Oily water separators (OWS), necessary for treating bilge water prior to discharge at sea, enable owners to comply with Marpol guidelines and corresponding Flag State rules. The OWS, officially called a ‘15 ppm bilge separator’ in IMO documentation (IMO Resolution MEPC.107(49), effective from January, 2005, is tied to a ‘15 ppm bilge alarm’ designed to measure the oil content of the discharge mixture and sound an alarm if the effluent exceeds the maximum oil content allowance. The guidance also specifies that an ‘automatic stopping device’ be tied into the outlet line to recirculate the discharge water back into the system’s bilge tank.
The U.S. Coast Guard (USCG), in its 2008-2009 Proceedings, lays out its rule: “All vessels greater than 400gt and oil tankers greater than 150gt are required to have an oily water separator”.
Rear Admiral (Retired) Robert North, of regulatory compliance consulting firm, North Star Maritime, Inc., explains: “Though the international standard is 15 ppm, the U.S. Environmental Protection Administration (EPA), in its draft Vessel General Permit (VGP) proposal, has asked for comments on whether the standard should be tightened down to 5 ppm. Although some systems have been type approved to 5 ppm…many existing systems might not make it; for ships entering U.S. waters subject to the revised VGP, existing systems not type approved to 5 ppm would have to be re-tested or vessels would not be able to discharge overboard”.
Another issue identified by Admiral North concerns the upgrading of systems to meet the current standard: MEPC 107(49). The United States has made proposals at IMO that vessels be required to upgrade systems installed before January 2005 and type approved prior to the current standard.
Shipowners will find no shortage of equipment complying with the latest requirements. IMO’s listing of approved devices includes 471 bilge separators, 21 bilge alarms and 57 oil content meters for bilge alarms. The ranks are swelled by approvals of individual Flag States, who certify that the equipment meets the MEPC specifications, and class societies issuing type approvals.
OWS technologies have evolved from simple, gravity-based separation. A review of the U.S. National Pollutant Discharge Elimination System (NPDES) database, maintained by the EPA, shows that suppliers to the large fleets include a variety of well-known names with multi-stage OWS. A look at deployment among some of these fleets shows state-of-the-art technology that has moved far beyond simple decanting, where oil floats to the top.
The MEPC 107(49) standard includes additional type-approval testing with an oil/water emulsion more reflective of actual bilge water. Systems type approved to previous standards were only tested with pure oil/water mixtures. Such upgrading could include either a replacement of existing equipment or installation of an upgrading package. While these have been approved, there is no mandatory requirement to replace or upgrade systems installed prior to 1 January 2005 to meet 107(49).
Stena vessels in the database are outfitted with Skit S-Deb from RWO. With more than 13,000 systems in operation, RWO claims to be the world OWS leader. It offers a two-part approach. The USCG-approved equipment combines an open porous coalescer in the first stage, with a second-stage emulsion filter; this can be bypassed if the output from the coalescer is under the acceptable limit, extending the life on the filtration units. RWO’s Skit-S-Deb complies with the 5 ppm guideline of Germanischer Lloyd’s ‘Environmental Passport’ (a voluntary notation).
General Maritime Corporation has several tankers outfitted with Marinfloc equipment. Marinfloc offers a ‘white box system’, described as a fail-safe overlay. The OWS, with effluent content described as under 5 ppm, is supplemented with a white-painted wire cage and a recorder. According to Marinfloc: “The system works online and monitors the oil content in the water from your oily water separator or bilge water cleaning system. When the water from either of these systems is clean enough for discharge, a valve is opened and the water is pumped overboard”.
Even though 5 ppm is not a standard, this lower discharge threshold is currently one component of Det Norske Veritas’s Clean Design notation for newbuilds. Marinfloc, along with Alfa Laval, has earned the new DNV 5 ppm type approvals.
Though oil company tanker fleets have seen more outsourcing in recent years, one of the major ones, Chevron, has held on to its fleet of owned and operated ships. A scan of its controlled vessels with permits filed reveals OWSs from Sasakura Engineering, DVZ Services, Poseidon, Westfalia and Alfa Laval.
