Wastewater Treatment Plant overview

    What has been proposed as the preferred option to upgrade the Rotorua Wastewater Treatment Plant?

    To upgrade the treatment plant processes so that all wastewater is fully treated and safe before the water is returned to the environment, including

    • Increase the capacity and provide some storm flow storage
    • Additional phosphorus removal
    • Ultra-filtration
    • UV treatment
    • Land contact bed 

    Below shows the current Wastewater Treatment Plant system.  It also illustrates the preferred option which was recommended by the community-led, Rotorua Project Steering Committee.

    Why does the Rotorua Wastewater Treatment Plant need to be upgraded?

    • Rotorua’s current plant has to date been the most successful initiative in reducing nitrogen going into Lake Rotorua.  Our treatment plant is among the best in the country, treating wastewater to a very high standard.  But it is in need for an upgrade to meet higher projected demand and to continue to reduce and maintain nutrient levels below the targets agreed under the Lakes Water Quality programme
    • Discharging into Whakarewarewa Forest is no longer viable as it is not a sustainable option for several reasons including cultural concerns.  It is also resulting in ground over-saturation that’s detrimental to trees, making it an unreliable filtering system and adding to pollutants entering the Puarenga Bay. 

    Who has been responsible for investigating the options?

    A community group called the Rotorua Project Steering Committee has been charged with the job of exploring options to upgrade the Wastewater Treatment Plant.

    • At a 2014 Lakeswater Quality Society workshop it was suggested that Rotorua Lakes Council collaborate with the community to work together to find a suitable solution for the future, to first and foremost improve the mauri (vitality) of the treated water and make it as clean as possible before returning it to the environment
    • Council agreed, and with key stakeholders including mandated hapū representatives, the Steering Committee was formed

    How was the preferred location option selected?

    Rotorua Project Steering Committee considered three options all incorporating a Land Contact Bed system:

    • Puarenga Stream discharge
    • Offshore lakebed discharge into Lake Rotorua with diffuser
    • Sulphur Bay (Te Arikiroa) discharge after recovered water is infiltrated through specified aggregates within existing storage ponds

    Two of the three options were strongly opposed because of cultural concerns, which only left the preferred option available. The preferred option met the required threshold however it was not unanimously supported by the committee.

    How many options have been canvassed?

    The community-led Rotorua Project Steering Committee has investigated numerous options which include:

    • Whether the Rotorua Wastewater Treatment Plant should be upgraded
    • What type of system would ensure the removal of pathogens and phosphorus from effluent to ensure its treated before it is disposed of
    • Rotorua Project Steering Committee is unanimous on the need to upgrade the Wastewater Treatment Plant, however members did not unanimously agree on the point of effluent release 

    Why is an alternative effluent disposal location being sought?

    Rotorua Lakes Council and CNI signed a deed in 2014 agreeing to end effluent disposal in Whakarewarewa Forest by December 2019.  The forest spraying system is now considered unsustainable as it is much less effective than when first implemented.

    Is wastewater only sewage?

    No, it also includes contaminated groundwater, sediment, industrial wastewater and storm water.

    Why treat wastewater?

    Nature eventually cleans water through the water cycle, but this takes time. Treating wastewater accelerates the natural process. Wastewater has a very high number of water-borne bacteria and pathogens. Some of these are completely harmless: others are responsible for life-threatening diseases.

    Wastewater is also nutrient-rich. It contains high levels of nitrogen and phosphorus. In the 1980s, wastewater was a major contributor of nutrients which added to Lake Rotorua’s declining water quality problems.

    Council’s upgrades of the wastewater treatment plant have substantially reduced the nutrient load to Lake Rotorua. Treatment now involves biological nutrient removal with carbon dosing and land treatment.

    How much will the upgrade of the plant and disposal to Sulphur Bay cost?

    In 2017, Council estimated the cost of the upgrade would be about $30 million. 

