Biological filtering treatment (also known as biofiltration or biological filtration) is a wastewater treatment method that relies on microorganisms – primarily bacteria but also protozoa and fungi – attached to filter materials to break down and remove organic pollutants from the water.
The treatment method is well established, both in New Zealand and overseas. It is relatively economical and simple to operate when compared to most other treatment processes and does not require sludge transportation or disposal costs. It also avoids the use of chemicals, which would eventually become part of the discharge.
Industrial waste is also received at the Awatoto Wastewater Treatment Plant but does not pass through the biological filtering treatment system. A separate building houses rotating screens specifically for industrial waste flows and the domestic grit classifier equipment.
Napier’s treated wastewater meets strict discharge consent conditions set by Hawke’s Bay Regional Council. Regular testing and monitoring show that the environmental impact on Hawke Bay remains low, although some challenges have been identified and are being addressed, including:
Post-Cyclone Gabrielle, sampling results have been compliant with consent standards.
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Council has almost finished building two new storage cells (ponds) at the Awatoto Wastewater Treatment Plant, adding nearly 31,000m³ of capacity. These will help manage peak flows during heavy rainfall and reduce the risk of overflows into waterways.
Council is required to monitor and report on the performance of the wastewater treatment plant every year, with an in-depth review every three years. The plant’s processes and discharge are regularly reviewed to ensure discharge standards meet conditions set by Hawke's Bay Regional Council. Where upgrades may be required to meet proposed national environmental performance standards, planning, budgeting and consultation take place to ensure an appropriate treatment option is selected.
Napier City Council is currently reviewing its wastewater treatment processes and developing a masterplan to refine treatment options, set priorities and forecast budgets for future improvements, including alignment with new national standards once they are finalised.
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