Modification of conventional rapid sand filter into granular activated carbon-sand dual media filter has become increasingly attractive to drinking water producers in many Chinese urban regions. In this study, a pilot-scale dual media filter was constructed to monitor its performance. The operational results indicated that the dual media filter performed well both on nitrification and on reduction of chemical oxygen demand. Microbial community structures at different sampling sites were also compared using 16S ribosomal ribonucleic acid gene clone library analysis to identify the spatial heterogeneity the filter. Clone library analysis illustrated the difference of microbial community structure and an increase of microbial diversity along the filter depth. Moreover, potential pathogens from genera Chromobacterium and Sphingomonas were detected in the filter samples, which deserved further serious consideration in downstream treatment such as disinfection. These findings also provided an illustration of the utility of molecular techniques to discover microbial community change and potential pathogens in the drinking water biofilters.

AB STRACT: Leachate and reclaimed wastewater have become the important sources of polycyclic aromatic hydrocarbons in soils. However, the information on bioremediation of leachate and reclaimed wastewater-contaminated soils is still lacking. Identification of changes in microbial structure or of enriched genera related to biodegradation could aid identification of particular organisms or consortia capable of degrading polycyclic aromatic hydrocarbons in these contaminated soils. In this study, terminal restriction fragment length polymorphism, coupled with 16S Ribosomal ribonucleic acid clone library analysis, was applied to investigate the composition of bacterial community in leachate-contaminated soil or grassland soil irrigated reclaimed wastewater and the response to phenanthrene amendment. Results showed that phenanthrene amendment had significant but different impacts on microbial community structure, dependent on soil source. Several greatly enriched terminal restriction fragments with phenanthrene biodegradation were identified. Moreover, genus rhizobacteria, possibly linked to phenanthrene biodegradation, was firstly reported in this study. This work might provide some new insights into bioremediation of polycyclic aromatic hydrocarbons-contaminated soils.

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