At the core of Oily Water Treatment systems designed by OPS is an absorbent media - “RM25” - specifically designed to chemically attract and retain hydrocarbons from water. The consumable media is used as the last “polishing” stage of a process, just prior to discharge and removes final traces of oil down to below 5ppm (or mg/l), whether the oil is freely dispersed, emulsified or dissolved in the water. RM25 media is a granule, typically 2-8mm in diameter, formed by chemically coating a clay or starch substrate with a powerful surfactant.

RM25 media performs the same function as granular activated carbon (GAC), which was used for many years to remove gasoline and diesel leakage into groundwater sources at gas stations, refineries and other oil storage depots. New types of synthetic media were developed to compete on both price and effectiveness with GAC, and RM25 typically absorbs up to 5 times the quantity of oil per litre of media than GAC. This permits the use of smaller vessels and leads to more compact plants. Operating costs for a media system are typically 30% less than GAC systems per kg of oil removed.

The “designer” nature of the media means that by careful selection of the many thousands of different types of surfactant available, a media bed may be tuned to meet the particular objectives of a client, depending upon the chemistry of the contaminated water and the targets set by legislators for removal standards. A variety of media types will selectively remove different types of hydrocarbons and/or heavy metals depending upon the constituents of the waste stream. Such products are now in extensive use in both groundwater and contaminated soil remediation projects around the world and are proven technology.

Because the media is a consumable, absorption should only be used as a technology of last resort. Before treating a flow with an inlet oil-in-water level of, say, 1,000 ppm appropriate conventional physical technologies such as Oil/Water separators, Dissolved Air Flotation or liquid/liquid hydrocyclones should be employed upstream to reduce the OIW level as much as possible. Ideally the economic inlet level to an absorption system will fall somewhere in the range of 30-50 ppm which is typically the lower limit of hydrocyclone technology. Absorption should only be used as a final polishing step in the removal process, or as a “catch-all” system to be employed in the event of a process upset.

Applications

OPS RM25 media systems are used in many different industries and applications including Groundwater treatment, Oilfield Produced Water Polishing, Ships’ bilge and ballast water treatment and in OPS designed soil remediation systems. Please refer to the Case History section of the website.

Further information about the design of media systems can be found on the Process Design Considerations page by clicking here.