The management of municipal solid wastes is becoming a global problem. During processing of solid wastes in composting facilities or in landfills, generation of gases with complex mixtures of compounds creates odor concerns and environmental issues. Odorous compounds in this type of facilities are mainly originated from the decomposition of the organic fraction contained in the solid waste. Amongst others, volatile organic compounds, ammonia and hydrogen sulfide are the most produced during the decomposition process. Other industrial facilities, as pig and poultry housing facilities, also produce emissions with high content of greenhouse gases and particulate matter a part from ammonia and odors in general. Biological waste air treatment processes have become an excellent alternative to conventional physical-chemical processes to control low concentrations of odors, volatile organic and inorganic compounds or hazardous air pollutants in large air streams. In our research group both biofilters and biotrickling filters have been operated and studied to treat low-loaded off-gases with high removal efficiencies. Particularly, biofilters have been used in our research group as one of the best technology to treat gases containing low concentrations of organic volatile pollutants since the packing material is hydrophobic and favors the abatement of these compounds. Indeed, we have a large expertise in biofiltration of odorous effluents by seeking new packing materials and the optimization of the operational conditions of biofilters to maximize the removal of pollutants.
One of the goals of this research line is the optimization of the design and operation of biofilters and biotrickling filters to improve the simultaneous reduction of odorous compounds and other organic and inorganic volatile compounds in an efficient and cost-effective manner. This research is focused on testing different packing materials, trickling velocities and empty bed residence times with different compounds (separated or mixed) or with mimics of waste gases (composition and flow pattern) that can be found in industrial facilities in order to the best conditions for their removal applying this technology.
Another objective of this research line arising from the previous one is the development and application of a standard procedure for retrofitting such chemical scrubbers into biotrickling filters. Several full-scale applications have been carried out for the treatment of low-loads of waste gases containing H2S, NH3 and VOCs. The conversions mainly require replacing the original carrier material and recycle pumps as well as modifying the controls and operation of the reactors. The most interesting aspect of the conversions in general is the assessment of the biological system capacity since chemical scrubbers are usually configured to treat high gas flows at really low contact times. In each conversion performed by our research group the advantages of the biological process (as the large economical benefits (short payback time of the conversion investment) as well as technical advantages in terms of efficiency of treatment) have been certainly scrutinized and demonstrated.