x__32__fill__social media twitter voice record__64__outline__user profile avatar contact person volume sound users member human speaker record voice recorder speach speak voice record__64__outline__user profile avatar contact person volume sound users member human speaker record voice recorder speach speak apartment__64__fill__building home house hotel apartment property flat residence

Kāeo Wastewater Treatment Plant Q&As

The project team hosted a webinar on Wednesday 23 March, 2022. A recording can be viewed on YouTube here.

A number of questions were raised during that webinar. Answers are provided below.

Yes, it is possible to discharge to land, instead of to the harbour. We are investigating this option but unfortunately, there is no quick solution.

Initial desktop analysis shows discharge to land is not affordable for ratepayers under the current funding framework. However, we continue to investigate the feasibility.

Discharge to land systems require time to design, install, and commission. If discharge to land becomes a viable option in the future, the discharge to the Kāeo River needs to continue until a new system is operational.

We will continue to make improvements to the existing treatment process as recommended by our technical advisors to avoid adverse effects to the health of the Kāeo River and the Whangaroa Harbour.

There are swimming holes on the Kāeo River that are popular with our community in summer.  Does the discharge of treated water downstream affect their safety?

The operators discharge on the outgoing tide to prevent wastewater backing up into the river environment during low flows.  This is not a condition of the current consent, but we do it anyway.

As part of our application to replace the existing consents, we propose to introduce a condition of consent that discharge occurs for a maximum of three hours in each 12-hour tidal cycle between one to four hours after high tide. This will ensure that the treated wastewater will be diluted and transported downstream on the outgoing tide, away from the upstream swimming holes noted by the community.

A wetland was installed as part of the treatment process. It is not in use because of issues with its ability to “treat” the wastewater after UV disinfection. Could locals have access to try and revitalise the wetland?

There have been three attempts to get the wetland to a state where it performs as needed for treatment of the wastewater.

We worked with Wai Care Consultants and members of the community in 2014 to re-plant the wetland with locally-sourced plants. Due to the shallow nature of the wetland, a large population of bird life, including pukeko, accessed the wetland and pulled out many of the plants.

The UV disinfection chamber is doing a good job of reducing micro-organisms in the wastewater so the wetland is not critical to the process, therefore it is not our focus at this point. We haven’t given up on the wetland as a part of the treatment process and are open to revisiting this in future, in collaboration with the community.

There are 240 properties connected to the reticulated wastewater network.

There is no plan to upgrade the Kāeo wastewater treatment plant, other than to comply with water quality standards.

Kāeo wastewater treatment plant has capacity to receive, treat, and discharge more wastewater than it currently receives under the existing conditions of the consent. This extra capacity is available for those rated properties within the area of benefit that have not yet connected.

Areas like Tauranga Bay, Whangaroa, and Ota Point are not within the area of benefit so additional funding (via rates) would be needed to connect these areas. Any extension to the plant would need to be publicly consulted on as part of the Long Term Plan process.

How is the quality of the wastewater monitored to assess whether it is compliant with conditions of consent, and what is monitored?

When we monitor the discharge quality, we focus on the impact to the receiving waters of the Kāeo River. We collect samples monthly from two points, about 10 metres upstream and 15 metres downstream of the discharge point. We also do weekly samples at the wastewater treatment site itself.

We measure for several things (analytes), which includes discharge volumes, F-specific bacteriophage, pH, dissolved oxygen, faecal coliform, E.coli and ammoniacal nitrogen. Not everything we measure has a consent limit. Also, the frequency and timing of when we measure these is variable. This is because we are trying to compare the quality of the wastewater before and after treatment at the plant as well as comparing the river water quality upstream and downstream of the discharge. We are revising our approach to monitoring as part of our consent application, with the goal of improving our ability to gather good, comparable data.

The table below shows number of times the consent limit was exceeded on any of these, and what that figure is as a percentage of the total number of measurements taken in the 3-year period ending October 2021.

Analytes

Exceedances

Frequency

Discharge volume (effluent)

0

0%

F-Specific bacteriophage[1] (influent & effluent)

12

35%

pH (downstream)

6

15%

Dissolved oxygen (upstream & downstream)

0

0%

Faecal coliform (upstream & downstream)

1

3%

E.coli (upstream & downstream)

0

0%

Ammoniacal nitrogen (downstream)

2

5%

Is the quality of the wastewater being discharged to the Kāeo River compliant with conditions of consent?

The quality of the wastewater being discharged is generally compliant. When it is not compliant, the variation from required quality is minimal and infrequent.

The table shows there are times when some analytes have exceeded consent conditions over a three-year period. Monitoring shows that F-specific bacteriophage* exceeded the limit 12 times during that period. It means we are non-compliant for F-specific bacteriophage 35% of the time. It sounds a lot, but consider this percentage relative to the stringent conditions and in terms of how much it has been exceeded by. The consent requires removal of 99.99% of bacteriophages after UV disinfection. When non-compliant, this measure has only dropped very slightly to between 99% and 99.9%. That’s It is still a good result. However, we aim to reduce these incidences of non-compliance.

We have a limit for blue green algae at our downstream monitoring site which has been exceeded four times over a ten year period. Blue green algae blooms occur in certain conditions when temperatures are high, the river level is low and there is a certain nutrient level in the water. Some blue green algae are toxic and are known as cyanotoxins. They are a threat to humans and animals when consumed in drinking water or upon contact with the skin during recreational activities. We don’t monitor blue green algae upstream of the discharge site so we are not sure whether they are present in the river water already.

