Martinborough wastewater treatment plant consent compliance upgrade
On behalf of the South Wairarapa District Council we are upgrading the Martinborough wastewater treatment plant to ensure it meets resource consent requirements.
If you have any questions about this work, please contact:
Wellington Water, 04 912 4400
The project team is currently working through the procurement process for the desludging works, which is scheduled to start in December 2024.
The Martinborough Wastewater Treatment Plant (MWWTP) is located approximately 1km north-east of Martinborough, close to the Ruamāhanga River. The treatment ponds have filled with sludge and need to be cleaned out. They have not been cleaned of sludge since the 1970s.
The MWWTP has an existing resource consent that expires in 2051. Following two non-compliance letters from Greater Wellington in August 2022, they issued South Wairarapa District Council (SWDC) abatement notices for:
- Exceeding hydraulic load constraints when discharging to land and river, and
- Exceeding E. coli and nutrient limits when discharging to the river.
Project summary
The MWWTP is in need of upgrades to improve plant performance, improve consent compliance and reduce future adverse effects on the environment. The plant has reached its design capacity.
The upgrade works include:
- Removing the build-up of sludge within the treatment ponds to restore treatment efficiency. See our information sheet for more details here
- Additional monitoring of wastewater to inform future upgrades at the treatment plant and meet consent requirements.
- Investigating and optimising the existing ultraviolet (UV) treatment system for improved performance.
Project benefits
Desludging the ponds will:
- Improve the plant’s operation and compliance in line with resource consent requirements.
- Improve treatment efficiency and the long-term treatment performance.
- Minimise the risk of future failures and odour issues.
- Remove the risk of sludge carryover out of the ponds and into the treated discharge.
- Reduce the release of nutrients from the sludge back into the treated discharge.
- Increase the hydraulic retention time of the ponds to optimise treatment performance.
- Improve environmental outcomes and minimise public health risk.
Monitoring the wastewater flows will:
- Meet consent compliance requirements.
- Provide data for future population growth.
- Allow for sizing future plant upgrades.
Investigating the current UV treatment process and possible optimisation will:
- Identify the most cost effective and preferable future upgrade options.
- Identify possible existing issues within the UV treatment system and opportunities for future improvements.
For more information on the desludging process see our information sheet here
FAQs
What caused the abatement notices from Greater Wellington?
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.
When will the plant be considered compliant again?
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.
What else did Greater Wellington request SWDC and WWL to do as part of corrective actions?
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.
What is geobag desludging? Why was this method chosen?
For more information on the desludging process, view our Information Sheet.
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.
What works are planned as part of this project? How much activity is expected?
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).
How long will the geobags remain in place? What happens to the laydown area after dewatering?
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.
What is the duration of the project?
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.
Will the desludging smell?
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.
What are the long-term improvements planned for the treatment plant?
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).
This is a repository of documents related to the project.
Information Sheet
You can view the information sheet by clicking on the link below