Identification of bacteria assimilating formaldehyde in a biological activated carbon filter by means of DNA stable isotope probing and next-generation sequencing

Ozonation followed by a biological activated carbon (BAC) filter is a common process of advanced water purification. Ozone can generate formaldehyde (FA) as a harmful by-product, while the subsequent BAC filter is efficient at removing FA. FA adsorption is limited on activated carbon because of its hydrophilic property and low molecular weight. Thus, biological degradation by biofilms associated with the BAC is regarded as the primary treatment mechanism for FA. However, little is known about the microorganisms involved in the removal of FA. To identify specific microorganisms assimilating FA in a BAC filter, this study applied DNA stable isotope probing (DNA-SIP) combined with next-generation sequencing (NGS) technology. DNA-SIP with NGS clearly revealed that facultative methylotrophs affiliated within the specific taxonomic groups, such as Hyphomicrobium and Methylibium, were suspected to be the key players in FA removal.