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Aco Marine S.R.O.

How a yacht handles its wastewater increasingly dictates where it can cruise in the world, which means wastewater collection and treatment should be critical considerations during the design phase. What are the latest technologies available, and how do they impact the design of today’s superyachts?How often, when using the heads, washing the decks or flicking the air-con on, do we think about where the water and waste go? Chances are the answer is hardly it all – yet the handling of wastewater on yachts is mission critical, not just for the comfort and health of guests and crew, but also increasingly for where the yacht can go.Complying with regulations also doesn’t just mean getting a wastewater system signed off. Proper crew training is essential. Even a simple system that relies on holding tanks can be fraught with danger, as anyone whose tanks have automatically discharged in the wrong place can attest – hefty fines and criminal charges have been known to have been levied against unfortunate superyacht captains caught unawares.<img src="https://photo-assets.superyachttimes.com/photo/380492/image/large-ce0e502c9330a0437b0b34f2241a4700.jpg" data-gid="gid://syiq/Photo/380492">Yachts present certain challenges when it comes to selecting the best form of wastewater treatment. For a start, water usage on board per person is typically considerably higher than on commercial vessels, thanks to increased use of guest showering, laundry and other factors – and, of course, the obligatory washdowns.Wastewater systems manufacturer <a data-gid="gid://syiq/Company/8602" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Hamann AG (Company)">Hamann</a> estimates that a cargo ship, when combining head, showers, washbasins, galley and laundry, produces in the region of 135 litres of wastewater per person per day, but for a yacht the guideline is around 450 litres per person per day. Solutions manufacturer <a data-gid="gid://syiq/Company/3624" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Aco Marine S.R.O. (Company)">ACO Marine</a> reckons 160 to 200-litres per person for a cruise ship compared to up to 500-litres per person for a yacht.Yacht wastewater also includes sources that can quite easily be overlooked. There’s black water (the water that comes from toilets and urinals) and grey water (comprising drainage from showers, washbasins, laundries, galley sinks and dishwashers), but there’s also wastewater from special systems such as spa pools, deck drains, and even HVAC condensate – a particular issue in hot cruising regions. Then there’s the issue of peak flow moments, such as after breakfast, which can easily overwhelm systems if the correct buffers aren’t built in.<img src="https://photo-assets.superyachttimes.com/photo/380489/image/large-431a108cc2db03cd6ea8c7101c64e7cf.jpg" data-gid="gid://syiq/Photo/380489">“One of the biggest mistakes you can make is to walk into a project thinking, ‘We just need a sewage treatment plant for X number of people’,” begins Mark Beavis, Special Projects Director at <a data-gid="gid://syiq/Company/3624" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Aco Marine S.R.O. (Company)">ACO Marine</a>. “Moreover, there’s always room for toys like jet skis and tenders, but rarely for the wastewater treatment system. Every part of the yacht generates wastewater, and once you understand where and how, you can manage it responsibly.”“A sewage management system needs to be designed properly, from sewage collection via sludge handling to effluent discharge,” adds Olaf Hansen, Head of Technical Department at <a data-gid="gid://syiq/Company/8602" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Hamann AG (Company)">Hamann</a>. “Sewage treatment plants, black and grey water lines, grease separators, system separators preventing microbes from spreading against the flow from waste water lines into fresh water systems, holding tanks, tank aerations, transfer systems, sludge tanks, sludge processing facilities and performance monitoring are all part of the system. Of course, every project is different, therefore a sewage management system has to be customised to cover the specific conditions on board.”Beavis concurs: “We’ve built dozens of systems and no two are the same. This is miniaturised cruise ship tech, adapted to yachts. We also need to understand where every drain is – from bow to stern, port to starboard – and how that flow is transferred to treatment.” <img src="https://photo-assets.superyachttimes.com/photo/380493/image/large-124582f1d9876ac6bbdf2755cebc6652.png" data-gid="gid://syiq/Photo/380493"> Treatment optionsTreatment systems come in several forms. At the most basic, that could be a simple collection and holding system, which is then discharged in a port facility (or at sea under certain criteria), but that has a cost and it limits operational flexibility. The next step up are systems utilising a combination of filtration and sterilisation by chemical dosing or electro-catalytic action, but these are not very environmentally friendly and certain aspects – such as the use of corrosive hydrogen peroxide or chlorine – bring significant problems.The global operating profile of large yachts (and other passenger ships) means membrane bioreactor treatment (MBR) technology is a popular option. MBRs utilise biological processes to eat the waste, producing an inorganic sludge that