Wanganui Mayor Annette Main said the city's wastewater treatment plant had been badly designed and even under ideal conditions it would never cope with the city's wastewater.
And she said a decision about the future of the plant was several months away.
Ms Main was speaking after a month of a stench from the malfunctioning wastewater treatment plant wafting across the city. The malfunction - and the smell - was caused by an excess amount of protein waste being dumped into the plant by one of Wanganui's six wet industries. The company responsible has never been identified.
Two more dumps - one of sulphides and one of fat - have since entered the plant.
Ms Main told the Wanganui Chronicle as the problem progressed it had become obvious the plant would not cope with the sort of waste going into it.