Discharge to water

There are separate treatment requirements that are tailored to small wastewater treatment plants that service very small populations. More information will be available once standards are enacted.

The discharge to water standards will be implemented through future resource consents for public wastewater treatment plants and networks as they come up for renewal or new infrastructure is consented.

The certainty generated by wastewater standards will help to streamline these consent processes and decisions.

Plain language definitions and guidance will be developed for key elements or requirements of the standards, such as:

• monitoring and sampling requirements (e.g. 90th percentiles)
• clear indications where standard provisions are to be adopted as consent conditions
• parameters of a breach and expected responses.

More detailed guidance will be developed, including  best practice examples for procedural elements of the standards. Some examples are set out below.

• The discharge to water standards require the use of a Quantitative Microbial Risk Assessment (QMRA) when a proposed discharge is in a certain proximity to shellfish gathering beds. To ensure a nationally consistent approach to QMRAs, guidance will be developed to outline the proposed QMRA rationale, methodology and assumptions.
• Periphyton is the slime and algae that grows on the bed of primarily hard-bottomed waterbodies such as streams and rivers. While it is essential for healthy ecosystems, periphyton can have significant environmental impacts when it proliferates. For discharge to environments where periphyton may be impacted, a risk assessment will be required. Guidance will be developed that outlines the proposed assessment methodology and outcomes.

Consenting authorities such as regional councils implement the standards through consents as they come up for renewal. Consenting authorities maintain responsibility over how discharges to land and water should be managed, e.g. whether they should be treated as a non-complying activity.

Where a regional plan enables discharges of treated wastewater to land or water, a consenting authority cannot grant a resource consent that imposes requirements that are different from those in the standards. This includes treatment limits for core contaminants, as well as monitoring and reporting requirements. Where a consent is approved, it must be issued for a 35-year duration.

Consenting authorities maintain discretion over matters not covered by the standards, e.g. the volume and timing of treated wastewater being discharged and limits for other contaminants.