The outdated system pumped water through a DAF (dissolved air floatation) unit where polymers were added to break oil emulsions and float as much oil as possible to the surface. This oil on the surface was then removed by skimming before entering a settling tank, from which it was discharged.
The Regional Water Quality Control Board”s standard for oil and grease was five PPM. The refinery met the standard occasionally, but spikes overtaxed the system. As a result, the refinery found itself frequently being fined for discharge violations. To bring the refinery into compliance, a treatment system was designed by Biomin
(www.biomininc.com), a manufacturer of water filtration media and flocculants for removal of oil, grease, and other organics .
The system included two particulate filters with two 25 micron cartridges and supporting valves, pipes, and hoses, followed by a number of string-wound polypropylene cartridges to remove sediments from five to as low as one micron in size. This was followed by two carbon steel pressure media filter vessels containing 720 feet cubed (35,000 lbs. each) of OilSorb organoclay running at a flowrate of 1,000 GPM each. Once the system was in place, the refinery was able to achieve the five-PPM discharge limit without fail.
OilSorb organoclay (organically modified clay) consists of bentonite modified with quarternary amines. This modification allows the organoclay to remove oils and other organic hydrocarbons of low solubility by partition, meaning the clay can remove oils at any pH, in fresh or salt water. The organoclay is blended with anthracite to prevent early plugging of interstitial pores.
|Stormwater cleanup system at a refinery in California where
70,000 lbs. of OilSorb was used at 2,000 GPM.
|Before & After (from left to right): 3 percent oil, 3,000 PPM emulsified; 200 PPM oil after it passed through an oil/water separator; one PPM after it passed through an absorber filled with OilSorb organoclay; Nondetect after it passed through a carbon tank.
— Flow Control Staff