Where no sewer is available you will need to provide an on site system which has been designed and constructed in accordance with the On-site Effluent Treatment Regional Plan. The purpose of the OSET Plan is to ensure that wastewater is discharged safely and that the effects are managed.

The systems must have been tested and approved (see below approved systems).

If you are building a new home that will utilise on site systems, this will be approved as part of the building consent process.

Domestic wastewater treatment

Where there is no council sewer, such as in many rural communities, wastewater is generally treated with septic tank systems. However in some situations, like those described in this section, you may choose (or be required) to install an aerated wastewater treatment system, rather than use a traditional septic tank system with a soakhole or soakage trenches. This is to prevent degrading the quality of water in nearby water bodies.

Choosing an aerated wastewater treatment system

What is an aerated wastewater treatment system?

Systems similar to septic tank systems which provide 'on-site' treatment. However they treat wastewater to a much higher standard. They involve pre-treatment and secondary treatment involving aerobic biological processes. Some may also include tertiary treatment such as ultra-violet light disinfection.

What is happening in the Rotorua Lakes catchments?

Concerns about water quality in the Rotorua lakes means that there is a higher performance standard required for wastewater systems installed in the Rotorua Lakes' catchments. We are carrying out trials in Rotorua of aerated wastewater treatment systems to measure how they perform.

What are the approved aerated wastewater treatment systems for Bay of Plenty?

We have compiled a list of approved on-site effluent systems for new installations throughout the Bay of Plenty, including the Rotorua lake catchments here.

Note that for new systems in Rotorua to be installed as a 'permitted activity' they must also meet the requirements of Rule 13 and Schedule 4 of the Bay of Plenty Regional Council's On-Site Effluent Treatment Regional Plan.

If you are unsure if you are in one of the Rotorua Lakes catchments select 'Map 4' of the On-site Effluent Treatment Regional Plan.

Since 2005 many advanced (aerobic) wastewater treatment systems (also known as On-site effluent treatment or OSET) have gone through the trial facility established by Bay of Plenty Regional Council in conjunction with Waikato Regional Council and Rotorua District Council and now operated by Rotorua District Council, to determine which system could meet the approved standard.

The table below highlights the systems approved for 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. Unless there is a council sewerage scheme planned for your area, any new septic systems installed into the Rotorua catchment must be of an approved model or a resource consent needs to be obtained.

Trial 1 (2005-2006)* See Trial 1 Note below Approved for installation in Rotorua Catchments Irrigation Pump included in test? Measured power use (kWh) per day? Equivalent annual power cost
Devan Blue DB900NRS  - Yes 6.3 $517
Hynds Lifestyle - Yes 1.7 $140
Innoflow AdvanTex Ax20  - No 0.6 $49
Oasis Membrane MBR  - Yes 7.3 $600
Smith and Loveless (Microfast 0.5)  - No 7.2 $591
Biolytix BF6 2500 PAT  - Yes?1 0.2 $16
Supertreat SB440 (N12) - Yes 10.8 $887
Waipapa Tanks Nitro-Treat P-N-12-2 (refer to Note A) - - - -


Trial 2 (2006-2007) Approved for installation in Rotorua Catchments Irrigation Pump included in test? Measured power use (kWh) per day? Equivalent annual power cost
Bio-Microbics MicroFAST 0.9 - Yes 8.9 $731
Devan Blue 9000NRS  - Yes 2.7 $222
Hynds Lifestyle Ultimate - Yes1 2.2 $181
Reflection Textile EW  - Yes1 2.5 $205
RX Plastics Airtech 9000 NR - Yes 5.3 $435
RX Plastics Airtech 9000 - Yes 4.9 $402
Waipapa Tanks Econo Treat P-10-2 - Yes 1.3 $107


Trial 3 (2007 - 2008) Approved for installation in Rotorua Catchments Irrigation Pump included in test? Measured power use (kWh) per day? Equivalent annual power cost
Biocycle 6300  - Yes 2.5 $205
Innoflow AdvanTex AX20  Yes Yes 1.1 $90
Oasis Clearwater S2000  Yes Yes 2.0 $162
Waipapa Tanks Maxi-Treat MV-C3000 Yes Yes 8.4



