After Wessex Water wrote to residents recently about their netting trial at Frome Water Recycling Centre (see here) we had a very positive meeting with their area wastewater manager and scientific team, with MDC’s Environmental Health Officer, councillors Janine Nash (MDC) and Steve Tanner (FTC) and three local residents.

The monitoring during the trial revealed that the netting installed by Wessex Water in March over five of the nine sewage treatment filter beds has reduced the number of adult flies leaving the five netted filter beds by c. 80-90% compared to the four other filter beds. Retaining and monitoring the un-netted beds as a scientific control has enabled Wessex to clearly demonstrate the effectiveness of the netting, and could be written up as a paper to inform the water industry (it is understood that no other water company has undertaken this). To date they have also not seen any detrimental effect on water quality leaving the works.

As a result, to control fly numbers, Wessex Water will install and maintain netting at the remaining four filter beds in August and review the results next spring. Monitoring of fly larvae and flies coming off (and under) the nets will continue, with the trial extended to June 2023, after which another meeting will be called. During the extended trial, the frequency of larvicide use will be reviewed. Assuming the success continues, Wessex Water intend to keep the nets installed permanently, and will update the Fly Management Plan accordingly. Things do look very positive, although nothing is guaranteed. The nets need daily maintenance to clear moss and other vegetation, including from a new full-time site maintenance operative, as well as regular monitoring, to ensure the nets are not blocked and wastewater treatment is not affected. Care will be needed when nets are periodically removed (perhaps every 3 years) for cleaning, to not release flies underneath.

The idea of netting the filter beds was pursued by local resident Joe Chedburn, who researched the issue and persuaded the company to look into netting again early this year. The extent of the fly nuisance problem being suffered up to this spring was highlighted in our residents survey (see here). Wessex Water have clearly responded with enthusiasm and commitment, led by Paul Knight (head of waste water for the area) and their scientific team who are clearly on top of the situation, so they deserve credit for that. Thank you to everyone who contributed to the survey, and to all other local councillors who helped residents with this – you have made a difference here.

Wessex have also recently installed over 100 bat and swift boxes on site (and residents have installed more on local houses), and WW ecologists have identified a bat colony on site, which will help reduce fly numbers further through predation in spring and summer.

As ever, please let Wessex Water and MDC know if there is a problem from fly nuisance or odour or noise associated with the works – see here. Please also let me know if there continues to be any problem.

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