*F-specific bacteriophage is a virus type that infects and replicates bacteria (such as E.coli) that are known to reside in the enteric system (our stomachs). They are measured because their numbers are likely to correlate the number of a range of stomach bacteria present in the wastewater. These enteric bacteria can be harmful to human health. As part of the consent replacement process, we are considering changing this analyte to something that has more direct relation to the issue we are trying to address – presence of harmful bacteria in the treated discharge.

Our engineers have made some recommendations to enhance our ability to monitor accurately and to improve the quality of discharge. These include:

  • Measure more conventional indicators of human health risk (e.g. E.coli) instead of the indicator species F-specific bacteriophage
  • Focus on the quality of the discharge from the treatment plant (instead of upstream/downstream) as this is a direct measure, instead of as a dilutant of a receiving environment, which may include other pollutants unrelated to the discharge
  • Do regular maintenance of the UV disinfection chamber
  • Implement methods to remove additional solids to make the UV disinfection process more effective
  • Improve the biofiltration process to enhance reduction of nutrients in the wastewater.

We are looking into these recommendations as a part of the consent application.

A maximum consent duration of 35 years is available under the Resource Management Act 1991 for discharge permits.

We are likely to propose a 25-year consent duration. This is long enough to give us confidence that we can continue to operate the community wastewater facility and to know what funds we need to reserve for its operation, maintenance, and any required upgrades.

We haven’t received much feedback on the preferred duration of a consent term from the community, tangata whenua, or stakeholders. We are keen to hear your feedback. You can email our project lead, Martell Letica on Martell.Letica@fndc.govt.nz, or you can place feedback via our webpage.

People will be able to submit on the application when it is publicly notified by Northland Regional Council.

Does FNDC issue any warnings to the community about water quality issues which could compromise people’s health or mahinga kai?

Yes. Council must immediately notify Northland Regional Council, the Regional Shellfish Coordinator, and the Whangaroa Delivery Centre Manager in there is a discharge of raw sewage to the Kāeo River or any watercourse that flows into the Kāeo River from the sewage reticulation network.

There are no other notifications required under the current consent. The independent commissioner decided that, subject to conditions of consent, treated wastewater posed little risk to human health once discharged and after reasonable mixing.

Northland Regional Council has a river water quality monitoring site on the Kāeo River near the Omaunu and Dip Road bridge’s as shown in the figure below. This monitoring site is approximately 1 kilometre upstream of the discharge point.

Our analysis of the water quality monitoring from this site found elevated levels of bugs like E.coli, which indicates that the safety of the swimming holes may be compromised by other activities in the area.

Is climate change considered in the resource consent application especially considering the area is already impacted by floods?

Yes, we have commissioned a flood risk assessment that looks into the effects of flooding (including accounting for sea level rise) on the ability to discharge wastewater at the level that the pipe is set in the bank of the Kāeo River and also the risk of inundation of the treatment plant which is raised off of the flood plain.

We are awaiting the recommendations of this flood risk assessment and will make this available online.  We are also working closely with tangata whenua and circulate all reports to their nominated representatives.

Our operators have a maintenance plan that they must adhere to. The Kāeo wastewater treatment plant has minimal day-to-day maintenance requirements. Some longer-term maintenance activities we have planned include:

  • Maintaining the distribution arm over the biofilter gravels
  • Renewing the gravels in the biofilter
  • Maintenance of the lamps in the UV chamber (clean/replace as required)

All our plants are monitored remotely and have alarms where necessary so that if there is a disruption our operators are alerted so that they can respond accordingly.

Does sludge build up in the ponds and does it affect the treatment process?We monitor the sludge levels in the main oxidation pond at Kāeo and have found it takes a while for sludge to accumulate in a large pond like this one. We expect to desludge it once every 10 years to maintain effective operation of the plant.

What happens to the wastewater during consecutive high rainfall events, considering both the oxidation and stormwater ponds may be full at that time?

Flows into the wastewater treatment plant increase when it rains. To manage this increase and prevent spills we increase the volume of treated wastewater discharged from the plant. We do this by running the UV system for longer so we can try to match outgoing volumes with incoming volumes. We aim to remove 99.99% of the bacteria first too.

When we can’t keep up with the incoming flow, we store untreated wastewater in the oxidation pond. Once the storage capacity of the oxidation pond is exceeded it overflows into a storm surge pond where it is stored.

These storm facilities generally perform well to prevent spills into the environment.  In some unprecedented high rainfall events we will have to discharge this highly diluted wastewater in what are termed “emergency overflow events”.  These events are exceptional.

If a discharge to land option was funded by ratepayers would their rates also be paying for public facilities which would benefit from the scheme as well (i.e. the public toilets)?

No. A targeted rate for a wastewater upgrade would not extend to public facilities that benefit from that upgrade. This is because it is recognised that public facilities like toilets are often used by others, including visitors. Instead, funds for facilities like public toilets are generated by way of a rate on every rating unit in the district which is maintained as a district-wide reserve fund.

Have other alternatives been investigated to dispose of the wastewater like steaming or evaporation?

No, only discharge to land has been considered because this option is good value for money across New Zealand and internationally. Evaporative losses via the land surface and evapotranspiration through plant uptake will occur under a discharge to land scenario.

Last updated: 02 Apr 2024 4:19pm