Long-Term Performance of Biofilters Packed with Manure-Derived Media for Trimethylamine Removal: Operational Responses and Microbial Succession

Four laboratory-scale biofilters were designed and evaluated for treating trimethylamine (TMA). Each biofilter was measured as being 68 cm in height and 15 cm in diameter. The filter media consisted of various mixtures of dairy manure compost, dairy barn bedding, crushed corn cobs, wood chips, and sawdust. This study aimed to compare the removal efficiencies of TMA achieved by biofilters packed with different media compositions, as well as to analyze the succession patterns in the structure of microbial communities on the media surfaces during operation. Contaminated air streams were artificially generated by bubbling air through a TMA solution, resulting in inlet concentrations ranging from 1.88 to 4.23 mg/m3. Under empty bed residence times (EBRTs) ranging from 42.7 to 28.0 s, all four biofilters achieved removal efficiencies exceeding 60%. However, the performance varied among the biofilters. The biofilter packed with a mixture of matured compost, wood chips, and crushed corn cobs at a volume ratio of 10:9:1 exhibited the highest removal efficiency (>83%). Ammonia was detected at the outlet of the biofilters as a byproduct of microbial TMA degradation, accompanied by the accumulation of ammonium nitrogen in the filter media. Microbial community analysis of the high-performance biofilter revealed a progressive increase in microbial complexity and diversity over 95 days of operation. Glycomyces was the dominant genus throughout the operation and showed a significant positive association with TMA removal efficiency, but its specific role in TMA degradation remains to be experimentally confirmed.