Certificates for sewage treatment plants: How to recognise non-conformities and magic boxes


Certification of sewage treatment plants without conformity to the rules is a real problem as the certification process does not always live up to the required standards. As regrettable as it is, it is a fact. We take a closer look at the problem and show you how to determine whether a plant is legitimately carrying its certificate or not.

Many ships have a sewage treatment plant (or marine sanitation device in U.S. terminology) that is approved under the inter-related regulatory regimes such as the IMO’s MEPC Guidelines (IMO certificates), the European Marine equipment Directive (EU-MED certificates), and the Code of Federal Regulations (CFR) of the US (USCG certificates), who is not party to the IMO’s sewage rules. The approval authorities are the gate keepers responsible for testing and evaluating candidate technologies of various features and claims. A successfully type approved sewage treatment plant is the basis for a series of models with the same design principles covering a wide range of treatment capacities.

However, some sewage treatment plants on the market are certified to the current standards of IMO MEPC.227(64) and/or the U.S. 33 CFR 159 despite obvious non-conformities or even scientific impossibilities. Ship owners and operators should be aware of this fact. Having a sewage treatment plant on board which is not only certified, but which actually complies with the rules and performs as required by the rules can save them a lot of trouble if their pollution prevention equipment is inspected and tested by the authorities.

Non-conformities and “magic box” issues are related to these four areas:

  • Handling of sewage sludge
  • Use of chlorine
  • Recirculation
  • Handling of greywater

The good news is that it is fairly easy to determine whether a particular plant is in breach of the rules. By asking the following four questions, you will get straight to the heart of the matter.


A sewage treatment plant that is claimed not to produce sludge is the classic example for what we call a “magic box”. 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 (further reading here). These magic boxes do not have the technologies to separate the sludge that develops in the treatment process. They cannot perform no matter how well they are operated. To identify the magic box is easy: Simply check if there are any de-sludge instructions and provisions, e.g. that a dedicated sludge holding tank is required.


Chlorination can be effective in disinfecting biologically treated sewage. But to meet the residual chlorine limit of 0.5mg/l, a de-chlorination step is necessary. However, many sewage treatment plants have been certified without de-chlorination –another scientific impossibility, given the level of chlorination and the short contact time (further reading here). To identify this magic box, check whether de-chlorination is provided for in the treatment process.


Recirculating sewage sludge back to a treatment plant’s inlet is explicitly prohibited by the Guideline for type approval tests (see IMO MEPC.227(64) Paragraph 5.2.1 and 5.2.3, and Figure 1  and 33 CFR 159.121 Paragraph (c) and (d). Also further reading here) It can artificially inflate treatment capacity, and, by replacing raw sewage with sewage sludge that has already been through the treatment process, invalidate the challenging characteristics of raw sewage. To identify such a certification without conformity to the rules, ask if the sewage sludge is required to be returned to the sewage treatment plant’s feed tank.


For ecological and economic reasons, it makes a lot of sense to treat grey water together with sewage (black water) in one process. It this is to be done, it inevitably leads to an increased size and capacity of the sewage treatment plant to accommodate the additional wastewater volume. However, in a few cases, certification has been awarded to sewage treatment plants having the grey water connected to the final sewage disinfection stage. This not only renders the disinfection stage ineffective, resulting in poor performance, it is a non-conformity (further reading here). IMO MEPC.227(64) introduced a Dilution Compensation Factor with the intention to rule out sewage treatment plants relying on dilution (e.g. with seawater) as a “treatment principle”. This factor Qi/Qe =1 means that influent volume to the plant must equal effluent volume from the plant. If greywater is sent to the sewage treatment plant downstream of the influent sample point Qi, then the factor is Qi/Qe <1. To identify such a certification without conformity to the rules is easy: If the sewage treatment plant treats grey water but does not receive it at the beginning of the treatment process, it is in breach of the rules.


