On average, the meat plant was marginally above its daily limit of BODs of 10,100kg.
But for six of the 10 days it was well in excess, ranging between 10,432kg and 20,588kg.
Its oil and grease limit is 1512kg daily but on average it was dumping 2781kg, and was over the limit on eight of the 10 days.
Imlay can discharge a maximum of 5200kg of suspended solids into the city's treatment plant daily, but on average it was releasing 6076kg a day, ranging from 1325kg up to 15,777kg.
The council operations and reporting committee this week recommended constant sampling at Imlay and using the existing bylaw to force the company to rectify the situation.
What action council takes will be decided at its full meeting on April 28.
Senior wastewater engineer Arno Benadie told the committee that waste loads from Imlay had been heavy but the company could not explain why.
"Processing more could be a reason but they have told us production has not gone up," Mr Benadie said.
Council deputy chief executive Julian Harkness said the plant manager Troy Lambly told staff Imlay took its own measurements and had recorded lower results.
"Our measures differ but they've disagreed with our measurements in the past," Mr Harkness said.
"We use a monitoring system that's covered off in our trade waste bylaw and is similar to systems used by other councils."
All the wet industries are involved in discussions with council about the new bylaw.
It will give the council more certainty of loads coming from those plants and will include a pricing regime so if discharges are higher, the industry will pay more.
Councillor Charlie Anderson said he was concerned council was looking to take a stiff line with AFFCO.
"Surely we should be accommodating them somehow," he said.
But councillor Hamish McDouall said enforcing the discharge limits "was the only way to get them to pre-treat".
The bylaw says council can give an industry 20 days to clean up its performance or connection to the city's wastewater scheme will be shut off, essentially stopping production.
Mr Harkness said taking more untreated waste from wet industries into the upgraded treatment plant "would cost the city millions of dollars more".
"If we don't work together we'll again be back to being a smelly city. The wet industries may not agree on everything we're trying to do but they're working with us which is the main thing," he said.
Councillor Rob Vinsen said AFFCO accepted it had to look after its own waste.
"They're paying $2 million a year for discharges now. Up front pre-treatment might cost but you can be sure they'll be looking very closely at the overall benefits of such a plant," he said.
The Chronicle asked AFFCO for comment but it had not responded by press time.
