Water Treatment and Supply of High-Quality Make-Up Water for Data Centers

• 1. Water consumption in data centers
• 2. Water pollution caused by data centers
• 3. Treatment of feedwater for cooling systems
• 4. Conclusion

1. Water consumption in data centers

Data centers house countless servers and control units, which occupy large built-up areas where a large amount of purified water is required to cool them and keep them in proper working condition.

Data centers consume large amounts of water, primarily for cooling. On average, data centers consume about 2,000^m³ of water per day. This is equivalent to the amount of water a city needs to supply about 10,000 residents.

2. Water pollution caused by data centers

Most pollution is caused by blowdowns in cooling systems. The most commonly used technology is cooling towers (semi-closed circuits).

Water losses occur in cooling towers due to evaporation and carryover (approximately 2% of the circulating flow) and blowdowns (approximately 3–5%). These water losses contain concentrated salts, metals, and chemicals.

Proper water management helps minimize water consumption and reduce the environmental impact of these facilities.

The water supplied to the system may come from the municipal water supply, wells, or reclaimed water. Before it is used, it is necessary to determine its physicochemical characteristics in order to select the appropriate treatment.

Contamination results from the introduction of suspended solids, organic matter, and microorganisms present in the air used in the tower, as well as from the increase in salinity, hardness, and metal content caused by the concentration resulting from water evaporation.

In closed-loop systems, corrosion problems—and consequently, leaks—may occur; therefore, corrosion inhibitors and polishing filters must be added.

The following table shows the average water analysis results from the semi-closed cooling circuits used in these facilities:

Parameter	Unit	Water intake	Cooling Water (drain)	Water treated in a cooling tower	Treated water in a closed-loop system
Hardness	mg/LCaCO₃	150–500	450 – 2000	50	5
Conductivity	µS/cm	500–1,500	1,500–5,000	200–800	100
Iron	mg/l	0,3	0.5 – 5	0,1	0,05
Turbidity	NTU	5	10	1	0,5
Biological contamination		Variable	High	Very low	Very low

3. Treatment of feedwater for cooling systems

Surface waters contain suspended solids and organic matter in varying concentrations depending on their source. Therefore, they must be characterized and a comprehensive analysis conducted to identify these contaminants and their concentrations.

The conventional treatment regimen consists of:

• Separation of coarse solids (sieving)
• Add pH adjustment reagents (acid, sodium hydroxide), if necessary
• Addition of coagulants and flocculants for the separation of colloids and small-particle suspended solids
• Dissolved Air Flotation (DAF) Clarification
• Media filtration (dual-stage or multistage filters)
• Filter membranes (µF/UF)

This treatment approach applies to two types of therapy:

1. The makeup water collected to compensate for blowdown and evaporation in the semi-closed cooling circuit.
2. The water that is recycled from the cooling towers once it has been cooled.           

When salinity is high, polishing treatments using reverse osmosis membranes or ion-exchange resins are employed.

Block Diagram of Water Treatment for Data Center Inlet Water

4. Conclusion

The high volume of make-up water required to supply the cooling circuits in data centers makes it essential to have appropriate systems in place to recycle and reuse as much of this resource as possible. This strategy is a key solution for ensuring the efficiency, reliability, and sustainability of these facilities’ cooling systems.

The greatest demand for water occurs in cooling systems designed to dissipate the heat generated by servers and other computer equipment, which emit significant amounts of thermal energy and must operate within very strict temperature ranges to ensure proper functioning.

The cooling systems used in data centers are primarily closed-loop and open-loop systems. In closed-loop systems, corrosion inhibitors and fine filtration systems are typically used to maintain the quality of the cooling fluid. In contrast, in facilities that use open-loop systems with cooling towers—which are the most common—water quality directly influences scale formation, equipment corrosion, microbial growth, and overall water consumption; therefore, it is necessary to implement a specific treatment.

As a general solution, a treatment process consisting of dissolved air flotation (DAF), followed by a microfiltration or ultrafiltration stage and a final polishing treatment tailored to the required water quality, is particularly suitable. The DAF system removes suspended solids, oils, fats, and organic matter; membrane filtration significantly reduces turbidity, colloids, and microorganisms; while the final polishing treatment—which may include softening, partial demineralization, chemical adjustment, and disinfection—ensures the conditions necessary for safe and efficient operation of the cooling towers.

This combination of technologies makes it possible to increase concentration cycles, reduce blowdowns, minimize chemical consumption, and extend the service life of heat exchangers, piping, and cooling equipment. It also facilitates the use of reclaimed water or water of varying quality, helping to reduce potable water consumption and improve the environmental sustainability of data centers.

Consequently, the integration of DAF processes, membrane filtration, and polishing treatment constitutes a robust, flexible, and technically proven solution for treating feedwater in medium- and large-capacity data centers that use cooling tower systems.

Bibliography and consultations

AI and Water: What Is the Environmental Impact of Data Centers?

Data Centers | Grundfos