Sewage is the most harmful form of pollution for our rivers, according to a new study.
University of Oxford found human wastewater is ‘radically altering’ animal, plant and microbe communities, and is more damaging than agricultural waste.
As a result, drinking, playing in, and farming with the water could all pose health threats to humans.
The experts developed a new method to detect dangerous outbreaks of ‘sewage fungus’ before it sets in, potentially killing masses of fish.
It was found to be the main driver increasing algae, nutrient, and sewage fungus in our rivers, the scientists said.
Worms and cyanobacteria, known as blue green algae, were increasingly abundant downstream of the sewage pipes.
Cyanobacteria is well known for producing toxic chemicals that can kill aquatic organisms and degrade critical ecosystems in the process.
The experts said rivers are a crucial part of the global water cycle and fundamental for human health, but that UK water companies are allowed to use them as a dump for treated wastewater.
‘Our study highlights the disproportionate impact that sewage discharge has on river quality, presenting an urgent need for a comprehensive action plan targeting the sewage discharge problem,’ said lead author Dr Dania Albini, from the University of Oxford’s department of biology.
‘Improvements to waste water plants should be implemented along with more regulations.
‘These efforts are crucial in safeguarding the integrity and safety of our rivers – fundamental elements of both ecosystems and human wellbeing.’
Sewage fungus is a complex mix of fungus, algae and bacteria formed when there are high levels of organic nutrients.
As well as smelling unpleasant, it reduces oxygen levels enough to negatively affect all river species and cause mass fish mortality.
At present, it has to be identified by eye – by which time it is already large enough to be harmful.
The experts hope their new water imaging techniques and machine learning could help rapidly spot sewage particles and fungus in water samples.
They believe it could be used as a ‘canary in the coal mine’ by water companies and monitoring organisations such as the Environment Agency, and could prove a valuable tool in limiting the build-up of pollution, helping to halt species decline.
‘There is ongoing debate about the cause of the poor ecological state of many rivers in the UK because it is difficult to disentangle different pollution sources,’ said senior author Dr Michelle Jackson.
‘Here, we show that even treated sewage appears to have a stronger influence on river communities than pollution from the surrounding land.
‘This important information should be used to prioritise the management and conservation of our rivers moving forward.
‘Rapid identification of sewage fungus pollution events will allow early intervention which would help prevent any potential negative consequences for local wildlife.’
Currently, there is intense public concern over the UK’s waterways. A recent investigation discovered over 90% of England’s freshwater habitats have been degraded by farming pollution, raw sewage, and water abstraction.
The authors stressed that while sewage is the bigger culprit, agricultural pollution still needs to be kept in check.
James Wallace, CEO of the UK-based charity River Action, commented on the findings published in the journal Global Change Biology.
‘This important research demonstrates yet again the damage from unregulated water companies and agriculture,’ he said.
‘In addition to the catastrophic impact on wildlife from nutrient pollution, the public should be aware that sewage systems do not remove dangerous bacteria such as E.coli and intestinal enterococci from treated sewage.
‘For instance, recent citizen science on the River Thames found that Thames Water’s outflows often have four to five times the safe levels of bacteria, that has likely caused serious illness in swimmers and rowers.
‘When will the government make water companies and farms clean up their act, especially in places where human lives and sensitive protected habitats are threatened?’
MORE : Government may have broken law over sewage disposal, watchdog finds
MORE : Water firms could face £800,000,000 fine for underreporting sewage discharges
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