[Characteristics of biofilm phase during the long-term degradation of a toluene-contaminated gas stream using BTF].

ABSTRACT

This study analyzes the accumulation and distribution of biomass and changes in properties of biofilm in a long-term biotrickling filter (BTF) system in order to investigate the correlation between the biofilm phase properties and the performance. After a long-term operation of 130 days, the BTF showed a deterioration in degradation performance and an increase in pressure drop with a gradual increase of biofilm thickness and uneven distribution of biomass. Meanwhile, the porosity of the upper and lower layers decreased from 85% and 82% in the start-up period to 65% and 40%, respectively, as a result of the excessive accumulation of biomass and its non-uniform distribution. The AWCD values showed a decreasing trend indicating that the biological activity decreased with the aging of biofilm in the long-term BTF. The contents of total extracellular polymeric substances (EPS) and protein in the later period were twice as much as those in the start-up period. The value of protein to polysaccharide (PN/PS) ratio increased from 0.3 to 0.95, and showed positive correlation with the surface hydrophobicity of the biofilm, which increased from 33% to 73% accordingly. The mean molecular weight of EPS decreased during the operation of BTF. The result of FTIR further showed that the main chemical composition of EPS changed in the long-term BTF accordingly, possibly resulting in the deterioration of performance in the long-term BTF. The above experimental results could be very helpful for reducing the clogging and performance deterioration in long-term BTF.