ControlofVOCandHAPbyBiofiltration.pptVIP

Control of VOC and HAP by Biofiltration 朱 信 Hsin Chu Professor Dept. of Environmental Engineering National Cheng Kung University 1. Introduction A biofilter consists of bed of soil or compost beneath which is a network of perforated pipe. Contaminated air flows through the pipe and out the many holes in the sides of the pipe thereby being distributed throughout the bed. The microorganisms are the same that degrade organic wastes in nature and in wastewater treatment plants. In soils the pores are smaller and less permeable than in compost. Therefore, soil requires larger areas for biofiltration. This technology has been used in Europe for many years and is considered to be a Best Available Control Technology (BACT) for treating contaminated gaseous streams. Biofilters function efficiently and economically for removing low concentrations (less than 1,000 to 1,500 ppm as methane) of VOCs, air toxics, and odor. Advantages:low installation and operation costslow maintenance requirementslong lifeenvironmentally safeeconomically applied to dilute gas stream For odorous compounds98 to 99% removal has been reported For VOCsgenerally in the range of 65 to 99% removal Characteristics of the biofiltermediatemperaturepHmoisture contentgas residence timeproperties of the compounds being removed Biofilters can also remove particulates and liquids from gas streams. However, care must be taken because particulates or greasy liquids can function to plug the biofilter. Industries including chemical manufacturing, pharmaceutical manufacturing, food processing, wastewater facilities, and compost operations have successfully used this technology for odor control. Biofiltration has also been used to reduce VOC emissions in aerosol propellant operations. 2. Theory of Biofilter Operation Biotransformations act along with adsorption, absorption, and diffusion to remove contaminants from the gaseous stream. The gas passes upward through perforated pipes and the biofilter me