Roger Descoteaux heads an award-winning industrial pretreatment program that protects his plant’s process and keeps the Merrimack River clean


There is more to being a regulator than enforcing regulations. Collaboration was one thing that helped Merrimack (N.H.) industrial wastewater pretreatment manager Roger Descoteaux earn the 2010 Regional Industrial Pretreatment Program Excellence Award from the U.S. EPA.

Merrimack’s 5 mgd treatment plant was designed for a large volume of high-strength wastewater coming from the industrial base in this community of 28,000. Merrimack is one of 13 communities in the state required to have a pretreatment program, although others have established them voluntarily.

“Our pretreatment coordinators group meets two, three, or four times a year,” says Descoteaux. “We discuss regulations, case studies, pretreatment methods, and enforcement actions. The EPA and state Environmental Services officials attend, and we invite representatives from other wastewater plants.”

Descoteaux talked about his program and his approach to working with the industries in Merrimack in an interview with Treatment Plant Operator.

TPO: How did the pretreatment program start?

Descoteaux: It was required by the EPA in 1983. I was hired to implement and run the program, which was designed by a consultant. We had more than 10 significant users then. The plant was designed for 5 mgd, and we were getting up to 4 mgd. We had to get a lot of companies into compliance, and we worked together and developed a good rapport.

TPO: How many permits do you issue now?

Descoteaux: We issue more than 60 permits and have four significant users: an Anheuser-Busch brewery (home of the Budweiser Clydesdales), Nashua Corporation (printing and coated products), Kollsman (avionics, electro-optics and medical instruments), and Saint-Gobain Performance Plastics.

TPO: What treatment process does the plant use?

Descoteaux: It’s a secondary activated sludge plant designed in 1970 to handle the high-strength wastewater from the brewery. It had a trickling filter that we took offline in 2008 when the brewery built its own wastewater treatment system with an anaerobic digester and bio-energy recovery. We’ve made additional modifications with anaerobic selectors to reduce nutrients in our effluent, mainly phosphorous and total nitrogen and to increase capacity with the removal of the trickling filter.

The BOD from Anheuser-Busch is much lower now, but it’s still around 600 mg/l, well above the 250 mg/l limit for a domestic wastewater plant. Total suspended solids is almost 1,300 mg/l, even with the anaerobic digester. That’s what drives us.

Nashua Corporation is a Categorical Industrial User for organics, chemicals, plastics and synthetic fibers. They have some heavy metal limits and very restrictive VOC and SVOC limits in the parts per billion range. They’ve done a good job with their treatment facility.

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TPO: How do you work with customers?

Descoteaux: I have a key contact at each one. We do a minimum of two inspections per year and monitor effluent twice a year. I inspect the significant industrial users four times a year just to make sure I stay on top of things.

I check for anything unusual and make sure they’re managing their waste properly, that they don’t have any spills and have a spill procedure, and that they make sure floor drains are sealed or have secondary containment. I make suggestions and recommendations and follow up between inspections.

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TPO: It sounds like a lot of paperwork.

Descoteaux: One of the reasons for the award was the annual pretreatment report. I also use that information as a reference tool. I track all my analytical data. We have charts for influent, effluent, all the compost data, organics, and everything else.

TPO: How do you keep up with process changes that may alter an industry’s effluent?

Descoteaux: They’re required to notify us of any change, and we evaluate it. If they’re looking at changing some chemistry, we require Material Safety Data Sheets (MSDS) to make sure it’s something we can handle. We may make some recommendations to use something different.

TPO: Do you use contributory flow limits or uniform concentration limits?

Descoteaux: Every pretreatment program has to develop local limits based on the type of industries they have. We use contributory flow limits so only those industries that have a certain pollutant in their discharge have a limit for that pollutant. Most pretreatment programs have uniform concentration limits that cover everyone.

TPO: How has the economy affected your customer base?

Descoteaux: : Our waste strength is significantly reduced due to some industries closing, but it’s still much higher than for a regular domestic wastewater treatment plant. We have plenty of capacity for future growth.

We were designed for 5 mgd but we’re down to 1.8 mgd as a daily average. A lot of places don’t have that excess capacity. We’ve lost some big users over the years, and Anheuser-Busch has done some significant water conservation. They used to discharge between 1.8 and 2 mgd and are down to a little over 600,000 gpd.

TPO: Are there unique challenges from having such a high percentage of your loading coming from a single source?

Descoteaux: They have the ability to overwhelm us. We’ve developed procedures to divert some of the flow to spill-diversion tanks if they have to bypass their anaerobic digester. We have a good relationship with them and all our customers. If someone has a problem, they call me right away.

TPO: What other steps do you take to protect the environment?

Descoteaux: We recommend and encourage drug take-back programs to keep pharmaceuticals out of the waste stream and give people alternatives to flushing them. We make sure automotive repair facilities have oil separators and manage their oils properly. We don’t issue permits to dentists, but I do inspections every year to work with them.

We accept 5 million gallons of septage every year from 10 surrounding communities. To protect our biological system, the septage can only be domestic wastewater. Our SCADA system monitors every load for pH. If it’s high or low, we will follow up to find out where the material came from. It hasn’t been a problem recently, but we have had problems in the past and have issued some fines against haulers.

TPO: What issues are looming on the horizon?

Descoteaux: We’ll have some new nutrient limits down the road, so we’re preparing to keep nutrients like phosphorous as low as we possibly can. We’re planning a $4.2 million upgrade to help us meet those limits and to replace some equipment that is more than 40 years old.

TPO: Are there any other challenges for your pretreatment program?

Descoteaux: Our plant has a major compost marketing and giveaway program. We monitor the biosolids for metals, VOCs, SVOCs, pesticides, dioxins, nutrients and other contaminants.

We also have a state limit for compost of 10 mg/l for molybdenum. On a couple of occasions, those numbers were getting a little over 10. We found some companies using molybdenum for corrosion control in their cooling towers and asked them to look at some other chemistry. A few made changes, and the concentrations went down.

TPO: How do you view your role as a regulator?

Descoteaux: You’re not trying to hammer them; you’re trying to help them. People don’t want to see you coming through the door if you’re just going to be a bearer of bad news. When there is a violation, we try to work together. That makes it in their best interest to not hold back and not be afraid to say, “We have a problem.” The key is that we all want to protect the Merrimack River and the rest of the environment.


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