Key Questions
What water quality do data centre cooling towers need?
Cooling tower makeup water should have hardness below 200 mg/L as CaCO3, TDS below 500 mg/L and a Langelier Saturation Index between 0 and +0.5. With proper chemical dosing, the target is 6–8 cycles of concentration, keeping blowdown TDS below 3,500 mg/L.
Getting this wrong is expensive. When cycles of concentration climb above 5 on high-TDS water, scale builds aggressively on heat exchanger surfaces, thermal efficiency drops and descaling shutdowns follow. Navbharat Water treats makeup water with RO and softening, optimises concentration cycles to cut blowdown, and pretreats municipal water with softening, desilicification and disinfection for chiller and cooling tower feed. Other circuits need purer water still: closed-loop cooling typically requires conductivity below 50 µS/cm, direct liquid cooling for GPU and CPU servers below 5 µS/cm, and humidification below 10 µS/cm to avoid white dust on server hardware. These are met with RO plus mixed-bed DI or RO plus EDI, with online conductivity monitoring. At a 2 MLD hyperscale data centre WTP in Pune, cycles of concentration rose from 3 to 6.5, cutting makeup water consumption by 50%, and blowdown treatment enabled 85% reuse.
How is Legionella risk managed in data centre cooling towers?
Navbharat Water implements ASHRAE 188-2021 compliant water management plans: oxidising biocide held at 0.2–0.5 mg/L free residual, quarterly Legionella testing by an NABL-accredited lab, supplemental UV or ozone disinfection, and side-stream filtration to 10 microns, with risk indicators tracked continuously on the Smart Water platform.
Legionella in cooling towers is a severe liability for data centre operators, and ASHRAE Standard 188 calls for an active risk management programme, not just quarterly testing. ASHRAE 188-2021 sets the minimum requirements for a building Legionella risk management programme, ASHRAE Guideline 12 addresses minimising Legionellosis risk in building water systems, and BSRIA BG 50 covers water treatment for closed heating and cooling systems. Navbharat Water combines chemical control with continuous visibility. The oxidising biocide, chlorine or bromine, is matched to the system, with a non-oxidising biocide such as DBNPA added where needed, and the Smart Water platform tracks conductivity, pH, biocide dose and Legionella risk in real time, sending automated alerts to the facilities manager and to Navbharat Water remote support. This turns Legionella control from a periodic lab result into a continuously monitored process, with every dosing change and alert recorded for the site team.
Can data centres reuse treated sewage for cooling?
Yes. An on-site MBR STP with tertiary polishing can supply cooling tower makeup water. At a 150 KLD IT park STP in Hyderabad, Navbharat Water recycles 120 KLD daily for cooling towers and landscaping, saving ₹36 lakh a year in municipal water charges.
Data centres in water-stressed regions face municipal supply restrictions, and on-site STP reuse for cooling tower makeup is increasingly mandatory. The constraint is space, because data centre plant rooms have no room for oversized water treatment equipment. MBR technology fits because its membranes replace the secondary clarifier, producing outlet BOD below 10 mg/L in a footprint 30–40% smaller than an equivalent SBR, and the plant can be installed in a basement. The Hyderabad IT park plant sits in a basement plant room and obtained HMDA Occupancy Certificate clearance. Navbharat Water supplies these STPs as compact, basement-compatible and OC-ready units. Water efficiency also matters for building compliance: the ECBC 2017 Energy Conservation Building Code from BEE sets water efficiency requirements for data centres, and the CPCB OCEMS guidelines extend online effluent monitoring to designated industries including large commercial complexes.
