Application Of Microbial Embedding And Immobilization Technology In Biofiltration Of Waste Gas

Biofiltration is a common technology for the treatment of volatile organic compounds due to its environmental friendliness and low operating cost.Most of the current biofilters are inoculated by traditional auto-attached biofilm process,which requires long-term stable operating conditions.The immobilized microbial technology not only maintains the advantages of common biological methods,but also adapts to the waste gas containing high pollutans concentration,shock loading,starvation operation,and toxic compounds.In this study,a new gel capsule was made using embedding immobilization technology.The gel capsule is made of polyvinyl alcohol(4%)and sodium alginate(6%),and the addition of powdered activated carbon(1%)enhances its mass transfer performance and strength.A three dimensional crosslinked network structure in gel capsule can be observed by SEM.Consequently,gel-encapsulated microorganisms assembled in a 3D mesh material were used as packing materials in a biofilter(GEBF),while the other identical biofilter packed with perlite(BF)was used as a control.The performance of the two biofilter under different operating conditions were investigated.The overall chlorobenzene removal performance in GEBF was superior to that in BF.Kinetic analysis showed that the maximum biodegradation rate of GEBF was around 26 g m^-3 h^-1,which was higher than that of BF(18 g m^-3 h^-1).The recovery time after shock loading for GEBF(3 h)was shorter than that for BF(more than 4 h).Starvation results showed that GEBF and BF needed 3 and 6 days for fully recovery after the short-term(6 days)starvation,respectively.For the long-term(20 days)starvation,GEBF fully recovered the removal performance after 9 days,whereas BF recovered only 70%within the same period.The microbial characteristics of the two biofilters were also analyzed.Biolog plate analysis showed that the average metabolic activity of microorganisms in GEBF(0.052h^-1)was higher than that in BF(0.038 h^-1).Microbial community analysis showed that the microorganisms in GEBF had lower abundance than the microorganisms in BF.The flow cytometry was used to investigate the survival status of the microorganisms in the two biofilters during starvation.The results indicated that the intact cells in GEBF did not change during the period of starvation and after starvation.However,the number of intact cells in BF during starvation was about 10%less than that after 9 days of recovery.And the proportion of early apoptotic cells in BF increased significantly after 20 days of starvation.The average metabolic activity of microorganisms in GEBF remained a relatively high during and after starvation(0.0049 h^-1).However,the average metabolic activity of microorganisms in BF decreased from 0.0042 h^-1before starvation to 0.0033h^-1 under starvation.Notably,the microbial community structure in the two biofilters showed different behavior during starvation period.