To gauge the health of their treatment plant, Mike Fox and his staff just have to check with their fish. The North East Wastewater Treatment Plant in Conover, N.C., has an aquarium in its laboratory and two ponds on the grounds outside, both fed with plant effluent and stocked with fish and other aquatic creatures. Besides giving the staff a “miner’s canary” assessment of effluent quality, these features help show the public that the plant is protecting life in local waterways.
Monitoring quality
The original plant went online in 1991, serving Conover’s population of 8,016, spread over 10.2 square miles. Situated on 35.7 acres along Lyle Creek and three tributaries draining the Appalachian foothills, the plant processes about 0.75 mgd on average.
The 55-gallon aquarium receives a continuous flow of plant effluent. It is fed by tapping an effluent sampler line. The average flow rate allows about three minutes of detention time.
Fox, supervisor of wastewater treatment, got the idea from a trade magazine as an interesting way to monitor effluent quality. “My background was in marine studies, so I was interested in fish anyway,” he says. “When I saw that flow into the lab, it seemed obvious we could tap into it for the aquarium.”
The idea was that plant staff would know immediately from the fishes’ behavior if effluent was carrying an overload of residual chlorine or was deficient in some other way. “Well before it reaches a level that would be detrimental to the receiving stream, the fish will let us know,” says Fox.
“It’s probably the most valuable operational tool we have. We can walk by it any time of day and immediately see any escaping solids, unusual color, or turbidity. We weren’t sure when we put it in how it was going to play out or how valuable it would be. But now I could hardly operate a plant without it. It would seem like flying blind.”
The aquarium fish are all native species. Chubs, pumpkinseeds and darters are more hardy, while dace are fragile. Accustomed to high-dissolved oxygen from their native swift-water environments, dace are good environmental quality indicators. The tank also holds crayfish, frogs and salamanders.
