Multi-stage biofiltration for air pollution control in composting processes

Odor is often produced in composting processes especially when the operating conditions are not optimal. To control the odor, the prior methods include improving the management and operation conditions, as well as treating waste gases through mitigation measures. Biofiltration has become one of the most commonly used odor control technologies due to its advantages of low cost, high efficiency, and capability of simultaneously processing several contaminants without secondary pollution. Biofilter adopts a solid filling bed supporting biological activities to absorb (or adsorb) and degrade contaminants in effluent gases. In this study, a multi-layer biofilter setting was developed. The filter was filled with compost, timber sawdust, charcoal powder, and gravel in order to build a stereo-reticulation structure with properties of high porosity, adequate humidity and large permutation area. Microorganisms were screened from other composting processes and natural surroundings. The obtained microorganisms were domesticated with the existence of odorous components and/or BTEX compounds at different pH values and different temperatures to enhance their adaptability. They were classified according to growth compatibility. The obtained classified microorganism complexes were inoculated into different layers hi the biofilter. A bench-scale odor control process was performed in such a biofilter setting. Odor sources from composting processes were well controlled during the operation.