A high performance biofilter for VOC emission control

Biofiltration is a cleaning technique for waste air contaminated with some organic compounds. The advantages of the conventional biofilter over other biological systems are a high-superficial area best suited for the treatmen t of some compounds with poor water solubility, ease of operation, and low operating costs. It has crucial disadvantages, however; for example, it is not suitable to treat waste gases with high VOC concentrations and it has p oor control of reaction conditions. To improve on these problems and to bui ld a high-performance biofilter, three structured peat media and two trickl ing systems have been introduced in this study. The influences of media siz e and composition have been investigated experimentally. Feat bead blended with 30% (w/w) certain mineral material with a good binding capacity has ad vantages over other packing materials, for example, suitable size to preven t blockage due to microbial growth, strong buffering capacity to neutralize acidic substances in the system, and a pH range of 7.0-7.2 suitable for th e growth of bacteria. Dropwise trickling system offers an effective measure to easily control the moisture content of the bed and the reaction conditi ons (pH, nutrient) and to partially remove excess biomass produced during t he metabolic processes of microorganisms. The influence of nutrient supplem entation has also been investigated in this study, which has revealed that the biological system was in a condition of nutrient limitation instead of carbon limitation. The biofilters built in our laboratory were used to treat waste gas contami nated with toluene in a concentration range of 1 to 3.2 g/m(3) and at the s pecific gas flow rate of 24 to120 m(3)/m(2).hr. Under the conditions employ ed, a high elimination capacity (135 g/m(3).hr) was obtained in the biofilt er packed with peat beads (blended with 30% of the mineral material), and n o blockage problem was observed in an experimental period of 2-3 months.