The Upper Lachlan Shire Council is currently working with the NSW Department of Planning, Industries and Environment (DPIE) and the NSW Environment Protection Authority (EPA) to enact the best processes at the sewage treatment plant.

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It is expected that they will either upgrade or replace the plant to meet contemporary environmental standards.

"The council did and is working with DPIE and EPA to meet licence requirements," a spokesperson for the council said.

Processes and systems at the plant were under investigation by the EPA following a discharge of contaminated effluent from the plant in 2017.

It has not been disclosed how much effluent was discharged into the wetlands and into the Crookwell River from May to October at the time.

"The system was lacking in bacteria numbers, so they could not complete denitrification which resulted in high concentrations of ammonia and nitrate," a spokesperson for the council explained. Contributing to bacteria growth in the EAT was the cold weather, lack of rain causing frosts, a spokesperson said.

A full report is expected to be provided to the council, however detailed costs to upgrade or replace the plant are not completed.

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