Experimental Study of Biodegradation of Ethanol and Toluene Vapors

emoves only water-soluble gases. Water usage is high and average costs are
considerable.
Biofiltration requires a longer retention time, so the volume of soil or compost
bed must be relatively large compared to the space required for other methods, thus the
installation and maintenance costs will be higher. Thermal oxidizers are commonly used
to destroy the concentrated VOCs. The operating cost benefits of using a concentrator in
conjunction with a small oxidizer make this a very attractive option (Hussey and Gupta,
1998).
Biological treatments of waste gases have the specific advantage of microbial
metabolism. Whereas other conventional methods may not eliminate the pollutants,
microbes convert the pollutant into their metabolic products. These processes generally
do not lead to further environmental problems and the cost is low because they are
carried out at normal temperatures and pressure (Ottengraf, 1986). These processes are
cheap, reliable and do not usually require complex facilities. Bohn (1992) reported the
cost of a typical biological air treatment system as $8 per million cubic feet of air
treated compared to other costs shown in Table 2.3.
Among all the technologies of waste gas treatment, the main advantages of
biological treatment are high removal efficiencies, low installation, operation and
maintenance costs, and high reliability. Most importantly, biological treatments can
convert many organic compounds into oxidation products such as biomass, water and
carbon dioxide.
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