Wastewater Treatment ProcessTe Whare O Whiro

Depending on where your house is it takes between three to five hours from the Hastings urban area.

The treatment process takes approximately 40 minutes.

The final combined treated wastewater discharge (domestic and industrial) is cloudy due to excess biomass (organic material) from the domestic wastewater treatment process. The biomass in the biological trickling filters transforms the ‘bad bacteria’ to ‘good bacteria’, this is then discharged out to sea. There is no sludge production from this treatment process.

The establishment of this wastewater treatment plant has been a highly collaborative and effective process with tangata whenua.

Working together, the Biological Trickling Filter (BTF) wastewater treatment was identified as the most effective way to biologically transform kūparu (human waste) within domestic wastewater to a culturally and environmentally acceptable state. Pilot studies demonstrated that treatment occurs in a natural way, harnessing microorganisms to do the work.

In addition to the BTF, the Rakahore passage was also introduced to the treatment process in order to restore the mauri of the treated waste stream through contact with Papatūānuku. Rocks were selected by local iwi and blessed for this purpose, and this contact happens immediately before the waste stream is released into Hawkes Bay, Te Moananui a Kiwa (via the ocean outfall). 

HDC has worked alongside tangata whenua since 2000. The consent issued in 2001 included conditions that specifically required equal decision-making between HDC and tangata whenua during the search for a culturally acceptable treatment and disposal solution for the plant. A significant period of engagement and consultation was undertaken between 2003 and 2009 to arrive at the BTF and rock passage (later named the Rakahore passage) as a culturally acceptable solution.

The HDC Tangata Whenua Joint Wastewater Committee was formed under the Local Government Act 2002 (previously LGA 1974). Half the members must be tangata whenua, and this committee continues to this day. To our knowledge, this is the only arrangement of its type in New Zealand, with a joint committee having decision-making powers as a sub-committee of the council.

Under the resource consent requirements, a wide range of regular monitoring of the treated wastewater discharge into the ocean is undertaken every year. We monitor:

• the wastewater arriving at the plant
• the wastewater immediately after treatment (prior to discharge)
• the conditions in the area of sea between 100 metres and two kms from the ocean outfall.
• the sea floor in the vicinity of the outfall
• marine life (including shellfish) in the vicinity of the outfall
• odour (e.g. any bad smells at the plant or outfall)
• colour and composition of the treated wastewater discharge.

Once a year we submit a report to Hawke’s Bay Regional Council detailing all or the monitoring results and compliance with the consent conditions. These reports are publicly available on the Hastings District Council website. Every nine years, the consent for the East Clive discharge is reviewed to ensure that environmental and cultural values are being protected to the best of our abilities, and to identify opportunities for improvements. The first of these reviews under the current consent is underway and is scheduled to be completed in early 2024.

Sea level rise and coastal retreat could impact the site, and will also results in higher ground water levels across the district increasing the amount of water getting into the wastewater network, producing more wastewater to process. Extreme wet weather will also increase inflow and infiltration resulting in increased wastewater flows, which could lead to overflows in the network. The emergency beach outfall can be used in situations where the ocean outfall is out of operation for critical maintenance, or other reasons such as an emergency.

We are looking into the impact of climate change on the wastewater treatment plant to better understand what the impact will be and when this will occur to ensure the ongoing treatment of wastewater for the Hastings district.

Different components of the East Clive Wastewater Treatment Plant have different lifespans. For example, concrete components typically last 50 years or more (tanks, pipes, chambers), mechanical components 20 to 30 years, (pumps), and electrical equipment 15 to 20 years. Routine maintenance, inspections, assessments and planned renewals ensure that equipment remains fit for purpose for the expected lifespan and that infrastructure is renewed and upgraded as necessary. This allows operations to continue uninterrupted and the treatment plant to cater for future population growth and be resilient to climate change.

The East Clive Wastewater Treatment Plant has a consent to discharge treated wastewater until 2049.

Annual expenditure to maintain the East Clive site ranges from $1 million to $1.3 million.

The East Clive Wastewater Treatment Plant has proven itself to be a leading-edge, technically robust, cost-effective and culturally acceptable facility. The design and operation of this plant has challenged conventional approaches to municipal wastewater treatment in New Zealand, particularly in its use of the ‘no sludge’ BTF solution. Traditionally, New Zealand municipal plants use primary and secondary treatment using clarifiers (large tanks where wastewater is held over several hours to allow solids in the waste stream to fall out of suspension). The BTF process was a first of its kind in New Zealand, and potentially internationally. It; uses natural biological activity to transform the human waste components of wastewater into plant cell biomass, carbon dioxide and water. This is then discharged through the Rakahore (rock-lined) passage to spiritually cleanse the treated human waste before its disposed via the 2.75km-long offshore ocean outfall.

The innovative arrangement meets tangata whenua aspirations, complies with resource consent conditions and eliminates the requirement for any sludge treatment and disposal.

Other councils have followed Hastings’ lead in Napier, Gisborne and Greymouth to date.

Yes, recreational fishing and commercial flatfish dredging happens near the outfall. Regular surveys of flatfish monitor the impact of the treated wastewater discharge.

Having the two is more economically effective and targeted, allowing for the different treatment needs of both to be met. The two types of wastewater are:

1. Domestic and non-separable Industry stream (DNSI): Non-separable industry wastewater is treated on-site to comply with Council’s Water Services Bylaw, and is discharged along with the domestic wastewater to the WWTP. It is treated by screening through a 3mm diameter hole screening unit and then treated through the two BTF’s and passes through the Rakahore passage before joining the separable industrial wastewater stream.

2. Separable industrial wastewater: This is treated on-site to comply with the Water Services Bylaw prior to discharge into Council’s industrial wastewater collection system. It is screened through a 1mm slotted screen before being mixed with the treated DNSI wastewater stream and then discharged to sea via the ocean outfall.

Since the current resource consent was issued in 2009, the plant has generally complied with the consent conditions aimed at ensuring the discharge does not have a harmful effect on Hawke Bay.

The collated information indicates there has been no noticeable changes in the condition of the ecosystems in Hawke Bay (within the area potentially affected by the discharge) as a result of the discharge. This includes water quality, potential risks to human health, aquatic ecology, and benthic (seabed) sediments and fauna.

The current consent for the discharge of treated wastewater into Hawke Bay through the offshore ocean outfall expires in 2049. Prior to that date, full investigations will need to take place to determine the requirements for a new consent. Before the consent expires there will be two further nine-yearly reviews.