Biofilter response to gradual and sudden variations in operating conditions

摘要

Biofiltration is an efficient technology that involves passing chemical-laden gases through a moist,porous medium containing active microorganisms.Although this technology is apparently simple,its effectiveness relies on the optimisation of several operating parameters and the selection of a suitable packing or carrier material.In this study,four organic packing materials were tested for biofiltration purposes.The highest removal efficiency for hydrogen sulphide(H_2S)inlet concentrations ranging from 0.03 to 0.32 gm~(-3)was achieved when filling the bed with the material based on a mixture of pig manure and sawdust.After selecting this carrier material,the response of the biofilter to gradual and sudden changes in the H_2S loading rate and gas flow rate was studied.A combination of high contaminant inlet concentrations(0.28 g m~(-3))and high gas flow rates(1.3 m~3 h~(-1)with a EBRT time lower than 22 s)would require two biofilters in series in order to ensure a contaminant outlet mass loading rate lower than 15 g m~(-3)h~(-1)is discharged into the atmosphere.The packing material was able to recover high degradation rates after brief starvation periods,but increasing the gas flow rate from 0.81 to 1.85 m~3 h~(-1)rendered a decreasing elimination capacity(a subsequent increase in non-degraded outlet amounts of contaminant),even when H_2S feeding rate was gradually decreased from 0.55 to 0.26 g m~(-3).