Be critical! Certification without conformity to the rules is more common than one might think. While it is very unfortunate that an IMO, MED or USCG certificate cannot be trusted blindly, it is fairly easy to check whether a sewage treatment plant is legitimately carrying its certificate or whether it should not have been certified in the first place. When considering the costs that can be imposed on owners and operators if plants fail official tests in real operation, only few arguments remain in favor of installing such a plant, however small or low-priced it may be.

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HAMANN AG is supplying sewage and wastewater management systems for three new US REGIONAL CLASS RESEARCH VESSELS currently under construction at GULF ISLAND SHIPYARD in Houma, Louisiana, USA.

The 199 feet / 60 meters long REGIONAL CLASS RESEARCH VESSELS were designed by Glosten from Seattle, USA, in cooperation with OREGON STATE UNIVERSITY. They provide accommodation and workplaces for up to 16 scientists and are operated by a crew of 13. Their purpose is the exploration of the coastal marine environment. The highest environmental protection requirements and the lowest possible noise emission played an important role in the development of the vessels design. The extensive new building project is financed by the NATIONAL SCIENCE FOUNDATION (NSF) and managed by the OREGON STATE UNIVERSITY.

Regional Class Research Vessel equippend with HAMANN sewage and wastewater technology

The first of the three research vessels will be launched this year as “RCRV Taani 1” and will be commissioned by the OREGON STATE UNIVERSITY on the west coast as part of the UNIVERSITY-OCEANOGRAPHIC LABORATORY SYSTEM (UNOLS).

The sewage and wastewater management systems on board the vessels are designed to treat black water from toilets and grey water from showers, washbasins, kitchen sinks and laundries, and can process a peak of 6,000 litres of wastewater per day. HAMANN HL-CONT PLUS 025 wastewater treatment plants with IMO MEPC.227(64) and USCG Type 2 (33 CFR 159) certification are used as a basis. The HAMANN DISSOLVED AIR FLOTATION (DAF) technology used in these plants does not require any filters or membranes, making the plants particularly low-maintenance and reliable. Even strong fluctuations in the volume of wastewater to be treated due to fluctuating numbers of people on board are no problem for these plants.

Regional Class Research Vessel equipped with HAMANN sewage and wastewater management system

Highly efficient HAMANN grease separators separate the grease components from the galley wastewater to prevent clogging of the pipelines by grease deposits and the formation of hydrogen sulphide in holding tanks.

Automatically controlled HAMANN tank aerators compensate for the lack of oxygen or oxygen consumption in the wastewater holding tanks, which, especially in connection with too high fat contents in the wastewater, promotes the formation of toxic and odorous hydrogen sulfide and ultimately of aggressive sulfuric acid.

Further information on the REGIONAL CLASS RESEARCH VESSELS can be found under the following link: https://ceoas.oregonstate.edu/ships/rcrv/

All graphics courtesy of Glosten, Seattle, USA

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Wastewater treatment terms: Wastewater, sewage, blackwater, greywater, graywater. Which term means what?


There are several terms around that are used in the context of wastewater treatment. Some of them are very specific while others aren’t specific at all. Let’s dive into it and get it straight!


“Wastewater” is a generic term and can mean either black and grey water together or separately, depending on the context. The term “wastewater” is also used synonymously with the term “sewage”. While “wastewater” is the most commonly used term, it is less selective than “Sewage”, “Black water” or “Grey water”.


“Sewage” is the most official among the wastewater treatment terms. It is the term used by the IMO (International Maritime Organization) both in the MARPOL Convention (International Convention for the Prevention of Pollution from Ships; “MARine POLution”) as well as by the IMO’s Marine Environment Protection Committee (MEPC) when dealing with the subject. All IMO resolutions issued by the MEPC on this subject speak of “Sewage” and “Sewage treatment”. Therefore, IMO certificates are issued for “Sewage treatment plants”, they don’t say “Wastewater treatment plants”.

MARPOL Annex IV gives the following definition of “sewage”:

“3. Sewage means:
drainage and other wastes from any form of toilets and urinals;
drainage from medical premises (dispensary, sick bay, etc.) via wash basins, wash tubs and scuppers located in such premises;
drainage from spaces containing living animals; or
other waste waters when mixed with the drainages defined above.”