    As a result of detailed investigations such as compiling specification information including tendering details for the resource consent, Council's latest estimate for the update would be between $40m and $45m.


    In 2017, the upgrade is estimated cost was about $30 million.  As a result of 

    At present, where does waiparapara/ wastewater go after it is treated?

    Treated wastewater undergoes a land treatment system and is irrigated into Whakarewarewa Forest.  It has been released there since 1991.

    Disposal in the forest will end by December 2019 as a result of Rotorua Lakes Council and CNI signing a deed in 2014, which also encouraged the exploration of an alternative option to the current Land Treatment System.

    Where is the preferred location for the release of waiparapara (treated wastewater)?

    • Council suggests the provisional release location should be Te Arikiroa / Sulphur Bay
    • The site would be close to the newly designed Land Contact Bed on the Sanatorium Reserve 

    What is the history of the Wastewater Treatment Plant?

    The plant was constructed in 1973.  To find out the significant plant milestones please click on the following LINK.

    Where is the Wastewater Treatment Plant located?

    Rotorua’s wastewater (sewage) is treated daily at a central Wastewater Treatment Plant on Te Ngae Road.  It is sited on the eastern edge of Lake Rotorua in the Sanatorium Reserve - a reserve gifted by Ngāti Whakaue for public purposes under the 1880 Fenton Agreement.  The plant uses a combination of a 5-stage Bardenpho process and Membrane Bioreactor, the first full biological nitrogen and phosphorus process that is used for municipal wastewater in New Zealand.

    To protect the quality of the water in Lake Rotorua, the treated effluent from the plant is currently irrigated to pass through CNI land in Whakarewarewa Forest before the groundwater discharges to Lake Rotorua.

2017 Consultation

    Why is Council doing additional engagement in 2017? Isn't consultation over?

    Council is undertaking some additional engagement before applying for Resource Consent.  While the formal consultation leading to the decision to move forward with the upgrade and preferred discharge option has occurred, some affected iwi and hapū have raised cultural concerns with the preferred discharge option.

    Council, following recommendations from the Rotorua Project Steering Committee and its Cultural Assessment Subcommittee, has significantly enhanced the proposed Land Contact Bed design by incorporating mātauranga and mātāpono Māori (Māori knowledge and principles/values) to try to address the cultural concerns that have been raised.  The engagement occurring in August through to mid- September 2017 focuses on the enhanced land contact bed design.   

    How long is the engagement process?

    Rotorua Lakes Council engaged with the community from April through to September, 2017.

    Given some iwi/ hapū oppose the preferred option, how is Council looking to address the respective issues?

    Rotorua Lakes Council undertook a supplementary engagement process to update key stakeholders such as iwi and hapū about the cultural treatment design for the land contact bed as part of the Wastewater Treatment Plant upgrade. 

    Council has applied for resource consent for the Wastewater Treatment Plant upgrade and waiparapara release location point after taking into account all feedback received from the 2017 engagement as well as all previous consultation rounds.  

    Why isn’t Council only consulting Ngāti Whakaue given the Water Restoration Contact Land Bed and release location is on land gifted to Council by the tribe?

    Rotorua Lakes Council will engage with Ngāti Whakaue as mana whenua of Sanatorium Reserve, as well as other affected iwi / hapū and other significant stakeholders. 

    How has the feedback from the engagement process in 2017 been used?

    Community feedback has helped shape Rotorua Lakes Council’s resource consent application to upgrade the Wastewater Treatment Plant.

    In 2013, the Environment Court directed Council to find an alternative effluent disposal method to replace the irrigation of waiparapara in Whakarewarewa Forest following on-going concerns from tangata whenua.

    Council’s objective is to mitigate concerns while at the same time adopting cultural practices in the operation of the plant. 

Land Contact Bed

    How would the Land Contact Bed Water Restoration work?

