Surface Skimmers

Surface skimmers are devices that selectively collect and remove floating materials — oil, grease, fats, oils and lubricants (FOG), scum, and suspended solids — from the water surface in treatment tanks and collection pits. Because oil and grease have lower density than water, they naturally float and accumulate at the surface. If not removed, this floating layer inhibits atmospheric oxygen transfer in aeration basins, interferes with settling in clarifiers, coats biomass in biological reactors, and creates fire and odour hazards in storage pits.

Two principal types of skimmer are used in industrial wastewater treatment. The API oil skimmer uses a continuously moving endless chain with oil-collecting flights (scrapers or belts) that travel through the oil layer at the water surface, collecting free oil and directing it into a side launder or collection trough. A level controller maintains the floating oil level for efficient collection. This type is widely used in API gravity separators at refineries, petrochemical plants, automotive service facilities, and restaurants.

The floating suction skimmer is a free-floating device that rides on the liquid surface, with its suction inlet positioned just at or fractionally below the water line. As the surface level fluctuates, the skimmer floats with it, maintaining optimal suction position. A dedicated centrifugal pump draws the floating oil and grease through a rectangular funnel inlet and discharges it to a slop oil collection pit or recovery vessel via a flexible rubber or braided PVC hose. This design is effective for bulk oil and grease recovery from large tank surfaces where the oil layer thickness is variable.

Both skimmer types are fabricated from stainless steel (SS304 or SS316) to resist corrosion in the oil-contaminated wastewater environment. Floating skimmers use engineered floats for buoyancy and are designed to handle elevated temperatures and turbid conditions without loss of performance.