Sewage most harmful form of pollution for rivers: study

By Pol Allingham via SWNS

Sewage is the most harmful form of pollution for our rivers, according to a new study.

The 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 potentially dangerous outbreaks of “sewage fungus” before it set in, potentially killing masses of fish.

It was found to be the main driver of 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 complained rivers are a crucial part of the global water cycle and fundamental for human health, but UK water companies are allowed to use them as a dump for treated wastewater.

Dr Dania Albini, Department of Biology, University of Oxford, and lead author of the study, said: “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.

“Improvements to wastewater 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 being smelly, 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 then 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 organizations such as the Environment Agency and could prove a valuable tool in limiting the build-up pollution and halting species decline.

Dr. Michelle Jackson at the Department of Biology, University of Oxford and senior author of the study, said: “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.

“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 prioritize 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 and a recent investigation discovered over 90 percent of England’s freshwater habitats have been degraded by farming pollution, raw sewage, and water abstraction.

Agricultural run-off encouraged sensitive insect groups of mayflies, stoneflies and caddisflies, suggesting sewage is a greater threat to rivers than farming – though they added the field 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.

“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?”