can be safely discharged ashore, or at sea if local rules permit. The membrane is so effective that no sterilisation chemicals nor UV treatment are required, and the clear effluent, while not considered potable without additional treatment, can be recycled for toilet flushing, deck washing, or engine cooling. “There’s still a psychological hurdle with the drinking part, but technically it’s doable,” advises Beavis.There are also now enhanced conventional biological treatment systems that offer a simpler alternative to MBRs that are suitable for LY3 yachts of no more than 12 passengers that do not require additional compliance for nitrogen and phosphorus removal. Any large vessel, yacht or otherwise, has to have a functioning sewage treatment plant on board, or an <a data-gid="gid://syiq/Company/4531" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="International Maritime Organization (Company)">IMO</a>-approved holding system and selection is made on number of people rather than length of yacht.“With a yacht for only 12 passengers a conventional system is often used with utilises extended aeration and steeling processes – we’ve used those on yachts up to 100 metres in length and that works fine,” says Beavis. “A biological system is a volumetric process – it needs a certain volume of waste per person and it needs a certain amount of residence time for the biology to eat the waste and then for the sludge to settle out.”When it comes to considering a system for a yacht, both simplicity for the crew and system flexibility are key so the vessel can be either stood down with just a few crew on board, or do a marathon charter with a full complement of guests.“That flexibility is critical,” insists Beavis. “Because if you have one size of treatment plant and it’s sized for 100 people on board, that’s great when you’re at capacity, but if it drops to 25 people it will be under-loaded – there’s not enough food coming through to keep the biological quality, and the biology dies off because there isn’t enough to feed it and that can lead to system collapse. Aerators keep the bacteria alive from an oxygen point of view, but they need food.”<img src="https://photo-assets.superyachttimes.com/photo/380491/image/large-ec72942adb8affd6a6132a27a8a5f2a6.png" data-gid="gid://syiq/Photo/380491"> System considerationsIt’s not just about the core sewage treatment plant: pre-treatment is vitally important too. Galley waste, grease separation and solid separation need to be carried out, not least because these aspects can lead to biological overloading. For the laundry, a flimsy little lint filter in the washing machine is not enough – it needs to go through a proper industrial filter system.&nbsp;“Pre-treatment is also critical in terms of toilets as you’d be surprised what ends up going down them, from Rolex watches and wedding rings to condoms and sanitary products,” continues Beavis. “The latter seem to find their way through every part of the system including the macerators, before wrapping themselves around float switches and causing tanks to overflow!”Sewage treatment plant and wastewater tank ventilation, plus the aeration of those tanks to make sure they don’t go anaerobic – which can lead to the production of deadly hydrogen sulphide – is also vitally important. Post-treatment using an ultraviolet ozone deodorising system can be an effective way of scrubbing odours and particles from vent gases.“The vents go up the funnel and that has to be considered – on one very big yacht the owner arrived in his helicopter, got out, and what’s the first thing he smelt? To say that the effluent hit the fan would be an understatement.” <img src="https://photo-assets.superyachttimes.com/photo/380496/image/large-9c7482a0715ccc24532820f4215b89a6.jpg" data-gid="gid://syiq/Photo/380496">Planned approachesProfiling a yacht’s requirements and mapping out its systems is key to ensuring an effective and efficient outcome, and that means getting expert input when still in the engineering phase. “The earlier we get involved in a project, the better the results can be,” says Hansen. “We often do workshops with ship design companies and naval architects before or at the very beginning of a project to improve the sewage management system as a whole. During construction we closely work together with the shipyard engineers on creating the best possible conditions on board in order to operate our systems properly.”Wastewater management of superyachts is a challenging dilemma often not addressed early enough. This easily leads to compromises and getting it wrong can be a very costly mistake, which is why naval architects, yacht designers, and yacht builders should seek expert advice from an established wastewater solution provider at the earliest opportunity.CertificationOne essential element to check when specifying a system is that any certifications (<a data-gid="gid://syiq/Company/4531" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="International Maritime Organization (Company)">IMO</a>, EU-MED or USCG) it holds are both real and accurate – in other words, be wary of so-called ‘magic boxes’.