Abstract:
The objective of this study was to determine the optimum conditions for maximum oil removal in treating the petrol-station wastewater by using froth flotation. Chemicals used in this experimental work were classified into 2 types : surfactants and coagulants. The surfactants studied were sodium dodecylsulfate (SDS). Dodecyltrimethyt ammonium dromlde (DTAB) and nonylphenol ethoxylate (Teric N10). The coagulants used in this study were cationic polyelectrolytes (Novous CE2680, polyrmer 1192 and polymer 1154L), anionic polyetectrolyte (Qemifioc 720) and ferric chloride ( FeCl₃ ). In this experiment, two types of froth flotation were column and tank to be tested. The flotation column made of glass had 5 and 118 centimeters in diameter and height, respectively. The air bubbles were generated by passing air through the sintered glass plate at the bottom of the column. The flotation tank made of stainless steel had three compartments in series, total working volume of 16 liters and a scraper on the top of the flotation tank for removal of the foam. From the experimental results, it was found that the treatment efficiency depended upon the hydraulic retention time, the flow rate of air, type and concentration of chemical used. An addition of cationic polyelectrolyte (Novous CE 2680) gave the highest treatment efficiency of oil removal. The optimum conditions for treating the petrol-station wastewater were HRT of 30 min, air flowrate of 5.55x10³m³/m³ liquid-s and the cationic polyelectrolyte (Novous CE 2680) of 100 mg/l that gave the 100% highest oil separation. In comparison with the two froth flotation systems, the flotation column gave much higher efficiency in oil removal than the flotation tank.