Water considerations for data centre development
At a glance
Following the Accredited Technical Masterclass Future-ready data centres: Designing and optimising for power, water and permitting, this page brings together water-related questions raised during the session alongside the responses shared. Concerns around water supply remain a central aspect of data centre development that needs to be addressed to align community and industry expectations.
Following the Accredited Technical Masterclass Future-ready data centres: Designing and optimising for power, water and permitting, this page brings together water-related questions raised during the session alongside the responses shared. Concerns around water supply remain a central aspect of data centre development that needs to be addressed to align community and industry expectations.
Your questions answered
The Q&A highlights key themes from the masterclass, including data centre cooling, water quality, AI concerns, use of recycled water, and trade-offs between energy and water constraints.
1) How much reclaimed water can realistically be used?
The cooling processes can use 100% reclaimed water or any other water sources. However, depending on the location in the process where it is used, a varying degree of further treatment is required (i.e. filtration, disinfection, desalination) which will produce a waste stream (which includes the solid/dissolved impurities and an amount of rejected water).
In general (and there are always exceptions):
- Closed loops require very high purity demineralised water.
- Water-assisted air-cooling cooling sources may use demineralised water or water of similar quality to drinking water or surface water. Demineralised water has effectively zero blowdown waste whereas surface water produces a small amount of blowdown waste.
- Evaporative cooling sources may use a wide range of water qualities, from desalinated water / high purity recycled water (“Class A+”) to secondary or tertiary treated sewage effluent (“Class B” to “Class A”) to sea water, however it typically uses water quality similar to surface water. The choice between water sources relates to availability.
In general, lower quality water will require a lower number of “cycles” which will result in higher make-up water requirements and higher waste production rates.
One important consideration relating to data centre blowdown streams is the compatibility of the chemicals used and cycled up constituents with local sewers / trade waste regulations and downstream wastewater treatment plants. The cumulative effect of multiple sewer mining systems upon the sewer network should also be considered.
2) What is the most desired water disinfection i.e. sodium hypo, UV etc.
The type of disinfection chemical used depends on the source water quality, where the water is being used in the cooling process (i.e., is the water compatible with the process in terms of corrosion / redox potential, scaling, biological growth potential, etc.) and the route for which the resultant waste stream is being disposed of.
A combination of disinfectants and treatment barriers are used for recycled/reclaimed water including advanced oxidation and UV in some cases. If drinking water or surface water is being used for evaporative cooling, sodium hypochlorite or chlorine dioxide are often used. Non-oxidising biocides such as DBNPA can be used, which typically aren’t used for human consumption scenarios.
3) What do you think about rainwater recapture systems which store the water in buried underground plastic containers which can be used for cooling systems?
Rainwater capture systems have potential as long as the volumetric buffering storage is cost effective and close to where the water needs to be used. This depends on the frequency of rain and the method of storage. Groundwater recharge at a nearby location with high aquifer hydraulic conductivity is one effective method. Dams are another (although significant footprint is required and impurity introduction via algae, etc., needs to be considered). Tanks can work on a small scale but are typically not effective at large scale. Appropriate treatment is required and the disposal of the “first flush” volume is the first line of defence.
4) How does shifting to direct-to-chip or immersion cooling impact the facility's overall Water Usage Effectiveness (WUE)?
Liquid immersion cooling and direct-to-chip cooling accepts a higher cooling water temperature from the facility’s water circuit closed loop, resulting in lower overall cooling demand and the ability to operate at higher ambient temperatures compared to air cooling systems. This means that heat removal from the system at the “cooling source” can rely upon free air cooling (i.e., air introduced from ambient) more often as a higher ambient temperature for the incoming air is acceptable. This means that the cooling source doesn’t need water assisted air cooling as often (which is typically used on hot days). The direct translation to WUE cannot readily be provided as it is very much project and location specific.
