QMRA Raglan WWTP discharge

Waikato District Council (WDC) has existing consent to discharge treated wastewater via a pipeline to the channel that connects Raglan Harbour to the Tasman Sea. This consent is, however, due for renewal. Watercare Services Ltd (Watercare, which has a management contract for WDC’s water and wastewater services) is considering a series of options for future treatment and discharge of wastewater. Future options being considered include retention of the existing pond with an ultraviolet (UV) disinfection system, a combination of “pond + tertiary membrane + UV” or a combination of “membrane bioreactor + UV” treatment under varying discharge scenarios (i.e. tidally staged discharge from the existing discharge location or a new outfall, or continuous discharge from Wainui Stream. To support the “preferable treatment and discharge option” decision-making process, Watercare commissioned QMRA Data Experts (QDE) to conduct an initial Quantitative Microbiological Risk Assessment (QMRA) to address health risks related to treated wastewater discharge into the Raglan Harbour, for each of the considered discharge options and treatment scenarios