Weekly testing of wastewater downstream of where the Queenstown Lakes District Council(QLDC) has an emergency discharge consent, is showing low levels of E.Coli.

A new water monitoring programme started at the end of March at sites adjacent to, upstream of and downstream of the Shotover wastewater treatment plant.

Otago Regional Council chief executive Richard Saunders said some initial monitoring on the first day of the discharge showed some high levels of contaminants present, “which can be expected with the flushing of the wastewater outlet channel, which bypasses the disposal field.”

Preliminary monitoring results from the second week (April 7), showed low levels of E.coli at the treatment plant outlet, which gave the regional council confidence processes were operating as expected, he said.

Treated water samples taken on any given day would take at least 10 days to be processed by the independent laboratory and returned, and then be assessed by staff, before being added to the ORC website.

Compliance updates and sample results are publicly available on a page dedicated to the Shotover Wastewater Treatment Plant. It can be accessed here 

The six water testing sites that the Otago Regional Council have added since treated wastewater started being discharged into the Shotover River.SUPPLIED.

Richard said alongside the regular testing, staff would continue to respond to any complaints from the public when reported - but made it clear at the last council meeting they could not monitor the sites 24/7.

Read more: Systemic failure of ageing wastewater treatment plants highlighted

Richard highlighted the regional council had taken several steps since problems arose with the plant’s operations, going back to 2021.

On January 23, ORC sought an Enforcement Order from the Environment Court to address current compliance issues at the treatment plant, and that process was ongoing. 

The application followed the issuing to date of two abatement notices and 10 infringement notices.

Richard said the Environment Court mediation was ongoing; however they were hopeful for an outcome in the near future.

“It’s important to note that QLDC is responsible for ensuring that the discharge from the Shotover plant remains compliant with the consented limits. Where there are issues identified by QLDC staff or contractors we expect these to be reported to ORC,” he said.

The Shotover River feeds into the Kawarau River downstream, which then enters Lake Dunstan at Cromwell. FILE SHOT

The first samples taken on March 31 were from the discharge channel itself and upstream and downstream in the Shotover River. 

Those samples showed E. coli levels of 730 CFU (colony-forming units) per 100mL of water in the discharge channel and 370 CFU/100 mL at the downstream location.

“These higher E. coli results are not a reliable indication of the treatment performance of the Shotover WWTP, as they were taken after the discharge left the treatment process and were likely affected by the first flush of any natural materials in the channel, such as rabbit droppings and decaying vegetation.”

The sampling round conducted on April 7 was more extensive and included the final discharge at the official sampling point downstream of the UV tertiary treatment stage as well as the discharge channel and other upstream and downstream locations.

The Shotover final effluent sampled at the official point post-UV was fully compliant with the consent limit of 260 CFU/100 mL, showing an extremely low result of less than 1 CFU/100 mL. 

The sample taken in the discharge channel April 7 showed E. coli was 4 CFU/100 mL.

For comparison, in New Zealand, the drinking water standard for E. coli is less than 1 CFU/100 mL.

Follow this story next week when we look more into other council’s discharge consents including the Central Otago District Council.