Grey Water
Grey water is the water coming from showers and sinks. It is generally laden with grease and cleaning products. In theory, and up until now, the discharge of this water is not clearly regulated for small recreational vessels. However, the lack of regulation does not prevent responsible treatment, just as for black water.
Black Water
Black water, or sewage, is the water and waste from toilets. This water contains harmful bacteria, such as E. coli. Discharging this water into the sea is prohibited, without treatment, within the 12 NM (nautical mile) limit unless the vessel has a specific treatment system. Without such systems, vessels must have a holding tank to be emptied at port.
In inland waters, the situation varies by country.
In France, the poor performer, black water is dumped into canals. With slow-moving waters, the effect is not pleasant. In Germany and the Netherlands, such discharges are banned and punishable.
In August 2023, E. coli contamination in swimming waters in the Glénan archipelago highlighted the issue of wastewater discharges from recreational boats. In Porquerolles and along the Var coast, several E. coli outbreaks have been linked to wastewater from recreational vessels. In the Caribbean, 80% of wastewater from anchored boats is thought to end up in the sea within the 3 NM zone.
With the increase in synthetic textiles, the volume of plastic micro-particles released during washing and into the water has significantly grown. This is an issue not just at sea since sewage treatment plants are not yet capable of capturing these particles, which are harmful to marine life.
Products used for boat cleaning, laundry, dishes, and personal hygiene often contain phosphates and other chemicals that, when discharged into water, contribute to eutrophication. This process leads to excessive algae growth, consuming the dissolved oxygen in the water, which can create dead zones where aquatic life disappears.
Lawmakers have addressed this issue, and water quality regulations, whether through the IMO’s MARPOL Annex IV or national laws, all converge toward the goal of only discharging clean and treated water into the natural environment.
This is the case with the Directive 2013/53/EU of the European Parliament, dated November 20, 2013, relating to recreational craft and personal watercraft, which states:
"All toilets installed on recreational craft must be connected exclusively to a holding tank system or a wastewater treatment system. Recreational craft equipped with integrated holding tanks must have a standard connection for wastewater, allowing the holding tank's piping to connect to the craft's sewage system. Additionally, human waste evacuation pipes crossing the hull must be fitted with valves that can be locked in a closed position."
Regarding the emptying of these tanks, reference must be made to the IMO's pollution regulations, MARPOL.
Although MARPOL regulations do not apply to small recreational boats (only those capable of carrying at least 10 passengers must comply), the description of systems that allow the release of wastewater within the 300-meter limit of the European Directive 2013/53/EU originates from MARPOL Annex IV. This text provides the standards for sanitation systems on recreational vessels.
It refers to the "Recommendation on International Standards for Effluent and Performance Tests of Sewage Treatment Plants", adopted by the IMO’s Marine Environment Protection Committee under resolution MEPC.227. This resolution outlines three scenarios based on the type of onboard storage or treatment system and specifies that:
On a local level, ports regulate their operations in their policing rules, which may impose additional restrictions to address these issues. These rules always prohibit the discharge of untreated black water in ports.
In theory, no problem: new boats must be equipped with black water holding tanks since 2013, and pumping stations exist onshore. Additionally, certain popular areas (the Golden Isles in Hyères) require all live-aboard boats at anchor to have a black water tank, regardless of their age.
This is the theory, a world where everything goes perfectly...
I'm sure you've noticed, but on Sunday afternoons, there's a lot more activity at the gas pump than at the "waste" pump.
It's not just an impression. The ports of Sète report fewer than 50 pump-outs per year for 800 berths, and Port-La Forêt has fewer than thirty annually for 1,130 berths... No figures are available for Port Camargue and the Ports of La Rochelle, which together total more than 5,000 berths.
In reality, pumping stations are rarely used, and most boaters empty their tanks well within the 12 NM zone when returning to port. These are often the same boaters who complain about poor bathing water quality. Schizophrenia?
A bioreactor is designed to receive all the dirty water from the boat, both grey and black water. Its internal volume must correspond to the volumes of water delivered to it daily.
However, these volumes vary significantly depending on users.
