REMOVAL OF VOCS FROM REFINERY AND PETROCHEMICAL WASTEWATERS USING DISSOLVED AIR FLOTATION

A field sampling and analysis program was carried out at a refinery and petrochemical industrial complex in the Shuaiba Industrial Area to characterize the volatile organic compounds (VOCs) emitted from wastewater and examine their removal by dissolved air notation (DAF) and granular activated carbon (GAG) treatment. Compounds such as benzene, toluene, ethylbenzene, and xylene were identified. The total VOC emission of these compounds ranged from 0.1 to 3.2 mg/m(3). The VOCs concentrations in wastewater ranged from 34 to 4445 g/l. An actual refinery wastewater was fed at a rate of 10 l/min into a pilot scale 592-liter dissolved air flotation(DAF) unit connected to a granular activated carbon column. Results indicated that liquid detention time and air/water ratio were the main factors affecting VOCs stripping from the DAF basin. Up to 20% of influent VOCs concentrations were last by volatilization at an ah-to-water ratio of 0.5. Adsorption by dry granular activated carbon (GAG) was capable of reducing the VOCs concentration in off-gas from the DAF unit by more than 99%. It is recommended to couple covered DAF units with dry GAC columns to minimize occupational exposure to VOC emission.