AERATION OF VOC'S IN WASTEWATER BY USING GAS DISPERSION IMPELLERS

Abstract

A number of Volatile Organic Compounds (VOCs) found in the wastewater and some of these VOCs are very harmful for the human health as well as environment. Although there are several methods which are being used for the removal of VOCs, but the Air Stripping process is the low energy usage, low preventive and maintenance cost and high efficiency process which can stripes VOCs from wastewater. The present dissertation work consists of aeration system for the removal of VOCs. The aeration of VOC based on the mass transfer rate of VOCs from the liquid phase to the gaseous phase. Principle of air stripping involves the mass transfer of volatile organic contaminant from water to air. The system can be easily upgraded to strip greater amount of VOCs with relatively small increases in capital cost. Aeration tanks strip volatile compounds by bubbling air into tank through which contaminated water flows. The emission rate of VOCs during surface aeration can be estimated from the oxygen mass transfer coefficient KLao2 and a modified coefficient Pm. which incorporate the fraction of liquid phase mass transfer resistance to total resistance. The present study shows that aeration of a VOC by using advanced designed gas dispersing radial impeller i.e. Rushton, CD-6 and BT-6 and the factors which affects the design of a aeration tank baffles.and the impeller used for best possible result. This study also shows the removal efficiencies of VOCs of these impellers and it compares the efficiencies of impeller used at different height of submergence. It also shows the effect of air supply on the removal efficiencies and wide study of the effects on mass transfer coefficient of VOCs at different operating condition. A comparison of the result from experiment shows the emission rate of VOCs during aeration is a function of mass transfer coefficient of air and it increases with increase of submergence of height, by supply of air, and increase in impeller speed. Air supply can increase the removal efficiency up to 8-12%. Best aeration result can be obtained at the 2/3rd height of the submergence of the total depth of water for impeller used. Study also shows the gas dispersion impeller BT-6 impeller larger removal efficiency (up to 96%, with air supply at 4 hrs run) compare to Rushton and CD-6 impeller.