Data Centre Water Treatment in India: Cooling Water, Treated Sewage Reuse and ZLD Options

Introduction: Digital Growth Meets Water Stress

India's data centre capacity is expanding quickly, driven by cloud services, artificial intelligence, digital payments and data localisation. Most of the attention goes to electricity and land. Water, quietly, is becoming just as important. A large data centre removes a lot of heat, and the cheapest way to do that in most Indian cities is to evaporate water in cooling towers.

Industry estimates give a sense of scale. One white paper reported that India's data centres used around 150 billion litres of water in 2025, with demand expected to more than double by 2030. In another development, Amazon Web Services said it plans to use treated sewage water for cooling at future data centres in cities including Mumbai and Hyderabad, while some state governments are reviewing data centre policies with water use in mind. In Hyderabad, the water board has proposed public private partnership projects to supply treated water to industrial and commercial hubs, with data centres named among possible users, as described in our article on treated wastewater reuse in Telangana.

For an owner or developer, this changes the planning order. Water supply, wastewater disposal and local permits can decide whether a site is approved, how large it can grow and what it costs to run. A water strategy that treats cooling water well, reuses what it can and reduces discharge is becoming a basic part of a data centre project.

This guide explains where data centres use water, how to estimate demand with a worked example, how to treat make-up and blowdown, how to use treated sewage safely and when ZLD makes sense. It is written for data centre developers, facility managers, MEP consultants and sustainability teams.

Where a Data Centre Uses Water

Cooling Towers and Other Uses

The largest water use in most data centres is evaporative cooling. Chilled water or condenser water loops carry heat from the server halls to cooling towers, where a portion of the water evaporates. That evaporation, plus drift and blowdown, has to be replaced with make-up water.

Smaller uses include humidification in some halls, domestic water for staff and facilities, fire water storage, landscaping, cleaning and, in some designs, water for fuel and generator cooling. Wastewater streams include cooling tower blowdown, sewage from the building and sometimes RO reject or filter backwash.

Cooling Choices and the Water to Energy Trade-Off

Designers can trade water for electricity. Air cooled chillers and dry coolers use little or no water but consume more power, especially in hot weather. Evaporative towers use water but less power. Hybrid systems use dry cooling in cool conditions and evaporation when it is hot. Direct liquid cooling and immersion cooling, which are spreading with high density AI racks, remove heat more efficiently and can reduce the need for evaporation, but they bring their own heat rejection needs.

There is no single best choice. The right design depends on local water availability and price, power cost and carbon goals, climate and the heat load. A site in a water stressed area may accept higher power use to cut water, and a site with cheap reclaimed water may use evaporative cooling confidently.

Estimating Water Demand: A Worked Example

From IT Load to Evaporation

Almost all electricity consumed by IT equipment turns into heat that must be rejected. Evaporating one kilogram of water absorbs about 2,257 kJ. So one megawatt of heat rejected by evaporation needs about:

3,600,000 kJ per hour ÷ 2,257 kJ per kg = about 1,600 kg per hour, or about 1.6 m³ per hour

Consider a 10 MW IT load facility with a cooling system rejecting roughly 10 MW of heat entirely through cooling towers. Evaporation is about 16 m³/h, or about 384 m³ per day. In practice, only part of the heat goes through evaporation in many designs, and the real figure depends on the cooling system and the climate, so treat this as an upper bound for planning.

Make-Up, Blowdown and Cycles of Concentration

Blowdown prevents dissolved solids from building up in the tower. With drift ignored for simplicity, blowdown equals evaporation divided by the cycles of concentration (COC) minus one, and make-up equals evaporation plus blowdown.

• At 3 cycles: blowdown = 16 ÷ 2 = 8 m³/h, make-up = 24 m³/h, or about 576 m³/day
• At 5 cycles: blowdown = 16 ÷ 4 = 4 m³/h, make-up = 20 m³/h, or about 480 m³/day
• At 8 cycles: blowdown = 16 ÷ 7 = 2.3 m³/h, make-up = 18.3 m³/h, or about 440 m³/day

Moving from 3 to 5 cycles saves about 4 m³/h of make-up, which is about 35,000 m³ a year. Raising cycles needs better make-up quality, for example softened or RO treated water, since hardness, silica and chloride limit how concentrated the tower water can get. The same logic applies to any cooling tower, as explained in our guide on designing a water recycling system for cooling towers.

