Removal of Hydrogen Sulfide and Ammonia Using a Biotrickling Filter Packed with Modified Composite Filler

Abstract

The purpose of this study was to evaluate the performance of laboratory-scale biotrickling filters (BTFs) packed with composite filler and pine bark filler under different operating conditions in purifying mixed gas containing H2S and NH3. The composite filler was prepared with modified activated carbon and loaded with functional microbes, using the microbial immobilization technology combined with a nutrient sustained-release composite filler. The results showed that the composite filler could better adapt to low empty bed retention time (EBRT) and high inlet concentration than the pine bark filler. When EBRT was 40 s and the inlet load was 41 g/m3·h, the NH3 removal efficiency of the composite filler was kept above 80%, and when the inlet load was 61.5 g/m3·h, it could be stabilized at about 60%. When EBRT exceeds 34 s, the H2S removal efficiency of the two BTFs was maintained at 100%. Yet, when EBRT was 34 s, the H2S removal efficiency of the bark filler BTF dropped to <80%. The microbial diversity and richness of the bark filler BTF were significantly higher than those of the composite filler BTF, which had higher community similarity under each working condition. However, the proportion of predominant bacteria in the composite filler BTF was higher than that of the bark filler BTF. As the inlet load increased, the diversity of predominant bacteria of the composite filler BTF increased, which means that the predominant bacteria were less inhibited by high-concentration odorous gases. The predominant bacteria with deodorizing function in the composite filler BTF included Pseudomonas, Comamonas, and Trichococcus, which might jointly complete nitrogen’s nitrification and denitrification processes. The proportion of these three bacteria in the composite filler BTF was higher than in the bark filler BTF.