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Watercare has begun desludging work on oxidation ponds at the Waiwera Wastewater Treatment Plant, an important early step in a $45 million upgrade that will permanently end treated wastewater discharges into the Waiwera Estuary.
This process helps prepare the site for a new wastewater system that will see the ponds converted into storage ponds and wastewater from the Waiwera catchment pumped through a new 4.5 km underground pipeline to Hatfields Beach then to Army Bay Wastewater Treatment Plant.
Once there, wastewater will receive a higher level of treatment before being discharged offshore, the company says.
Currently, Waiwera wastewater is treated locally in large open oxidation ponds.
These use sunlight, algae and naturally occurring bacteria to break down wastewater over time.
As wastewater sits in the ponds, heavier material naturally settles on the bottom and gradually breaks down into a layer known as sludge.
When this layer reaches approximately 60 to 70 per cent of a pond’s storage capacity, it must be removed through a routine maintenance process known as desludging.
Watercare head of wastewater Jon Piggot says removing sludge restores capacity, improves performance and reduces the risk of odour.
“At Waiwera, around 10 tonnes of dewatered sludge are currently being removed each day and taken offsite.”
Watercare project manager Martin Hughes says the work is critical to preparing the ponds for their future storage role.
“Completing the desludging allows us to drain the smaller of the two ponds and begin building the new pump station, including connecting the inlet pipe into the pond,” Hughes says.
“By reusing the existing ponds, we can maximise their combined storage capacity of 17,500 cubic metres – roughly the equivalent of seven Olympic size swimming pools while helping to minimise odour.”
Watercare says work on the water and wastewater transmission mains are progressing well, with just over 300 metres of the 840-metre water main on Hibiscus Coast Highway laid.
The installation of the wastewater pipeline along Weranui Road and Hibiscus Coast Highway is also progressing well with around 1.7km now installed out of a total of 4.5km.”
Auckland Transport is also carrying out geotechnical investigations to guide permanent repairs to two slips that occurred in February.
“While the slips have caused some minor disruption, the project remains on track, with the water and wastewater upgrades expected to be completed by the end of the year.
“We understand this work may cause some inconvenience for motorists, and we appreciate your patience as we deliver essential upgrades for Waiwera,” he says.
