More Improvements to New Plymouth Wastewater Treatment Plant

02 May 2016

The next stage of significant upgrades to the New Plymouth Wastewater Treatment Plant begins this week.

Phase two of Wai Taatari (‘filtered water’) will result in lower costs for drying the plant’s excess sludge into the fertiliser Bioboost, and also provide the Council with more options for disposing of sludge if the thermal drying facility (TDF) is ever offline.

“It’s about making the plant more efficient and cheaper to run, and building more redundancy into our disposal options,” says Manager Infrastructure David Langford.

“When phase two has been fully commissioned by the middle of next year we’ll have cut the TDF’s gas use by between 30 and 45 per cent – which will also reduce the plant’s greenhouse gas emissions – and we’ll be saving between $110,000 and $170,000 per year.”

The first phase two project, which starts this week, is to upgrade the plant’s thickening system. This will result in better quality sludge that will require less energy to dry in the TDF.

The remaining projects of phase two are the replacement of the dewatering system and an upgrade of the plant’s inlets, which will take place in 2016/17.

The $11.5 million phase one of Wai Taatari was officially completed in March 2014 and resulted in the plant’s two aeration basins being upgraded into bioreactors, making them more efficient in treating the district’s wastewater. Phase two will cost $12m.

  • The sludge that is dried in the TDF is surplus micro-organisms that are used in the bioreactors to eat the waste in the wastewater. These micro-organisms are separated in the clarifiers from the water effluent, concentrated in the thickeners, have excess water squeezed out of them in the belt presses, and then are dried, sterilised and palletised in the TDF to make Bioboost.