Since all sanitary water ends up in the bioreactor, it must be sized accordingly. If the bioreactor is too small, the final effluent becomes too concentrated, filters clog, or UV lamps become ineffective when faced with highly turbid liquids.
Black water holding tanks are retention devices that do not treat the water they contain. MARPOL regulations prohibit discharging these tanks within 12 NM of the coast.
The professional maritime sector is required to weigh its final waste and residues and maintain records, whereas recreational boating is subject to rules that are poorly enforced.
In practice, there are two types of devices:
Treatment devices that grind and disinfect (comminuting and disinfecting equipment), permitted beyond 3 NM. These are Marine Sanitation Devices Type 1, like the Raritan Electroscan.
These devices coarsely grind the contents of the tanks before mixing them with chlorine and discharging them into the water. The Electroscan shown in the illustration generates chlorine through seawater electrolysis.
Discharging treated water from these devices is not permitted within 3 NM of the coast.
Sewage Treatment Plants or Type 2 Marine Sanitation Devices
These devices are bioreactors that, like a septic tank, break down waste before releasing only clean effluents that meet specific criteria defined by the IMO through MARPOL regulations.
Only a handful of devices are considered to comply with this regulation.
A bioreactor introduces oxygen to the wastewater (both gray and black) to accelerate the enzymatic degradation processes that occur within its tanks. The output is a clear liquid, which passes through a filter or is disinfected by a product or UV lamp.
These devices are bulky, and the smallest, like the Enteron discussed below, take up about 1500x600x650 mm of space, making them challenging to install on a recreational vessel undergoing refit. Shipyards should take the initiative to incorporate these systems by mass-producing bioreactors in a form factor that allows for easy integration.
They vary in size and final water treatment methods, as well as the maintenance challenges they present.
These all-water tanks collect both black and gray water, treating them by oxygenation to promote oxidation and bacterial proliferation. In the end, all waters are filtered.
I don't know the results of this innovation at Bali, but I believe that filter systems should be avoided. Predicting filter clogging is difficult, obtaining new filters can be tricky, and cleaning them is cumbersome.
German manufacturer Tom Logisch developed a Sewage Treatment Plant (STP) called Enteron, installed on over 300 pleasure boats, half of which are houseboats. The device comes in two small sizes, suitable for vessels with reduced water consumption, such as sailboat owners.
Tom Logisch's standard tanks are designed to treat 100 to 160 liters of water per day. The company also builds systems with higher capacity. Enteron does not use filtration. A UV LED lamp disinfects the effluents.
These devices are bulkier than others because they optimize the enzymatic "digestion" of organic matter in wastewater. At the end, the effluents pass into a second tank where they are mixed with a disinfectant.
Most systems, like the Skimoil TheTankMSD, use a chlorine-based disinfectant, and the non-degraded discharge must be minimal.
Another generation of devices uses a more neutral disinfectant. Peracetic acid breaks down into three harmless components for the environment: acetic acid (vinegar), oxygen, and water. Thousands of MarineFAST systems are in service on vessels of all sizes. These devices are also available in form factors suitable for recreational boating.
Disinfection bioreactors have no filters or moving parts, making them the easiest systems to use and maintain.
Freeze protection must be considered if boats are used in winter without draining. This can be achieved inside the hull by installing a hydronic radiator or an air heater with a temperature sensor controlling the heating in antifreeze mode.
When mounted outdoors, an electric heating element (heating coil) should be installed in the tank to ensure freeze protection.
Using composting toilets means that the waste must be disposed of ashore for composting. This is an impractical daily solution, and regulatory compliance is problematic. In fact, waste should be composted in a sealed area with specific drainage.
An interesting option when gas is available on board. These toilets incinerate all waste, leaving only inert ashes in a tray that can be emptied into the water or ashore.
Norwegian manufacturer Cinderella is the specialist in these objects.
If you don’t have the space to install a bioreactor (and they are bulky), the least you can do is empty your blackwater tanks in port or beyond the 8 NM zone. Shipyards should include these solutions in their catalogs. However, without pressure from demand, regulations, or authorities, they have little interest in addressing such difficult-to-market issues with elegance!
