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Mooresville officials detail repeated wastewater upsets, say IDEM working with town
Summary
Town and consultants reported three recent plant upsets from abnormal discharges that killed treatment microbes; town reseeded the plant with mixed liquor, plans a pretreatment coordinator and ordinance updates, and warned of potential enforcement costs if violations are proven.
Mooresville Town officials told the council they have traced three recent treatment upsets at the town’s wastewater plant to unusually high pollutant loads and acidity that damaged the plant’s biological treatment system.
Town wastewater consultant and plant staff said the plant saw a series of events — beginning Sept. 5, continuing Oct. 17 and most recently Nov. 12 — during which incoming wastewater showed extremely high biochemical oxygen demand (BOD) and low pH readings. “On Sept. 5, we believe the plant seen a lot of high ammonia in the raw, and it was upwards of 30 parts per million,” the plant representative told the council, saying those spikes “disrupted the bugs, disrupted treatment, killed all the bugs.”
Council members were told the response included bringing mixed liquor from a neighboring treatment plant to reseed biological life at the facility. The transcript records roughly three loads (about 18,000 gallons each) were brought in multiple times, and participants referenced a total on the order of tens of thousands of gallons to restore the process. Officials said the most recent weeklong incident included BOD readings well above design levels and that lab BOD tests require several days to complete.
Town and consultant speakers said they have worked closely with the Indiana Department of Environmental Management (IDEM) and expect additional monitoring and procedural changes. The council was told the town is establishing a pretreatment coordinator position and updating sewer-use and pretreatment ordinance language to help identify sources and, where permitted, require industries to control discharges before they reach the town system. “We’re gonna have a pretreatment coordinator very soon,” a plant official said, and the council signaled support for updating local ordinance language with guidance from state regulators.
Legal counsel explained that the town’s existing ordinance allows for enforcement if the source can be proved and that penalties and recoverable costs could be applied to a violator. “If it reaches a certain level, you gotta throw that one out and use different ones,” counsel said about testing requirements; later she noted penalties could include fines and expenses to get the plant back online.
Council members asked for continuing updates and for staff to work with IDEM on a checklist and procedural steps to narrow possible sources, including manhole sampling and reviewing permitted industry reports. Officials said the process of narrowing a source is painstaking but necessary to assign liability and recover costs.
