Targeting Sewage Pollution: a little BOD story for the budding environmental detective.

Over the last 18 months there have been countless articles and discussions about the state of our rivers here in the UK. Recent Environment Agency reports do not provide a good light on the situation and most recently it has been reported that only 14% of our rivers meet good status. We at Proteus Instruments would challenge even that statistic and the only reason why its that good is because there is ineffective monitoring and policing of our rivers and water resources to say otherwise. Not only do we not measure the quality of our rivers continuously, water quality monitoring is inconsistent and sporadic at best.

There is little doubt that the sources of our pollution (namely sewage, agricultural and industrial) need to be dealt with and monitored but the lack of policing, legal drivers and the actual inability to measure the parameters we need most has meant that our rivers have ended up being the dumping grounds of all sorts of pollutants from sewage through to face masks and micro-plastics.

So what is the scale of the problem? Well nobody really knows because the most comprehensive report to date is only based on sporadic and often inaccurate sampling. So what can be done? It has to date been the lack of innovation in the water industry and the environment agency which has meant that the UK has lagged way behind Europe. A recent report published by the EU has shown that the UK has the lowest bathing water status of all European countries! Yet, the UK is recognised as one of the best innovation sources in the world but we are unfortunately as a nation very bad at adopting said innovation; principally due to bureaucracy and ineffective management. Innovation will be the driver for change; its adoption will see new and better ways of doing things.

So we have a big problem in our rivers, but how big? To put it into perspective we randomly decided to install a Proteus in a small river called the Laugherne Brook, Worcestershire, UK. There was no reason to select this river over any other, other than it was relatively local to one of our employees. The river itself looked just like any other lowland river, with lush fields and tree-lined banks although generally the exposed muds in the river bed were somewhat malodorous. There is no industry in the catchment, just a couple of small villages, a school, some farms and some wastewater treatment plants (WWTPs). Just a very unassuming river…or so you would think!

The Proteus with its portable telemetry system was installed temporarily on a river bank one weekend in early March 2021; the whole process took about 5-minutes even with connecting the sensor, cable, telemetry system and solar panel. What little did we know we were about to be bombarded with real-time alerts from the sensor informing us of multiple organic pollution events which had probably been occurring for many years but undetected.

With it only being installed on the Sunday, by Monday morning we had already received our first alert. Obviously surprised but we decided to watch and learn. Again it happened the next day on Tuesday. Yet again it happened on Thursday morning with a BOD increase from 2mgl to 7mgl for the whole river.

We therefore decided to investigate immediately; the Proteus was disconnected from the telemetry system and connected to an Android phone using the Proteus App. We took live measurements every 250m whilst walking up river. Within 40mins and 2kms upstream the readings had returned to 2mgl so we knew that the pollution source was between the last two sample points. Walking slowly downstream we could see the readings increase again and hidden in an overhanging bank there was an old land drain spewing animal slurry into the river. We subsequently found out that this was likely to have been happening for at least 10 years! The Environment Agency approached the farmer and demanded a response plan which has subsequently been actioned; not before the farmer was instructed to pay costs and charges. The slurry was being discharged with an ammonia level of around 2mgl and a BOD level of 15-25mgl! Even if the Environment Agency had monitored this river the data would look something like the following and as you can see there are no real signs of pollution apart from a small increase in ammonium. This is the same situation around the world. These parameters still just leave us guessing as to what is happening and they are not causal parameters but more just indicators.

This is in effect a small and seemingly inconsequential story but scaled up to every catchment across the UK paints a much truer picture. These events just are simply not monitored and there is no technology being used that will alert the Environment Agency to take samples.

With the recent dry weather, a second problem arose which has only made the pollution story of this river much worse. With a lack of rainfall runoff into the river, the water levels have lowered significantly which has only increased the polluting effect of the slurry. To make matters worse the WWTW (Martley) upstream, which has not been upgraded for many decades despite a tripling in population, is discharging more or less the same amount of effluent. This has meant that the proportion of the river made up of final effluent from Martley WWTP has dramatically increased. As such, the river water quality strongly reflects the quality of the discharged water from the WWTP for DO, pH, conductvity, BOD, COD and coliforms; really not good for the river or its ecosystems.

Now here’s the scarey bit…the only reason that this pollution source was found was due to the innovation behind the Proteus. Not only is the river not monitored, none of the parameters that would have been measured by the Environment Agency would have triggered an investigation. This is why the pollution in this river and countless others is unchecked. Every WWTP in the UK (and probably worldwide) has a consent limit for BOD but not one WWTP has a real-time sensor for measuring it! Truly shocking.

There are so many takeaways from this little investigation:

1. We cannot begin to imagine how many pollution sources there are like this just in every corner of the UK, let alone worldwide; this Proteus had only been installed for just two days before it noticed this seemingly untraceable pollution event. Surely this marks a step change in our capability to detect organic pollution.
2. Until Proteus we have not had the instrumentation to pick these events up; this one incident was promptly stopped and will ensure the local ecosystem rebounds back.
3. Identifying sources of pollution like this can actually be very quick and should no longer be guess work using secondary parameters such as ammonia, pH, turbidity and DO. A dangerous depletion in DO takes days so there is no chance in identifying sources in real-time. In this instance the pollution was stopped so that the DO levels did not drop further.
4. It feels good to make a difference to your local environment and we should encourage everyone to get involved. We have worked with various organisations doing exactly the same and the data is startling!
5. Little actions with defensible data like this will allow us to protect our rivers; instead of (a) using instrumentation that cannot measure it or (b) using inherently inaccurate BOD sampling that at best can only provide a result 5 days later (after all the fish are dead and the pollution is long gone).

So thanks to Proteus, this little stretch of river and its wildlife now stands a chance of being restored to its former glory. One little step for Proteus but perhaps one giant step for river-kind?????