Variation of Operating and Microbial Community of BTF Process With Conventional and Modified Filler by Immobilization Technology

Polyurethane (PU) sponges were surface modified with 10% polyvinyl alcohol (PVA), 2% sodium alginate (SA), 1. 5% activated carbon (AC), and 2% calcium carbonate (CaCO₃) using immobilization techniques. The performance of ethylbenzene removal in a biotrickling filter (BTF) packed with modified filler was studied under different harsh operating conditions, and shifts in microbial communities in the BTF systems were analyzed by high-throughput sequencing techniques. At the same time, the performance of the BTF packed with PU filler was compared with that of the BTF with modified filler. The modified PU filler had a good water-holding capacity. The startup time of the BTF packed with modified fillers was shortened from 10 days to 4 days, and the removal efficiency of ethylbenzene was increased from 90% to 100% . It was capable of endure short-term shock loading with mass concentration fluctuations of 800 - 2 000 mg/m³; the recovery time required for a 7-day stagnation was shortened from 6 days to 4 days. At the inlet concentration of 800 mg/m³ and the empty bed residence time (EBRT) of 28 s, the elimination capacity of ethylbenzene in the BTF packed with PU filler was 63. 6 g/(m³·h), while that with modified filler reached 85. 9 g/(m³·h). The results of high-throughput sequencing showed that the Chao, Ace, and Shannon index of microbial community in the modified fillers were obviously higher than those of the unmodified PU fillers in the same period; the number of OTUs increased by 33; the dominant groups before modification were mainly Bacteroidetes, Proteobacteria, Candidatus Saccharibacteria, and Actinobacteria. The relative abundances of Chlamydiae and Firmicutes also increased after the modification. The stability and removal performance of the BTF packed with modified filler were superior, and there was a notable enhancement of the biomass, microbial community richness and diversity within the modified filler also increased.