Bacterial community structure in a biofilter used as a pretreatment for seawater desalination

•Two biofilters (GAC and anthracite) used as a pretreatment to seawater desalination.•First detailed study on functional marine bacterial community in the biofilter.•Variation of biological community with operation time and filter depth.•Bacterial community structure (by T-RFLP) influenced the organics removal.

In this study, two biofilters with different media, anthracite and granular activated carbon (GAC), were used to pre-treat seawater for desalination. Both biofilters had the same operating conditions that lasted for 75 days. The bacterial community structures in the filter media were studied during the biofilters' operation using terminal restriction fragment length polymorphism (T-RFLP) combined with principal component analysis (PCA), clustering of samples and sequencing based on the 16S rRNA gene. Bacterial community structure analyzed from T-RFLP patterns showed a dynamic shift at the top parts of the biofilters, while relatively stable bacterial community structures were observed in the middle and bottom parts of biofilters. The GAC biofilter consisted of diverse heterotrophs while the anthracite biofilter was mainly composed of sulfur-oxidizing and reducing bacteria, and alkalitrophic heterotrophs. This is associated with sulfur being a present impurity in the anthracite medium.