Feast-famine biofilter operation for methane mitigation

Packed bed clogging and channeling derived from the accumulation of biomass still represent technical challenges to be addressed in gas biofiltration in order to enable a more cost-effective performance under long-term operation. In the present study, multiple feast-famine strategies were assessed, for the first time, in two alternate biofilters and compared with a standard continuous biofilter using CH4 as the model carbon source. The robustness of the biofilters towards increasing famine periods, the decrease of the irrigation frequencY and air deprivation was evaluated. The alternate biofilters, where the lowest average pressure drops were recorded, exhibited higher CH4 elimination capacities (by 27.2 +/- 6.4%) and mineralizations (by 18.3 +/- 8.6%) than the standard biofilter (CH4 elimination capacities and mineralizations of 10.3 +/- 3.6 g m(-3) h(-1) and 79.7 +/- 20.8%, respectively), along with the lowest recovery period so far reported in biofiltration after pollutant supply resumption (1.5 +/- 0.0 h). Metagenomics analysis revealed a significant shift in the structure of the microbial population induced by the feast-famine regimes, which favoured the occurrence of Planctomycetes and Proteobacteria phyla. Type I/II methanotroph ratios in the alternate units were 7.5 times higher than those found in the control unit, Methylomonas becoming the most resilient genus under feast/famine operation. The current work represents a scaled-down study that demonstrates the feasibility of applying feast-famine strategies at full-scale to increase the performance of biofilters under long-term operation and the lifespan of the packed bed. (C) 2017 Elsevier Ltd. All rights reserved.