Covid 19 Delta outbreak: Wastewater testing shows no sign of virus

Whanganui wastewater samples are collected twice a week and cover the whole of the Whanganui urban area and Marybank. Photo / Bevan Conley

Latest wastewater testing shows no sign of Covid-19 in Whanganui.

Whanganui District Council's general manager of infrastructure Mark Hughes said that, as of Thursday morning, wastewater testing from Whanganui samples had not delivered a positive Covid-19 result.

The council has been providing wastewater samples for testing since August 23 as an extra tool to help monitor for the SARS-CoV-2 virus, which causes Covid-19.

Wastewater is also being tested in neighbouring areas including Feilding, Levin, Palmerston North, Taumarunui and Taranaki.

Wastewater is used water from toilets, showers, baths, basins, sinks and laundries that passes through the sewerage system. A positive detection in the wastewater indicates that at least one person has been shedding the virus into the wastewater in the 24 hours before each sample was collected.

Samples from Whanganui wastewater are requested and tested by the Institute of Environmental Science and Research at their Wellington lab on behalf of the Ministry of Health.

Hughes says Whanganui wastewater samples are collected twice a week and cover the whole of the Whanganui urban area and Marybank.

"The samples that the council provides are 24-hour flow proportional composite samples covering the periods Monday morning to Tuesday morning and Thursday morning to Friday morning," Hughes said.

The one-litre flow-proportional composite samples are where a pump automatically collects a small volume of wastewater periodically over 24 hours. Instead of fixed time intervals (every 15 minutes) the collection frequency varies according to the flow. The higher the flow, the more frequently the pump takes a sample.

"If a positive wastewater test is found for Whanganui wastewater, the protocols around informing the DHB and the council are activated by the Ministry of Health.

"[As of this morning,] we have not received a notification that there has been a positive Covid-19 result via wastewater testing from Whanganui samples."

Whanganui District Health Board also confirmed yesterday there had been no notification of any detection.