Rich microbial communities inhabit water treatment biofilters and are differentially affected by filter type and sampling depth

摘要

Factors affecting microbial diversity (richness) and community structure in biofilter columnsnwere investigated. At a pilot filtration plant, granular activated carbon (GAC), anthracite andnsand-based filters were used to treat stormwater from an urban catchment. After 12 weeksnoperation, sand media filters clogged (hydraulic conductivity declining by 90%) and all filtersnwere destructively sampled. All biofilters had similar levels of polysaccharide in the surface layer,nhowever only the sand columns clogged. This clogging may have been due to a combinationnof polysaccharide and small particle size, the development of a sand-specific microbialncommunity, or other biogeochemical interactions. DNA fingerprinting was used to show thatnbacterial, archaeal and eukaryotic communities were present in all filter types and at all samplingndepths (to 45 cm). The bacterial community was far richer (Margalefs index, d, 1.5–2) thannthe other groups. This was consistent across filter types and sampling depths. The structurenof the bacteria and archaea communities in sand filters differed to those in GAC and anthracitenfilters (P , 0.05). In contrast, eukaryotic communities were similar in surface biofilm layers,nirrespective of filter type. As such, physicochemical properties of filters differentially influencenthe microbial community. Furthermore, we have established that archaea are distributednthroughout biofilters; the role of these microorganisms in water treatment and filter function,nparticularly clogging, requires attention.