OBJECTIVEIt aims to investigate the changes in composition and structure of bacterial communities developing on biological activated carbon (BAC) particles, and the bacterial functions.

METHODA pilot plant had been in service for 180 days, aiming to develop bacterial communities on activated carbon naturally. After 180 days of operation, the bacterial communities were determined by denaturing gradient gel electrophoresis (DGGE) analyses of PCR-amplified 16S rRNA genes. The study on community composition and the phylogenetic relationships of the organisms was complemented by a sequence analysis of cloned PCR products from 16S rRNA genes. Gas chromatography-mass (GC-MS) measurement was used to determine organic chemical composition of inflow and outflow water on the 300th day. TOC and NH(4)(+)-N were also tested in this experiment.

RESULTSIt showed that the stable bacterial structure did not develop on BAC particles until the 9th month during running time of the BAC filter. The communities were finally dominated by Pseudomonas sp., Ba-cillus sp., Nitrospira sp., and an uncultured bacterium. Stable bacterial communities played an important role in removal of NH(4)(+)-N and total organic carbon (TOC). Results from gas chromatography-mass (GC-MS) showed that 36 kinds of chemicals in feed water were eliminated, and concentrations of 5 kinds of chemicals decreased. These chemicals served as nutrients for the dominant bacteria.

CONCLUSIONThe findings from the study suggested that the stability of microbial structure was beneficial for improving NH(4)(+)-N and TOC removal efficiencies. The dominant bacteria had the advantage of biode-grading a wide range of organic chemicals and NH(4)(+)-N.