Bacterial communities in nanofiltration membranes used for drinking water production from anoxic groundwater

Next generation sequencing of the 16S rRNA genes was used to study the bacterial diversity of two nanofiltration installations that treat anoxic groundwater and do not suffer from rapid biofouling problems as commonly occur in the membrane-assisted treatment of oxic water. The relative abundance of dominant bacterial phyla, after extended periods of operation without chemical cleaning (> 300 days), were: Firmicutes (2.9 – 46.2%), Nitrospinae (0 – 65%), Actinobacteria (0.7 – 55%), Proteobacteria (7.8 – 16.9%), Nitrospirae (7.3 – 11.3%), Chloroflexi (3 – 13.3%), TM7 (0.5 – 12.5%), Bacteroidetes (0.7 – 14%), Planctomycetes (0.1 – 4.3%) and Acidobacteria (0.2 - 3.5%). The majority of the bacteria affiliate with environmental sequences of yet uncultured lineages. Microbial communities differed substantially between installations and the position of the membrane elements within the installation, but are also markedly distinct from those found during filtration of oxic feed waters (typically dominated by the a, ß and ? Proteobacteria classes). The absence of biofouling in this plants was linked to the reducing feed water conditions, selecting for anaerobes with slow metabolism.