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Sewage in the sea: How worried should we be?


With Environment Agency warnings to stay out of the sea at 40 UK beaches after monsoon-style rains led to masses of untreated sewage being pumped into the sea, we quizzed Aquatic Ecotoxicologist Dr Edwin Routledge...

­­­­­How dangerous is this? 

Storm overflows certainly carry risk of harm to the environment and to public health ­- contamination with sewage increases the risk of exposure to pathogenic bacteria, preventing safe bathing and recreational activities. However, the alternative would be to allow sewage to back up into businesses and homes which would potentially have a large and direct impact on people’s health and their livelihoods.

Why is this happening? 

Climate change is altering the intensity of rainfall, and our sewage network infrastructure cannot always cope at certain times. To prevent sewage backing up in the pipes and spilling back into businesses and homes that generated it, the excess flow is directed through the storm overflow pipes to be released directly into rivers and coastal areas in untreated form. Add to that increasing population, and greater demands on our ancient sewage system anyway, and you have the perfect storm!

What could we do short-term and long-term, to curb it?  

Investment is key. If we can separate stormwater drainage from sewage systems (thereby eliminating storm overflows altogether) then the issue would disappear instantly, but the cost of doing so would be enormous (predicted in the region of £350 billion to £600 billion pounds) with large impacts on household bills to make this happen. However, there are many things we could all do to improve the efficiency of our sewers to stop them blocking and backing up when we have intense rainfall. For example, avoid flushing rags, plastics and other items down the toilet. Also to avoid pouring fats and oils down the drain would help as these can solidify to form blockages (fatbergs) that interrupt normal flow of sewage. 

Rainwater harvesting systems including water butts can also store water, and reduce the amount that enters the drains during rainfall. Other land management measures at different scales can also help to prevent or slow surface runoff during downpours too. In short we should all behave responsibly to ensure that our sewage system is clear of preventable obstructions. 

What is raw sewage?

In addition to human excrement, sewage contains a complex mixture of different chemicals used in society, including household cleaning products, personal care products, pharmaceuticals and pesticides. Added to this are industrial discharges containing other types of chemicals. Releases directly to coastal areas would mean that sea-life would be exposed to more of these chemicals as sewage treatment is designed to eliminate many of these pollutants before they are discharged into rivers.

What’s in it?

Raw sewage is essentially a complex mixture of all biological and chemical waste that society releases into the sewer system (from domestic, business and industrial use) suspended or dissolved in water before it reaches a sewage works.  It is unprocessed, and as such would not be expected to be compliant with environmental standards used to protect the environment.

Does it need closer policing? 

I believe monitoring of storm overflows already happens (called Event Duration Monitoring), so there is policing by the Environment Agency, and fines can be made to Water Authorities who are not managing or maintaining their sewers (leading to frequent ‘events’).  There is realisation by Ofwat (the regulating body responsible for privatised water and sewerage industry in England and Wales) that the current situation cannot continue.

Investment is happening (albeit arguably too little) and the Environment Bill has been strengthened to put in place more measures to prevent water pollution (including more accountability on water companies to reduce the impact and frequency of stormwater discharges). These are all small steps in the right direction, but I do not see a simple, inexpensive or ‘pain-free’ way out of this situation.