PRESCOTT – At the Feb. 26 Prescott City Council meeting, City Administrator Matt Wolf gave a brief history regarding City Well #3 that hasn’t been in use since 2021. In September 2021, the City of Prescott tested Well #3 and received a test result totaling 12.1 mg/L for nitrate levels which exceeded Wisconsin DNR standards for safe drinking water.

After the city turned off Well #3, it began to look for feasibility options for remediation with engineering firm CBS Squared. After exploring many options, the city decided to move forward with reverse osmosis treatment in April 2022.

In May of the same year, the city again tested the water and found trace levels of 3-8 ppt combined in each of the wells which is below the Wisconsin Safe Drinking Water standards of 70 ppt. After discussions with CBS Squared and the DNR, it is believed that the State of Wisconsin will eventually adopt new proposed national standards set at 4ppt for PFAS once it is finalized by the EPA.

In October 2023, the DNR gave full approval for the City of Prescott to move forward with reverse osmosis and granular activated carbon (GAC) treatment filtration, which is a type of water treatment commonly used to remove chemical contaminants and for taste and odor control.

The most recent change will have Well #3 use anion exchange instead of GAC filtration. Anion exchange devices remove anions (negatively charged ions such as arsenic and nitrate) and replace them with chloride. The plan then calls for the treated water to be sent to the Wastewater Treatment Plant after the anion exchange removes the PFAS from the concentrated RO waste.

On Monday evening, Jon Strand, project manager at CBS Squared, discussed the water treatment project for City Well #3 with the city council. He briefly explained the plans and specifications regarding the 2024 Water Treatment Project at Well #3.

“The plans and specs were submitted to DNR,” Strand said, adding that the DNR approved them with one significant change to the previous plans. “As we have been finalizing the design there has been one major change and that is to go with the anion exchange resin process instead of the granular activated carbon process or GAC.”

He said the reason comes down to cost, citing that anion resin will last longer. When working with Water Surplus, the designer of water treatment products, they found that anion exchange would be a more cost-effective solution in the long-term operations cost and the short-term construction cost.

“It will also provide actually a better treatment for the types of PFAS molecules that are in the drinking water and so that’s another advantage of using it,” he said.

The DNR gave its verbal approval to go along with the anion exchange process.

“What’s the price difference between them?” Alderperson Bailey Ruona asked.

 Strand didn’t have exact numbers, but said it would be about $50,000 less.

“The importance of the DNR approval and the anion exchange was that they did not require another pilot test because anion exchange and GAC primarily do the same thing,” he said. Strand said the building addition to Well #3 will be a 1,300 square-foot addition that will primarily house the reverse osmosis and the anion exchange equipment. It will also house a break tank or large water reservoir and a booster pump. The reverse osmosis system operates at a certain temperature that requires the back pressure to be around 60 PSI and the booster tank allows the water to be collected.

 “It’s a brief storage area but then a booster pump boosts the pressure up to your working pressure at that area of town of 90 PSI,” he said.

The constructed building will be masonry on the inside with cement-based board siding along with a gable roof added to both building portions.

Ruona said, “Talk to me about the difference between GAC and this one more time, please.”

Strand began, “So the anion exchange resin is a proprietary resin that is basically, it’s a one-time usage and then it does have to be replaced but it lasts a lot longer than GAC does because GAC is essentially the same thing, granule activated carbon. It has a one-time usage and then it has to be replaced with, in this case it would be brand new GAC or anion exchange with brand new resin.”

“Who developed it?” Ruona questioned.

Strand said anion resin and the reverse osmosis equipment are both provided by Water Surplus.

“How widely is it used right now compared to GAC for treating PFAS?” Ruona further pressed.

Strand said GAC has been more traditionally used for PFAS, but as of late more plants have turned to the anion exchange because it’s able to absorb more of the short-chain PFAS molecules where GAC is better suited for absorbing the long-chain PFAS. He said the anion exchange has an “edge” on that.

Mayor Robert Daughtery asked, “What’s the disposal of the resin after it meets its life?”

“There is a procedure for that,” Strand stated. “So, it goes to a hazardous waste landfill and the GAC would be of similar nature. There is an alternate method for GAC where it would be regenerated but it would not go back into water treatment again. It would be used for some other industrial purpose.”

“Do they both take out the same number, I mean will they meet the new state requirements when that’s implemented?” Alderperson Maureen Otwell asked.

Ruona interjected, “There’s not even a way to effectively measure the new requirement that the EPA is trying to do. There’s three places that I know of personally that can do it so I don’t know what they are thinking, but that’s a whole other topic.”

“Largely both take out of the PFAS. The GAC requires a little bit more room, volume wise to do the same thing than the anion exchange resin,” Strand stated.

“So, are we going to have training from our public works people to operate the reverse osmosis and all that?” asked Daughtery.

Strand told him, “In the contracts when we get to the point of startup, there is training on all the pieces of equipment which includes the reverse osmosis, the anion exchange, the different chemical feed systems that provide the anti-scalant chemical for the RO system, and then as well as any pumps and valves and piping within the building. So, we’ve already talked about how that process would work and that with the suggestion that the city would want to videotape those training sessions so that as you have new staff come on board at different times you’d have that digital video that you can show the staff then.”

“When did this change occur when we decided to go from GAC to this?” asked Ruona.

“It’s been the last few months,” Strand answered looking to Wolf who said, “Yeah, I think once we saw that the process for treating wasn’t any difference and we were going to be saving. The startup cost is about $75,000 in savings and then the annual operations cost is about $24,000 in savings so once we saw those numbers and the fact that we weren’t going to have any difference in treatment, that’s when the thought was to move forward and talk with the DNR and bring that proposed change forward.”

“And how long has this been used? This new method?” Ruona asked.

Strand replied, “Anion exchange. It’s been used for a few decades.”

“For this specific type of treatment?” Ruona pressed.

“No, no, because PFAS is brand new, so it’s been used for other contaminants in drinking water similar to GAC. GAC’s been around much longer than this anion exchange. Both have been well suited for PFAS,” Strand explained.

Ruona said the majority of studies have been around GAC.

“Yes and no,” Strand clarified. “There’s been more pilot testing data now coming out with anion exchange also.”

“I’m a little apprehensive because I haven’t had a chance to look into this quite yet but if that’s our only option because it’s lower cost, I just don’t know much about it.” Ruona remarked.

“Do you feel the need to do your own research on it?” Otwell asked her.

“If there’s no other option from a cost perspective and this is it. I just have not looked into it a whole lot and I know what other places are doing and it’s mainly GAC so this is new what I’m hearing, so that’s all I’m saying,” Ruona answered.

The motion unanimously passed.