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.

QUESTION 1:
WHAT HAPPENS TO THE SLUDGE?

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.

QUESTION 2:
IF CHLORINATION IS USED FOR DISINFECTION, IS THERE A DEDICATED DE-CHLORINATION STEP?

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.

QUESTION 3:
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 (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.

QUESTION 4:
IS GREYWATER SENT TO THE SEWAGE TREATMENT PLANTS LAST TREATMENT STAGE?

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.

SUMMARY

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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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.

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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What is wastewater, sewage, black water, grey water? There are a multitude of definitions of these terms, which sometimes differ more, sometimes less. These definitions are given by the INTERNATIONAL MARITIME ORGANISATION (IMO), the U.S. ENVIRONMENTAL PROTECTION AGENCY or classification societies. Here you can find out what is meant and what it is all about!

WHAT IS WASTEWATER?

Wastewater is to be understood as a generic term that can include many different substances. Ballast water, bilge water, wash water from exhaust gas cleaning systems, residual water from food waste, drainage from toilets, showers, wash basins, etc. – all this basically falls under the term wastewater.  The term wastewater is therefore not very selective.

When we speak of wastewater in our field of activity, we mean sewage. Both terms are often used as synonyms, although this is not very accurate.

WHAT IS SEWAGE?

HAMANN AG defines Sewage as follows:

• Drainage and other wastes from any form of toilets, urinals and WC scuppers
• 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
• Grey water when mixed with the drainages defined above

Sewage therefore contains black water in any case and can also contain grey water.  The technology of HAMANN sewage treatment plants is designed to always process a mixture of black water and grey water – i.e. sewage in its entirety.

Different definitions of the term sewage come from e.g. the IMO, the EPA and classification societies.  Our definition above is largely congruent with that of the IMO. The IMO, however, formulates the last point more openly and speaks of “other waste waters when mixed with the drainages defined above”. We are more specific here by limiting this point to grey water. One reason for this is, for example, that mixing black water with residual water from food waste (which would fall under “other waste water”) would mean that the rules of MARPOL Annex IV (Sewage) would no longer apply to this mixture, but those of MARPOL Annex V (Food Waste).

WHAT IS BLACK WATER?

The term blackwater is not officially used by regulatory authorities such as the IMO, but it is used by the industry and classification societies. As with the term sewage, the definitions of black water also differ depending on the source.

HAMANN AG defines blackwater as follows:

• Drainage containing faecal matter, e.g. from toilets
• Drainage from medical premises if present

Black water is therefore a subcategory of sewerage. The terms blackwater and sewage are often used synonymously, as they both contain faecal matter.  However, HAMANN AG distinguishes between the two due to the higher concentration of faeces, pathogens and other potentially hazardous substances in black water.

WHAT IS GREY WATER?

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.

HAMANN AG defines greywater as follows:

• Drainage free from faecal matter or fat, e.g. from dishwashers, showers, wash basins, laundry, etc.
• Galley water after it has been processed in a grease separator.

The IMO (International Maritime Organization) resolution MEPC.227(64) point 2.7 also includes galley water in its definition of grey water, without making the treatment in a grease separator a requirement. However, due to the high fat content in galley water, separate treatment in a grease trap is important not only for the performance of sewage treatment plants, but e.g. for the entire piping system for sewage and greywater on board, which can otherwise quickly become clogged by fat deposits.

WHAT IS GALLEY WATER?

At HAMANN AG, we distinguish between grey water and galley water – unlike IMO, for example. The reason for this is the high fat content in galley water. Fat impairs the performance of sewage treatment plants and can, for example, clog the piping system for sewage and greywater on board due to deposits. That is why we require galley water to be treated in a grease separator so that it can subsequently be considered greywater and processed further in our wastewater treatment plants.

HAMANN AG defines kitchen wastewater as follows:

• Drainage from kitchen premises via sinks and scuppers located in such premises as it likely contains fat

WHAT IS SLUDGE?

Sludge, or sewage sludge, is an unavoidable byproduct of sewage treatment. Sewage treatment plants always generate two output streams:

• Treated sewage, also referred to as effluent
• Sewage sludge

Treated sewage (effluent) can be discharged into the sea (local/regional discharge bans such as in no-discharge areas must be complied).

Sewage sludge mus first be kept on board in holding tanks. There are two options for the discharge of sludge:

• Sludge can be discharged in ports via appropriate fixed facilities or by specialised service providers using tankers to land-based receiving stations
• Sludge can be discharged at sea at a distance of at least 12sm from the nearest shore. The requirements of IMO Resolution MEPC.157(55) (Recommendation on standards for the rate of discharge of untreated sewage from ships) shall be observed.

WASTEWATER IS NOT GARBAGE!

Solid garbage is to be considered separately from wastewater. Garbage is defined in MARPOL Annex V as follows:

“1.1 Garbage means all kinds of victual, domestic and operational waste excluding fresh fish and parts thereof, generated during the normal operation of the ship and liable to be disposed of continuously or periodically except those substances which are defined or listed in other Annexes to the present Convention.”

Garbage also includes food waste. Important: If garbage as defined in MARPOL Annex V, e.g. food waste from the galley, is mixed with sewage as defined in MARPOL Annex IV, i.e. mainly from the toilets, the stricter requirements of MARPOL Annex V apply to the treatment of the mixture.

HAMANN sewage treatment plants are exclusively designed for the treatment of sewage according to MARPOL Annex IV and grey water according to IMO resolution MEPC.227(64) and are not suitable for the treatment of garbage according to MARPOL Annex V.

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

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