In a statement last week, the district council said it had received an abatement notice from the ORC because the Hāwea plant failed to achieve its 12-month rolling mean for nitrogen levels in its treated wastewater discharged to an oxidation pond on site.
The notice came amid QLDC’s troubles at its Shotover treatment plant, which is discharging 12,000 cubic metres of treated wastewater directly into the Shotover River daily, bypassing the plant’s failing disposal field.
Otago regional councillor Michael Laws said the failure at QLDC’s Hāwea plant provided further evidence of past under-investment in infrastructure, which had been exposed by rapid population growth.
However, a QLDC spokesman said the Hāwea wastewater treatment plant, while approaching capacity, was not overloaded.
"The plant is consented to receive an average daily flow of 370 cubic metres per day, at an average total nitrogen concentration of 35mg per litre.
"The average daily flow over the past 12 months has been 366 cubic metres per day, so while the plant has very limited capacity to accept additional connections, it continues to meet current demand."
He said prior to 2023, the plant consisted of a traditional oxidation pond with supplementary aeration.
"The plant was unable to achieve compliance with the resource consent at the time and was subject to an abatement notice associated with persistent non-compliances — namely exceedances of the ammonia and nitrogen concentrations in the discharge, and the associated usage of the land treatment area (LTA)."
Given historical non-compliance of Hāwea’s treatment plant and the need to cater for significant growth in the catchment, he said plans were already in place to connect the township to Project Pure/Wānaka Wastewater Treatment Plant.
"This planned connection is part of the wider Upper Clutha Wastewater Conveyance Scheme project, which will see significant investment in wastewater management capacity across both the Hāwea and Wānaka schemes."
Funding for the project was included in the adopted QLDC Long-Term Plan 2024-34, and had an overall budget of $80.1 million which included about $22 million of funding from the Infrastructure Acceleration Fund, he said.
"As a result of the timeframe to implement this long-term solution, investment was made to upgrade the existing plant during 2021-22 to improve its performance, funded through a 3 Waters Reform Stimulus grant.
"The upgrade employed a side stream process to reduce the levels of ammonia and nitrogen in the treated water, with improvements also made to the oxidation pond and LTA.
"A new resource consent was also obtained at this time, expiring July 7, 2033."
Following the commissioning of the upgraded facility in February 2023, the plant had largely performed as anticipated, he said.
However, the operational team had encountered some challenges in "learning and optimising the new treatment process", which resulted in fluctuations which have impacted the plant’s 12-month rolling average nitrogen levels.
He said the present average of 41mg per litre was above the consent requirement of 35mg per litre.
"The elevated nitrogen levels are predominantly being driven by challenges in managing the algal solids in the discharge, which contain organic nitrogen.
"The upgrade is actually largely performing as intended and we are focused on optimising operations to enable compliance."
