Treatment of Volatile Organic Compounds From Gas Streams Using a Three- Phase Circulating-Bed Biofilm Reactor

摘要

This study focuses on the biofilm kinetics of removing benzene, toluene, and p-xylene (BTX) from gas streams in a three-phase circulating-bed reactor using porous carriers. In the biofilm reactor, gas-liquid equilibrium existed for BTX, but not for oxygen. Oxygen was consumed as a cosubstrate in the oxygenation reactions and the terminal electron acceptor during respiration. When toluene was the sole substrate, oxygen mostly controlled its removals, and toluene inhibition mostly controlled the removals of the toluene intermediate. With increased toluene or decreased oxygen loading, more toluene intermediate was removed inside the biofilm, and the intermediate mass flux changed in direction from out-of to into the biofilm. The mass transfer resistance in the biofilm relieved the intermediate from toluene inhibition. However, higher biofilm accumulation showed adverse effects on reactor performance due to increased demand for oxygen for respiration. The suspended biomass contributed to the removals of toluene and its intermediate and played its most important role when oxygen limitation was significant When toluene/benzene or toluene/p- xylene were removed simultaneously, their inhibition forced more volatile organic compounds to be removed inside the biofilm, where mass transfer resistance relieved the inhibition effects. The removal efficiencies for the lower-concentration compound were smaller.