These numbers show why water strategy matters. A single 10 MW facility could need several hundred cubic metres per day, and a campus of many halls multiplies that. At such volumes, borewell or tanker supply is neither dependable nor popular with neighbours.

Treatment and Reuse Options

Make-Up and Blowdown Treatment

Cooling water needs treatment to prevent scale, corrosion and biological growth, which would reduce heat transfer and damage equipment. A typical programme combines:

• Make-up treatment: filtration through a multi grade filter, softening with a water softener and, for higher cycles or poor quality water, RO, discussed in our industrial RO plant page
• Chemical dosing: scale and corrosion inhibitors, and biocides, with Legionella control as part of the water safety plan
• Blowdown control: conductivity based automatic blowdown
• Side-stream filtration: to keep suspended solids low
• Blowdown recovery: treating blowdown through softening or antiscalant, ultrafiltration and RO, so that permeate returns to the tower

Data centres also demand reliability. A cooling water failure can shut down servers, so the treatment plant needs redundancy, bypass lines, storage tanks and automation with alarms. Design with N+1 equipment for critical stages, and keep a storage tank that gives hours of buffer.

Treated Sewage, Rainwater and ZLD

Treated sewage from municipal plants or from the campus's own sewage treatment plant is an attractive make-up source, especially where fresh water is scarce. It needs additional treatment, because it carries ammonia, organics, phosphate and bacteria that cause scaling, corrosion and biofouling in cooling systems. A typical train includes tertiary filtration, UF and RO, as explained in our guide on tertiary water treatment for industrial reuse. Check the supply reliability and quality with the provider, and keep a fresh water backup.

• *Rainwater harvesting** adds a seasonal supply. It needs storage and treatment but reduces the demand on other sources.
• *Zero liquid discharge (ZLD)** may be needed where there is no sewer or storm drain to discharge to, or where permits forbid discharge. ZLD concentrates blowdown and RO reject through evaporation and crystallisation so that only solids leave the site. It adds capital and energy cost, so use it where it is needed, and see our article on ZLD plant cost, technology and mandates and our zero liquid discharge systems page.

Cost, Planning and Choosing a Partner

Water as a Project Risk

Treat water as a project risk from the first day of site selection. Check the source, quantity, quality and permit for water supply. Check how wastewater will be disposed of, including blowdown, sewage and reject. Ask about local policy on data centres and water, which is evolving. Plan storage tanks for continuity. Estimate the cost of treated water over the life of the facility, including the cost of water, treatment, energy, chemicals, membranes and labour.

A reuse system does not need to be built at full scale on day one. Design the layout and utilities so that tertiary treatment and RO can be added in phases as capacity grows, and install metering that records each water stream. Good data supports reporting on water use effectiveness (WUE) and sustainability disclosures that customers increasingly ask for.

Questions to Ask Before You Order

• What water balance and demand scenarios did you use for my cooling design and growth plan?
• What cycles of concentration do you plan, and what make-up quality does that need?
• How will the system handle reliability, redundancy and failures?
• What treatment train do you propose for treated sewage or blowdown, and what quality do you guarantee?
• How are RO reject and sludge handled, and is ZLD included or optional?
• How will water use be metered and reported?
• What operation and maintenance support do you provide?

Our wastewater recycling system and wastewater treatment plant offerings, project execution services and an annual maintenance contract cover design, supply, commissioning and long-term support.

Monitoring and Reporting Water Use

Meter every stream: make-up, blowdown, domestic, treated sewage, RO permeate and reject. Track water use effectiveness against IT load and review it monthly. Good data supports permits, sustainability reports and customer audits, and it shows quickly when a cooling tower is running at too few cycles.

Also check how local policy treats data centre water. Some authorities are reviewing permissions and may ask for water sourcing plans, reuse commitments or monitoring data, so build these into the design and the approval file early.

Industry Comparison / Operational Parameter Table

Why Choose Trity Enviro

Trity Environ Solutions is an ISO 9001:2015 certified and QCI-approved wastewater recycling system and water treatment plant manufacturer and supplier in India, delivering robust, high-efficiency systems engineered for CPCB and SPCB regulatory compliance.

Every installation is supported by pan-India Annual Maintenance Contract and Operation and Maintenance services.