Cautionary notes about OWS
UK company Victor Marine has joined other manufacturers of oily separators in the test procedures and the methods by some to achieve approval. The company says that it has been building oily water separators for many years, previously under the Hodge Separator trade mark. When the new MEPC 107/49 resolution was introduced it designed a range of separators to comply with these more stringent regulations rather than 'tacking' bits of equipment on to the front or back of old units to upgrade them to meet the new criteria, as some other manufacturers are advocating and marketing.
According to Victor, it has recently been suggested that a pre-treatment unit can be fitted to existing separators which not only breaks down the emulsions but treats the water to below 15 ppm. The old OWS then merely becomes a monitor and a pump to deal with the treated water. Unfortunately most of these add-ons, particularly pre-treatment units and filters, will not upgrade the existing separator to comply with 107/49 unless a new monitor is fitted at the very least.
The test procedures in 107/49 would make it very difficult for a ship-owner to get certification for an old system with filters or pre-treatment even if a new monitor is fitted. It could be argued that these additional treatment processes would have to be tested with all the separators presently on the market. The 107/49 regulations endorsed the limit of a 15 ppm oil content in treated bilge water discharge with the additional need to treat emulsions. These rules apply to new vessels built since January 2005 but with environmental issues becoming ever more prevalent there is a feeling that the same rules should also be applied to older vessels. Responsible shop-owners have already taken the decision to upgrade older OWS to meet the current regulations. Some manufacturers are openly proposing that the oil content should be reduced to 5 ppm but realistically, unless oil content monitoring equipment improves, these very low levels are impractical. The company believes that neither of these ideas would prove to be very popular with the shipping industry at large especially
with the present global financial situation, which is not set to improve in the foreseeable future.
Three Stage
The three stage method of filtration used in Victor Marine units is claimed to have proved popular with both new buildings and the retro-fit market where owners are replacing older units which only comply with 60/33. The success of the CS unit is said to be due to the high performance, small footprint and the low spares requirement. On average the spares costs are around US$ 1,000 per annum/per tonne (where “ton” refers to the tonnage of the unit.) The advanced granular media used in the third stage for instance can take 12 times more loading than activated carbon.
The treatment of the bilge water in both the CS and VM units is a continuous process with no back-wash or cleaning cycle and unlike chemical batch treatment there are no hazardous chemicals to store or handle. Oil is taken off after the first stage only and there is therefore little chance of contaminating the dirty oil tank with water. Some manufacturers compound the problem of disposing of the waste by introducing water into the sludge tank and therefore the ship-owner is paying to pump water ashore. This is somewhat ironic when the only purpose of the equipment is to remove oil from water which can then be safely pumped overboard. Under the testing procedures laid down by IMO the CS series is claimed to consistently return oil content results of under 5 ppm and the more sophisticated VM series is even more efficient with results
