Wetlands trial 2016
We carried out trials to see whether treated human wastewater could be spread on to native plants in a wetlands complex.
With ESR, NIWA and the Centre for Integrated Biowaste Research – we trialed growing wetland plants in barrels filled with sand and gravel at our city's wastewater treatment plant.
For decades, Gisborne’s untreated wastewater was discharged on to city beaches at the low tide level, leaving the high tide to wash the sewage away.
In 1965, an innovative new system saw wastewater discharged 1.8km into the bay through a new outfall pipe.
From 1991, sewage was put through a screen to remove the “lumps” before being discharged to sea. But there was no treatment as such.
In 1988, East Cape Catchment Board was set to prosecute Gisborne City Council because of a more than 50 percent increase in discharge over 20 years.
Council gained permits through to 1999 on the condition a long-term disposal scheme was put into action. It had to gain new coastal permits to continue using the outfall and this called for an upgrade – by then strongly influenced by legislation and regional plans, which place high values on meeting tangata whenua concerns. Tangata whenua and others in the community wanted no wastewater discharge to sea.
A Wastewater Working Party was formed in the late 1990s to find out what the public wanted but progress towards the ‘zero waste to sea’ goal was slow.
In 2005, the Environment Court criticised council’s lack of progress.
In 2007, 35-year resource consents were granted. The build of the $39.5m wastewater treatment plant in Banks Street started in late 2009. The plant was operating in December 2010.
More information on the city's wastewater treatment plant
Where we're heading
What’s happening now?
Our 2007 wastewater consent said ultra-violet disinfection had to be added to the Biological Trickling Filter (BTF) treatment plant by the end of 2014.
Since the BTF began operating in 2010, Council, WTAG members and their science partners researched various parts of the plant’s operation to see how well it was working. With increased knowledge, they realised the high cost of installing disinfection treatment would be better spent on an alternative system. Wetlands offered a more cost-effective, sustainable long-term result but more time was needed to investigate this option. A variation to the consent, granted in May 2015, allowed time for trials. If these are successful, and Council approves, construction of a wetland complex could begin in late 2019. The aim of ridding the bay of human wastewater could be a reality by late 2020.
Three groups were set up as conditions of the 35-year wastewater resource consents granted in September 2007 – the Wastewater Management Committee, an Independent Review Panel and a Technical Advisory Group.
Wastewater management committee
This is a statutory committee of Council comprising 4 councillors and 4 tangata whenua representatives of Turanganui a Kiwa. Part of its role is to:
- commission and monitor the wastewater treatment plant in line with consent conditions
- explore and recommend feasible options for alternative use and disposal of domestic and industrial wastewater
- identify, monitor and plan projects to improve the mauri and water quality of Turanganui a Kiwa (Turanganui a Kiwa Water Quality Enhancement Project)
- ensure appropriate educational information is developed to help reduce domestic and industrial wastewater.
Independent review panel
Three people with expertise in wastewater management, resource management and kaupapa Maori were appointed to this watchdog group overseeing the wastewater upgrade.
Wastewater Technical Advisory Group (WTAG)
This group was asked to monitor the BTF plant and guide a 3-year study to find out if the treatment process was effective and how much biotransformation was being achieved.
Individual members, representing tangata whenua, council, industry, health, environment and science, have looked at social, environmental, economic and cultural aspects of biotransformation, and chemical, physical, biological and atmospheric components.
The group works with the community and council to manage the kaitiakitanga, guardianship, of the treatment process.
As part of investigating the feasibility of a wetland, WTAG is involved in 5 work streams:
1 Overall wetland design – how a complex should be engineered and constructed to achieve most effective wastewater management. WTAG is working with NIWA scientists Dr Chris Tanner and Dr Jason Park, and Centre for Integrated Biowaste Research (CIBR) environmental microbiologist Dr Jacqui Horswell on Council-CIBR joint funded trials at the Banks Street wastewater treatment plant to investigate the most appropriate plant species and growing media to use in the wetland design.
2 Biosolids – looking at ways the biosolids can be beneficially used, eg, as a soil conditioner or compost
3 Virus investigation – looking at how to treat viruses within a wetland and through exposure to sunlight.
4 Sensitive materials – eg, mortuary waste and emerging organic contaminants like triclosan that could bioaccumulate in organisms
5 Alternative use – looking at the best sustainable solution for treated wastewater once it has passed through a wetland complex.
About the wetlands trial
Questions and answers about the wetlands trial