This summer in Les Glénans (Brittany), the level of contamination by Escherichia Coli bacteria led to a ban on swimming in the archipelago. This contamination by a bacterium that, in this case, comes from human defecation, raised the issue of wastewater management for pleasure craft.

In the boating world, black water never really concerns anyone, as everyone prefers to assume that so little material in so much water - in the manner of Fukushima - will inevitably have no impact. And yet, this summer's example of the Glénan, and before that of Porquerolles, demonstrate the opposite!

Although more and more harbours are equipping themselves with recovery systems, they are still rarely used by yachtsmen, who find it simpler and quicker to throw everything back into the sea on a short trip out to sea before returning home.

Yet bilge water is notoriously harmful to the environment, since it can contain oil and fuel; and black water, which is the result of discharges from toilets on boats, can also have harmful consequences for the environment, and even endanger our own health, as the events at Les Glénan proved.

But even if the issue is back on the agenda, the majority of yachtsmen, if they are careful with bilge water, are not worried about discharging black water into the sea, thinking that since it is natural waste, which will feed the fish, and which will ultimately be diluted in the water, it will not pose a problem.

But all this is based on the assumption that organic waste cannot pollute, which is totally false.

Yet human excrement is a persistent and notorious pollutant in our oceans. It is toxic, since it can have an impact on human health and degrade living conditions in ocean environments. And contrary to popular belief, they are not all that biodegradable, since near the coasts they persist in the environment for some time, resisting natural biological degradation in the water.

More generally, organic waste is directly responsible for the disappearance of many species and the degradation of marine environments.

While technical advances are making boating less and less polluting, notably with the arrival of electric motors, technology alone cannot solve all the pollution problems caused by boating activities, especially when boaters themselves are not informed about the impact of their own waste.

It should also be noted that only boats built from 2008 onwards are required to have a tank to collect black water, and that they only represent a quarter of the fleet.

However, since 2003, the International Maritime Organisation (IMO) has been laying down strict rules on ship-generated waste water, in the 4th MARPOL Annex.

So there's no need for yachtsmen to worry about discharging their wastewater into the sea:

• If you do not have a wastewater treatment system on your boat, it is forbidden to discharge your black water within 12 nautical miles of the coast.
• If you have a grinding and disinfection treatment system, you are prohibited from discharging black water within 3 nautical miles of the coast.

It should be noted that wastewater treatment systems on boats are generally expensive and cumbersome, so very few are available.

But in the final analysis, while few pleasure boats have treatment systems and it is rare for yachtsmen to sail further than 12 nautical miles from the coast, at the end of the day few boats stop to pump their black water at the station. Whether it's the waiting time, the lack of interest or simply 'laziness'. Most yachtsmen are not worried about discharging their untreated black water into the sea, less than 12 miles from the coast, not even about being caught in the act.

At a time when human pollution is already responsible for the disappearance of entire ecosystems, simple gestures such as respecting the rules in place or regularly pumping out black water in ports equipped with recovery systems should be self-evident.