The groundswell of media interest in river water quality is unlikely to have escaped your notice. European legislation in the form of the Water Framework Directive is still in force in the UK and, given the guidance contained within it only 14% of rivers meet good ecological standard and none meet good chemical status. The waters of the Colne catchment are not immune with a huge array of pollutants entering our rivers and lakes from a myriad of sources. 

The impact of some of the pollutants is known but the individual impact of others is less well understood – that is even more true when combinations and accumulative effect are considered. As analytical processes improve we identify new chemicals and that compounds our problem. These new pollutants are often referred to as chemicals of emerging concern. It does not mean they are ‘new’ chemicals – many have been around for years but only now are we beginning to understand the variety and concentrations in our water sources.

The means by which these chemicals and other pollutants can enter our water bodies is varied but includes agricultural, industrial, road and urban run off, historic land fill sites, deliberate disposal, property misconnections*, unregulated businesses – the list goes on. Sewage treatment works STW’s require specific mention. Storm discharges or ‘spills’ are well documented through the media, the Thames Water event duration map provides live information on such spills. Thames Water also have a problem reporting app  which allows you to report incidents directly to Thames Water.

Whilst we would all wish to see storm discharges cease it is a complex issue. Although there are exceptions to the rule most discharges occur at times of heavy rainfall when the STW’s may receive volumes above what they can cope with. When certain levels are reached as agreed with the Environment Agency (EA), discharges to river of dilute sewage can occur – the alternative would be for it to back up into homes and businesses. Such discharges can have devastating impact on the environment.

There is another unseen issue however that arguably presents a greater threat. On a 24/7 basis our waste is received at STW’s and is treated using a filtration but mainly biological process. Crucially the process is not designed to take out the chemicals, cosmetics, pharmaceuticals, pet medicines etc that we put into the system. Any that are removed occurs through good fortune and not by design.  

So, although an STW may (and should) meet the final treated effluent discharge criteria agreed with the EA for nutrients, Ammonia, phosphates etc many of the other micro pollutants are not monitored thoroughly.

It is important to understand however that our river and indeed groundwater well upstream of any obvious and direct impact from STW’s is often found to be contaminated. A study undertaken by the Colne Valley Fisheries Consultative with support from both Affinity and Thames Water identified 267 micro pollutants across various sites on the Colne. We believe that many more were undetected, so that work will continue. The report that was compiled is available here: Micropollutants and the river Colne.

Whilst many of the long term effects of these complex chemicals and combinations remains unknown other impacts are much easier to explain. 

Sediment can be released into rivers as a result of some cultivation practices on arable land and allowing livestock to trample river banks. Sediment is also washed off roads into highway drains and into the river. It causes damage by clogging up river gravels, preventing fish from spawning and reducing the viability of their eggs.

Elevated phosphate levels can cause excessive plant growth leading to rivers being choked by weed and algae, reducing flows, removing oxygen from the water and reducing the capacity of the river to support animals, such as invertebrates and fish, which are the foundation of the catchment food chain.

To help achieve an improvement in water quality we must work with local industry, agriculture, and households to help them understand how to best store, use and dispose of chemicals to support the environment. We will continue to work with the water companies to improve discharges from sewage treatment works and with domestic households and trades to understand the impacts of misconnections * 

To enable these initiatives and better partnership working ColneCAN has established (with effect from Nov 2023) a Water Quality working Group that will bring all key stakeholders together.  We are also undertaking a project to locate, record and map every potential pollution source into every river and on-line lake in the catchment. It is a huge undertaking but is a vital piece of work. Identified troublesome sources of pollution can then be the subject of our efforts to have them corrected. We are liaising with academia on this too and seek to establish a partnership that will facilitate the continued study of water quality in the catchment but over a wider geographical area and with access to wider ranging analytical processes than we have had to date.  

We will need volunteer help for sure to find the sources and then to monitor them. If you think you can help please contact the project lead This email address is being protected from spambots. You need JavaScript enabled to view it. or call  07756 284692

Should you discover a pollution incident a number of options are available to you:

Report it to the EA on their emergency number 0800 807060

Report it on line to Thames Water 

So that we may keep a local record we would also like you to report this on the CVFC app 

You might also like to check out Discover which  allows people to check how their local water company is performing and to compare with other companies. Led and funded by water companies, (with overview and scrutiny from regulators and consumer watchdog), it brings together information about how water and sewerage services are provided.

A property can be said to be misconnected when drains from baths, showers, hand basins, washing machines, dishwashers etc and even toilets are connected to surface water drains and not the foul water system. Equally, if a surface water drain (from your gutters for eg) is directed into a foul water drain that too is deemed to be a misconnection. Once identified, if not corrected, the home or business owner could be liable to prosecution. 

Design by LTD Design Consultants and build by Garganey Consulting. From an original concept by the Herts and Middlesex Wildlife Trust.