Trial 4 (2007-2008) See Trial 4 note below Approved for installation in Rotorua Catchments Irrigation Pump included in test? Measured power use (kWh) per day? Equivalent annual power cost
WaterGurus NovaClear - Yes 4.6 $378
Humes FR1 Yes Yes 5.2 $427
Hynds Lifestyle Yes Yes 1.8 $148
Waipapa Tanks Econo-Treat VBB C-2200-2 Yes Yes 1.8 $148

The On-Site Effluent Treatment (OSET) National Testing Programme (NTP) has now been taken over by WaterNZ

Trial 1 Note

In early 2009 Bay of Plenty Regional Council decided to no longer recognise the results of Trial 1 in approving waste water treatment systems for installation in our region. Trial 1 had a number of limitations in terms of flow variability which may have influenced systems' performance. The current trial facility has undergone a complete rebuild since the early days and now has very robust systems in place to ensure a high degree of flow uniformity and consistency.

Note 'A'

This system is almost identical to the trialled SuperTreat SB440(N12), however it is marketed by Waipapa Tanks and includes a modified venturi (pat pend) for improved energy efficiency.

Notes on Power Use

  1. The irrigation pump trialled in the Reflection treatment system is too small for most irrigation applications. The electricity use in a Biolytix treatment system in a typical household setup totals about 0.6 kWh per day. Electricity use by irrigation pumps associated with household wastewater treatment systems is around 0.5 kWh per 1000 litres (i.e. approximate average household daily flow). This will vary depending on pump efficiency, difference in elevation, distance to irrigated area, pipe size etc.
  2. The electricity usage figures presented need to be treated with caution. Various factors could influence them including blockages and pump efficiency. Note that only some systems included irrigation pumps in the trial.
  3. The annual power cost was calculated using a nominal cost per kWh of 20 cents plus GST. The exact cost will vary depending on the region, pricing plan and discounts available.

Trial 4 Note

Trial 4 testing was the first full trial under OSET NTP supervision. SWANS-MAG Trial 4 and subsequent audit reports are available on request through the individual companies. Company contact details are available from the WaterNZ website.  

These comparative results reports are not publicly available as they are restricted to Funding Partners only. However, the performance certificates are available to the public at the WaterNZ website.

Other factors to consider:

Visit our page about choosing a system.

If you want to install an advanced system, Rule 13 of the On-site Effluent Treatment Regional Plan applies.

Existing conventional septic tank systems in Rotorua Lakes' catchments

Refer to Rule 2 of the On-Site Effluent Treatment Regional Plan for more information.

Standard septic tanks

Outside the Rotorua Lakes' catchments new conventional septic tank systems can be permitted, provided that the conditions of Rule 3 and schedule 1 of the On-site Effluent Treatment Regional Plan are met. Refer to the Onsite Effluent Treatment Regional Plan to view these.

When dealing with district and city councils it is helpful to have a printout of tables 6 and 7 of schedule 1.

Advanced wastewater system

If you want to install an advanced system rule 12 of the On-site Effluent Treatment Regional Plan applies.

Choosing a system

Things to consider when choosing an advanced wastewater treatment system (not a septic tank system):

Fixed Costs - When getting a quote, check if it includes delivery, and installation. Does it also include the irrigation system and pump?

Running Costs - Do these include electricity, maintenance, servicing, etc? Use the table above in the 'Yes I am in a Rotorua Lake catchment' section to get an indication of electricity usage of the models we have tested.

Servicing/Maintenance - How often is this required? What is involved? How much servicing is included in the purchase price? Who is available to repair the system if it breaks down?

Operation - Is it noisy? Does it smell? How does it handle peak loads - for instance for the extended family at Christmas time. Some chemicals and cleaners can cause the useful 'bugs' to die off, which can result in the entire system malfunctioning.

Size - How much space does it require?

Warranty - What guarantees are offered?

References - Check at least one or two references from people who own them.

Compliance with Regional Plan

Will the manufacturer take responsibility for ensuring that the system meets the regional plan requirements, including providing the necessary certification to Bay of Plenty Regional Council? Refer to rule 12 or 13 of the On-Site Effluent Treatment Regional Plan.