5) With AI density driving up heat loads, what is the maximum sustainable pumping rate you have seen for deep-well cooling before triggering localised water table drawdowns?
This is highly dependent on the local geology/hydrogeology and the cumulative effect of other human interactions with the local water table.
6) What are the main regulatory hurdles when transitioning a facility to use recycled or grey water?
This is very much dependent on the location of the facility. The main hurdle is whether or not the locality has recycled water or grey water regulations.
7) Are there any of your projects that are looking to use treated final effluent?
Most of our projects look at the potential to use treated final effluent of varying qualities and sources. The projects are both for data centre developers and water utilities. These projects examine both the supply of water and the management of waste from either the treatment of the raw sewage or effluent and the waste from the data centre itself.
8) How is scope 2 water usage factored into closed loop cooling system?
Scope 2 water typically relates to water used for energy generation i.e. indirect water use. Closed loop systems would be considered Scope 1 water i.e. direct water use.
A broader definition of Scope 2 water could relate to the water used to produce the closed loop system water with the difference being the wastewater stream. If using surface water or drinking water, which is typical, the amount of waste is very small.
A broader definition of Scope 2 water could relate to the water used to produce the closed loop system water with the difference being the wastewater stream. If using surface water or drinking water, which is typical, the amount of waste is very small.
9) What volume is needed for the water requirement for data centres? And what level of quality does it need?
The water volumes are dominated by the “cooling source.” See the slide deck for approximate numbers on this for a 100 MW cooling load at the cooling source itself. Keep in mind when translating this to a data centre that the numbers are somewhat lower as the cooling load is a little higher due to loss of heat from the system via incidental losses or even free air cooling via air loss from the building. See Q1 for a more detailed answer.
10) What extent can modern data centres operate with zero or near-zero water consumption (e.g. air-cooled, dry cooling, or closed-loop systems), and what are the practical trade-offs in terms of efficiency, capex/opex, and scalability, especially for high-density AI workloads?
Data centres with 0.01 L/kWh WUE exist already, however this is in locations where free air cooling is possible year-round. The trade-offs are typically CAPEX/OPEX when implementing more water-efficient technology (liquid immersion cooling or direct-to-chip cooling at the chips/computer racks or water-assisted air cooling at the cooling source). High-density AI data centre developers and operators are possibly better positioned to afford the increased CAPEX/OPEX related to increase water usage efficiency.
11) Has anyone looked at using effluent to then treat it themselves to meet their cooling WQ objectives?
Yes, many are looking at “sewer mining” where it is possible technically and from a regulatory perspective.
12) Is anyone seeing opportunities for capital investment into Local Government Infrastructure, such as water or sewerage (recycled water) infrastructure?
Yes, there is an opportunity to establish recycled water treatment facilities at locations where waste stream disposal is more convenient (i.e., next to the sewage treatment plant), yet transport of treated water is cost effective (from a CAPEX/OPEX perspective).
13) Do we have an example of complete closed loop water cooling system?
Yes, there are examples where it is claimed that make-up water addition only occurs at commissioning. In practice, this may be difficult if leakage or cycling up of impurities occur. In any case, the claimed WUE of 0.01 L/kWh for these systems is close to normal closed loops that use demineralised water.
14) To what extent can data centres utilise recycled water from wastewater treatment plants as a cooling source, and are there existing case studies or successful implementations of this approach?
There are many case studies worldwide (Brisbane’s Western Corridor Recycled Water Scheme, Arizona, etc). GHD has been involved in projects that use both “Class A+”, “Class A” and even recycled coal mine water. Care needs to be taken with respect to the waste stream compatibility with the selected disposal route, e.g., trade waste limits for the local sewer network and downstream sewage treatment plants or, in one case, where blowdown water was used for irrigation, the boron limits. See Q1 for details.
15) Is there a trade-off between energy and water when designing data centres? Is water generally seen as cheaper, and hence we are using more water in these centres than we should?
