Sustainable Water Initiative for Tomorrow (SWIFT) Project in Hampton Roads

the Sustainable Water Initiative for Tomorrow (SWIFT) Project pumps treated wastewater into aquifers underneath Hampton Roads
the Sustainable Water Initiative for Tomorrow (SWIFT) Project pumps treated wastewater into aquifers underneath Hampton Roads
Source: US Geological Survey (USGS), Groundwater can be recharged naturally and artificially

Withdrawal of groundwater from the Potomac Aquifer increased starting in the 1940's and peaked in 1990. Paper plants in Franklin and West Point were particularly heavy users, and land subsidence near them was the greatest in the Coastal Plain. Groundwater levels declined until 2007, and have been increasing since then. Withdrawal permits issued under the state's 1973 Groundwater Management Act were revised in 2017, reducing authorized withdrawals to essentially the level being used at that time.1

starting in the 20th Century, groundwater withdrawals from the Potomac Aquifer exceeded the natural recharge rate
starting in the 20th Century, groundwater withdrawals from the Potomac Aquifer exceeded the natural recharge rate
Source: Virginia Department of Environmental Quality (DEQ), Virginia Coastal Plain Aquifer System (presentation by Scott Kudlas, June 27, 2022)

The Hampton Roads Sanitation District (HRSD) has committed to spend $1 billion for an innovative solution to two problems. In 2017, wastewater from all but one of the district's 13 treatment plants was discharged into the Chesapeake Bay or a tributary. That wastewater carried too much phosphorous and nitrogen into the bay, adding to the excessive levels of nutrients that resulted in low levels of dissolved oxygen.

In addition, extraction of groundwater in the region had led to ground subsidence significant enough to increase the predicted destructive impacts from future sea level rise, and to increase the threat of saltwater intrusion into the bottom of existing wells. Sea level was rising 4 millimeters a year, the second-highest level of sea level rise in the United States after New Orleans. Continued subsidence would result in greater damage to local infrastructure in times of high water, such as king tides.

The innovative solution was the Sustainable Water Initiative for Tomorrow (SWIFT). The Hampton Roads Sanitation District planned to treat wastewater to drinking water standards, then inject it deep into the Potomac Aquifer. Injecting the treated wastewater underground into the Potomac Aquifer rather than discharging it on the surface would eliminate the delivery of nutrients into the bay and retard or even reverse land subsidence.

SWIFT was designed to recharge the Potomac Aquifer, the primary source of groundwater extraction on Virginia's Coastal Plain
SWIFT was designed to recharge the Potomac Aquifer, the primary source of groundwater extraction on Virginia's Coastal Plain
Source: Virginia Department of Environmental Quality (DEQ), Virginia Coastal Plain Aquifer System (presentation by Scott Kudlas, June 27, 2022)

The natural recharge rate into the Potomac Aquifer was far below the amount being withdrawn, with an average of 155 million gallons being withdrawn each day. Sustainable Water Initiative for Tomorrow (SWIFT) was designed to inject over 100 million gallons a day, of the 150 million gallons per day processed by the Hampton Roads Sanitation District. Injection would increase pressure in the aquifer to offset the effects of groundwater withdrawal, as well as eliminate delivery of nitrogen to the Chesapeake Bay.

recharging the Potomac Aquifer was planned by injection of treated wastewater at five sites
recharging the Potomac Aquifer was planned by injection of treated wastewater at five sites
Source: Hampton Roads Sanitation District (HRSD), SWIFT capacity context (June 23, 2022)

The $1 billion price tag was staggering, but alternative ways to reduce nutrient pollution and Save the Bay could have been even more expensive. Wastewater treatment plant upgrades could match the success of Northern Virginia plants, upgrading to maximum feasible treatment technology in order to reduce nitrogen levels to 3mg/l.

However, the space available at different wastewater treatment plants for additional tanks required for additional nitrogen removal capacity was limited. Another likely alternative was to reduce stormwater runoff into local creeks, but the land and cost required to build stormwater ponds would be high and the water quality improvement would not be sufficient to meet the limits established in the Total Maximum Daily Load (TMDL) developed by the Environmental Protection Agency (EPA).

In the Sustainable Water Initiative for Tomorrow (SWIFT) project, wastewater would be treated to drinking water standards but it would not be re-used for that purpose in a "toilet to tap" program. The proposal by Newport News to build the King William Reservoir revealed that there was an adequate supply of drinking water in the region; additional groundwater withdawals were not required to meet projected demand.

The Hampton Roads Sanitation District had no market for selling wastewater that met drinking water standards. However, injecting it would create an underground reservoir in the aquifer that localities might tap in the future:2

Hydraulic modeling suggests that this initiative may reduce the effects of sea level rise by up to 25 percent and positively impact nearly the entire Potomac aquifer, as far north as Maryland and south beyond the North Carolina border. With the addition of 120 million gallons of clean water each day, the model also predicts that the aquifer can support all existing permits for groundwater use, with capacity to allow future withdrawals practically anywhere within the Eastern Virginia Groundwater Management Area.

The concept of injecting wastewater was tested at the Nansemond plant, starting in 2016. The Janes River Treatment Plant in Newport News was chosen to be the first facility with full-scale injection capacity. In 2022, construction started on a four-year project that would allow injection of nearly 16 million gallons a day by 2026.

Groundwater models predicted that at the James River Treatment Plant:3

...SWIFT water takes one-to-two weeks to move 50 feet through the aquifer, and then eight or more months to travel 400 feet. The first full-scale SWIFT facility, the James River plant, will have a target flow rate of 16 MGD and is scheduled to start up in early 2026. Once all five full-scale facilities are operational, the SWIFT facilities will have a total capacity of about 100 MGD.

Wastewater Reuse: Eliminating Discharge to "Receiving Waters"

Sewage Treatment in Virginia

predicted pressures in the Potomac Aquifer in 50 years without SWIFT replenishment (left) and with replenishment (right)
predicted pressures in the Potomac Aquifer in 50 years without SWIFT replenishment (left) and with replenishment (right)
Source: Hampton Roads Sanitation District (HRSD), The Potomac Aquifer: A Diminishing Resource

Links

References

1. "Draft Meeting Minutes," The Potomac Aquifer Recharge Oversight Committee, June 27, 2022, https://www.hrpdcva.gov/library/view/1837/paroc-minutes-june-27-2022/ (last checked June 30, 2022)
2. "What is SWIFT?," Hampton Roads Sanitary District, https://www.hrsd.com/swift/about; "The Potomac Aquifer: A Diminishing Resource," Hampton Roads Sanitary District, https://www.hrsd.com/swift/potomac-aquifer-diminishing-resource (last checked July 22, 2022)
3. "Draft Meeting Minutes," The Potomac Aquifer Recharge Oversight Committee, June 27, 2022, https://www.hrpdcva.gov/library/view/1837/paroc-minutes-june-27-2022/; "HRSD expanding project to turn sewage into drinking water at James River plant," WHRO, July 21, 2022, https://whro.org/news/30867-converting-sewage-to-drinking-water-hrsd-initiative-expands-to-james-river-plant (last checked July 21, 2022)


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