Broken sewage treatment plants Anyone bathing in Lake Geneva risks diarrhea
Several wastewater treatment plants in Valais were destroyed by the floods. The canton is now calling on people to stop flushing toilet paper down the toilet - and warning against swimming in Lake Geneva.
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- Wastewater treatment is also affected by the storm damage in Valais: Several sewage treatment plants are out of operation.
- Wastewater is currently being discharged untreated into the waterways.
- The canton has now issued corresponding recommendations to the population.
- There is a risk of environmental damage.
The recent storms in the canton of Valais have caused major damage in various regions. Seven sewage treatment plants were initially no longer able to operate. The untreated wastewater is released into rivers and other bodies of water such as Lake Geneva.
Wastewater treatment plants use the natural decomposition process of organic material in water and accelerate it by stirring, introducing oxygen and returning the microorganisms that break down the pollutants. "When the wastewater treatment plants are out of operation, this decomposition takes place in nature, but it is slower," writes the Valais Environmental Agency (DUW) in response to a blue News inquiry.
This can lead to problems with the oxygen content of the water - especially in lakes that are less aerated by water movement. Low oxygen levels in the water pose problems for fauna in particular.
However, the Valais authorities give the all-clear: "With the large amounts of water from this weekend, the pollutants are well diluted and aerated, so there is no risk of fish mortality at the moment."
No toilet paper in the toilet
However, wastewater treatment plants also filter out materials that do not actually belong in wastewater. For example, coarse solids such as sanitary towels currently end up in nature and are gradually broken down by the weather or mechanical action. "Among other things, small pieces of plastic pose a problem for some animal species, whose stomachs fill up with indigestible material," says the Valais Environment Agency.
In order to keep the pollution as low as possible, the canton is calling on the population to avoid discharging synthetic materials into the sewage system wherever possible. For example, toilet paper should be thrown in the waste or oil should be avoided in the cooking water when preparing pasta. Environmentally friendly products should be used for personal hygiene.
The danger for the environment is there - and for people? "Naturally, large quantities of faecal bacteria have found their way into the water. It is therefore advisable to be careful when swimming in Lake Geneva if you don't want to risk contracting diarrhea," writes DUW. However, the water of the Rhone is cold and therefore sinks in Lake Geneva. It is therefore possible that the impact on bathing water quality is minimal.
Repairs continue
The first repairs have already been completed and some of the affected villages are once again fully connected to the sewage treatment plant, for example Zermatt.
In other places - such as Sierre - the damage is more extensive, according to DUW: "Provisional pre-treatment operations have been resumed there, but it is likely to take several weeks to months before everything is fully functional again."
It is also likely to be several weeks before all the damage to the pipes is repaired - particularly in Evolène, where three kilometers of sewage pipe were torn away, and in Anniviers, where an unstable slope must first be secured before work can even begin on the damaged pipe.
