Overview

Contech was engaged by McConnell Dowell to rehabilitate and protect the biofilter floors at the Rosedale Wastewater Treatment Facility in Auckland.

Across the programme, six biofilters were successfully rehabilitated, covering approximately 900m² of floor area, making it one of the largest biofilter floor rehabilitation projects undertaken at the facility. 

The Challenge 

Years of exposure to biogenic corrosion and aggressive wastewater conditions had deteriorated the concrete floors, leaving surfaces damaged and affecting the original drainage falls. 

The project required a solution that would restore the existing concrete, reform the floor geometry, reinstate drainage performance and provide long-term protection against future biogenic corrosion. 

The Solution 

The works included: 

• Detailed condition assessment and survey 

• Ultra-high pressure water jetting to prepare the concrete substrate back to uncorroded concrete 

• Localised concrete repairs 

• Application of Sewpercoat using a specialist trowel finish to restore drainage falls and floor geometry 

• Quality assurance inspections throughout installation 

• Independent pull-off testing to verify the bond of the Sewpercoat to the prepared concrete prior to handover 

Restoring the Falls 

Unlike conventional protective coatings, Sewpercoat is a calcium aluminate-based rehabilitation mortar and lining system. On this project, it was used to rebuild the floor geometry while also providing long-term protection against biogenic corrosion. 

Careful hand-finishing allowed the installation team to recreate the designed drainage falls across each biofilter, helping restore operational performance as well as long-term durability. 

The project demonstrated Sewpercoat’s capability as both a rehabilitation material and protective lining system for biofilter floors. 

The Result 

The completed project restored both structural performance and operational functionality. 

By combining rehabilitation with corrosion protection in a single system, Contech delivered a durable solution designed to minimise future maintenance while extending the service life of the biofilter infrastructure for many years to come. 

The project also demonstrated a new application for Sewpercoat, proving its capability as both a rehabilitation material and long-term protection system for wastewater environments affected by biogenic corrosion.