Army Bay Sewage Treatment Plant Expansion, Rodney District, New Zealand


Army Bay Sewage Treatment Plant Expansion, Rodney District

The expansion of Rodney District's Army Bay Sewage Treatment Plant, North Island, New Zealand, was completed in 2007. The plant required an increase in treatment capacity because of the additional sewage wastewater from reticulated areas on the Hibiscus Coast, which includes Orewa and the Whangaparaoa Peninsula.

Rodney District Council, which is responsible for the area, also considered the ability of the plant to protect the marine environment on the Hibiscus Coast. There are currently 35,000 residents in the Rodney area with a projected population increase of 81,000 by 2051.

Army Bay Sewage Treatment Plant construction

"There are currently 35,000 residents in the Rodney area with a projected population increase of 81,000 by 2051."

The Rodney District Council asked Sinclair Merz Knight (SKM) to conduct a study on the plant and determine what could be done to increase its operational life. SKM recommended upgrading the plant.

The NZD$10m upgrade was approved and commissioned in March 2006. SKM produced a detailed design for the plant and provided civil, structural, mechanical and electrical engineering services, construction supervision, project management and commissioning of the plant.

The design also formed the basis for the design of three new wastewater treatment plants for the neighbouring Thames-Coromandel District Council.

Components and contractors of the New Zealand facility

The plant was equipped with a new grit removal and handling system along with new enhanced sequential batch reactors (ESBRs) including a new decanted and aeration system. An ultraviolet light (UV) system was installed for the final disinfection of the treated effluent. The existing sequential batch reactors (SBRs) were also upgraded.

"An ultraviolet light (UV) system was installed for the final disinfection of the treated effluent."

HEB Construction was granted a $1.8m contract to construct two pumping stations, a concrete SBR tank, concrete grit trap chamber and channels and a blower building. The two batch reactor tanks at the plant, SBR1 and SBR2, were retrofitted with baffle walls. The existing flow splitter was modified and other metal work was carried out by HEB.

The aeration, mixing, pumping and piping works were carried out by Service Engineers Limited on a design build basis.

The electrical works and upgradation of the SBRs were handled by Current Electrical (CE). Under this contract, the controls for the dissolved air flotation tanks, centrifuges and the discharge pump station were upgraded.

CE was responsible for installing one new SBR and rewiring the existing two SBRs. The existing SBRs were fitted with a new 750KVA control panel and VESDA (very early smoke detection apparatus) alarms.

In 2009, CE won another contract to install a new Alpha Level Centrifuge and other equipment. CE also installed a Sindico Gravity Belt Thickener in 2010, along with all the necessary controls.

Award for the sewage treatment facility

The upgraded plant won a silver award for SKM at the Association of Consulting Engineers of New Zealand (ACENZ) INNOVATE NZ awards of excellence in August 2007 for its environmental consideration and relationship management of the project.