Water Separation Techniques
Water is considered as a contaminant species that invades lube oil during use. For any used oil recycling/reuse option, water has to be removed as a waste. For example, in re-refining process, water is removed in the early dehydration step by flashing the processing oil at near atmospheric condition. Water vapor is condensed and collected for treatment. In most cases, phenolic compounds and oil residues are two major concerns in the wastewater stream that have to be removed according to discharge standards prior to their discharge to POTW. According to Ms. Burn, a field operating engineer in Evergreen Oil, the size of the dehydration tower is about 30ft high in order to treat 43,000 gal/day oil during a 24 hr/day operation (the average water content in their used oil feedstock is 7-8%). For industrial-size operation, flashing/distillation may be a good choice for the separation of water from lube oil. For this research, water separation is an important task. After ultrasonic irradiation treatment, water phase and organic phase in the emulsion samples have to be separated for individual analyses. Although we are more interested in the concentration level of pollutants left in the organic phase, it is necessary to determine the wastewater quality for the purpose of material balance study and for future suggestion of wastewater treatment options. Furthermore, if water phase can be separated from the organic phase in pretreatment steps, any consequent treatment in the recycling/reuse process will be simplified. It is crucial, however, not to alter the characteristics of both water and oil phase and not to lose targeted contaminants during water separating process. Otherwise, the results will be highly affected.