Overseas Shipholding Group (OSG), a major transporter of crude oil and products, has a number of foreign flag vessels using kit from Sasakura, DVZ, and Poseidon. A group of OSG’s U.S. flagships have gone with the Turbulo line from Blohm & Voss. Their OWS are also deployed on vessels in the fleets of Rickmers and a number of Greek owners. A two-stage process runs the bilge mixture through a gravity separation system (enhanced with oil-attracting coalescer plates), and then smaller particle emulsions are broken up mechanically as oil droplets adhere to fibres in a proprietary ‘HycaSep’ element. The units deployed on OSG’s vessels are rated for 5m3/hour discharge.
Wärtsilä’s USCG-approved Senitec line of separators (where reference accounts include Finnlines, Laurin Tankers and Rederei Transatlantic) also offers a multi-stage approach: oil is skimmed off (and circulated to the vessel’s sludge tank); emulsified suspended substances are then broken down via coagulation and flocculation – an electrical process that creates larger particles, called ‘flocs’, that can also be skimmed off; dissolved air is used to separate solids; culminating in active carbon filtration prior to discharging.
The class societies play a major role as recognised organisations in enforcement on behalf of the Flag States, which, in turn, are signatories to relevant IMO conventions, (Marpol Annex 1 in the case of OWS). Class also issues the International Oil Pollution Prevention (IOPP) Certificate, which certifies that compliant equipment has been fitted and details the vessel’s bilge and sludge tanks; the societies will also approve company plans for managing shipboard operations. The American Bureau of Shipping (ABS), in the ‘Marpol Surveys’ section of its Onboard Routine Maintenance Check Sheet, reminds owners that: “Findings noted during surveys and audits include: missing oil record keeping book or entries not up to date; poorly maintained, misoperating or inoperative equipment for separating oil from water including oil-content monitoring devices; sludge tank connected directly overboard.”
Similarly, a DNV ‘Master’s Checklist’ on Preventive Maintenance and Port State Control (PSC) identifies the bilge pumping arrangement, the OWS/filtering arrangement, the 15 ppm alarm and the oil record book as items for vigilance. There is good reason for this. A November 2011 IMO Resolution on PSC, aimed at harmonising inspections worldwide, includes OWS-related problems in a list detailing deficiencies of “a serious nature that may warrant the detention of the ship involved”. OWSs figure prominently in PSC detentions; a 2010 GL compilation of deficiencies on GL-classed vessels during 2008–2009 found OWS to be the fourth most frequent reason for detentions, followed by record book issues.
Complying with technical specifications is far easier than the shipboard management of the crew. A guide on OWS published by the International Chamber of Shipping reminds members of owners’ associations that: “Ship operators have ultimate responsibility for establishing a compliance culture within their companies”. The equipment suppliers are helping support such cultural changes. Marinfloc’s ‘White Box’ (as well as Alfa Laval’s ‘Blue Box’ and Wärtsilä’s ‘bilge water guard’) combines tamper proofing with record keeping and recording. The audit trail is a key feature of such units. Marinfloc emphasises that, “all vital monitoring and control equipment for the overboard discharge is in a locked cabinet connected to the vessel’s GPS. All vital data, such as oil content and valve positions, flow through the oil content monitor, and overboard flow, door open/closed, vessel’s position and time is recorded in a digital recorder”.
In spite of good intentions, advanced technologies are still prone to human intervention. Hendrik “Rik” F. Van Hemmen, president and senior partner at Martin Ottaway, a New Jersey-based Naval Architect/Engineering firm, described OWS in a 2006 paper as “the beginning of many systems that have been and will be installed aboard ships to serve the public rather than the shipowner or crew”. In recent years, dysfunctional onboard management systems and the resultant compliance failures have featured regularly in trade press reports on ‘magic pipes’ and falsified logbooks of discharges. George Chalos, a well-known New York maritime lawyer, told Marine Propulsion: “I am familiar with this type of equipment and the manufacturer’s ‘tamper-proof’ claims. Candidly, there is no such thing as a tamper-proof system. Regretfully, we have seen some of the best companies with the best ‘tamper-proof’ systems find themselves in the midst of intrusive investigations concerning suspected Marpol violations occurring on board their ships in very creative ways”.
Mr. Chalos, a veteran in OWS judicial cases, added: “In my view, the best way to make properly designed and properly functioning pollution prevention systems effective will be to do away with the practice of giving exorbitant ‘whistleblower rewards’ to crewmembers who fail to follow well-established environmental protection practices, laws, and procedures. The goal should be to incentivise compliance, not reward wrongdoers who purportedly speak up once the damage is done”. MP