Evaluation of porous ceramic as microbial carrier of biofilter to remove toluene vapor

Three kinds of porous ceramic microbe media are fabricated from fly ash, di atomite and a mixture of fly ash and diatomite powders. Water holding capac ity, density, porosity, pore size and distribution, compressive strength an d micro-structure of each of the fabricated media are measured and compared . The fly ash and diatomite mixture ceramic is evaluated as the best biofil ter medium among the three media because of its high compressive strength. It is selected as an experimental biofilter medium inoculated with thickene d activated sludge. The laboratory scale biofilter was operated for 42 days under various experimental conditions varying in inlet toluene concentrati on and flow rate of contaminated air stream. The experimental result shows that the removal efficiency reaches up to 96.6% after 4 days from the start -up. Nutrient limitation is considered as a major factor limiting biofilter efficiency. Biofilter efficiency decreases substantially at the build-up o f backpressure, which is largely due to the accumulation of excess VSS with in the media. Periodic backwashing of the biofilter is necessary to remove excess biomass and attain stable long-term high removal efficiency. The bed needs to be backwashed when the overall pressure drop becomes greater than 460.6Pa at space velocity of 100h(-1). A maximum flow rate of 444.858 m(-3 )hr(-1) of toluene elimination by the mixture ceramic biofilter, which is h igher than the previously reported values. This indicates that the fly ash and diatomite mixture ceramic biofilter can be effectively applied for remo ving toluene vapor.