• Client: Downer Group
• Year: 2018

In 2017, Service Engineers (SE) were contracted by Downer Infrastructure (previously Hawkins Infrastructure (NZ) Ltd) to supply and install the principal parts of the mechanical plant for the new Wanganui Waste Water Treatment plant. On the water side, this includes various pumps stations, penstocks and stop-boards as well as all manual and control valves. SE are responsible for the services piping and pipe materials which comprise PE, PVC, and stainless steel. Supply and installation of major mechanical items include two mechanical clarifier mechanisms and an aeration system including the submerged oxygen distribution network and diffusers.

The rest of works included the complete sludge processing plant which SE designed, supplied and installed. This included a mixing tank, two silos for both dewatered and dried sludge and a number of screw conveyors to transport the sludge through the process and final delivery to trucks, the polymer thickening and sludge dewatering system, a fibreglass foul air extract system comprising fibreglass tank covers, fans and ductwork including an underground air distribution system to the bio-filters. Also included in the sludge process was a bolted steel storage tank. All associated pipe supports, access-ways and platforms were designed and supplied by SEL.

SEL also fabricated and installed two AWE (Australian Water Engineers) designed clarifier scraper mechanisms. The clarifier mechanisms were 33m in diameter and designed to cope with an average flow of 350 l/s. The mechanisms are comprised of prefabricated galvanised mild and structural steel components. They were supplied complete with a peripheral drive, scraper 1.5R, access bridge with access stairs, central diffuser drum, v-notch weirs and launder brushers. The mechanisms were pre-fabricated in our workshop in Takapuna before being bolted together on-site by our installation team. SEL also commissioned the clarifiers in conjunction with the Head Contractor.