Coal-based power plants account for about 70 per cent of the fresh water withdrawn by industries in India. This adds pressure on limited freshwater resources already facing competing demands from agriculture, industry and urban centres. The challenge is expected to only intensify. A World Resources Institute study estimates that 70 per cent of India’s thermal power plants (TPPs) will face high water stress by 2030 due to climate change and rising demand from other sectors. To address these risks, the government has notified water consumption standards for TPPs, meeting which will require effective water management strategies to reduce their water footprint.
Water norms
The Ministry of Environment, Forest and Climate Change (MoEF&CC) notified specific water consumption (SWC) norms for TPPs for the first time in December 2015. Plants with once-through cooling (OTC) were required to install cooling towers and limit SWC to 3.5 cubic metre per megawatt-hour (m3/MWh). Existing cooling tower-based plants installed before January 1, 2017 were also required to meet this limit, while plants installed thereafter had to meet a stricter norm of 2.5 m³/MWh and comply with zero liquid discharge (ZLD) requirements. However, the norms did not distinguish between freshwater- and seawater-based plants.
In June 2018, the SWC limit for new plants was raised from 2.5 m³/MWh to 3 m³/MWh, while retaining the ZLD requirement. In addition, seawater-based OTC plants were exempted from these norms.
The regulatory framework was further amended in July 2025. The Environment (Protection) Third Amendment Rules, 2025 empowered the MoEF&CC, in consultation with the Central Electricity Authority (CEA) and Central Pollution Control Board, to exempt TPPs from mandatory cooling tower installation, subject to specified conditions.
Meanwhile, the Tariff Policy notified in January 2016 envisaged the reuse of treated sewage water for cooling. As per this, TPPs within 50 km of municipal sewage treatment plants (STPs) must use treated sewage water for their purposes.
Consumption requirements
Cooling accounts for about 80 per cent of a TPP’s water demand, followed by ash handling at 18 per cent and other process and domestic uses at 2 per cent. Water requirements vary significantly by cooling technology. According to the Centre for Science and Environment, OTC plants withdraw 70-200 m³/MWh, making them highly exposed to fluctuations in water availability. By comparison, cooling-tower-based plants withdraw about 4 m³/MWh on average due to repeated water circulation. However, evaporative, blowdown and drift losses result in higher water consumption than OTC systems.
Ash handling is another major water consumer as water is used to carry ash slurry to ash ponds. Generally, cooling tower blowdown is used for slurry preparation. Furthermore, as per a notification issued by the Ministry of Environment and Forests in 2014, plants located far from coal mines are required to use coal with ash content below 34 per cent, necessitating coal washing before transportation.
The operation of flue gas desulphurisation (FGD) systems further leads to an additional water consumption of about 0.3 m³/MWh. Besides, water is also required for steam generation, boiler feed, cleaning, maintenance and personnel facilities.
Measures to conserve water in TPPs
Improving water efficiency in TPPs requires a combination of cooling optimisation, wastewater reuse, water-efficient ash handling and continuous monitoring. Cooling is the largest area of opportunity. Increasing the cycles of concentration (CoC) in cooling towers allows water to circulate longer before blowdown, thereby reducing consumption. Dry cooling systems, particularly air-cooled condensers (ACCs), and hybrid systems combining wet and dry cooling also reduce water use. NTPC’s 1,980 MW North Karanpura supercritical plant in Jharkhand, commissioned in June 2025, is India’s first supercritical plant with ACC. The system reduces water consumption to about one-third of conventional water-cooled condensers and saves around 30.5 million cubic metres annually.
Further, replacing conventional wet slurry ash disposal with high-concentration slurry disposal (HCSD) reduces the water required for ash transport. While lean slurry typically contains 25-30 per cent ash, HCSD increases the ash concentration to 65-75 per cent, substantially lowering SWC. Ash water recirculation systems and dry ash utilisation avenues also reduce the need for ash ponds and support zero discharge.
Municipal wastewater can also replace fresh water for applications such as gardening, green belt development, dust suppression and firefighting. In this aspect, Maharashtra State Power Generation Company (MAHAGENCO) has been implementing large-scale reuse projects to treat municipal sewage through STPs and further through fibre-disc filtration, ultrafiltration and reverse osmosis (RO) for meeting the cooling tower make-up requirements. Over their approximately 30-year operating life, the projects are expected to save nearly 7,335 billion litres of fresh water. FGD wastewater can also be utilised after filtration, RO, forward osmosis and crystallisation.
Further efficiency gains can come from efficient boilers and turbines, periodic water audits, real-time monitoring and leak detection. For instance, Adani Power uses flow meters to track water consumption, wastewater generation and treatment. Level transmitters and alarms in sumps and pits also help prevent overflows.
Emerging trends
Intelligent water management systems combining sensors, internet of things and artificial intelligence (AI) are enabling real-time monitoring of water intake, treatment, reuse and discharge. AI can use real-time data collected from smart sensors to optimise water recirculation, blowdown and make-up, improve reuse strategies, and optimise CoC to improve water reuse while preventing scaling.
Challenges in water management
Despite their potential to reduce water consumption, advanced technologies and ZLD systems have seen limited adoption in India due to technical complexity and high capital costs. ZLD also increases plant footprint and operations and maintenance requirements. Highly polluted FGD and ash-handling wastewater further complicates ZLD. Dry cooling presents another trade-off, reducing power output by 7-8 per cent and affecting plant efficiency, which necessitates supportive policies and financing for wider deployment. While treated municipal wastewater can reduce freshwater dependence, only 5-8 per cent of coal plants have access to it. Limited STP capacity, weak conveyance infrastructure, pricing, water quality concerns and competing irrigation demand remain key barriers.
Additionally, water consumption reporting remains non-uniform, SWC data is often incomplete, and compliance figures are largely self-reported. Recently, in February, a right to information application seeking plant-wise treated sewage water use by Haryana Power Generation Corporation Limited found no supporting documentation. The company’s response provided only freshwater consumption, amounting to several hundred million litres. The absence of documented transition to treated sewage water raises concerns over both compliance and monitoring.
The way forward
India plans to invest nearly $80 billion in coal plants by 2031 to meet rising power demand from data centres, according to Reuters. However, 37 of the 44 planned projects are in water-stressed regions, making stronger water management and treated wastewater reuse imperative. The opportunity is significant. A Council on Energy, Environment and Water report estimates that sewage generation will rise to 120,472 mld by 2050, while treatment capacity will increase to 80 per cent. This could make 96,378 mld of treated wastewater available for reuse by 2050. The CEA is also exploring the use of sewage treated water for TPP cooling. As of FY 2024-25, nine TPPs totalling 10,611 MW capacity were already using 639 mld of STP water. Scaling this alongside advanced water management technologies will be essential for the thermal sector to move towards zero discharge.
Khushi Rohatgi