PREVENTION OF CLOGGING IN A BIOLOGICAL TRICKLE-BED REACTOR REMOVING TOLUENE FROM CONTAMINATED AIR

Removal of organic compounds like toluene from waste gases with a tric kle-bed reactor can result in clogging of the reactor due to the forma tion of an excessive amount of biomass. We therefore limited the amoun t of nutrients available for growth, to prevent clogging of the reacto r. As a consequence of this nutrient limitation a lower removal rate w as observed. However, when a fungal culture was used to inoculate the reactor, the toluene removal rate under nutrient limiting conditions w as higher. Over a period of 375 days, an average removal rate of 27 g C/ (m(3) h) was obtained with the reactor inoculated with the fungal c ulture. From the carbon balance over the reactor and the nitrogen avai lability it was concluded that, under these nutrient-limited condition s, large amounts of carbohydrates are probably formed. We also studied the application of a NaOH wash to remove excess biomass, as a method to prevent clogging. Under these conditions an average toluene removal rate of 35 g C/(m(3) h) was obtained. After about 50 days there was n o net increase in the biomass content of the reactor. The amount of bi omass which was formed in the reactor equaled the amount removed by th e NaOH wash. (C) 1996 John Wiley & Sons, Inc.