Call for Action on Sewage Treatment with No-Sludge Production


Published Feb 9, 2019 5:30 PM by Wei Chen

In late 2018, The Maritime Executive featured an editorial by me, Dr. Wei Chen of Wärtsilä Water Systems, on the subject of pollution by sewage from ships which suggested a widening gap between the marine rules and realities. It also mentioned a number of non-conformity issues associated with some certified sewage treatment plants. 

Now, a group of equipment suppliers, independent laboratories, academia, representatives of an environmental NGO and a shipowner, have come together to explore one particular issue regarding sewage sludge – a inevitable by-product generated from a wastewater purification process. The question is simple: why have approval assessment bodies have certified something that is deemed scientifically impossible? The group has published a statement (below). They have not provided answers but rather they point out the uncertainties in the current type approval process for marine sewage treatment plants and called for reviews by the approval assessment bodies and their respective Administrations. 

Sewage Treatment with No-Sludge Production – A False Claim, and a Non-Conformity

Co-authored by (in no particular order): 

Dr. Wei Chen, Future Program Development Manager, Wärtsilä Water Systems Ltd, UK 
Mark Beavis IEng IMarEng FIMarEST, Managing Director, ACO Marine s.r.o., Czech Republic, ACO Marine Systems GmbH, Germany 
Dr. Elmar Dorgeloh, Manager Director, Development and Assessment Institute in Waste Water Technology at RWTH-Aachen University (PIA), Germany 
Holger Hamann, Managing Director, Holger Hamann Consulting GmbH, Germany
Matthew MacGregor, Executive Director, TEi-Testing Services, LLC, USA
Dr. Daniel Todt, Project Manager R&D, Ecomotive AS, Norway
Niclas Karlsson, Managing Director, Clean Ship Scandinavia AB, Sweden
Mark Mellinger, President, Headhunter Inc., USA

Endorsed by (in no particular order): 

Benny Carlson, Chairman and owner, Marinfloc, Sweden
Antony Chan, Engineering Manager, Victor Marine Ltd., UK
Helge Østby, Senior Technical Advisor, Jets Vacuum AS, Norway
Melissa Nacke, Specialist, Arctic Shipping and Marine Conservation, World Wildlife Fund, Canada
Tjitse Lupgens, Advisor Environmental, Boskalis, Netherlands
Markus Joswig, Head of Marine Department, Testing Institute for Wastewater Technology GmbH (PIA GmbH), Germany
Tobias Kaulfuss, Manager, Marine Sewage Treatment, RWO - Veolia Water Technologies Deutschland GmbH, Germany
Dr. Gerhard Schories, Head of Institute, ttz Bremerhaven, Germany

Sewage pollution control is one of the first environmental initiatives in human history. Sewage treatment plants protect the aquatic environment of our cities, towns and villages. They turn raw sewage into clear and less harmful effluent. They also produce sewage sludge as a by-product. The treatment technologies are supported by wastewater science and engineering [1,2], whilst their compliance performance is assured by effective regulatory frameworks. A significant part of wastewater industry concerns sewage sludge: its characteristics, production, management and disposal [1,3], including possible re-use as a natural resource [4,5]. Sewage treatment produces sewage sludge. It is science, and it is a fact.

Some people in the marine industry disagree. Some marine manufacturers claim their sewage treatment plants do not produce sludge. Unfortunately, conformity assessment bodies have approved their equipment by crediting them with IMO and MED certificates. Thus, they have certified impossibilities, and created certified “magic boxes.”  These magic boxes contravene science. They are non-conformities. 

Magic boxes are easy to spot: there is an absence of sludge separation features within the treatment process. 

The sewage sludge, instead of being separated from the treatment process, is flushed out in the effluent. These magic boxes would not be able to perform no matter how well they are operated. Many are concerned about their poor performance status [6]. MEPC.227(64) Guideline tried to tighten the abusive use of dilution water during performance tests, and yet this has not stopped the impossibilities from being “proven” by “good laboratory results.” Certificates have become licenses to pollute. Something is very wrong, and we all need to know why, what and how. 

As a way of keeping the status quo, some say none of the Guidelines explicitly prohibits no-sludge claims. This is farcical and brings the approval regime into total contradiction to the IMO’s intentions.  Meanwhile, the non-conformities are spreading; the gap between rules and realities is widening [7]. 

Over the years, these magic boxes have become popular and influential. Consequently, valid technologies are under competitive pressure, and some have resorted to mimicking the no-sludge claims and been forced into a race to the lowest levels of functionalities. It’s been awkward, to say the least. 

There is a lot at stake: the credibility of the approval regimes, the liabilities to shipowners and yards, a level playing field, the IMO’s environmental aspirations and ultimately, the marine environment that we have agreed to protect. 

It may be time for the IMO, its Member States and the assigned approval assessment bodies to identify and to acknowledge this issue, to undertake transparent and timely reviews and to conclude what has happened and how to prevent such non-conformities from reoccurring. 

For those who wish to be contacted for further updates on this subject, please email [email protected]


[1] Wastewater Engineering, Treatment and Reuse, 4th ed, Metcalf & Eddy (2004)
[2] Wastewater Treatment: Concepts and Design Approach, 2nd ed, G.L. Katia (2013)
[3] Sewage Sludge Management: From the Past to Our Century, A. A. Zorpas, V. J. Inglezakis (2012) 
[4] 86/278/EEC, EC Directive on the Use of Sewage Sludge in Agriculture (1986)
[5] US EPA, 40 CFR Part 503 Rule, Standards for the Use or Disposal of Sewage Sludge (1993) 
[6] MEPC 64/23; MEPC 67/8/1; MEPC 71/14/2; MEPC 71/INF.22; PPR 6/14.
[7] Sewage from Ships – Rules and Realities https://www.maritime-executive.com/editorials/sewage-from-ships-rules-and-realities-1

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.