VERIFICATION STUDIES OF A SIMPLIFIED MODEL FOR THE REMOVAL OF DICHLOROMETHANE FROM WASTE GASES USING A BIOLOGICAL TRICKLING FILTER .1.

The removal of dichloromethane from waste gases in a biological trickling filter was studied experimentally as well as theoretically within the concentration range of 0-10,000 ppm. A stable dichloromethane elimination performance was achieved during two years of operation, while the start-up of the system only amounted to several weeks at constant inlet concentrations. The trickling filter system was operated co-currently as well as counter-currently. However, experimental and theoretical results revealed that the relative flow direction of the mobile phases did not significantly affect the elimination performance. Moreover, it was found that the gas-liquid mass-transfer resistance in the trickling filter bed applied was negligible, which leaves the biological process inside the biofilm to be the rate limiting step. A simplified model was developed, the "Uniform-Concentration-Model", which showed to predict the filter performance close to the numerical solutions of the model equations. This model gives an analytical expression for the degree of conversion and can thus be easily applied in practice. The dichloromethane eliminating performance of the trickling filter described in this paper, is reflected by a maximum dichloromethane elimination capacity EC(max) = 157 g/(m3 . h) and a critical liquid concentration C(lcr) = 45 g/m3 at a superficial liquid velocity of 3.6 m/h, inpendent of the gas velocity and temperature.