Wastewater Treatment
Treatment plant upgrades
The Wastewater Treatment Plant is currently undergoing an upgrade. Work started in December 2022, with planned completion in 2027. Read more about what's being upgraded and the progress of work in the Projects section of our website.
Wastewater Treatment Service
Rotorua's wastewater (sewage) is treated daily at a central Wastewater Treatment Plant on Te Ngae Rd, that uses a 5-stage Bardenpho process, the first full biological nitrogen and phosphorus process used for municipal wastewater in New Zealand. The sludge produced (biosolids) is transported to Kawerau for composting.
To protect the quality of the water in Lake Rotorua, the treated effluent from the plant is irrigated to pass through the land in Whakarewarewa Forest before the groundwater discharges to Lake Rotorua.
- The Rotorua Wastewater Treatment Plant serves a population of approximately 60 000 people. It has the capacity to serve a population of 75 000.
- At the plant, we treat an average of 18 000m3 (18 000 000 litres) of wastewater each day. We have the capacity to treat a daily average wastewater intake of 27 000m3.
- Most of Rotorua's wastewater is generated by domestic use. A small percentage is from industrial use.
Infiltration and Inflow to the Wastewater System
Infiltrationis rainwater and ground water that seeps into the sewerage system through defective pipes and joints.
Inflow is stormwater and surface water that enters the sewerage system directly - usually from local flooding into low-lying gully traps, and roof downpipes directly connected to the sewer.
In periods of heavy rain, increased inflow to the sewerage reticulation network can cause overflows, which can lead to contamination of private properties, watercourses and lakes. The overloaded system may also mean reduced levels of treatment at the wastewater treatment plant.
For more information on our Inflow and Infiltration program contact the Utilities Department.
On-site Systems
Unless there is a council sewerage scheme existing or planned for your area, any new septic systems installed into the Rotorua catchment must be of an approved model; otherwise resource consent needs to be obtained.
See the Environment BOP website for systems approved for an installation in the Rotorua Lakes' catchments. All systems shown may be installed elsewhere in the Bay of Plenty; however conventional septic tanks are still permitted in most areas outside Rotorua lake catchments.
Forest Irrigation
Council sprays treated effluent from the wastewater treatment plant onto blocks in Whakarewarewa Forest. Blocks are sprayed for 2 - 3 hours each day.
All of the designated public roads, main biking and walking tracks have a 15-metre-wide buffer zone of trees on each side that prevent spray drift.
You can see the location of the spray blocks on noticeboards at the forest entrances, adjacent to the ponds on Katore Rd and outside Council's visitor centre in Longmile Road.
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.
Odour Complaints
Rotorua's wastewater treatment plant is situated in an area which has a very high level of hydrogen sulphide (H2S) gas. The hydrogen sulphide gas, which smells something like rotten eggs, masks much of the odour from the plant.
If you detect an offensive odour which you think is coming from the plant, contact us and we will follow up your complaint immediately.
Odour Off Sewerage Pumpstations
Carbon filters are installed at pumpstations where odour may be a problem.
Other Odour Problems
