Nature River Mel Restoration Group

Nature

River Mel Restoration Group

Early spring is when the river Mel is arguably at its most attractive, with early flowering marginal plants along its banks and the trees coming back into leaf. It is also a time when river levels are high, and we await the exciting first sighting of trout hatchlings. Yes, the river is looking good, but it is increasingly under threat from various factions.

One thing that has been of concern for some time is the quality of effluent released into our river by Anglian Water’s Waste-Water Treatment Plant, otherwise known to most of us as the Sewage Treatment Works (STW). Increasingly we have been concerned about the normal, everyday, discharges into the Mel, as we now see a change in the colour of the water in the river when the sewage treatment works are discharging into the Mel. Moreover, in times of high rainfall, raw or part-treated sewage is also frequently discharged directly into the river. Published data show that in 2020 this occurred 62 times.

These worries are not excusive to the Mel. The Environment Agency has been quoted in the local press as saying that downstream of us in Cambridge, the Cambridge (Milton) Water Treatment plant has been releasing more treated sewage effluent into the river Cam than its permit allows since 2015. Even the national press has taken up the call to arms, reporting on widespread pollution of rivers and other chalk streams across the country.

With this background in mind, we were very interested to hear that the Cam Valley Forum (CVF), a Cambridge based environmental group that campaigns to protect the River Cam and its environs, had last summer carried out a pilot study to monitor the water quality on the River Cam, as well as at points further upstream in the Rhee. Preliminary samples were taken to test for E coli and other faecal pollutants in the river and at the sewage works at Milton and Haslingfield. Unexpectedly, the results showed that the river Rhee was much more contaminated than the Cam, and that this seemed just as bad further upstream towards the Meldreth-Orwell Road bridge in Malton Lane. This suggested that there must be a major discharge of pollutants, usually associated with sewage (though agriculture can contribute), occurring somewhere upstream of Malton Lane. While there are several sewage treatment works that ultimately discharge into the Rhee, could this, at least in part, be from the Melbourn STW via the river Mel?

So, when the Cam Valley Forum approached the RMRG with their proposals to carry out a more extensive study we were delighted to get involved. The first round of sampling took place in mid-January at multiple points along the Rhee, the Cam and its tributaries. Our task was to collect samples from different points along the Mel at a time when the treated effluent was being discharged. Samples were collected at four points: a sample of the effluent from the Melbourn STW as it was discharging into the Mel, plus a sample of the river water from upstream to act as a direct comparison. Samples were then collected from two further points downstream of the discharge point, in an attempt to understand any dilution effect as the effluent mixes with the natural river flow. Once collected, the samples were immediately taken to a central collection point in Cambridge so that they could be sent by courier to the analytical laboratories for testing. As we write, we are still awaiting the results…

Since collecting our samples, we have heard that the CVF has secured funding from the Technology Partnership (TTP) that will allow two further rounds of comparative testing in late winter and early summer. This should provide a much more robust set of data.

Of course, we realise that these studies are relatively crude and could be affected by many variables, such as the level and flow rate of the river at time of sampling. However, they will be highly indicative. We hope that this study is just the beginning of our understanding of how STWs affect our local rivers, and that it will lead to improved water quality in not only the Mel, but in all our local rivers for the benefit of wildlife, its habitat, and for recreational users (children, swimmers, and dogs). The River Mel Restoration Group can be reached by emailing: info@rivermel.com