Lancaster Laboratories Environmental

Environmental NEWS - Spring 2010

Hydrocarbon oil index method validated for bilge water testing

Senior chemist Heather Williams sets up a calibration to run
samples for the new ISO method.

Every year, millions of gallons of hydrocarbon contaminated water are discharged into the oceans from ships and industrial plants located in coastal regions. Multiple national and international agencies regulate the allowable hydrocarbon concentrations of this wastewater. So plant and ship operators are required to monitor and record their discharges, which usually go overboard directly into the waterway.

Large commercial vessels typically carry treatment apparatus on board to reduce hydrocarbon contaminants in bilge water to an acceptable level, and the wastewater is monitored by onboard devices, which measure hydrocarbon levels on a real-time basis. Although these controls are usually effective in maintaining compliance, substantial fines are levied against ship operators who violate discharge limits.

Recently, the corporate owner of a super tanker decided it would be prudent to verify that their onboard monitor was providing accurate hydrocarbon concentration readings and contacted Lancaster Labs for assistance.

The chemists at Lancaster Labs have years of experience analyzing hydrocarbons for compli ance with USEPA and various state specific methods, but for this application, it was thought that using an internationally recognized testing method would be the best approach. They developed and validated a method based on ISO 9377-2:2000, Determination of Hydrocarbon Oil Index. In addition to being recognized by a number of foreign regulators, this gas chromatographic method uses hexanes rather than more toxic chlorinated solvents to extract hydrocarbons from the water, making it a more environmentally friendly technique. The hexane extraction is more selective for hydrocarbons, and after concentration, polar substances are removed using a Florisil column cleanup.

The contaminants in bilge water present an analytical challenge because they come from multiple sources, including machinery wash down, marine fuels and lubricating oils. To analyze this demanding mix, a gas chromatograph fitted with a flame ionization detector (FID) is used. Samples are fortified with hydrocarbons C10 and C40 to mark the area for analysis, and all peaks between these two markers are quantitated to determine the hydrocarbon oil index. The reporting limit achieved was 0.1 mg/L, which is well below the discharge limits allowed for most waterways. Using this method, Lancaster Labs was able to verify that the meters in use on board the tanker were providing accurate hydrocarbon results for the bilge water being discharged.

Another application for the hydrocarbon oil index test was identified when a different client submitted wastewater samples from an off-shore island power plant that was discharging its wastewater into the Atlantic Ocean. Again, the request was to verify that the monitoring system for the discharge was providing accurate data, and Lancaster Labs’ chemists were able to use the ISO based method to answer that concern. For more information on hydrocarbon oil index and other hydrocarbon analytical techniques, contact Environmental Business Development at 717-656-2300 or email env@lancasterlabs.com.