"When they are poisoned they stop digesting waste properly. That makes it harder for us to clean the wastewater."
In recent years during the Christmas/New Year period the treatment plant has experienced problems where the beneficial bacteria which are vital to the treatment process have been killed off by unauthorised discharges of toxic materials such as paint solvent, detergent and disinfectant into the system.
"When this type of problem occurs the treatment plant has difficulty in treating the incoming wastewater. While all wastewater is still treated by UV to destroy harmful pathogens, when treatment is reduced this ultimately has an effect on our harbour as more nutrients are released into the water. In addition, some substances are unable to be removed during the treatment process and eventually end up in our waterways and harbour," Keith said.
"Other impacts include increases in odours from the plant and resource consent compliance issues, along with costs for remediation."
He is asking businesses or households having a clean-up before or during the holiday season to remember not to dispose of toxic chemicals down the drain.
Hazardous chemicals can be taken to Resort on Kioreroa Rd or, for large quantities, people can contact the council on 09 4304200 and speak to the pollution prevention officer to arrange collection.
"These must be disposed of in the approved manner. We'd like to remind the community that under the Wastewater Bylaw 2014 the discharge of any prohibited material is an offence and is liable to prosecution under the Local Government Act 2002."