Cheri Cousens found out early that wastewater treatment was interesting. Her Girl Scout troop visited the South Essex Sewerage District in Salem, Massachusetts, when she was 8. “To get the Water Badge, we had to tour a water or wastewater facility or something like that, and that’s where we went,” Cousens says. “I thought it was fascinating.” Now she is the executive director of the Greater Lawrence Sanitary District in North Andover, Massachusetts, and winner of the New England Water Environment Association’s 2021 William D. Hatfield Award. 

STEADY PROGRESS

The line from that Girl Scout trip to her present position isn’t perfectly straight, but she never ventured too far off course. In college at Wentworth Institute of Technology, she started as a biology major but switched to environmental engineering.

“My studies and thought processes veered here and there over the years, but I ended up wanting to do something in the water or wastewater field,” she says. “I’ve always loved math and science. I was going the route of biology or possibly the medical field, and I enjoyed it but it didn’t feel right.

“Then when I switched to environmental engineering and really got into water, wastewater, air pollution control and site remediation and those types of topics, especially the water-based topics. I really enjoyed it.”

One of her college summer internships was at the Charles River Pollution Control District in Medway, Massachusetts. After graduation, she landed a job there after a short stint working for the consulting firm CDM Smith. She worked for 11 years with the Charles River district as an engineer and industrial pretreatment coordinator, and in 2010 she became the executive director.

Charles River had a staff of 10, and she was responsible for all aspects of wastewater treatment for four towns. In 2014 she assumed her current role, responsible for a much larger facility with a staff of 40. The district serves the communities of Lawrence, Methuen, Dracut, Andover and North Andover in Massachusetts as well as Salem, New Hampshire.

UP TO THE CHALLENGE

Although she has all the degrees and certifications appropriate to her position, Cousens is a firm believer in gaining hands-on experience. Treatment plants, even those designed similarly, have their own personalities.

“If you transplanted me to another plant, it would take me a good year or two to really get a good feel for it,” she says. “There are so many nuances to a treatment plant that make it different from a sister plant.”

Clean-water plants that are well maintained and professionally operated can still have unexpected difficulties. “Whenever you’re operating a mechanical system of any sort, things don’t always work right,” she says.

“We’re trying to meet the expectations of the community and make sure the equipment is properly maintained and replaced ahead of a failure. But with all of that work, it’s still not 100%. Outside things can happen that could cause a breakdown. It’s a team effort to get things back online properly in a fairly quick manner.”

The plant she oversees is automated to a large extent, but it still requires the hands-on experience of operators: “We have a SCADA system (GE Intellution Software, Allen-Bradley PLCs by Rockwell Automation) that provides data from all the different processes, but certainly this facility still requires the human element. That means walking the plant, listening, making sure everything is running properly.

“Each piece of machinery has a normal sound, and you can tell something might be wrong by the sound. You need to walk through the plant and listen and look. The SCADA system is phenomenal, but I think anyone in this industry would agree you cannot rely on it totally.”

SOLVING PROBLEMS

Soon after starting at Greater Lawrence, she encountered one of those difficult situations: Sometimes one or more of the digesters would overflow without warning. The overflows had to be collected with vacuum trucks and returned to the front of the treatment process.

“It was messy, and it was labor-intensive, and I felt like it was an urgent situation that needed to be corrected,” Cousens says. She worked with a team including Richard Weare, Steve Harwood and Glen Wilson to adjust variables, one at a time.

They changed the temperature in the digesters and changed the way they were fed and how they were mixed. For added insurance, they tested different defoaming agents. “We completely turned the whole situation around, and we haven’t had an overflow event since mid-2014,” Cousens says.

The combination that worked was a slight rise in temperature, continuous mixing 24 hours a day, and measurement of the inputs, not just by volume but also by loading — pounds of volatile solids going into the digesters. The team also worked with a chemist to custom-mix a defoaming agent that worked if something still went wrong.