    Treated water would leave the wastewater treatment plant and enter the land contact bed system which mimics mother nature to further purify the waiparapara/treated water leaving it just short of drinking standard

    • Entering the land contact bed system it goes through a bubbling water filtration process
    • Followed by a series of rock and wetland vegetation filtering bands
    • A water fountain system to create turbulence and aeration follows
    • Before the waiparapara moves through rills that emulate streams
    • Into a calm rock pool / pond where aquatic life is present before the water is released through a rock filtration waterfall into a cascading channel out to Puarenga Bay

    What is the purpose of the cultural treatment design for the Land Contact Bed?

    The land contact bed design has been enhanced by incorporating Māori knowledge and principles/values to address cultural concerns that were raised during consultation.

    At a minimum the design aims to incorporate the following principles/values:

    What prompted the creation of a Deed of Understanding between Council and CNI to stop irrigating recovered (treated) water in the Whakarewarewa Forest?

    The Deed of Agreement between Council and CNI was sparked by a directive from the Environment Court to look for alternative methods of disposing of waiparapara/ treated water.  The directive resulted from on-going tangata whenua concerns about the impact the current wastewater land treatment disposal system on the Puarenga catchment.  The agreement between Council and CNI was signed in 2014 and symbolised a vow to end effluent disposal in Whakarewarewa Forest by the end of 2019.

    How much water can the proposed land contact bed hold?

    • It holds about 15 million litres

    How long will it take for water to flow through the land contact bed?

    Based on current levels, the plant treats about 20 million litres of wastewater every day.  This amount of recovered water will take about 18 hours to flow through the proposed land contact bed.

    If more houses are connected to the plant, will the rate of flow change in the land contact bed?

    Yes, the current system allows for a daily flow of up to 25 million litres a day which can service an extra 7,000 households than at the moment.

    If we did service 7,000 more households, the flow rate though the system would take about 15 hours.

    The plant upgrade will increase capacity to treat more than 70 million litres a day, what will this mean for the Land Contact bed?

    The maximum capacity of the upgraded plant will be about 70 million litres a day which will help us deal with significant weather events. If an event was to occur that makes us run at maximum capacity, it would take about five hours for the water to flow through the land contact bed (at a peak flow of about 825 litres per second). However, peak flows, caused by severe weather, usually happen in short durations and are unlikely to be sustained at this level for a full 24 hours.

Technical faqs

    How does the Wastewater Treatment Plant currently treat wastewater?

    How much wastewater is treated at the plant?

    • The Rotorua Wastewater Treatment Plant serves a population of about 60,000 people. It has the capacity to serve a population of 75,000
    • The plant receives 20 million litres of wastewater every day
    • We have the capacity to treat a daily average wastewater intake of 27million litres
    • Most of Rotorua's wastewater is generated by domestic use, while a small percentage is from industrial use
    • Wastewater going into the plant includes rainwater, sediment, sewage, industrial wastewater and stormwater

    How would the proposed Wastewater Treatment Plant upgrade treat wastewater, if it's adopted?

    *30 tonnes (t) of nitrogen per year is the current consent limit, which the Lakes Programme Integrated Framework applies to urban land. 

    The 30 tonne nitrogen mass is predicted to increase as rural land is converted to urban dwellings as the population grows. This use would not change the total level of nitrogen entering the lake. 

    How much better will the water be if the upgrade is done?

    Current levels (as the water leaves the plant) 

    Post upgrade levels

    Percentage improvements


    5-6 mg/litre

    <4.3 mg/litre

    30% improvement


    3-4 mg/litre

    0.4 mg/litre

    90% improvement

    Pathogens – E coli bacteria

    5400 per 100ml

    <1 per 100ml

    >99% improvement

    Pathogens - viruses

    Millions per litre (different amounts for different viruses)


    >99% improvement

    How long has Council been irrigating effluent in Whakarewarewa Forest?

    Waiparapara/ Treated wastewater has been released in Whakarewarewa Forest since 1991

    Why can't the recovered wastewater continue to be irrigated into the Whakarewarewa Forest?