Among all the wastewater treatment terms, the term black water is not officially used by the regulatory authorities and is therefore not clearly defined. In general, the term black water is used to mean “Sewage” as defined in Annex IV of the MARPOL Convention.


First of all this term is spelled in two different ways: Graywater with an “a” is mostly used in American English and greywater with an “e” is used in British English. Grey water is defined in IMO (International Maritime Organization) resolution MEPC.227(64) as follows:

“2.7 Grey water – is drainage from dishwater, galley sink, shower, laundry, bath and washbasin drains and does not include drainage from toilets, urinals, hospitals, and animal spaces, as defined in regulation 1.3 of MARPOL Annex IV and does not include drainage from cargo spaces.”

To find out more on HAMANN sewage and wastewater technology, click here!

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Food waste and wastewater handling onboard ships

Food waste and wastewater: Don’t mix and match!

Food waste does not belong in the wastewater system of a ship, not only regarding the efficiency of the system but also from a legal point of view. The handling of food waste is strictly regulated for good reasons, and making it disappear with the help of the sewage system is at best non-compliance. Disposing of ship sewage mixed with food waste on land is in breach of national biosafety regulations and poses a potential biohazard to local communities and the environment. Mixing food waste with wastewater on board a ship already violates Annex V of IMO’s MARPOL convention as such.

Food waste can spread plant pests, as well as livestock and poultry diseases such as swine fever, rabies, foot and mouth disease or avian flu. Some countries have strict biosecurity regulations falling under the jurisdiction of the national agricultural authorities, while others have ad-hoc measures.

In short, these rules demand that food waste be either discharged to the sea beyond 3 nm or 12 nm from the nearest land or transferred to the approved facilities for disposal. In the meantime, it must be managed in a way that is leakproof.

Annex V of IMO’s MARPOL Convention permits three routes for a ship’s food waste: to the sea (beyond 3 or 12 nm from the nearest land); to an onboard incinerator; and to port reception facilities. The actual disposal route must be recorded in a Garbage Record Book.

However, on many ships, food waste and its derivatives are sent, in whole or in part, to the grey water system, where it vanishes without a trace. The technical standards of some classification societies permit food waste to be sent to the sewage treatment plant instead of a food waste holding tank as stipulated in section 2.9.2 of IMO MEPC.259(71). Such standards create further non-conformity because sewage treatment plant is not one of the three permitted routes in the Garbage Record Book, which is completed and signed by the ship Master.

The diagram below illustrates the extent of potential non-compliances, looking at a food waste disposer as one of many potential examples.Non-conform food waste handling through wastewater system

Food waste entering the system from the top left corner of the diagram never comes out from the system; it simply vanishes. Tracing the lines to the port reception facilities (PRF), it is clear how food waste gets ashore in disguise, escaping the ‘approved facilities’ intended by the local biosecurity rules. From there it can end up on the agricultural land, carrying biosecurity risks with it.

Read the full article by Dr. Wei Chen on The Martime Executive

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Remote support by HAMANN AG


While this is a difficult time for the world in general, facing the COVID-19 pandemic, it is a good time to talk about remote support. Technical equipment doesn’t care whether it is an appropriate time to cause trouble or not. So what to do when a customer can’t fix a problem himself and help won’t be able to get there in person? Remote support is the answer.

Remote support is a sustainable way to offer technical customer support, because it does not only make sense in a crisis situation. With all the audiovisual communication tools at hand today, many issues can be solved remotely without having to physically travel thousands of miles. And to reduce travel, specifically air travel, helps us in another crisis that has been pushed from the news top spot by the current virus: the climate crisis.

However, what is HAMANN REMOTE SUPPORT able to do for our customers?

First of all, our highly skilled service engineers will communicate with the customer via telephone or email to narrow down the problem. Then, they will set up a videocall and the customer’s mobile device will enable our service engineers to “come on board” and take a look at the plant or component themselves. Under the guidance of the HAMANN service engineers, the customer carries out the appropriate actions.

No special equipment is needed and the amount of time, effort and cost to set up a remote support session is far less than actually flying in a service engineer in person.

