By Kalle Matso, PREP Coastal Science Program Manager
These are the stories that make people interested in collaboration. A food company in Greenville, NH needs to find a new place to dispose of acetic acid, left over from its mustard, vinegar and fruit juice production. A city that discharges cleaned up wastewater into the Cocheco River needs a carbon source to feed the microbes upon which its operations depend. New Hampshire Department of Environmental Services, the state agency regulating the environment, plays matchmaker and creates a win for the food company, the city and the environment.
The company in question is Pilgrim Foods and the city is Rochester, NH. This is the latest in a series of innovative upgrades the city has implemented in order to improve the quality of water it releases into the Cocheco River, which flows into the Great Bay Estuary, a prized resource for Seacoast, NH communities. This latest innovation came to fruition in the Fall of 2013 and helped Rochester reach levels of 6 mg/Liter for total nitrogen. In estuaries, nitrogen is often the most critical nutrient for growth and too much of it can lead to too much algae and ecosystem degradation.
Before this improvement, the Rochester plant effluent had around 40 mg/Liter total nitrogen. That number is in accordance with its existing permit from the Environmental Protection Agency (EPA), which is currently considering a new permit for Rochester.
You’ve Come A Long Way, Rochester
It’s hard to believe, but in 1985, when you flushed your toilet in Rochester, the contents went right into the Cocheco River without receiving any treatment whatsoever. Rochester did have a treatment system in the late 1960s but it failed and sat dormant and inactive until 1986. The problem was that the large lagoons didn’t have enough oxygen for the microbes to break down the waste. In 1986, Rochester added additional lagoons and added mechanical mixers—what’s known as an “aerated lagoon” system—so that the plant began to provide “secondary” treatment of the waste.
The plant operated under those conditions until 2000. During that time, it was considered the third best secondary plant in the entire state. In 2000, EPA required Rochester to remove ammonia-based nitrogen from the wastewater; EPA also set more stringent biological oxygen demand—the amount of oxygen required by microbes to breakdown a certain amount of waste in a certain amount of time—and total suspended solids limits. To achieve this, Rochester upgraded again to an “activated sludge extended air” system that also has filtration and UV disinfection as well as post-aeration.
In 2013, EPA became more concerned about levels of total nitrogen in the water and asked Rochester to agree to an 8-point action plan to reduce nitrogen. If Rochester completed these 8 actions, the agency would defer the requirement that Rochester upgrade its plant to the “limit of technology,” which is considered 3 mg/Liter of total nitrogen. This agreement officially ended last month (August, 2016) and EPA and Rochester are discussing next steps for the plant.
One of the 8 EPA requests in the 8-point Plan was for Rochester to use its best efforts to keep the effluent below 8 mg/Liter of nitrogen. The tertiary plant was getting close to that number but the microbes needed a better food source to more effectively process the waste and get below the 8 mg/Liter threshold.
Rochester considered doing what many other plants have done: buying methanol from private sources to provide the carbon that the microbes craved. But methanol is expensive (approximately $400K per year) and hazardous.
Enter NH Dept. of Environmental Services (NHDES), Pilgrim Foods and the “pickle juice” solution. Pilgrim Foods now drives its waste by-product (acetic acid) from Greenville to Rochester five days a week, either 1 or 2 loads per day. Win #1; Greenville has found a way to dispose of its waste without overwhelming the small treatment plant in that town; Win #2; Rochester gains a carbon source for its microbes at the cost of zero dollars; Win #3; the effluent being discharged into the Cocheco River dropped to approximately 6 mg/Liter nitrogen.
That number has recently crept back up to 8 or 9 as the plant’s diffusers need to be replaced, a task that is high on Chief Operator David Green’s “to do” list. In 2014, for these innovations and others, Green, who is born and raised in Rochester and has worked at the treatment plant for 28 years, was awarded EPA’s Region 1 “Wastewater Treatment Plant Operator of the Year” award.
David Green also happens to be PREP’s latest “Water Champion.” Read more about David in our CLEAN WATER CHAMPION feature.