Oil skimming is a simple, dependable and effective means of removing oil from water. And unlike some other processes, it offers users the potential for major cost savings.
At Schenectady Chemicals Canada, Ltd., plant manager Fred Soukereff estimates that his company has saved $ 5,000 annually by using the skimmer instead of former methods of waste removal. 'The real saving, however, is in the fact that we have a much cleaner plant effluent discharge,' he points out.
The individual designs employed in oil skimmers may vary widely, but all oil skimming devices rely on two well-known scientific principles: specific gravity and surface tension.
Oil is lighter than water so it floats to the surface. Floating oil clings to materials more readily than water so it can be picked up by passing a belt or pick up media through the surface. Oily material adheres to the media and is removed, while water runs off.
Schenectady selected an Abanaki Oil Grabber Model 8 Skimmer for its Toronto, Ontario plant. The unit which is installed outside the plant operates with an 8 inch wide, 13 foot stainless steel, corrosion resistant belt.
Results, to date, are impressive. Schenectady's waste water discharge meets Toronto municipal bylaw standards for ratio of oil to water, measured in parts per million. The new Toronto standards limit the discharge of mineral oil to 15ppm, and natural oil and grease to 150ppm. The Abanaki system is capable of skimming solvents as well as resins and oil.
Soukereff explains the operation: 'We use a two stage interceptor system to separate any oils and solvent in our waste water. Prior to the installation of the Abanaki skimmer, this interceptor had to be cleaned out annually, at considerable cost. The high costs were partially due to the premium we had to pay for the water content of the mixture.
'It was a trade magazine article that caught my attention. It discussed how oily waste could be removed from water using an oil skimmer. That's how we came in contact with Abanaki.'
Schenectady had a mixture of solvents, resin and oil/water interface so they were skeptical as to whether an oil skimmer would work for them. Test strips of the stainless steel belt material appeared to pick up some of the solvent.
Based on the ease of installation and the low cost of the Abanaki skimmer, Schenectady decided to try a unit with a 6 foot belt. The results were encouraging, says Soukereff. 'We found that the belt picked up the solvent and the interface readily, and kept the interceptor relatively free of the solvent resin layer.'
'Once we found that the skimmer worked, we installed a more permanent and winterized system with a longer belt. It has been in routine service since March 1991, with little problem, says Soukereff. At Schenectady, one maintenance operator monitors the operation on a routine basis.
According to oil skimmer manufacturer Abanaki, the experience at Schenectady of actually saving money after installing a skimmer to assure compliance with environmental regulations isn't all that rare. Skimming is a simple, effective means of removing floating oils, and other similar contaminants, and skimmers like Abanaki's are so easy to install, operate, and maintain that users often achieve savings based on decreased maintenance costs alone.
A second source of savings results from the fact that a properly installed system can provide a very good separation of the oil and water. For some users, the important part is to be able to re-use of discharge the water without further treatment, while for others, the important part is having to pay only for the disposal of the actual contaminating material instead of a much larger volume of contaminates mixed with water.
Picture : Plant manager Fred Soukereff stands by the enclosure built to house the Abanaki Model 8 Oil Grabber. Panels have been removed to show the skimmer, which operates 24-hours per day, seven days a week. The endless stainless steel belt drops down into the sump about five feet to assure that it is always working even if the water level fluctuates, and lifts the skimmed material about eight feet for disposal in the large 2000 gallon tank to the right.