The Wellington City Council has come up with a $ 247 million preference solution for Wellington’s sewer problems, as a four-year countdown begins before 30 trucks are likely to transport our distilled waste to a small town 163 km north of the capital every day.
Within four years, Wellington’s irwhiro Valley landfill will no longer be agreed to take up Wellington’s sewage “sludge” – effectively the concentrated version of what is flushed down toilets.
Papers from Wellington City Council this week show that without a solution, the capital would send that sludge to the nearest available option – which would likely mean 30 truckloads a week between Wellington and Marton’s Bonny Glen landfill in Rangitīkei.
The preferred solution will cost about $ 247 million, paid for by the State Infrastructure Funding and Financing Fund, and repaid at a rate of $ 162 for an average rated $ 1m home or $ 339 to an average commercial property owner.
READ MORE:
* Sewage solution can no longer mean dirt taxis, no more pipe mares
* Nasty smell as work continues on pipe ‘tied’ deep below Wellington
* Only two weeks’ ‘drum taxis’ left for the south coast
Wellington’s current sewage system means all wastewater pipes lead to Moapunt near Wellington Airport, where they are partially treated before being led 9 km to a “drainage plant” at landfills. Here it goes through a centrifuge where solids are removed and disposed of at the tip, while the rest is pumped back to Moapunt to be treated and dumped deep into Cook Street.
KEVIN STENT / GOOD
So-called ‘drum taxis’ had to transport Wellington’s wastewater to the landfill for months after a pipe under Albert Albert broke down.
That Moapunt-to-landfill pipe failed in 2020, which means that a parade of so-called “drum taxis” had to transport the waste product to and from the landfill. The repair and transportation were previously costing Wellington Water $ 16 million, although this week’s board documents show the cost was closer to $ 20 million.
Four options, boiled down from a long list of 25, to the council this week aiming to solve the problem with one that will get rid of the need for the Mount Albert pipe – a “single-point-of-failure risk” for the council – and reduce the amount dumped at the landfill, where the disposal permit expires in 2026.
Monique Ford / Stuff
Paekawakawa / Southern Ward councilor Laurie Foon – the “Poo Queen” of the council – was excited about the plan.
The preferred option would mean that wastewater is led to Moapunt before it goes through “thermal hydrolysis” – which essentially exposes wastewater to high temperature and pressure through a series of reactors. The process significantly degrades cells and organic matter.
From there it will go through “anaerobic digestion” where it is broken down by microorganisms before it is “dehydrated”, where any excess fluids are removed.
The water is eventually thermally dried, a process in which the water evaporates. Any remaining material will be taken to the landfill, but it is expected to be 20% of the quantity currently going there. It is understood that this smaller quantity, which has already been processed and dried, is unlikely to require a new permit.
The amount is expected to be small enough to be transported by truck without significant disruption – rather than by pipelines.
Councilman Laurie Foon said it was an exciting plan because it had achieved climate change targets to reduce emissions, reduce waste to the landfill and enable the council to “get serious” about its zero-waste plan.
“Finally there are opportunities [for the remaining 20% of biosolids] to be reused as bio-solids and bio-gas re-use which will make it a circular economy success, ”said Foon.