Public works director seeks remedy for high chlorine levels in waste water plant’s effluent

Posted 6/24/20

High levels of chlorine in effluent from Owensville’s wastewater treatment plant, first detected in April through required monthly testing, appears to have been caused by the local efforts to …

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Public works director seeks remedy for high chlorine levels in waste water plant’s effluent

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High levels of chlorine in effluent from Owensville’s wastewater treatment plant, first detected in April through required monthly testing, appears to have been caused by the local efforts to disinfect amid the COVID-19 pandemic.

“We sent a letter last month to DNR with our monthly report, seeking permission to start the dechlorination process at the headworks,” said Jeff Kuhne, the city’s public works director, this past week.

Kuhne said reports received back from the independent testing lab the city uses for effluent in February were good. By mid-March, when the lockdown due to the new novel coronavirus went into place, Kuhne said the tests started showed elevated CBOD levels (carbonaceous biochemical oxygen demand).

These higher CBOD readings specifically started showing elevated levels of chlorine in processed waste water leaving the plant as effluent. 

“It steadily kept going up from that point,” he said.

On April 14, the city was notified a test result showed a “chlorine qualifier” when effluent water going out of the system was tested specifically for chlorine.

Kuhne sent the Department of Natural Resources a letter dated May 13 notifying the regulatory agency of the elevated chlorine levels, citing a suspected cause of “disinfection activities that are ongoing in our community aimed at combating the spread of COVID-19.”

He said he spoke with managers of the community’s two residential nursing homes and a retirement facility, along with shopping centers in the community, and was told all “have been performing daily deep cleaning with chlorine bleach to mitigate the spread of COVID-19,” Kuhne’s letter to DNR noted. “We believe that these disinfectants are making their way into the waste stream and have upset the biomass present in the lagoon system, ultimately affecting the performance of the facility.”

Kuhne, noting many of the DNR staff he is in contact with regularly are working remotely, said he’s exchanged emails with them about these concerns. He said he was told the DNR hadn’t received an influx of these reports but was told they “were surprised they hadn’t” given the circumstances.

“We haven’t changed anything else at the plant,” said Kuhne. “This is the only thing we can figure out that’s changed with all the disinfecting going on.”

The city’s plant is permitted for a CBOD level of 8.3 milligrams per liter (mg/L) on a daily average and 5.5 mg/L on a monthly average. In the letter to DNR in May, the city acknowledges a CBOD level of 45 mg/L for a daily maximum and an 18.9 mg/L for the monthly average.

That level has now dropped into the “20s,” said Kuhne on the monthly average.

“We’ve never detected it in the plant before,” he said of the problem. “Our plant won’t operate properly.”

Working with the city’s engineering firm and the testing lab to “troubleshoot these performance issues,” Kuhne’s letter to DNR noted the city has asked the testing lab to report “numerical concentration of total residual chlorine” in weekly reports. The city’s engineers are also investigating adding a “dechlorination process prior to the headwaters” at the plant. And, the letter noted, “We are currently collecting data to size dosing pumps for the addition of sodium bisulfite.”

The problem has killed off the plant’s biomass, the “good bacteria” as Kuhne called it, which breaks down human waste.

“Currently, it’s not operating at the level we need it to due to the chlorine,” he said.

An option being considered is obtaining “actuated sludge” from another city’s plant and “reseeding” the plant here. “We would take actuated sludge, with active ‘bugs’ and we introduce it into our plant to, essentially, reseed it and get it back operating well,” said Kuhne.

Kuhne updated Owensville aldermen on the issue at their June 15 meeting, saying, “It killed off our biomass. We need to reseed the plant.”

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