How Much City Water Can Data Centers Drink?

Subject to City Council approval, residents now have some idea about the potential future water use for cooling electronic equipment at data centers constructed in the area, like the one proposed by Emergent Data Centers for use by Skybox Data Systems in north San Angelo.

According to the recommended regulations passed by the Planning Commission on Monday, these centers would be limited to closed-loop recirculating systems, that would be allowed up to 15-gallons per square-foot of gross building area.

That means a 10,000 square-foot facility could use 150,000 gallons for normal operations, which is less than half of an acre-foot of water, an amount experts say roughly represents the average household’s yearly water use: between 130,000 and 160,000 gallons.

After the initial charge, the data center would only be allowed to recharge the system once every three years. The center can replace water throughout this time, but the amount is required to never exceed 3-percent of the systems total volume per year.

An acre-foot represents the amount of water in an area the size of one acre at a depth of one foot. It is equivalent to 325,851 gallons of water.

Future Water Use Projections

According to basic calculations, to ensure compliance with the ordinance, a 60,000 sq. ft data center would be required to use no more than 900,000 gallons of water over a three year period (2.76 acre-feet).

Potential future construction of up to 10 same-size facilities would account for 10,500,000 million gallons every three years, equal to seven-hundredths of one percent (0.07) of the city’s water draw over that same period of time.

What Happens With The Flushed Water?

Regulations for the discharge of water would have to follow standard waste guidelines, and be discharged through sewer lines which would go through the standard wastewater treatment process.

The water used in this context would likely be treated with a glycol heat transfer, not too dissimilar to the type of antifreeze chemicals used in automobiles, which is hazardous to humans.

(Data center glycol heat transfer fluids are only food-safe if they use propylene glycol (PG), which is generally recognized as safe by the FDA. Ethylene glycol is toxic and not food-safe, although often used in non-food industrial applications including data centers.)

According to the draft ordinance, all discharge would be subject to city testing before being released into the sewer system, and would follow city ordinance for waste water discharge, which would require the water to contain no amounts of free or emulsified grease or oil; acids or alkalis, phenols or other substances producing taste or odor in receiving water, toxic or poisonous substances in suspension, colloidal state, or solution, no noxious or otherwise obnoxious or odorous gases.

The regulations also stipulate that discharge contain only trace amounts (in parts-per-million) of suspended solids, as determined by the state commission on environmental quality.

From preliminary research, several companies advertise water filtering systems that provide the ability to fully filter any glycol from discharged wastewater, though the systems are expensive, the requirement by statute is that the water meets standards before city testing, so the cost would be borne by the operator.

Questions about water use have dominated public debate on the subject; key details to watch would be if the city wanted to specify further water filtration requirements before used water was put into the sewer system, or if city operators feel that current systems meet TCEQ requirements.

The nature of the ordinance allows for both changes by City Council, which will hold a public town hall meeting with representatives with Emergent Data Centers at the McNease Convention Center on Wednesday, at 5:30 p.m. which residents can submit questions to by following this link.

Read more about San Angelo’s water systems here:

San Angelo Zeroes in on Future Water Sources

Four Questions About San Angelo’s Water

Inside the City’s Water Quality Report