Rights: The University of Waikato Published 29 July 2008 Download

Sanjay Kumarasingham (Watercare Services Ltd) discusses what tertiary treatment of wastewater involves at the Mangere Wastewater Treatment Plant in Auckland.

UV Comparisons/Emperor Aquatics


Following the secondary treatment, you get into the tertiary treatment. Tertiary treatment is the final phase before it gets into the harbour or wherever the water is going to. So this is the stage at which pretty much any microorganisms that are still existing need to be removed. Tertiary treatment at the treatment plant here is ultraviolet disinfection. It has got an anthracite media filtration process before UV disinfection. So we remove any of the physical solids, which come from the secondary process. And we filter the effluent and that goes into the ultraviolet disinfection plant. Wastewater, which is the used water, contains billions of bugs. The ultraviolet disinfection is a very interesting process – that is where there is a certain wavelength in which bugs, viruses and pathogens basically become zapped. So by the process of primary, secondary and tertiary treatment, most of the bugs are pretty much captured.