But off course there are limitations to what can be reasonably handled in a remote support session. The need to deploy a service engineer on location rises with the complexity of the issue at hand. Our experienced service team will advice our customers on what is the best way to deal with a given problem.

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by Dipl. Ing. Olaf Hansen, Head of Technical Department at HAMANN AG

During the last months, the industry of wastewater and sewage treatment technology has seen some notable and partly confusing actions regarding the certification of products. Due to increasing pressure from both the industry and the legislative side, certificates for some sewage treatment plants on the market have been suspended or withdrawn by certifying bodies. This indicates that the certification system needs to be revised. A group of industry players – we are among them – has issued a call for action to improve the guidelines for the certification of sewage treatment plants.

Fortunately, it is the intention of many ship owners to reduce the environmental impact of their ships or just aiming to comply with existing regulations. As a matter of fact, these owners are exposed to a high financial risk when the sewage treatment systems on board do not comply with required effluent standards.

Public authorities around the world are getting more and more sensitive to marine pollution by sewage from ships. A recent example is the Maritime and Port Authority of Singapore (MPA Singapore) which has just issued a circular to all owners, managers and masters of Singapore-registered ships in which they point out that malfunctions of sewage treatment plants have been the most frequent reason for ships to be detained by Port State Control in the year 2019 so far.

If a certificate of an operating plant gets withdrawn because it does not meet the required effluent standards, the ship owner might be forced to have it replaced by another plant with a valid certificate and/or to pay a significant fine.

Considering this, we encourage all ship owners and shipyards to look beyond the certificates and to challenge us – the manufacturers – to deliver sewage treatment systems that perform in terms of effluent quality, ease of operation and reliability. We suggest to broaden the perspective and to take a look at what a sewage management system actually is – or should be.

Sewage management is more than having a sewage treatment plant. A sewage management system needs to be designed properly: From sewage collection via sludge handling to effluent discharge. 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. Off course, every project is different. Therefore a sewage management system has to be customized to cover the specific conditions on board.

There are a few key factors that influence how well a sewage treatment system performs. First and foremost, food waste and sewage lines strictly have to be separated. Food waste has a much higher BOD5 (Biological Oxygen Demand) value than raw sewage and therefore heavily increases the organic load on the sewage treatment plant. Grey water from galleys needs to run through a properly designed and dimensioned grease separator before being stored in a holding tank. Grease from galleys not only plugs up pipes and sensors, but also catalyzes the build-up process of hydrogen sulfide which is a toxic and extremely smelly gas inside the holding tanks. In the worst case, sulphuric acid may be formed inside the holding tanks which then attacks the piping and leads to a degradation of the effluent values.

Last but not least, the organic load of the sewage treatment plant should be monitored and controlled in order to maintain the organic design-load which was certified. For example, IMO resolution MEPC.227(64) requires a sewage treatment plant to produce the defined effluent values based on a TSS (Total Suspended Solids) value of ≥ 500 mg/l in the influent. Our sewage treatment plants are designed within these parameters but with a margin allowing for varying load situations. Operating the plant for a longer period above this margin leads to reduced treatment effectiveness and therefore a degradation of the effluent quality. In extreme cases, overloading can lead to a complete breakdown of the plant.

For us as a manufacturer it is evident that we cannot leave the planning and design of a sewage treatment system to the customers and just sell them sewage treatment plants. An important part of our business is consulting. The earlier we get involved in a project, the better the results can be. 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 the detail construction we closely work together with the shipyard engineers on creating the best possible conditions on board in order to operate our systems properly.

Sewage management is more than having a sewage treatment plant. It’s a properly designed wastewater management system. But even the best system is useless if operation and maintenance overtaxes the crew on board. It makes no sense to expect a ship’s crew to have expert knowledge in the field of sewage treatment like staff of most land based sewage treatment facilities have. Marine sewage treatment plants should be operated safely without years of prior training. We incorporate this aspect in the design of our systems and put a lot of effort in the automation of routine operations, high usability and low maintenance requirements. Only then, a well-designed sewage management system performs well.

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