No one at the Berkeley Heights sewer department was familiar with paracetic acid — that is until they heard it could save them $1 million.

Facing permit regulations that required a new disinfection process, Berkeley Heights managers thought they were relegated to an expensive UV disinfection system, until sewer department superintendent Tom McAndrew started looking into paracetic acid (PAA) disinfection.

Though PAA has drawbacks in some systems, it was a perfect fit for Berkeley Heights, saving the municipality money on numerous fronts while providing efficient disinfection that actually eliminated some permit requirements.

“Everything that I’ve learned about the PAA, they tell you in the first 3 to 5 minutes, you will get 80 percent of your kill, and inside of 20 minutes, you’re doing 97, 98 percent, and that’s been pretty much accurate for us,” says McAndrews says.
 

The catalyst

Back in 2015, Berkeley Heights was running a chlorine disinfection process, using sodium hypochlorite and sodium bisulfide in dual-stage chlorination/dechlorination setup. It worked fine for them, but when Department of Environmental Protection auditors stopped by the plant at that time, they informed McAndrews that their next permit renewal, in 2017, would have heightened chlorine-produced oxidant (CPO) regulations.

CPOs would have to be cut by 25 percent — something they could never achieve while retaining their chlorine disinfection.

“We were tasked with finding an alternative, because there was no way we were going to meet the stringent requirements on the hypo and the bisulfide. So we started looking,” McAndrews says.

A chance encounter at the New Jersey Water Environment Association wastewater conference with an old colleague led him down the path to PAA disinfection.

“We did some investigative work. Engineers and myself kind of went round and round, figuring out what we wanted to do, and we approached the state with what we wanted to try,” McAndrews says.

Working with a third-party chemical supplier expedited the process for Berkeley Heights — the vendor offered complimentary testing with their product.

“They offered to do some free, no-cost bench testing just to see if this was the right type of product for us. So we did that, it came back very, very positive. That was just a grab sample. We sent it off to them and they supplied us with a report. The two engineers and I looked at it, and we went to the state and said OK, this is what we’d like to do.”

The team put together a quality assurance project plan, or QAPP, and with support from local leaders and political powers, it went through seamlessly.

Trial by fire

“Obviously this was unproven technology in New Jersey. It has been done elsewhere, and it has been done institutionally,” McAndrews says. “This product is FDA approved, but it was unproven as far as the wastewater field, and quite frankly I looked at it and said, if it can work for the FDA, why can’t it work for NJDEP?”

The testing period was an 11-week trial, including some data collection preceding the switch. After a few tweaks to the submitted plan, they were ready to go.

Two injection points were proposed, and they started by simply switching in the PAA at the same point where chlorine dosing had been.

Then, the whole concept hit a wall.

“Within 72 hours of starting it up, we blinded the sand filters, we used up the PAA residual, and we couldn’t get a kill.” McAndrews says. “We immediately went back to the hypochlorite and shut down the PAA, and tried to figure out what was going on.”

A second attempt after cleaning the sand filters yielded identical results. Engineers thought the problem might be related to lime additives in the denitrification basin — the sodium bicarbonate was binding to the sand with PAA in the mix. Unfortunately, if that was the case, it would rule out their backup injection point too.

“The dosing location was at the influent of the sand filters, which was where the dosing location for the hypochlorite was. So that’s why we chose that particular spot, but after we had the trouble with the sand, and the binding and using up of the residual, we moved it to the effluent, to the tail end of the sand filters,” McAndrews says.

Since they were on the clock, both predetermined dosing areas were scrapped, and the team moved injection to the effluent side.

“You don’t need as much of a contact time with the PAA as you do with the hypochlorite. They say that within about 20 minutes is all you need,” McAndrews says.

The gamble paid off.

“The DEP came back and said ‘look, you’re having great results there, don’t even bother trying anything else, leave it there.’” McAndrews says. “Once our 11 weeks was up, we had supplied all the data, and everything that they wanted.

“That’s where it has been ever since. The whole process was relatively painless, to tell you the truth.”

Savings abound

The PAA trial, which was meant to be a temporary small-scale version, cost the utility about $20,000 — peanuts compared to the estimated $1.1 million dollars for engineering, design and implementation of a UV system for a plant their size. Not to mention UV systems cost around $50,000 a year in O&M alone.

In yearly savings over the previous chlorine process, they are seeing annual budget decrease of 12 to 14 percent.

“What we were paying in both hypochlorite and bisulfide, because remember, this one product is taking the place of those two, so now instead of two delivery systems, you’re only maintaining one delivery system; you’re not buying two chemicals, you’re only buying one.”

The whole process, from inception to approval, took fewer than 15 months. Though paracetic acid turned out to be successful for Berkeley Heights, McAndrews cautions that it might not be the perfect solution for everyone.

“There were no adverse effects that we experienced. Now, if you do some reading on PAA, it’s not a magic bullet,” McAndrews says. “It will not work everywhere.”

He points out that for treatment facilities with industrial waste influent, such as landfill leachate or heavy metals, PAA might not work. Fortunately, the largely residential Berkeley Heights found it to be their perfect solution. “We’ve now received our new permit, which recognizes paracetic acid as our sole-source independent disinfection,” McAndrews says. “We no longer have any chlorine-produced oxidant requirements, and we’re good to go.”