Wanganui District Council will meet wet industries in the new year to tighten its monitoring procedures to ensure the calamity affecting the city's wastewater treatment does not recur.
An unexpected flash of trade waste - high in animal protein and 10 times the normal amount - was pumped into the system the weekend before last, clogging the treatment ponds and creating a foul stench that has been reported in most parts of the city and beyond.
It has prompted a formal warning from Horizons Regional Council as the district council scrambles to get the treatment plant back on track after days of complaints about the stench drifting from the ponds.
An extra 112 tonnes of trade waste was unexpectedly dumped into the treatment system over two days and it simply could not cope.
"We are normally dealing with about eight tonnes of wet industry waste a day so this was something abnormal," Mark Hughes, WDC infrastructure manager, said.
"The result was the protein in the water absorbed all the oxygen in the ponds and pure hydrogen sulphide was the end result," he said.
"The stench created by that extra loading of waste at the ponds was appalling. It was enough to make you gag," As well as increasing chemical doses into the ponds to tackle the waste and odour, a local waste recovery company was removing fat and faecal sludge every day and so far about 50 truck-loads have been removed. That waste has been taken to the Beach Rd pumping station where the fats and solids have been removed, dried out and buried at the Bonny Glen landfill.