    Discharging into Whakarewarewa Forest is no longer viable as it is not a sustainable option for several reasons including cultural concerns.  It is also resulting in ground over-saturation that's detrimental to trees, making it an unreliable filtering system and adding to pollutants entering the Puarenga Bay.

    The proposed upgrade would treat wastewater to an extremely high standard, removing pollutants like nitrogen and phosphorous and disinfect bacteria like E. Coli.  The recovered water would be clean and would not pollute the lake.

    There appears to be a misperception that because Council has easement in perpetuity ( ie a legal right to cross or otherwise use someone’s land for a specified use), it can simply continue to use the forest however this is not the case. 

    How often is it irrigated in Whakarewarewa Forest?

    Council sprays treated effluent from the wastewater treatment plant onto blocks in Whakarewarewa Forest for about two to three hours each day.

    Where are the irrigation zones?

    • There are a number of irrigation blocks in Whakarewarewa Forest, which are located away from main roads and forestry roads.
    • A map identifying these zones can be found here 
    • There are several signs erected in prominent spots in the forest telling people about irrigation spray sites, which have a buffer zone of trees preventing the treated effluent drifting on to forest roads and tracks used for recreational purposes.

    Given torrential rain has caused overflowing at the plant, is Council certain the proposed plant will have the capacity to cope with population growth and heavy rain?

    Yes.  The upgrade will manage a 45% growth in population (or roughly 7,000 more households) and will also be able to deal with significant weather events that reach a peak flow of 70 million litres per day or 825 litres per second. 

    Is Council proposing to pump sewage or effluent into Lake Rotorua?

    No.  Lake Rotorua is a taonga and Council, with support of the community-led rōpū (group) the Rotorua Project Steering Committee, has chosen the most preferred option which: 

    • Protects people's health 
    • Is environmentally sustainable 
    • And is culturally appropriate 

    Farmers are being asked to reduce the nitrogen going to the lake so why aren’t we proposing to remove more nitrogen?

    Lake Rotorua can sustain 435 tonnes of nitrogen each year. Targets set in the mid-1980s still apply today and include:

    ·  30 tonnes from treated wastewater from the urban area (150 tonnes in 1984/1985)

    ·  220 tonnes from farmland; and

    ·  185 from all other sources

    Nitrogen from urban wastewater has reduced from 150 to 30 tonnes per year, achieving its target. A further 10 tonnes of N has been reduced by the reticulation of lakeside communities, while urban growth has been accommodated within this figure.  Treated wastewater contributed 27% of the nitrogen to the lake in the 1980s and has reduced to 4% today.  The proposed option for the WWTP upgrade is close to the limit of technology, which represents the best performance that technology can achieve.  If consent is granted for the proposed option, Rotorua would achieve the lowest consented nitrogen limit for the entire flow, for a city in New Zealand.

    Over that same period nitrogen discharge from pastoral land use increased by 300 tonnes per annum from conversion of land to dairy, increased stocking rates (stock per block of land) and higher fertiliser use. Farmers are now being asked to reverse this increase and are being provided significant public funding to support them to do this.

    Does the plant deal with medical waste from the hospital?

    An independent company, Waste Management Technical Services, provide a specialised service for medical waste to our community. Medical waste is collected and taken to an Auckland plant where it is sterilised before being disposed of at their Class A landfill in Redvale, Dairy Flat.

    How well would the proposed upgrade treat blood and other bodily fluid in wastewaters?

    • The plant would be designed to break down and treat organic material such as blood and bodily fluids 
    • Bacteria breaks down organic matter in to simple compounds like carbon dioxide and water, as well as important nutrients such as nitrogen and phosphorus

    • Bacteria and other microorganisms grow and multiply under controlled ideal conditions in the plant

      • In parts of the process they are provided with as much oxygen (air) as they need to live (for respiration)  and in other parts they are starved of oxygen so they use the oxygen from the nitrate molecule and release the harmless nitrogen gas to the atmosphere

      • They absorb their food from the material they live in

      • Towards the end of the process they run out of food and energy (they have consumed all the organic waste from the wastewater) before they have removed all the nitrogen, so they are fed ethanol

      • All the organic waste is bio-transformed into more bacteria, water and gases

    • At the end of the treatment process, the wastewater also receives UV treatment to remove pathogens including viruses

    • Sludge produced at the plant goes to Kawerau for vermicomposting

    How is industry waste / trade waste dealt with?

