Waste at the Coastal Resources of Maine facility in Hampden on a conveyor belt heading towards a trommel, which separates materials by size and weight.

The new waste facility in Hampden accidentally dumped about 6,500 gallons of bleach into the local sewage system late last summer, a violation of its environmental permits that was punished by the largest fine in at least four years from Bangor’s wastewater treatment department.

After the bleach left the Coastal Resources of Maine waste facility between July 31 and Aug. 1, it flowed to Bangor’s wastewater treatment plant and killed off some of the microorganisms that the facility uses to clean sewer water so that it can be safely released into the Penobscot River.

Since then, Coastal Resources of Maine has replaced a faulty valve in its cleaning systems that it said caused the bleach to be discharged into the wastewater. It has also instituted a number of other precautionary measures that are meant to prevent the accidental release of the disinfectant, according to a corrective plan it sent to the city.

“Unfortunately, there was some discharge into the water system in Bangor, but we quickly rectified that,” said Shelby Wright, the facility’s director of community services.

The large load of disinfectant did not ultimately affect the ability of the Bangor plant to clean wastewater, but it did force staff to spend many hours ensuring that its microbes were still working properly, according to Amanda Smith, Bangor’s assistant director of water quality management.

Because of the work it took to respond to the discharge, the city levied a $4,390 fine on Coastal Resources of Maine. That was one of just two fines that Smith can recall her department issuing in the past four years, and she said that it was roughly four times greater than the one that came before it.

The discharge was found to be a significant violation of Bangor’s wastewater rules because it interfered with the plant’s operations, according to a notice of violation sent to Coastal Resources of Maine on Aug. 14.

The city also found that Coastal Resources of Maine violated another rule requiring prompt notification because the company did not try to contact an on-call worker at the Bangor plant immediately after it happened. Instead, Coastal Resources left a voicemail message at the plant that was not received for 15 hours.

Built by the company Fiberight, the Coastal Resources of Maine plant began accepting household waste from 115 towns and cities across Maine last spring. The plant has just passed a series of tests that were required as part of its agreement with an organization representing those communities, the Municipal Review Committee.

But the facility is still unable to sell all the end products that it makes from that waste and that will be integral to its long-term viability and its ability to divert a substantial portion of waste from landfills. It is waiting for state regulators to allow some of those products to be sold in Maine.

It is also still ramping up the operations of an anaerobic digester that is necessary to produce commercial-grade biogas that can be pumped into a Bangor Natural Gas pipeline, according to Wright. For now, the company is using some of that gas to power its internal operations and burning the rest with a flare.