There are six major industries in Castlecliff which are major dischargers into the treatment plant including Affco Imlay, Land Meats, Mars Petcare, Cavalier Spinners, Open Country Dairy and Tasman Tanning.
Some of the industries have disputed council measurements of the volume of their discharges.
Mr Harkness said the bylaw would also require a two-month public consultation period.
"Depending on when the new treatment plant is completed, the bylaw will need to be finished by June 30 next year or in 2016."
The upgrade is estimated to cost $25 million, with $16 million included in the council's 2014-15 budget.
Hawkins Infrastructure, which is part of the Hawkins Group, one of New Zealand's biggest construction companies, won the contract.
Mark Hughes, council's infrastructure manager, said the next steps involved what was called a period of "early contractor involvement" (ECI), that should take six to eight weeks.
"This phase addresses any changes and opportunities around buildability, procurement, innovation and scope of the contact," he said.
That process needed to be completed before the council and contractor agreed and issued the final contract price and sorted out the necessary construction documentation. It was expected the exact contract price would be detailed after that.
"We're incorporating all the additional items approved by council into the designs and updating the prices with Hawkins Infrastructure. We expect them to be on site early next month," he said.
The council decided last year it had no option but to have a major upgrade. It also decided to sue MWH Global, the company that designed the plant, citing shortcomings in the concept and final design of the facility.
The new design by Cardno-BTO has been peer reviewed by Australian company AECOM and then looked at again by New Zealand company CH2M Beca. Both reviews suggested changes to the design to "make it more robust".
There will be additional screening of waste coming into the Airport Rd plant to reduce potential sludge build up, and the pond will be completely covered to trap any odours. The sludge will also be removed from the pond and trucked away daily. It was the sludge build up which created problems at the plant.
At an earlier council meeting, Mike McCoy of Cardno-BTO said the design did factor in potential industrial growth in the city and the plant would be able to handle that.
Mr McCoy said the design would ensure that excessive trade waste loads would be handled, again as long as they did not exceed maximum loadings for an extended period of time - of days rather than weeks.
The new bylaw will not only be aimed at the six major wet industries who discharge into the system.
Smaller businesses or industries may discharge into the wastewater treatment plant, including about 80 food businesses.