    Industry waste is a form of trade waste and its disposal needs to be in line with the trade waste bylaw. A trade waste officer decides the necessary treatment needed onsite before any wastewater is discharged to sewer.

    Examples: Restaurants use grease traps to separate grease. Dentists separate mercury. Petrol stations have measures in place to address spills.

    For most other industrial / commercial outlets, the best place for their wastewater to be treated is the Wastewater Treatment Plant.  Their discharge is monitored and they are charged based on the volume and strength of their discharge.

    Are hazardous chemicals dealt with at the treatment plant?

    An independent company, Waste Management Technical Services, neutralises, sterilises and dewaters hazardous chemicals. Any solid residue is taken to the landfill and the remainder goes through filtrate treatment before being treated as trade waste.

Rotorua Project Steering Committee

    What is the Rotorua Project Steering Committee?

    It is a community-led Project Steering Committee which is made up of more than 15 representatives including:

    • An independent chair
    • Te Arawa Iwi and hapū 
    • Cultural Assessment Sub-committee representatives
    • Technical Advisory group
    • Rotorua Lakes Council and Bay of Plenty Regional Council officials 
    The Rotorua Project Steering Committee is an engagement mechanism made of citizens of Rotorua which sits at the empowered end of the engagement spectrum.  It is the cornerstone element of the engagement process for this project. 

    What is the Cultural Assessment Sub-committee

    The Cultural Assessment Sub-committee was made up of three Ngāpuna hapū/ iwi representatives as well as kaitiaki representatives of Tūhourangi/ Wāhiao, Ngāti Rangiwewehi, Ngāti Pikiao, Tapuika and CNI.

    The sub-committee was mandated by the iwi members of the Rotorua Project Steering Committee to pull together a Cultural Impacts Assessment report.

    The Cultural Assessment Sub-Committee was established in September 2014 to guide cultural considerations. 

    It commissioned, through Council sponsorship, Te Onewa Consultants to write the report. 

    How did the Mātauranga Māori panel come about?

    The Rotorua Project Steering Committee's Cultural Assessment Sub-committee recommended for a pool of Mātauranga Māori experts from Te Arawa to be brought together to consider the proposed cultrural treatment concept for the proposed Land Contact Bed upgrade concept. 

    The sub-committee identified an initial group of Te Arawa representatives including younger people with expertise in Mātauranga Māori (Māori knowledge) to join the panel.  

    The Māori knowledge (Mātauranga Māori) experts were asked to provide oversight an ensure the proposed Land Contact Bed adheres to the following cultural treatment values including: 

    • Restore the mauri of the wai 

    • Water is of Papatūānuku (Mother Earth) and Ranginui (Sky Father) 

    • Intrinsic to life 

    • Sustain life & be life-sustaining 

    • Kaitiakitanga (guadianship)

    Te Tūāpapa o ngā wai o Te Arawa  (Te Arawa cultural values framework for water)

    What guidelines have Rotorua Project Steering Committee considered when looking at alternative options?

    • Be life-sustaining and restore the mauri (vitality) of the treated water
    • Meet standards consistent with the National Policy Statement for Freshwater Management
    • Satisfy regulatory requirements and secure resource consents in partnership with the community and tangata whenua
    • Achieve a high level of public health and environmental protection
    • Be the best practicable option for Rotorua’s future wastewater management
    • Once the Steering Committee had identified options, it was worked through and shortlisted, a suite of potential discharge options identified and indicative costs estimated
    • The wider community was consulted and responses were fed back into the ongoing process