Tertiary Wastewater Treatment Plant at Waihi

Project Date





Wastewater Treatment 

IAF / DAF Solid Separators

Hauraki District Council, Waihi


Treated effluent from traditional oxidation pond had excessive amounts of phosphorus and suspended solids, exceeding legal limits. This was having an adverse effect on the Ohinemuri River through the Karangahake Gorge, a popular recreational area.


A tertiary treatment plant with chemical precipitation of the phosphorus, and an induced air flotation plant to separate out the solids was installed.


The treated water is now clear and has a total phosphorus of less than 1 g/m3 (limit 1.4 g/m3) and suspended solids of less than 15 g/m3 (limit 35 g/m3).  The treated effluent discharges now meet legal limits and the Ohinemuri River into which the treated water flows, is now cleaner and safer for recreational pursuits.

Download the project brochure