The level of bacteria in discharge pumped from the Whanganui wastewater treatment plant into South Beach is higher than the regional council allows.
Wanganui District Council has been issued a significant non-compliance notice by the Manawatu-Wanganui Regional Council for failing to meet its resource consent requirements.
A monitoring report shows the bacteria levels in the discharge have been increasing since September last year.
Mayor Annette Main says there is a build-up of sludge at the bottom of the ponds due to problems with aerators.
Ms Main says further testing has revealed there is no environmental or health risk to the public and they are working with the regional council to fix the problem.