Yes, lower water usage is typically used with an increase in energy requirements. However, the overall increase is very small compared to the total data centre energy consumption.
16) With the current increase in building data centres, do we see more fossil fuel-based electricity generations to see those demands or renewables?
There is going to be an increase in fossil fuel-generated power, because it is available. However, as renewable energy schemes develop off the back of PPAs, the reliance on fossil fuels will reduce. See Q10, more for more information.
17) What elements from the bring your own energy/behind the meter method do you think can be adapted for water? how might that look like?
“Sewer mining,” rainwater capture and onsite groundwater usage are examples that currently exist. All have their own challenges.
18) Can you explain how the waste produced by the data centres is being dealt with? Can you give a rough % on how much is produced compared to the size of the data centre?
The waste is typically disposed of via sewer systems. Some locations in the US undertake ground re-injection where it is allowed. However, this approach can have significant drawbacks if not undertaken properly (this has recently been reported in media). Remote data centres may undertake ZLD or disposal of blowdown in holding dams (although the latter does negate the final sustainable disposal of the intrinsic salts, etc). The % waste is very much dependent on the source water quality, cooling process design and location.
19) What conditions will enable zero water data centres? Where might that be possible?
Zero water systems are possible in locations with temperate climates often when liquid-immersion cooling and direct-to-chip cooling of the chips is undertaken.
20) What is the cooling energy percentage out of total energy consumption?
The cooling energy relates to use of fans, chiller compressors, etc. This is often small compared to the overall energy usage (but not insignificant) – of the order of 10% of the energy used by the computer racks. This is highly dependent on the design and location of the data centre.
21) What is the temperature of coolant leaving the data centres?
If using evaporative cooling at the chiller’s condenser, the coolant leaving the process (i.e., blowdown) would be approximately 30-40C. If using air cooling of the chiller condenser, it would be around 10C above ambient. The coolant leaving the closed loops (which is rare and in very small amounts) would be near ambient.
22) Are there established examples or case studies of data centres that utilise recycled water (RW) for cooling system demand, and what are the key operational (especially water quality) or regulatory considerations observed in these cases?
There are many examples of data centres, power stations and other large cooling processes using recycled water. The data centre examples are predominantly in the US but there are several operations in Australia with significant cooling loads (i.e., up to hundreds of MW) that use recycled water (sewage based and industrial reuse-based).
23) Any indication on how data centres with RO manage their concentrated brine discharges?
This is very much location, feed water quality and cooling system design-specific. Without doing a full survey, it is expected that not many yet employ RO due to the scale of the current data centres. Therefore, it is assumed most data centres currently dispose to sewer. However, once data centres frequently reach the GW scale, this will change. In this case, the disposal route, if sewer is not possible due to salt load and using recent reference examples from the power industry and other large industries, it will be a combination of ZLD and landfill or co-disposal (likely for inland locations) or ocean outfall release (for coastal locations).
24) Since the water is mainly used for cooling, could the water be recycled forever so that there’s no need to replenish the water?
Processes which use zero liquid discharge (ZLD) approaches can come close to this but, unfortunately, there are always water losses during treatment or incidentally (e.g., drains or atmosphere) which means at least a small amount of system make-up water is required. The challenge with ZLD approaches is that it is very expensive both in terms of CAPEX and OPEX and produces a salty solid waste stream which, although very small volumetrically, is often difficult to dispose of.
25) Are there regulatory and approval challenges limiting temperature of any water discharged?
Yes, this is very much a problem for once-through cooling which uses large amounts of water. Less of a problem for evaporative cooling but still a concern for the regulator in terms of environmental impact or impact on sewer if this route is being used (but less of a concern).
26) Is water quality an issue? For example, former open cut mines are being filled with water to make them stable, generally next to former power station, with good grid access.
Yes, these types of projects have been considered but are typically complex and expensive to undertake. They should not be ruled out but have a low likelihood of being successful.