Plant’s deodorising efforts impress neighbours

Results from an independent survey show that deodorising efforts at North Shore City’s wastewater treatment plant continue to impress neighbours.

The survey in March this year assessed the effectiveness of odour control at the 45 year-old plant, and the views of nearby residential and commercial land users.

Chairman of North Shore City Council’s infrastructure and environment committee, Tony Barker, welcomes the findings which reveal a significant decline in the number of people affected by odours since 1999, coupled with an increase in those who believe the Rosedale area smells better.

“We commission independent experts to conduct the survey every two years as required by the plant’s air discharge consent,” Councillor Barker says.

The council has invested $87 million so far upgrading the plant to reduce odours. This has included decommissioning some of the more smelly processes and, in other instances, capping tanks where the air is then extracted and put through odour filters.

“We’re delighted that the huge investment continues to pay off and we’re committed to continuing our long term upgrading programme to improve the plant’s environmental performance,” Tony Barker says.

A sample of 247 local residents and 81 businesses were invited to take part in the door-to-door survey.

Plant manager Steve Singleton says the biennial surveys reveal a trend towards residents and commercial landowners being progressively less affected by treatment plant odours.

“When we conducted our first survey in 1999, 70 per cent of respondents said they were affected by odours. In 2002 it was 48 per cent, in 2004 it was 39 per cent, and this year the figure is down to 19 per cent,” Mr Singleton says.

“Every year we work towards improving the plant’s odour-busting ability and each survey reveals that it’s working better.”

He says recent development of residential and commercial activities closer to the boundaries of the treatment plant is placing considerably greater importance on reducing odours.

Steve Singleton says the survey is just one of the ways the treatment plant measures the effectiveness of odour control.

“Air samples are collected for testing annually. Trained technicians carefully collect samples of air from the different wastewater treatment process units and take them to a laboratory for analysis,” he says.

“The best test remains the human nose. In the laboratory a panel sniff the different samples and come up with what’s termed an odour profile.

“We also have a fortnightly walkover inspection by an independent ‘trained nose’,” he says. “She patrols the plant, both within and around the perimeter, and records and reports any odours.”

The survey was undertaken by URS New Zealand Limited on behalf of North Shore City Council, between March 8 and April 8 this year.

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