Background
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Statutory Documents - IMO Publications and Documents - Circulars - Marine Environment Protection Committee - MEPC.1/Circular.677 – Guide to Diagnosing Contaminants in Oily Bilge Water to Maintain, Operate and Troubleshoot Bilge Water Treatment Systems – (22 July 2009) - Annex – A Guide to Diagnosing Contaminants in Oily Bilge Water to Maintain, Operate and Troubleshoot Bilge Water Treatment Systems - Background

Background

 There are a number of bilge water treatment technologies and products commercially available for use on board ships to remove oily waste from bilge water. A typical bilge water treatment system may be composed of the following components: a holding tank(s); a pre-treatment settling tank; an OWS; post-OWS secondary treatment and/or polishing units; and an oil content meter (OCM). Unfortunately, many of these basic bilge water treatment systems are unable to handle the mixture of contaminants presently found on board ships. Newer and more advanced systems are theoretically capable of handling most of these contaminants but there are still presently issues with the processing of bilge water.

The OCM is critical to the proper functioning of a bilge water treatment system. It controls the discharge of processed bilge water from the OWS, ensuring that the discharge does not exceed 15 parts per million of oil. Oil content meters are designed to detect oil particles in bilge water. They may also detect particles other than oil. Newer oil content meters are built to International Maritime Organization (IMO) standard resolution MEPC.107(49). They are specifically designed to detect oil emulsions particles and prevent their discharge. A design limitation in most oil content meters is that they are limited in their capability to discriminate between oil and some non-oil particles. Older resolution MEPC.60(33) oil content meters are poor at detecting oil emulsions. Newer resolution MEPC.107(49) meters are more finely tuned to detect emulsions and iron oxide particles; however, there are still limitations in their ability to detect some particles and non-oily emulsions. (See Appendix I for a discussion on the theory of OCM operation.) When there is a heavy particulate load in the processed bilge water, oil content meters can often prevent the discharge of processed bilge water. To this end, determining what contaminants, particulates, and particulate and emulsion forming chemicals are present in the bilge is essential.

A lack of understanding of present-day contaminants remains an obstacle in the efficient operation and troubleshooting of bilge water treatment systems. Furthermore, many equipment manufacturer’s maintenance, operating, and troubleshooting manuals do not adequately address the larger problem of contaminants, and the need for proper shipboard oily waste water and bilge water management. Improper bilge water management practices are a major factor in problems which can lead to equipment failure. This Guide provides the foundation for the development of bilge water contaminant identification skills, along with diagnostic and bilge water treatment system troubleshooting techniques. Sources of bilge water contamination and techniques to identify the potential contaminants are presented for the marine engineer to assist in both preventing and diagnosing system failures. A diagnostic decision tree for bilge water treatment systems operating in the full range of shipboard environments is provided for use in troubleshooting common system problems. The decision tree is annotated and includes detailed diagnostic techniques and recommended remedial or corrective measures for both acute and chronic conditions. The decision tree is designed to be used by shipboard engineers (from the “4th engineer” to the Chief Engineer) and shoreside technical support. Interviews with ship operators, marine engineers and others indicate the need for more information to make environmentally sound and cost (e.g., life-cycle costs) effective decisions to design, procure, operate and maintain adequate OWS and supporting components (i.e. the bilge water treatment system). The diagnostic and troubleshooting decision tree will also facilitate informed decisions by marine engineers and shoreside management on bilge water treatment options. These options include retrofitting or upgrading equipment or employing other oily waste water and bilge water management practices, including contaminant minimization. Contaminant minimization is directly associated with practices related to maintenance, cleaning and operation of all equipment, and systems within a machinery space.

Both the volume of waste oil to be separated and the volume of water entering the bilge are a major concern for the proper management of onboard bilge water. A ship operator’s inattention to excessive oily waste generation directly associated with the maintenance, cleaning and operation of equipment, and systems within a machinery space can increase the “wear and tear” on bilge treatment systems and the likelihood of system failure. Excessive introduction of clean water into the bilge also increases the likelihood of failure. A more detailed analysis and discussion of these issues are beyond the scope of this Guide.

Parent topic: Annex – A Guide to Diagnosing Contaminants in Oily Bilge Water to Maintain, Operate and Troubleshoot Bilge Water Treatment Systems
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