethyleneSt SteelFe Iron oreZn ZincCem CementMetal productsPlastic and rubber productsA contractor that builds and runs it
₹4,400 crWabag-Metito design-build-operate contractChennai Metro Water awarded the 400 MLD plant in 2023 to a joint venture led by VA Tech Wabag with Metito, on a design-build-operate contract of about ₹4,400 crore funded by JICA. The JV had 42 months to build and then runs the plant for 20 years, so it is paid for delivered water quality, not just for concrete poured.3,4,7
Constraint Schedule: the 42-month build awarded in April 2023 has slipped; commissioning is now expected in October 2027, on a project cost estimated at ₹5,814 crore. Cem CementSt SteelAgg Sand & gravelCon Construction chemicalsConstruction and infrastructureBuilding materialsFinance: banking, insurance, marketsMetro Water pipes it south
1,160 MLDplanned desalination capacity, ChennaiChennai Metropolitan Water Supply and Sewerage Board (Metro Water) takes the desalinated water, remineralised so it does not corrode pipes, and blends it into supply for southern Chennai. Perur's 400 MLD joins plants at Minjur and Nemmeli, including the 150 MLD Nemmeli unit opened in February 2024; with a second 400 MLD Minjur plant announced in 2026, capacity would reach about 1,160 MLD (plan).2,5,7
Constraint Energy cost: at a typical 3.5 to 4.5 kWh per cubic metre, 400 MLD needs roughly 1.4 to 1.8 GWh of electricity a day (calculated). H₂O WaterCaO LimeCO2 Carbon dioxideCl2 ChlorineDist Distribution grids, mini-grids and interconnectorsElectrical equipmentSoftware and IT servicesSewage turned into factory water
90 MLDsewage recycled for industry, two plantsThe same water comes back as sewage. Metro Water's two tertiary-treatment reverse-osmosis plants at Koyambedu and Kodungaiyur, launched in late 2019, each polish 45 MLD of treated sewage for industries around Sriperumbudur and Oragadam, freeing drinking water for homes. At full output they recycle about a fifth of the city's sewage (2021).1,6
Constraint Nationally the gap is wide: installed sewage treatment covered only about 44% of the 72,368 MLD generated in 2021 (calculated). H₂O WaterWT Water treatment chemicalsCl2 ChlorineAmn Specialty amines and ethanolaminesMachinery and equipmentWaste and recyclingPaid for by development lenders
₹1,259 crcost of the 150 MLD Nemmeli plantDesalination at this scale leans on concessional finance. Japan's JICA is funding Perur, while Germany's KfW development bank provided ₹700 crore of the ₹1,259 crore Nemmeli plant and Tamil Nadu paid the rest under the AMRUT scheme (2024). Regulators set the drinking-water quality the operator must meet, and the state carries the debt.4,5
Constraint Fiscal: where tariffs do not cover costs, debt service and 20 years of O&M fall on state budgets and sovereign-backed loans. Finance: banking, insurance, marketsPublic administration, defence and securityWhat the chain shows
Chennai shows water security can be bought with electricity, imported membranes and long O&M contracts; the bottlenecks are pipe-laying and finance, and Indian firms like Wabag can supply the rest.
Sources
- Chennai becomes first Indian city to recycle wastewater at scale World Bank Blogs, 2021
- Energy recovery in SWRO desalination: current status and new possibilities (Schunke, Hernandez Herrera, Padhye and Berry) Frontiers in Sustainable Cities, 2020
- Construction work on Perur Water Desalination Plant Project in Tamil Nadu likely to be completed by end 2026 Indian Infrastructure, 2026
- WABAG-led joint venture secures DBO order for 400 MLD seawater desalination project worth about INR 4,400 crore, funded by JICA EA Water, 2023
- Nemmeli Water Desalination Plant gets inaugurated Indian Infrastructure, 2024
- India's sewage treatment plants treat only a third of the sewage generated daily: CPCB Down To Earth, 2021
- New desal plant to reduce Chennai's dependence on monsoon DT Next, 2026