Fly swarm control at Burton-on-Trent STW

Severn Trent has taken a new approach to fly control at Clay Mills STW in Staffordshire. The plant, which serves Burton-on-Trent, uses biological filters to treat sewage with a high proportion of brewery waste.

In summer, Psychoda flies from the filters have become a persistent nuisance to the public who live close to the works.

Fly monitoring

Mr Williams said: “We need more adult fly data to obtain a clear picture of the seasonal variation in flies and the effectiveness of the control measures. Adult fly monitoring is very labour intensive, so we have streamlined the process.

Sticky card traps have been used along with an abundance rating system. Mr Williams said: “Instead of counting each fly, we can compare the number of flies on each trap with reference photographs, each of which relates to a particular % coverage of flies. It takes less than a minute to make an assessment.”

This task is now completed by the site operators. Adult fly emergence is routinely monitored to ensure that adequate control steps are taken.

Mr Jordan is now waiting to decide if it will be necessary to extend the existing control measures: “We have decided to be cautious about the low frequency dosing option.

“The change in filter ecology that it has induced, although reducing Psychoda, could encourage colonisation by other fly species, so we are continuing to monitor fly numbers for another season.

“However, we have decided to extend the fly screen and are currently erecting a further 300m of screens around the second filter unit.”

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