The Colne Valley Fisheries Consultative has published a report Micropollutants in the River Colne 2023 revealing detailed analysis of samples of water and sediment taken from the River Colne in Watford and upstream to the headwaters. 

These samples were taken over the last two years and analysed with the help of Affinity Water and Thames Water. The results are shocking: there were traces of more than 267 different substances, some of which are hazardous to the environment and to humans. Tony Booker chairman of Colne Valley Fisheries Consultative (CVFC), which represents the interests of angling clubs and the environment in the Colne Valley, explains what prompted the report and where the contamination is coming from.

As Tony explains:

“For more than ten years my colleagues and I have been trying to get a better understanding of the causes and impact of pollution on the river Colne.

Whilst we have answered many questions it is inevitable that any new study will raise yet  more – and that will be the focus of the next phase of research if we can secure the support to undertake it.

I hope this important report will give readers an accurate picture of the current position  and a better understanding of the issues. Here, I give a brief overview that will include some of my own thoughts on the situation, on what we should do now, and what the future should hold.

Where did CVFC’s interest in monitoring river pollution begin?

It all started way back in 2012 when we started trying to find the source of numerous serious pollution incidents. We found and logged all the outfalls – the end of waste pipes and channels originally intended to feed storm water directly into the rivers – and assumed those to be the cause. A couple of years ago, Sandy Belloni from Community Connections CIC (pictured in the River Colne), asked Affinity Water to run an analysis on water from near a constant polluting outfall in the hope we might identify a chemical that would lead us to a particular business in the area. That analysis proved more complicated than we expected, identifying a host of pollutants. The specialists at CVFC decided further investigation was needed once it became clear the outfall in question was not the source. That is where the whole project began.

What the micropollutant study has involved

During the study period we have logged and helped to monitor nearly 300 outfalls along the rivers within our catchment. The task is by no means complete and that number could easily double if a detailed survey of all tributaries and distributaries of the Colne is undertaken. Outfalls, landfill sites, sewage treatment works (STWs) can all be sources of river pollution.

Outfalls

An outfall is a pipe or channel that empties into a river but should only transport storm water. Unfortunately that rain run-off will contain pollutants washed from our agricultural land, roads and other urban areas. Many of the outfalls will carry neat sewage via misconnections made from homes and businesses into the surface water system. They should not have happened in the first place and are notoriously hard to find.

An outfall polluting the River Colne

We also have the deliberate dumping of chemicals either directly into a river, through surface drains or being poured into the sewage system.

Landfill sites

Historic landfill sites are another source of pollution that leaches into rivers and groundwater. The Colne flows through many such areas – no doubt creating these seemed like a good idea at the time, but it is something that has come back to haunt us.

Sewage Treatment Works

Sewage treatment works (STWs) are another source of pollution.  What they do is often misunderstood, so it is perhaps worth my taking a moment or two to explain how they work and why we are now seeing so many problems.

STWs have to be authorised to discharge to an agreed water body by the Environment Agency (EA). 

There are two types of discharge. The first is treated effluent ­– our waste that has been treated to an agreed but limited EA standard, and then discharged – in our area, normally to a river or stream.

Storm discharges or ‘spills’ as they are sometimes called, occur when a treatment works receives volumes above that agreed with the EA that must go through the full treatment process. Water companies are then allowed to discharge diluted sewage – as things stand at the moment if they didn’t do that it would back up into homes and businesses.  

It is these ‘spills’ that have received so much media attention recently. None are ideal, some have been shown to be illegal (ie discharges at times when the EA consents would not apply) and, of course, we would all like to see them stop whether they are legal or not.

However, It is important to understand what causes the problem. It has been stated that, at times of heavy rain, 70% of the liquid received at some STWs should not be arriving there. So why is that?

Groundwater getting into the sewer system is a huge contributory factor.

Misconnections (such as run-off from roofs or patios directed into sewers for example) is another. We continue to cover our land in non-porous concrete, tarmac, buildings etc, so the ability for the land to soak up and hold that water diminishes. The result is that storm drains become overwhelmed and that rain can then be re-routed to sewer. 

I do find it ironic that the Government is currently considering simplifying the process of fining water companies and, at the same time, increasing the amounts that can be levied. Yet it is the Government itself that is providing the storm discharge consents to the water companies which it will then seek to fine. (The picture shows Tony on a recent visit to Maple Lodge STW.)

How much of a part do ‘spills’ play in the amount of pollution entering our river system?

In my opinion that depends very much on the receiving water. If you were to consider a small chalk stream with relatively few other sources of pollution, then clearly contamination from an STW is very significant. If, however, we are talking about the Colne which is affected by all the other sources of pollution I have mentioned, then I would suggest ‘spills’ are far from the biggest area of concern.

What does a sewage treatment works treat?

The other thing to consider from a pollution point of view is that STWs, even when operating under normal conditions, will be discharging pollutants on a 24/7 basis. STWs are only designed to deal with the basics of human existence, using a biological process.  Everything else that arrives there may – or, crucially, may not ­– get some treatment on the way through. But if it does, it isn’t by design.

In simple terms the medications you take, the cosmetics you use, the pet medicines you apply, the chemicals you use at home to wash your car, put in your dishwasher, washing machine etc, are all going to end up at a sewage treatment works and then very likely in the river! And, that doesn’t account for the substances we just tip into the drain because it is an easy solution to a problem.

One final thought on STWs. They provide a significant amount of the water present in the rivers of our catchment. Especially at times of low groundwater, 75% of a river’s volume can consist of treated effluent and for an extended period last year, the Colne was completely dry upstream of the interaction with the furthest upstream STW. What a very fragile position we find ourselves in.

Conclusion

The truth is that we are all making a very good job of destroying our environment. It is widely accepted, both here in the UK and abroad, that surface and groundwaters are contaminated, many of us will have ‘forever’ chemicals present in our blood, and drinking water in some parts of the world is also known to contain such pollutants. Our own aquifers are not exempt – the report provides detail on this.

We can be certain that many of the individual pollutants found are harmful to the environment, human health or both. What we can be less certain of at this time is the impact given the level of concentration or what the combined and/or accumulative affect of these might be. If we can find the support and funding necessary I would like to see the investigation continue and expand, both in terms of scope and geographical area.

A note of thanks to my colleagues for their endeavour with this study and to Affinity Water Limited and Thames Water Utilities Ltd for their support and assistance with lab work.”

Reference

Micro-pollutants in the River Colne: Colne Valley Fisheries Consultative, April 2023

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