Fairfax County’s ‘purple pipes’ help reduce nutrients, water demand on Potomac
Treated waste water reused
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A golf course, five ball fields and a facility that burns trash to generate energy — each benefits from a Fairfax County water reuse program that provides the recycled liquid at discounted rates.
And so does the Potomac River.
The treated wastewater that goes onto the fields and into the generator’s cooling towers would otherwise be discharged back into the river after being treated to meet pollution limits — a process that costs the county millions of dollars.
By selling that treated water to another customer, the county actually makes money on the treatment process while finding another use for a resource that could be in shortern supply in the future.
“We tend to be water-rich in this county and in Northern Virginia,” said Michael McGrath, director of the Wastewater Treatment Division of the county’s Department of Public Works and Environmental Services. “Eventually, though, the population will reach a point where water resources will get tighter, so reuse is a way of helping with that.”
Fairfax County is among a growing number of municipalities required to treat municipal wastewater to increasingly strict levels before discharging it into sensitive waterways, that are considering how reuse programs might help their bottom line.
Nearby Loudoun County, VA, started a water reuse program around the same time as Fairfax County. Loudoun sells most of the recycled water to data centers that use it for cooling.
McGrath said that building the infrastructure to support water reuse has been easier in Loudoun County, which is able to lay new pipelines as it expands infrastructure into newly developed areas.
It cost Fairfax County about $15 million to build the water reuse program’s infrastructure, which includes a few miles of light-purple-colored pipelines that distinguish the recycled-water lines from those of other systems. The county began delivering water through this program in the summer of 2012 and is looking for new customers whose water needs are large enough to justify laying pipes to their facilities.
McGrath said the project had been “on the books” for a while, but not funded until the county received a $10 million grant from the American Recovery and Reinvestment Act to begin construction at the end of 2009.
He said the county would have gotten to the project eventually, but the grant moved things along. Even without the grant, the program would have been able to pay for itself and begin earning the county money within 13 years, McGrath said, the grant helped to expedite that timeline.
“This project is the one nutrient removal project that paid for itself,” he said. “All the rest that we’re putting in — these big multimillion-dollar facilities — this is the only one where we get some of that capital back.”
For treated wastewater that’s discharged into the Potomac River, the county’s Noman M. Cole Jr. Pollution Control Plant has to meet federal limits on more than 100 substances, including the Ph levels and the amount of dissolved oxygen, chlorine and total suspended solids..
The plant also adheres to monthly limits on the amount of phosphorous and nitrogen contained in the 45 million gallons of wastewater it discharges daily because of the role those nutrients play in the health of the Chesapeake Bay.
The limits for those nutrients have become stricter over the years, costing large municipalities millions of dollars to comply with new regulations. Fairfax County, for example, recently implemented a $40 million moving-bed bioreactor that uses floating plastic media — which look like wheel-shaped macaroni — to remove nitrogen from the water.
“In 2003, we had just put facilities online that we thought would do what needed to be done, and then, within two years, we were told that we needed to be doing more and had to immediately start planning again,” McGrath said. “We are now given a nutrient cap that we can’t exceed, but (water) reuse is going to help us with that in the future, if we’re discharging less flow.”
McGrath said the county’s clean record of wastewater treatment compliance for the last 15 years made getting regulatory approval for the new water reuse program that much easier, although parts of the process were still onerous.
The project’s early partners, like the Covanta Energy Resource Recovery facility, helped the county acquire easements on properties through which the new purple pipes were laid. Officials at Covanta say the reuse project also helps them meet their ecological and economical bottom lines.
Covanta and other reuse customers purchase the recycled wastewater at 75 percent of the cost of potable water it would otherwise purchase to fuel its cooling tanks. For Laurel Hill Golf Club, that extra demand for water would typically come at the peak of summer, when potable resources are tight. The golf course now receives up to 24 million gallons of reclaimed water to irrigate its course.
The ball fields at the Lower Potomac Park also are watered with the reclaimed resources.
The water used for reuse is treated to a slightly higher level than that which is discharged into the river, because of the possibility of public interaction, especially with water sprayed on ball fields or golf courses. McGrath said the county doesn’t necessarily have to treat all the reuse water to that level, but chooses to do so to streamline the process.
As more municipalities in the Chesapeake Bay watershed are required to build wastewater treatment plants to comply with their states’ cleanup plans, McGrath said the region could see more water reuse programs.
Building the pipelines and other infrastructure for reuse makes even more sense if it can be done alongside the construction of new plants, McGrath said. Conversely, it doesn’t yet make fiscal sense to pipe the reusable water to existing homes interested in using a few gallons over the summer to water their lawns, as nice as the idea might sound.
But, should the reusable water become a more precious resource — as it is in places with droughts like California or high-saline content in Florida — it could become cost competitive in the future.
For now, water reuse “is the most cost-effective way we have to help with nutrient discharge, because it pays for itself,” McGrath said. “So the more large customers we could get, the better from both those standpoints.”
- Category: Pollution
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