Wastewater Treatment

Treatment plant statistics

• The Rotorua Wastewater Treatment Plant serves a population of approximately 60 000 people. It has the capacity to serve a population of 75,000
• We treat an average of about 20,000 m3 (20,000,000 litres) of wastewater each day. The plant has the capacity to treat and discharge up to 44,000m3
• Most of Rotorua's wastewater is generated by domestic use. A small percentage is from industrial use.

Inflow and infiltration to the wastewater system

Inflow and infiltration (or I&I) means rainwater and groundwater that enters the wastewater system through a variety of defects on public and private property

• Inflow sources allow rainwater to enter the wastewater system directly from the surface. This includes through incorrect plumbing, crossed connections, and damaged or low-lying gully traps and manholes.
• Infiltration sources, like cracks or bad joints in wastewater pipes and manholes, allow groundwater to seep into the wastewater system.

A certain amount of I&I is unavoidable and is planned for in routine wastewater design. However, too much I&I, especially during severe weather events, can overwhelm the wastewater system. This can mean reduced levels of treatment at the wastewater treatment plant. The overloaded system can also cause overflows and associated risks to health and damage to the environment.

Forest irrigation

Currently, Council sprays treated effluent from the wastewater treatment plant onto blocks in Whakarewarewa Forest. Blocks are sprayed for 2-3 hours each day on a rotation.

All designated public roads and main biking or walking tracks have a 15-metre-wide buffer zone of trees on each side to prevent spray drift.

You can see the location of the spray blocks on noticeboards at the forest entrances, next to the ponds on Katore Road and outside the visitor centre in Titokorangi Drive.

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.

Other services at the treatment plant

Wastewater dump station

If you need to dispose of portable toilet waste, you can do this for free at the Dump Station at the Wastewater Treatment Plant 24 hours a day, seven days a week. Find out more about what's accepted below.

Accredited water testing

The plant is also home to Rotorua Lakes Council's Environmental Laboratory, who offer a wide range of accredited water testing services. Read more about the lab below.

On-site wastewater 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, you will need to get resource consent.

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 lakes' catchments.

Complaints about smell (odour)

Carbon filters are installed at sewerage pumpstations where odour might be a problem.

Rotorua's wastewater treatment plant is situated in an area which naturally has a very high level of hydrogen sulphide (H2S) gas. The gas, which smells a bit like rotten eggs, masks most of the odour from the plant.

If you detect an offensive smell which you think is coming from the plant, contact us and we will follow up your complaint immediately.