Using Recycled Water for Data Center Cooling

According to a recent study commissioned by the Prince William County Economic Development Department: Prince William County currently has about 5.2 million square feet of data centers generating $64 million in taxes, over 4.5% of the county’s budget.  In addition, of the 8,700 acres of land in the “data center overlay district” only 600 to 1,100 acres could be considered available for sale and viable for datacenters. There are also, 27 parcels of 40 acres or more in Prince William owned by data center companies or developers, many owned for three or more years that had not been built on. It is believed that developers were “land banking” for future building. 

In a desire to increase the industrial tax revenue, it appears that a majority of Prince William County Board of Supervisors want to see if more land can be made available to build data centers.  The supervisors and developers are looking to the Rural Crescent for this industrial development. The Prince William Board of County Supervisors initiated an amendment to the Comprehensive Plan for PW Digital Gateway to change the zoning from agricultural to Technology / Flex (T/F) on 2,000 acres along Pageland Lane for the development of data centers. The zoning being considered is for industrial uses - anything from data and distribution centers to asphalt plants. This could have serious implications for the environment, quality of life, our water supply and water use.

The advocates for the 2,000 acre Digital Gateway say that only recycled water will be used. They got that idea from the recent zoning amendment in Warrenton which will allow data centers to be built in their existing industrial zone with a special use permit; but require them to use recycled water for cooling. The amendment reads: “The data center shall utilize recycled water or air chillers, in conjunction with using recycled water, for cooling purposes.  Potable water shall not be used for cooling.”

Data centers consume water directly for cooling. A lot of water. According to a report from Dr. Venkatesh Uddameri of the Water Resource Center at Texas Tech, the typical data center uses about 3-5 million gallons of water per day. That is about as much water as 30,000-50,000 people.

Recycled water is intended to mean either treated effluent from a wastewater treatment plant treated to an adequate standard for this use or water that is recirculated through a closed loop cooling system and somehow supplemented from a non-potable source. This requirement was instituted to protect the drinking water supply in Warrenton from overuse. Fauquier County is having water supply issues and hopes to avoid the need to build additional reservoirs and water treatment plants to supply the residents.

In 2019, Loudoun County had around 100 data centers in operation with another 30 or so under development, according to the county's Department of Economic Development. Another 50 data centers were reportedly in the pipeline. Loudoun County supplies a significant number of data centers with recycled water, but nonetheless still had to build a water treatment plant and direct intake from the Potomac River to meet their water demand.

Beginning in 2010 Loudoun Water constructed the first portion of the pipelines for the reclaimed water distribution system to supply data centers with industrial cooling water. The reclaimed water distribution system has since expanded to 16 miles of pipeline and serves 35 of the facilities. In 2019, Loudoun Water delivered 640 million gallons of reclaimed water, helping to save an equal amount of potable drinking water. To provide the reclaimed/ recycled water, Loudoun uses the effluent water from the Board Run wastewater treatment facility near Ashburn. This facility is  near to the existing data centers. The effluent water used to be returned to the Potomac River upstream of the Fairfax and Washington Aqueduct water intake. The volume loss during dry years could be critical and require the building of more reservoirs to support the system. This will all increase the water costs for Loudoun County residents.

According to a disclosure made in the TEC “Water Reuse, CostAllocation and Pricing Survey,” Loudoun Water only recovers the incremental cost of service of recycled water. Revenues collected cover reclaimed water operations and maintenance costs, but not the capital cost recovery for system infrastructure. Loudoun Water believes the rates are likely under-recovering the true full cost of providing the service because they are based on the incremental costs alone. The remainder of the cost is born by the residential rate payers.

In Warrenton, neither of the nearby wastewater treatment plants produce wastewater effluent of the quality necessary for data center use; and the storage, piping and pumping infrastructure would also have to built at the rate payer’s expense. It is unknow what the potentially available volume of water is and how it will impact the recharge to groundwater a significant source of water in Fauquier.

In Prince William County where the proponents of the PW Digital Gateway have claimed that their development will used recycled water to allay the very real concern that there is inadequate potable water supply to meet the growth demands of the region and industrial use by data centers. However, the only nearby recycled water is already being used by Fairfax Water. In the 1970’s it was the acknowledgment that to continue supplying the region with drinking water, the Occoquan Reservoir would have to use not only the fresh water supplied by the Occoquan River, but also the recycled wastewater from the wastewater treatment plants.  UOSA was built to serve this need and all it’s recycled water is used by the Occoquan Reservoir to supply drinking water to our region.

The level of treatment required by UOSA for indirect potable reuse in the Occoquan Reservoir is more stringent than Level 1 or Level 2 treatment standards for the reclamation of municipal wastewater. Currently, Virginia has one facility, UOSA, which is permitted to produce reclaimed water that is used for drinking water in this manner. UOSA has been operating successfully for more than 40 years and includes the Occoquan Watershed Laboratory (OWL), established by the Virginia Polytechnic Institute Department of Civil Engineering to monitor and assure the water quality.

The only other recycled water in the region would be from the HR Mooney plant that is around 30 miles away. The impact on water supply and prices would impact all Prince William Service Authority customers. Before a single data center is built in the Digital Gateway plan, the Service Authority would absorb the cost to make sure that Mooney can treat the water to data center standards as well as build and expanded laboratory and build out the pipelines (at $350-$1,000 a foot for 30 miles) and pumping stations necessary to deliver water to the Digital Gateway development. The costs for this infrastructure would increase the average cost for water to Prince William residential customers. 

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