Compost no longer spread on wastewater treatment plant paddocks 

Council today received a report advising that compost from the Organics Processing Plant (OPP) is no longer being spread on the Wastewater Treatment Pond's paddocks. 

Since May 2021, compost from the OPP had been used on the paddocks to improve soil health for mass planting of native plants and trees. The plantings aimed to ease the midge problem in the area by providing a natural barrier between the oxidation ponds and the residential area; reduce carbon emissions; improve biodiversity; and provide an important habitat for native birds.

On 21 June, the Council requested a report come back to them by 2 August advising a date for when the use of compost on the paddocks could stop, to further prevent odour risk in the area. 

Staff advised the Mayor and Councillors that compost from the OPP had stopped being accepted at the Wastewater Treatment Plant on 30 June. 

Fulton Hogan, the Council’s contractor, spent the following week spreading the remaining compost stockpiles on the Dyers Road hardstand. Final clean-up of plant and removal of machinery from the site was completed by mid-July 2023.

Living Earth is now working to find other markets for the compost. 

Additional actions to mitigate odour risk 

At the 21 June meeting Council also requested information on any other immediate options to reduce odour from the Organics Processing Plant. Today's report to Council outlined the improvements that have been made at the plant since that time:

 Living Earth has got its AssureQuality re-certification following the removal of windrows and outdoor compost maturation. This allows Living Earth to supply certified compost to the market directly from the tunnel after it is screened. From an odour risk perspective, the re-certification opens further markets, minimising the amount of compost temporarily stored on site after screening.

• An independent review of the operation of the new biofilter has been scheduled. This is in response to a request raised at the May Community Liaison Group meeting. 
   
• Two replacement tunnel doors have been ordered. The seals on the new tunnel doors will mitigate odour enter the processing hall from the tunnel. Installation of the doors is expected to be completed by mid-October 2023.
   
• Pattle Delamore Partners (PDP) has been engaged to identify further immediate actions that can be taken to reduce offensive and objectionable odour. When PDP have completed this piece of work, staff will consider the results and work with Living Earth to address any immediate actions.

View today’s Council meeting on our YouTube channel.

Update on the wastewater treatment plant

• The recent wet weather has meant the oxidation ponds are at very high levels, and dissolved oxygen levels are stable.
   
• It’s difficult to predict how wet weather events can influence the health and odours of the ponds. On one hand, increased stormwater inflow can dilute wastewater, but on the other hand, the increased flow means some wastewater bypasses the flow-limited temporary activated sludge plant.
   
• There are currently no persistent odours beyond the ponds' site boundary, with temporary minor smells being detected close to the site boundary first thing in the morning during very settled weather conditions. We’ll continue to monitor pond health and odour levels and make any necessary actions to address these.
   
• We've undertaken a survey of the sludge blanket at the bottom of Ponds 1 and 2 to get an understanding of how the ponds are likely to perform in the future, and found that the layer of sludge is less than anticipated. This is good news, as it means the pond's sludge levels are still within normal operating parameters. As a result, the sludge is unlikely to be a future source of odours. 
   
• The poly-dosing trial on the temporary activated sludge plant continues to perform well.

Stay updated

We want everyone to be able to stay updated on developments at the Organics Processing Plant. If you know of anyone who would like to receive this e-newsletter they can subscribe online. 

If you have any questions, or would like further information on the project, please call us on 03 941 8999 or 0800 800 169 or email bromley@ccc.govt.nz  

Thanks in advance for your patience and co-operation as we carry out these improvements and prepare for the upcoming redevelopment programme. We’ll be in touch again soon.