Martinborough wastewater treatment plant consent compliance upgrade

The MWWTP uses wastewater stabilisation ponds, or oxidation ponds, to treat wastewater. Over time, bio-solids build up in the bottom of these ponds as ‘sludge’ – a by-product of the treatment process.  The sludge must be periodically removed, as it will reduce the treatment efficiency of the ponds.  The sludge levels in the MWWTP ponds are currently exceeding capacity limits, affecting the treatment plant performance.

An abatement notice is issued under section 322 of the Resource Management Act 1991. The abatement notice requires council to undertake a range of plant upgrades to enable the plant to work towards full compliance.

A corrective action plan is currently in place to work toward bringing the plant back into conformance with resource consent requirements. These short-term works are separate from the long-term staged programme of works to achieve long-term sustainable resource consent compliance. SWDC is working with Greater Wellington Regional Council, who will issue a new abatement letter with new dates after they receive the proposal on the current short-term solution.

Greater Wellington Regional Council requested two additional requirements within the abatement notices:

• Organise and hold two Community Liaison Group meetings in 2024.
• Initiate contact with Rangitāne o Wairarapa and Ngāti Kahungunu ki Wairarapa to:
  • Provide a summary of progress in meeting the requirements of ‘To Do Abatement Notices A1061 – A1063’; and
  • Provide a proposal for, or any updates to, the development of a Tangata Whenua Values Monitoring Plan.

For more information on the desludging process, view our Information Sheet (837KB PDF). (837KB PDF)

Geobags were the chosen desludging method, as it has been a successful method used at other pond-based treatment plants throughout New Zealand. It is used to remove excess build-up of sludge to improve treatment efficiency of the ponds and assist in improving treated discharge quality. It is also a safe option to keep high quality treated water from contamination, as any potential spillage is captured from the laydown area and pumped back into the waste pond for treatment. The sump pump will also be sized to remove all dewatering coming from the geobags.

The desludging works are planned from late 2024 to mid-2025. Nearby neighbours may notice trucks and excavators driving on the road. Once the initial desludging is complete (about 2-3 months), there will be ongoing maintenance staff checking the geobags and progress of the long-term geobag dewatering (about 3-5 years).

The amount of time the desludging process occurs depends on the amount of sludge needing to be removed and pumped into the bags. Once each bag is filled to capacity, the geobags will be in place for about 3-5 years. The sludge remains in the geobags and gradually dewaters and solidifies. It eventually stabilises into a form that is safer to re-use or dispose of. After the geobags are removed, the laydown area will remain for future desludging operations.

Activities on-site will be starting in late 2024 to setup the site and establish the pumping equipment and geobags. The initial desludging process is expected to take 2-3 months, with the site clearing in mid-2025. Moving forward, desludging of the ponds will be carried out on a 5-year cycle to maintain optimal operating conditions.

There is not expected to be any additional odours during the desludging process. This is a commonly used method that stabilises the sludge into a more solidified form that is simpler to dispose of. As part of the resource consents, there cannot be an objectionable odour past the boundary of the project property and monitoring will occur to ensure there are no violations of these consents.

The MWWTP has an existing resource consent that does not expire until 2051 that describes staged improvements and upgrades to meet the consent conditions prior to 2030. A 7-year prioritised improvement plan has been developed that includes a new inlet screen, pond optimisation, replacement of the UV system and design/construction of an irrigation site. 

The programme upgrades align to the plant’s current resource consent requirements, requiring a gradual transition to land-based disposal of wastewater (rather than to water).

You can view the information sheet by clicking on the link below

Martinborough WTP Upgrade Information Sheet (837KB PDF)