“We decided on a defoamant that we could manually add if the height was coming up a little bit,” Cousens says. “Over time we would do a little bench testing and fine-tuning. We had excellent success with it. I’m really proud that the team was able to find a solution, and do it in-house. It wasn’t with consultants; we actually figured it out.”

CONTINUOUS IMPROVEMENTS

In November 2019, the district brought a combined heat and power system online for the first time, powered by two Caterpillar 3520C generators (total capacity 3.2 MW) fueled with biogas. Cousens remembers that as a very good day: “We were making our own power and heading on the path toward self-sufficiency.” 

Now the district is more than self-sufficient with electrical power. A fourth digester was added, along with the capacity for adding high-strength food waste. The resulting increase in biogas production enables the treatment plant to produce more electricity than it uses.

The surplus is net-metered to the grid and credited to the district’s pump station, or to the plant to pay for utility power when a generator is down for maintenance. “It’s nice to have a cushion, so if we have to do maintenance on one or both engines, and they are offline for any period of time, we can use the credits to take care of the bill.”

The CHP system shuts down automatically if the electrical grid goes down, but it can be restarted with natural gas and operated off-grid to keep the plant running even during an electrical outage.

The treatment plant has a design flow of 52 mgd; average 30 mgd. After an aerated grit removal tank, the influent goes through screening, two 3 million-gallon primary clarifiers, biological treatment with fine-bubble membrane aerators (Sanitaire - a Xlyem brand), four 2.6 million-gallon final clarifiers, disinfection with chlorine, and dechlorination with sodium bisulfite. The effluent is discharged to the Merrimack River.

Digested solids remaining are dewatered in a centrifuge (Westfalia) and a rotary drum dryer (Baker-Rullman). The resulting Class A EQ biosolids can be used as fertilizer.

Over time, every facet of the facility has seen improvements, many accomplished before her tenure. Improvements to the plant on her watch include a major renovation of the pumping station along a 9-foot interceptor pipe to more efficiently bring the influent to the plant.

“We have continuously improved our design flow, meaning the maximum flow we can take into the facility,” she says. “It was less than 100 mgd, and now we’re at 165 mgd. We’ve added tankage and made process adjustments so we can take more flow in, and we’ve improved our pumping capacity.”

OPPORTUNITIES FOR ALL

When Cousens started her environmental engineering studies, she was one of only a few women in her class. “It was still a newer thought for women to be in the field, but I saw a lot of opportunity,” she says. “I worked hard. I pursued my master’s degree, my operator’s license, and my professional engineering license. I knew there were things I needed to obtain to be successful in this industry, and I just kept reaching out and working on those.”

She started working on her master’s immediately after graduating from college, taking classes at night while working for CDM Smith and then Charles River. “It was a lot of schooling and a lot of exams,” she says. “I got all that out of the way before I started my family,” which now includes two sons, 11 and 14.

“The opportunities are very good for women in this industry,” she says. “It’s an excellent field, especially as you move into more of an administrative role. It requires many facets, including communication, technical ability and collaboration with cities, towns and regulatory agencies. For someone interested in water or wastewater, it’s an excellent field, male or female.”

RECRUITING CHALLENGES

Nevertheless, bringing new people into the field isn’t easy. “I would say one of the biggest challenges is making sure we have enough staff and trained staff. That’s been a problem across many industries, but it has hit the wastewater industry as well.”

To bolster recruiting, the district recently reached out to a vocational school about setting up a co-op program for maintenance, operations and laboratory jobs. “We definitely need to make more of an effort to expose high schoolers to this career path,” says Cousens.

The district also gives tours to groups of elementary, high school and college students. As her own career demonstrates, sometimes those tours can make a significant impact.

Cousens was deeply humbled by the Hatfield Award: “I felt really honored that my peers nominated me. It validates that hard work and commitment to the industry, and to this work, is recognized.”