Impact of alternate use of methanol on n-hexane biofiltration and microbial community structure diversity

The impact of introducing and suspending methanol on n-hexane biodegradation in trickle-bed-air-biofilters (TBABs) and the associated changes in microbial biodiversity is evaluated in this study. Four TBABs with n-hexane loading rate of 13.2 g/m3 h were evaluated. Two TBABs operated at pH 4 and the remaining at pH 7. The concentration ratios of methanol to n-hexane were 3:1 and 5:1, providing methanol loading rates of 37.7 and 64.5 g/m3 h, respectively. The removal efficiency (RE) of n-hexane in presence of methanol under pH 4 fluctuated between 81 ± 5.7% and 88 ± 11.6%. While for TBABs operating under pH 7, the RE varied between 34 ± 12.7% and 69 ± 11.2%. Methanol suspension triggered n-hexane REs of 93% and 82% for TBABs operating at pH 4 and pH 7, respectively. 16S and 18S rDNA sequencing analysis suggested that methanol inhibited n-hexane biodegrading microorganisms, while its suspension enhanced the microbial community diversity and promoted enrichment of the functional microorganisms degrading n-hexane.