This Wastewater Treatment Plant (WWTP) serves a community of approximately 180 permanent residents. In summer, the population increases significantly due to visitors to the campground and holiday homes.
The Duvauchelle wastewater scheme was constructed in 1988. There were minor upgrades in 1996 and 2002. There are approximately 250 dwellings within the settlement.
There is currently a project underway to discontinue the discharge of treated wastewater from the plant into the Akaroa Harbour and instead use the treated water to irrigate land.
Current treatment
The raw wastewater is screened using an inlet screw screen. The screened wastewater then passes into the primary sedimentation tanks (PSTs) where primary and secondary sludge is settled out. The primary wastewater then passes through the rotating biological contactors (RBCs) where biological treatment occurs.
From the rotating biological contactors, wastewater flows into secondary sedimentation tanks (SSTs) where biomass created by the rotating biological contactors flocculates and settles out.
This secondary sludge is periodically removed from the bottom of the secondary sedimentation tanks and discharged to the sludge/supernatant return pump chamber, where it is pumped to the inlet manhole and flows to the primary sedimentation tanks where it settles along with the primary sludge.
The combined primary and secondary sludge is manually removed from the bottom of the primary sedimentation tanks by opening valves that allow sludge to flow into the sludge decant tanks.
The sludge is transported to the Christchurch Wastewater Treatment Plant in Bromley for processing into biosolids. The wastewater from the secondary sedimentation tank undergoes disinfection through a UV unit before being gravity-fed to the outfall in the harbour.
Flow is measured with a flowmeter following disinfection and is continuously recorded.
Future treatment
By 2029, a scheme to discharge treated wastewater to trees on Christchurch City Council land upslope of the Akaroa Golf Course and to the course itself will be commissioned.
The treatment plant will be upgraded so that it can treat water to the high quality necessary for land application.
Resource consent
The main resource consent for Duvauchelle wastewater discharge to the harbour (CRC230358(external link)) expires in 2031.