When it comes to solving river problems, nothing is ever simple
RECENT heavy rain has brought the discharge of raw sewage into our rivers and waterways back into sharp focus. Here, TONY BOOKER explains some of the complexities that make finding a lasting solution to the problem so depressingly elusive.
IT IS Sunday evening, November 24, and, as I write, the following sewage treatment works are steadily discharging raw sewage into various part of the Colne catchment:
Maple lodge – River Colne
Markyate – River Ver
Gerrards Cross – River Misbourne
Berkhamsted – Grand Union Canal and River Bulbourne
Dagnall – Groundwater *
Caddington – Groundwater *
*Groundwater is that which exists underground in aquifers – often from which our drinking water supply is abstracted.
It is raining heavily and has been for most of the day. But that doesn’t alter the fact Maple Lodge (and others) were discharging under so-called ‘storm conditions’ within just a few hours of the arrival of last week’s rain and snow.
A Dissolved Oxygen (DO) reading was taken on the Colne a mile downstream of the discharge point at Maple Lodge. The figure was alarming – 37%, which is dangerously low, and means fish and other aquatic life would be seriously affected, if not killed outright.
You would think that represents a pollution incident, but here we run up against a fundamental contradiction. The Environment Agency, while wanting to fine water companies for doing this kind of thing, simultaneously views this situation as a permitted discharge.
Confused? Welcome to my world!
I have reported worse in the past – incidents where I have been confronted with the sight of hundreds of dead fish, but those too have been passed off as ‘permitted discharges’.
Has anything changed since then? Are there new issues to consider?
There has certainly been more focus on water quality issues, with well-attended demonstrations in London. There is a newly-elected Government and therefore a new Environment Secretary. There is talk of Nationalisation, the well-documented financial woes of Thames Water and heightened rhetoric targeted at water company directors. But for all that, the answer to ‘has anything changed?’ is a resounding NO.
The situation is actually worse because we now generally suffer ‘storm’ discharges that start earlier after rain and last longer than was previously the case.
Before we consider the reasons why, let us look at some facts.
Each sewage treatment works (STW) will have an agreement in place with the Environment Agency (EA) determining the quality of treated discharge, but crucially, it will also state the amount of ‘product’ the STW has to send for full treatment before it can start to store and perhaps ultimately discharge that sewage into a river or groundwater. Yes, I’m afraid that happens and is ‘allowed’ too.
If the STWs did not release that additional quantity, it would back up into your houses, businesses and across your land. As many people have already discovered to their cost, unfortunately that happens sometimes anyway.
The problem is not new – it happened before the water companies were established, although the situation is worsening.
So how or why does an STW receive flows that it cannot cope with? The primary issue is groundwater ingress into the sewer system. That can happen because sewers are literally surrounded by groundwater – especially when levels of the latter are high as at present.
Combined Storm Overflows (CSOs) also play a part as do misconnections from private properties, but ultimately the problems arise because too much groundwater is reaching the STW.
Groundwater levels are obviously rain associated. In our catchment, it is impossible to ignore the fact that two massive concrete railway tunnels have been cut through the chalk aquifer; where has that displaced water gone, one wonders? It is also worth pointing out that HS2 was granted a permit to discharge up to 1,700,000 litres of waste and run-off per day to what was an already inadequate and failing STW.
It doesn’t take a genius to work out that the very times HS2 needs to exercise that permit is when the STW is already under enormous stress. The argument this additional flow will not be either fully responsible for the ‘storm’ discharge or is a contributory factor simply doesn’t wash.
There are other reasons, too. We seem hell-bent on covering our land with concrete, and once that is done it can no longer act as a soak-away that would slow down water movement. The population is rapidly growing and that in turn means huge demand for more houses, and yet more concrete.
It also means more cars, and so more pollution from ever-bigger roads and the need – if one accepts the argument – for a new motorway service area on the M25. Still more acres of impermeable concrete, more people and more stress on already overstretched infrastructure. Madness.
Planning applications are rarely refused on the grounds of the water companies (supply or waste providers) not being able to cope with the additional demand the development would bring.
We just keep on expanding, and they are mandated to provide us water and clean up our waste – all while Ofwat sits there sucking its teeth over the need to raise water prices to address some of these problems.
It should be noted that flows to Maple Lodge treatment works has doubled since September 2023 and is now receiving an additional 1bn litres or 1 million tonnes of rain and floodwater each week – that is equivalent to 400 Olympic swimming pools.
The bald truth is that while water companies are not blameless, the two regulators – Ofwat and the EA – have absurdly been pulling in opposite directions, and neither have yet fulfilled their core role of properly regulating and enforcing.
So there you have it: nothing has changed. Improvements that can be made are not keeping pace with the mounting pressures being applied elsewhere.
There is a solution – replacing or re-lining the sewer network, but the money needed to carry it out and the widespread disruption it would cause is off the scale.
In just the Misbourne catchment* alone, a tiny fraction of the whole Colne catchment area, Thames Water own c965km (73%) of the sewer network and c360km (27%) is privately owned. The estimated cost to repair just the Thames Water asset is c£1bn and obviously therefore the privately owned areas, that suffer all the same problems and are often misconnected** to, also needs huge investment.
*A catchment is basically the area from which water drains to feed a river and will include the tributaries.
**A misconnection is where either sewage is directed into a surface water drain or, as referred to here, rainwater from gutters etc directed into the foul sewer system.
There is still an elephant in the room. Just imagine we could wave a magic wand and immediately stop storm discharges. Would that solve our river and groundwater pollution problems?
Another no, sadly. Run-off from agriculture, roads, urban areas and other sources of pollution are even bigger issues and not enough is being done to address those either.
When we see a STW working correctly, sending everything it receives to full treatment, we assume all is well – it is doing what we ask of it, processing our waste using a biological process. But what it is not doing, and we do not ask this of the water companies, is removing all the nasty chemicals, PFAS, pharmaceuticals and other drugs, cosmetics, pet medicines etc that are showing up in our samples.
Any of those removed is a matter of luck, not design. Anything that isn’t removed biologically or by settlement/filtration will be retained in the ‘sludge cake’ that is often used as fertiliser – hence everything goes full circle with the contaminants it contains finding their way into our food and ground or surface water.
You can learn more about that here: PFAs Sewage Sludge
There is a solution to all this, too, but you guessed it – you’ll need to add a few more billions of pounds to that already needed for the sewer replacement to achieve it.
Sewage in our rivers always grabs the news limelight, but as you can see, this is going to be a fiendishly complex and eye-wateringly expensive problem to solve.
There must be the political will to fix this and to find the means to pay for it – whether from water companies, developers, taxes, increased water bills or a combination of all four.
More Information
Citizen testing finds 75% of rivers in Britain in poor ecological health 24/06/24
Local River Pollution Problems need Solutions 17/04/24
Sewage Pollution of the River Colne in Harefield Makes the National News 05/04/24
Sewage Pollution of the River Misbourne: its cause and effect 29/02/24
How Sewage Sludge Carries Toxic PFAS from Toilet to Table 08/02/24
The River Colne - A Toxic Soup of Chemicals ? 20/04/23
the Current State of Our Rivers and how we can move forward in a positive way 25/02/23