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Late last week, NPDC’s Cath Yateman got a call she had hoped would never come: two consecutive wastewater samples had tested positive for traces of Covid-19.

Cath is the Laboratory Lead at the New Plymouth Wastewater Treatment Plant, which receives wastewater from Ōākura, New Plymouth city, Bell Block, Inglewood and Waitara, and twice every week since the trans-Tasman bubble opened, samples have been sent to ESR in Wellington to check for traces of Covid-19. 

“It was confirmed at 7pm that night, on a Friday,” she says.

“Later that evening I was planning our follow-up tests with ESR, then at 7am the Saturday morning I was back here at work preparing everything I’d need for wastewater samples to be collected from separate lines to the treatment plant.”

The follow-up work required samples from each separate inflow so that if more Covid traces were found, NPDC and ESR could narrow down the area of New Plymouth District it came from. That included taking mobile wastewater samplers to some sites.

Cath and other NPDC staff ended up working through the weekend to make sure the 24-hour composite samples were properly collected.

The team will continue to send the additional sample to ESR every day until the Ministry of Health advises we can return to the regular composite samples twice a week.

“Some people are in this job because they really like working with wastewater and the systems here; I do it because I like keeping the community and environment healthy,” she says.

During summer 22 million litres of wastewater goes through the New Plymouth plant every day but at this time of year, with the winter rains, it rises to 30 to 40 million litres per day.

The plant has a rigorous treatment process of screening, aeration, clarification and disinfection. Cath’s team has the crucial job of making sure the treated wastewater is safe and clean enough to be discharged back offshore.

“This is very much a high-achieving lab with intelligent people working hard on a number of projects while day to day making sure our wastewater meets the right treatment standard,” she says. “Our main thing is that with everything we do, we’re working for a better environment.”