Have you ever experienced this feeling before? On a blazing hot day, the desire to plunge into a cool stream of water intensifies by the minute. The water appears pristine, clear, and incredibly refreshing. However, in reality, it could be extensively contaminated.
Even the purest rivers can harbor harmful bacteria, including fecal bacteria originating from livestock manure and human waste.
In a recent announcement, the Designated bathing area in the UK, a favored holiday spot, has been a subject of concern due to issues such as being submerged in sewage and incidents of rowers contracting E. coli infections. To address these concerns, we consulted with water and sanitation expert Professor David Werner to provide essential information for safely enjoying wild swimming this summer.
Werner’s research delves into treated sewage, stormwater (untreated sewage overflows following heavy rains), and occasionally illegal sewage disposal in dry weather. These factors impact both human health and ecosystem health. While human waste is discharged into oceans, rivers tend to exhibit higher concentrations of human waste and the accompanying harmful bacteria due to lower dilution levels compared to water bodies, increasing the risk of exposure to harmful substances.
(Notably, a microbiology professor, William Gays, mentioned in BBC Science Focus that rivers have only recently been subjected to the same microbial testing as coastal waters. Moreover, wastewater discharged into the ocean is often subjected to more stringent treatment standards than rivers, including ultraviolet disinfection.)
The following guidelines mainly focus on rivers but are also relevant for coastal swimming activities.
The key takeaway? Avoid swimming after rainfall.
How do diseases enter rivers, and what is the risk of swimming in them?
Fecal contamination doesn’t always mean significant. The majority of people’s stool contains beneficial bacteria essential for our health. However, the stool of an ill individual harbors bacteria responsible for the illness, potentially leading to disease transmission.
According to Warner, the risk of contracting a disease from a river is relatively low, but it escalates if you ingest river water (discouraged but not impossible).
This can result in unpleasant symptoms like infections and diarrhea. The worst-case scenario involves acquiring antibiotic-resistant bacteria, an eventuality deemed highly improbable by Warner.
So, should one abstain from wild swimming altogether? Ultimately, it boils down to whether you are willing to accept the (generally minimal) risk for the mental health benefits, as Warner highlights.
“There is no such thing as absolute safety or zero risk,” he states. “Each time we embark on a car journey, we weigh the trip’s advantages against the accident risks. Similarly, outdoor recreation offers significant mental health perks, particularly for urban dwellers.”
How to safeguard yourself from sewage while swimming
Warner and his team are currently devising a device capable of swiftly testing water for contaminants, akin to a lateral flow corona test, though substantial research is required to materialize this concept.
Until this technology is available, several straightforward methods can help identify sewage presence while swimming in rivers this summer. Here are Warner’s recommendations:
1. Choose your spot wisely
According to Werner, it is crucial to avoid swimming downstream from a sewage treatment plant under any circumstances. While untreated sewage overflows are a common concern, treating sewage does not completely eradicate the risks; it merely diminishes them.
“Treating wastewater significantly reduces the levels of harmful bacteria, possibly by a factor of 1,000, but it doesn’t eliminate them,” Werner explains.
“Hence, if a location is situated immediately downstream of a treatment plant discharge point, one can expect a consistent presence of fecal bacteria due to the continuous discharge.”
Individuals can consult the “Poop Map” and trace their local river upstream to identify any treatment facilities along the route.
2. Check the poop map
UK organizations such as Rivers Trust and Surfers Against Sewage have developed an interactive map showcasing regular treated sewage discharges and anticipated untreated sewage overflows across the UK in 2023.
To locate a wastewater treatment plant on The Rivers Trust map, click the yellow square corresponding to your area or tap the brown circle icon, peruse the cards to pinpoint locations. The phrase “Sewage Discharge – Final/Treated Effluent – Water Companies” typically indicates a wastewater treatment facility.
This year, the charity integrated near real-time data into its maps. “This marks a significant advancement for individuals seeking real-time updates,” remarks Warner. “We strongly recommend utilizing these online resources, offering current information.”
Presently, individuals can ascertain if sewage has been discharged within the last 24 hours, albeit inland data is exclusive to designated bathing locations and rivers within the Thames Basin (Northumbrian Water also provides a County-level map while coastal regions are included).
3. Monitor the weather
Despite the allure of swimming on a sunny day, verify there hasn’t been rainfall for a few days. Swimming post-rainfall significantly heightens the possibility of encountering contaminated water due to sewer overflows and increased water release during heavy downpours.
To compound matters, even as a dry spell seems to prevail and swimming appears safe, hidden risks could lurk upstream. Thunderstorms can unleash localized rainfall, implying that upstream areas may experience heavy showers despite sunshine at your location.
4. Steer clear of small rivers
In addition to potentially turbid waters, small rivers tend to exacerbate the situation as sewage, whether treated or untreated, is less diluted in these settings.
Warner adheres to a safety benchmark stipulating that raw sewage minimal dilution should be 1,000 times for paddling and over 10,000 times for swimming. While calculating these dilution levels is not advised, the underlying principle is straightforward: “A large river with vigorous flow signifies ample dilution,” Werner asserts.
Nonetheless, disparate river segments need not cause undue concern: while one side may seem stagnant relative to the center, the water mixes uniformly.
5. Keep tabs on the paper trail
Exhibit prudence: refrain from swimming if toilet paper is visible. Alarming indicators surpass toilet paper and include wet wipes and sanitary pads crafted from plastic materials that should not be flushed but often are.
According to Werner, unlike toilet paper and human excrement, these items do not disintegrate in swiftly moving waters.
6. Stay informed
“After frolicking in the river, diligently cleanse yourself. Embrace standard personal hygiene,” stresses Werner.
About our experts
David Warner serves as a Professor of Environmental Systems Modelling at Newcastle University. Previously, his research concentrated on sanitation and water quality in low-income countries by utilizing DNA sequencing and assessing microbial hazards in rivers. During travel restrictions amid the pandemic, he shifted his focus to the UK’s rivers. His research on post-rain fecal bacteria levels has been documented in various journals such as Water Science and Technology, Comprehensive Environmental Science, and Environmental Pollution.
William Gays, a Professor of Microbiology at the European Centre for Environment and Human Health within the University of Exeter’s Medical School, conducts research published in journals like International Journal of Antimicrobial Agents, Food and Environmental Virology, and Water Research.
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Source: www.sciencefocus.com
