On-Site Effluent Treatment (OSET) National Testing Programme (NTP)
About
The On-site Effluent Treatment (OSET) National Testing Programme (NTP) undertakes performance testing of ex-factory on-site wastewater treatment units at its testing facility (OSET TestFac) located within the Rotorua City Wastewater Treatment Plant.
Background
The OSET NTP was established in 2008 under a Memorandum of Understanding (MOU) between Environment Bay of Plenty (EnvBOP), Rotorua District Council (RDC), Water NZ, and SWANS-SIG (Water NZ Small Wastewater and Natural Systems Special Interest Group).It provides a testing and benchmarking facility for ex-factory on-site domestic wastewater treatment units. Benchmark testing is a pre-cursor to a parallel field testing programme.
The first NTP trial commenced November 2008 as Trial 4 following the Environment Bay of Plenty/Rotorua District Council earlier nitrogen reduction Trials 1 to 3 during 2005 to 2008. Trial 5 commenced November 2009. NTP trials are overseen by a Technical Manager (SWANS-SIG), Operations Manager (RDC), Reporting Manager (EnvBOP) and Laboratory Manager (RDC).
Accreditation / Audit Process
Each trial runs from November through to July, with a 2 month settling in period followed by a 6 month test period (of which the last three months involves benchmarking of six treated effluent quality parameters) and a 1 month high load test.Data sets from the laboratory testing are analysed and reported on by the Reporting Manager. A SWANS-SIG Management and Auditing Group (SWANS-MAG) has been established to review the test results and compile a benchmarking and performance certification report. This report assesses treatment performance in meeting the secondary effluent treatment requirements of AS/NZS 1547 for biochemical oxygen demand and total suspended solids, and in addition benchmarks the median values of treated effluent quality for biochemical oxygen demand, total suspended solids, total nitrogen, ammonia nitrogen, total phosphorus and faecal coliforms. Average daily energy consumption is also assessed.
SWANS-MAG is made up of representatives of SWANS-SIG, Environment Bay of Plenty, Rotorua District Council plus two independent wastewater specialists, and is administered by the NTP Technical Manager. The benchmarking and audit reports are provided to the individual manufacturers, the MOU Partners, and those Regional and District Councils providing financial grants as Funding Partners to the NTP.
Current Funding Partners are (April 2010):
- Environment Bay of Plenty
- Environment Waikato
- Rotorua District Council
- Gisborne District Council
- Marlborough District Council
- Auckland Regional Council
- Hawke’s Bay Regional Council
The OSET TestFac
The OSET testing facility is focused on security and repeatability for every trial by ensuring that there is a fair and accurate comparison for every participant.The trial sites are fully fenced (Figure 1 - below) and have multiple surveillance cameras installed. Each of the 7 sites has its own header tank with a certified volume. Once these tanks have been filled by the raw sewage pump the process is then gravity fed to the individual sites with the release of wastewater controlled by PLC to closely as possible follow a typical household flow.
Each header tank is currently filled with 500 litres twice per day with raw sewage to ensure the wastewater is fresh and has not settled. The 1,000 litres per day test flow volume represents a daily flow from a three bedroom 5 person occupancy dwelling.
Each site is 8m x 3m and is fitted with a 50mm slip fitting at an invert of 2.7m for the raw sewage supply, 25mm discharge point with a flow meter and 5lb back pressure valve for the treated effluent, 240V hard wired electrical point and a kW hour meter.
The system is fitted with many fail safe measures that are fed into a SCADA system with any failures sent to the operator on call via cellphone. There is a redox probe that monitors the wastewater, a flow switch which alarms if the pump is called to start and there is no flow and each individual header tank is fitted with a level monitor that will sound an alarm if the tanks fail to fill in a set time.
Laboratory Services
The RDC Environmental Laboratory is IANZ accredited (ISO17025:2005) and Ministry of Health approved to provide water testing services, and offers a comprehensive range of tests.Tests for the OSET NTP include:
- Alkalinity
- Biochemical oxygen demand
- Faecal coliforms
- Temperature
- Total suspended solids
- pH
- Total phosphorus
- Ammonia
- Nitrite
- Nitrate
- Total kjeldahl nitrogen
- Total nitrogen
- Total oxidised nitrogen
Operation and Funding of the Testing Programme
Establishment of the OSET NTP was funded by grants from the Ministry for the Environment, the Water Services Managers' Group of Water New Zealand, contributions in kind from Environment Bay of Plenty and Rotorua District Council, and grants from Establishment Funding Partners Environment Waikato and Gisborne District Council. The NTP involves benchmark testing at the Rotorua National OSET Test Facility, field testing of specific treatment unit models installed around NZ following benchmark testing, and product testing and certification to ensure structural and component operational integrity (Figure 2 - below).Manufacturers cover their own costs in setting up their test units at the facility, and are then charged a fee which includes site rental/operational costs during the 9 month test period together with all sampling and analytical costs.
Technical management and SWANS-MAG benchmarking and auditing activities are covered by Regional and District Council Funding Partner financial grants. A funding pool has been established to cover the supervision and audit costs for the benchmarking, field testing and product certification procedures.
Councils are one of the main beneficiaries of the national testing programme in that they will have certainty regarding performance certification of on-site domestic wastewater treatment units in replacing septic tank systems in areas with increasing demand for unsewered wastewater servicing. These include new subdivisions in rural residential and holiday area locations, and existing development where conventional on-site systems do not adequately protect environmentally sensitive land and natural water.
Only those councils supporting the OSET NTP as funding partners will have exclusive access to reporting on the comparative test results for each trial.
Trial Results
The reports on the nitrogen reduction Trials 1 to 3 under EnvBOP and RDC management are available on the EnvBOP website at: www.envbop.govt.nz/Environment/Rotorua-Lakes-Catchment.aspxDetails of the results of the NTP testing results will be restricted to the individual participating manufacturers and the Regional and District Council Funding Partners. Contact details for those manufacturers/suppliers whose treatment units have been performance tested under both the EnvBOP testing (Trials 1 to 3) and subsequent OSET NTP testing (Trial 4 onwards) are available in the On-Site NewZ Directory of New Zealand manufacturer/suppliers.
Download the directory
Trial 3 Performance Certification
Since publication of the EBOP test reports for Trial 3 participants SWANS-MAG has undertaken a review of the Trial 3 results and prepared audit reports and performance certificates as a means of evaluating the OSET NTP reporting and certification procedures. The SWANS-MAG Trial 3 audit reports are available on request through the individual companies.The participating companies and treatment systems audited are:
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Contact details for individual companies are listed in the manufacturers/suppliers directory.
The comparative results report for Trial 3 is not publically available as it is restricted to Funding Partners only. However, the performance certificates for each of the four treatment systems above are available to the public as below.
View and/or download performance certificates for Trial 3 treatment units:
OSET NTP Contacts
Acting Technical Manager:SWANS-SIG - Ian Gunn
ian.gunn@extra.co.nz
Operations Manager:
RDC - Alistair Bell
Alistair.Bell@rdc.govt.nz
Reporting Manager:
EnvBOP - Sam Weiss
Sam.Weiss@envbop.govt.nz
SWANS-MAG:
SWANS-MAG Chair - Ray Hedgland
rhedgland@ftl.co.nz
Funding Administration:
Water NZ - Peter Whitehouse
peter.whitehouse@waternz.org.nz
Figure 1: National OSET TestFac at Rotorua District Council Wastewater Treatment Plant
Figure 2: Structure of the OSET Testing and Auditing Process
