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

Wei Chen

08 February 2019

Sewage pollution control is one of the first environmental initiatives in human history. Sewage treatment plants protect the aqua 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.

These 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 the 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, which brings the approval regime into total contradiction to the IMO’s intentions. But 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 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 ship owners and yards, a level playing field, the IMO’ environmental aspirations and ultimately, the pristine marine water 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 supporting further updates on this subject, please email.


[1] Wastewater Engineering, Treatment and Reuse, 4th ed, Metcalf & Eddy (2004)
[2] Wastewater Treatment: Concepts and Design Approach, 2
nd 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] Prevention of pollution by sewage from ships – rules and realities, W. Chen, ShipInsight Prevention of pollution by sewage from ships – rules and realities, W. Chen, ShipInsight Prevention of pollution by sewage from ships – rules and realities, W. Chen, ShipInsight (2018).

Co-authored by (in no particular order):

Dr Wei Chen, Future Program Development Manager, Wartsila 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
Felix von Bredow, Board of Hamman AG, Hamman AG, Germany

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