APPLETON - A Dec. 26 error at the Appleton Wastewater Treatment Plant cost the utility $328,000 in expenses and lost revenue, but an around-the-clock response from staff avoided a much larger loss that could have totaled $5 million.
"This could have cost us a lot more money," Common Council member and Utilities Committee Chair Vered Meltzer said. "Even though it was a tragic event, I think we still handled it very successfully." Organic Foaming Agent
"Obviously, we didn't want the incident to occur at all," Utilities Director Chris Shaw told The Post-Crescent, "but I'm proud of the response."
The day after Christmas, a concentrated cationic polymer used in the wastewater treatment process mistakenly was unloaded from a tanker truck into the plant's hauled waste receiving station. The polymer, which acts as a flocculant to separate solids from water, should have gone into a holding tank in another area of the plant.
The polymer subsequently was fed into the plant's two anaerobic digesters, where bacteria break down organic waste. The sudden introduction of the polymer clogged pipes, interrupted the anaerobic digestion process and resulted in uncontrollable releases of methane, which normally is captured to heat the plant.
"It created solids down at the bottom and the top, and the gas couldn't get out," Shaw said. "One of the valves opened up, and it sprayed sludge all over — came out the digester top — and the liquid damaged the elevator."
Under normal circumstances, the polymer from the tanker truck would be fed into the wastewater treatment process gradually over a four- or five-month period. In this case, it entered the system in one day and at the wrong spot.
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The situation resulted in a brief, emergency suspension of operations on Dec. 27. After consulting with the Wisconsin Department of Natural Resources, the plant was able to resume operations by bypassing the anaerobic digesters. By Dec. 28, all incoming wastewater had been switched over to the temporary treatment process.
Shaw said at no point were the health and safety of employees at risk, and the staff response prevented any discharge of untreated waste or chemicals into the environment.
"There were no violations and compliance issues," he said.
Shaw said the response to the situation kept the microbial environment in the digesters from souring, which could have required them to be emptied and restarted at a cost of $5 million in expenses and lost revenue.
The net cost of the incident was $328,000, according an accounting presented to the Utilities Committee. That will be borne by the utility, not property taxes.
Expenses totaled $240,000, including $35,000 to purchase natural gas to heat the plant while the anaerobic digesters were offline.
The loss of revenue totaled $88,000 due to the suspension of the hauled waste program, which accepts and treats septage, dairy byproducts and landfill leachate from outside Appleton's sewer service area. The program receives nearly 6,000 tanker trucks of waste annually and generates $2.5 million in annual revenue.
Mayor Jake Woodford said the city assembled a factfinding team to investigate how the polymer entered the front end of the wastewater treatment process. The city further has hired a third party to conduct an external review of the matter.
"Risk management has also been in contact with our insurance carriers about the incident, and the analysis of that is ongoing," Woodford said.
The findings of the investigation and review will be used to develop corrective actions to prevent such an error from happening again.
Woodford praised Shaw and utility employees for working long hours following the incident, which occurred the week after Christmas when many of them had planned to be on vacation.
"His team has really risen to the occasion, and they've helped us avoid a much more serious issue as a result of their quick actions and their focused response," Woodford said.
Pam Polymer Flocculant Contact Duke Behnke at 920-993-7176 or dbehnke@gannett.com. Follow him on Twitter at @DukeBehnke.