Ohope WW Resource Consent Renewal
How Ohope wastewater system operates
Wastewater is collected from properties and conveyed through a network of pipes and pump stations to the wastewater treatment plant (oxidation ponds). Solids larger than 2.0mm are removed and disposed to landfill. The remaining wastewater is treated through the oxidation pond system and discharged to the Ocean via an outfall pipe.
Resource consent is required to continue disposal of the treated wastewater to the ocean. The existing Resource Consent expires on 31 July 2010.
What do oxidation ponds do?
Oxidation ponds are a simple secondary treatment of effluent using natural resources. Bacteria degrades organic matter in wastewater using oxygen and sunlight. This produces cellular material and minerals which support the growth of algae in the ponds. The growth of algae facilitates further decomposition of the organic matter by producing oxygen which is then used by the bacteria.
Present treatment plant
The present treatment system was upgraded in 2003/2004 to meet the existing Resource Consent conditions. Since then the wastewater system has been operating reasonably well. The quality of the water in the ocean at 100m from the diffuser (where the treated wastewater outfall in the ocean is) meets Bathing Water Quality Guidelines.
Future treatment options
The following three options were considered for the Ohope wastewater system:
- Do nothing – This option is unlikely to be pursued as future Resource Consent are likely to require better quality effluent discharged in to the environment.
- Complete new treatment system using advanced technology – Although an advanced treatment option will produce much better quality effluent, the cost of installation, ongoing operations and maintenance will be very high.
- Upgrading of existing treatment plant in stages to produce better quality effluent and to meet the future demand – This option is the preferred option as it will improve the effluent quality and the cost of construction, ongoing operations and maintenance will be lower.
The third option of upgrading the exisitng treatment plant in stages has been selected following discussions with the Working Party and community consultation.
The Resource Consent has been lodged and will in due course be notified.