Data analysis shows Paraparaumu wastewater treatment plant working well

Kāpiti Coast District Council says the treated wastewater leaving the Paraparaumu Wastewater Treatment Plant is of high quality and there are plans in place to further improve the quality of the Mazengarb Stream it discharges to. 

Water and Wastewater Services Manager Ramesh Pillai says recent data analysis and reporting on the plant’s performance shows the treated effluent is discharged is at the upper end of water quality measures.

“What the data shows is that the water that leaves the treatment plant into the Mazengarb Stream is comparable with safe swimming water standards,” Mr Pillai says. 

“This is a great result for us and a testament to a lot of work done over the years to continually improve the performance of the plant. 

“Managing wastewater is one of our most important roles and Council is committed to ensuring we do the best possible job.” 

Work to improve the plant includes installing a new aeration system to maintain dissolved oxygen, lining and expanding the storage basin to cease discharges to land and provide more storage capacity for community growth and extreme weather events, commissioning a new pH correction system ensures treated effluent leaving the plant has the right pH level, and investing in treatment capability to improve discharge quality through reduced nutrient and bacteria concentrations. 

Mr Pillai says while the treated wastewater quality is good, the Mazengarb Stream has low quality. Improving it requires a catchment management approach. 

“It is an urban waterway so things like run off from the expressway and surface washdowns from other sources impact its quality. 

“As a tributary to the Waikanae River we understand its quality needs to improve and we have plans in place to do this.” 

An extensive riparian planting programme designed to enhance the habitat and water quality of the Mazengarb Stream, while ensuring its important flood protection role remains in place, is scheduled to kick off in May and June 2025. Council is currently working with mana whenua (Te Atiawa) on this.  

The first stage will involve planting between Mazengarb Reserve and Paraparaumu College.   

“We’re working with iwi to supply, plant and maintain the right species of plant at identified locations along Mazengarb stream and look forward to seeing work commence in the next planting season.” 

Read the wastewater treatment plant report.