“A sewage treatment plant that is claimed not to produce sludge is the classic example of what we call a ‘magic box’,” warns <a data-gid="gid://syiq/Company/8602" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Hamann AG (Company)">Hamann</a>. “This is not only a certification without conformity to the rules, it is a scientific impossibility, as sludge is an inevitable by-product of sewage treatment. If chlorination is used for disinfection, is there a dedicated de-chlorination step? Is sludge required to be recirculated back to the feed tank? Recirculating sewage sludge back to a treatment plant’s inlet is explicitly prohibited by the Guideline for type approval tests. Be critical. Certification without conformity to the rules is more common than one might think.”<img src="https://photo-assets.superyachttimes.com/photo/380495/image/large-8be73ff3088de6d998b6e16904d0ba09.jpg" data-gid="gid://syiq/Photo/380495">RegulationsThe treatment and discharge of sewage at sea is regulated under the <a data-gid="gid://syiq/Company/4531" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="International Maritime Organization (Company)">International Maritime Organisation</a>’s Annex IV of MARPOL (marine pollution) regulations which applies to vessels of 400 GT and above or certified to carry more than 15 persons. According to Annex IV, it is generally considered that on the high seas, the oceans are capable of assimilating and dealing with raw sewage through natural bacterial action. As a result, says the <a data-gid="gid://syiq/Company/4531" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="International Maritime Organization (Company)">IMO</a>, “the discharge of sewage into the sea is prohibited, except when the ship has in operation an approved sewage treatment plant or when the ship is discharging comminuted and disinfected sewage using an approved system at a distance of more than three nautical miles from the nearest land. Sewage which is not comminuted or disinfected may be discharged at a distance of more than 12 nautical miles from the nearest land when the ship is en route and proceeding at not less than 4 knots.”MEPC.227(64) deals with the type of wastewater treatment equipment that has to be on board, how it has to perform, how it has to be tested and how it should be monitored. But it also goes further in one clause which is very specific, and very relevant to PYC superyachts: Section 4.2 addresses passenger vessels operating in <a data-gid="gid://syiq/Company/4531" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="International Maritime Organization (Company)">IMO</a> Special Areas, and they have to meet additional standards for the treatment and removal of phosphorus and nitrogen (using membrane bioreactor technology). Although the Baltic Sea is currently the only <a data-gid="gid://syiq/Company/4531" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="International Maritime Organization (Company)">IMO</a> Special Area under Annex IV (sewage pollution), other regions such as Western Australia and parts of the Mediterranean are either applying to become SAs or looking to introduce equivalent local rules.“MEPC.227(64) Section 4.2-compliant MBR systems offer a truly future-proofed solution to all current and anticipated legislation,” says Beavis. “The days for other alternative chemical and dilution systems are seriously numbered. No yacht should ever find itself in a situation where it is prohibited from either sailing from – or into – any given port anywhere in the world.”<img src="https://photo-assets.superyachttimes.com/photo/380494/image/large-72826adcd8e42e34f60d9efda55bfd7d.jpg" data-gid="gid://syiq/Photo/380494">Size mattersThe problem facing larger yachts, in particular, is the extreme variation in system requirements depending on who is on board at any given time, from solely crew to full guest and VIP modes complete with additional staff and entourage. Such fluctuations can be hard to accommodate if the system isn’t thought through. For <a data-gid="gid://syiq/Company/3624" href="#managed-by-system" rel="noopener noreferrer" target="_blank" title="Aco Marine S.R.O. (Company)">ACO Marine</a>, that has involved developing a multi-mode system that can be scaled up or down via a selector switch, an example being the Maripur 150 system they installed aboard Azzam that has settings for 50, 100 and 150 people.”If the yacht is at capacity with 150 people on board then all membranes are brought online, all pumps operate at rated capacity, and everything is running. With owner and some guests plus crew on board, or just the crew on board, the selector is switched to the 100 or 50 people setting, and the pumps run at reduced capacity controlled via frequency converters, with the flow rate through the membranes reduced.&nbsp;“The operating levels are lower because there's less coming in, but we want to keep the concentration at the same level, and so it re-tunes itself to that reduced input level,” Beavis explains. “Then when the call comes that the owner and guests are coming on board, they just turn the system back up.”This article was first published in <a href="https://www.superyachttimes.com/magazine/how-to-build-it-issue-9-download" rel="noopener noreferrer" target="_blank" title="">Issue 9 of How To Build It</a>. You can read all the articles from this edition <a href="https://www.superyachttimes.com/magazine/how-to-build-it-issue-9-download" target="_blank">here</a>, and stay up-to-date with all previous editions <a href="https://www.superyachttimes.com/magazine" target="_blank">here</a>.

superyacht wastewater treatment systems

Wastewater regulations now shape where superyachts can cruise. Explore modern treatment tech and the design choices needed for compliance.