Denitrification performance and microbial diversity in a packed-bed bioreactor using biodegradable polymer as carbon source and biofilm support.

A novel kind of biodegradable polymer, i.e., starch/polycaprolactone (SPCL) was prepared and used as carbon source and biofilm support for biological denitrification in a packed-bed bioreactor. The denitrification performances and microbial diversity of biofilm under different operating conditions were investigated. The results showed that the average denitrification rate was 0.64 ± 0.06 kg N/(m(3)d), and NH3-N formation (below 1mg/L) was observed during denitrification. The nitrate removal efficiency at 15°C was only 55.06% of that at 25°C. An initial excess release of DOC could be caused by rapid biodegradation of starch in the surfaces of SPCL granules, then it decreased to 10.08 mg/L. The vast majority of species on SPCL biofilm sample (99.71%) belonged to six major phyla: Proteobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Spirochaetes and Actinobacteria. Proteobacteria were the most abundant phylum (85.50%) and mainly consisted of β-proteobacteria (82.39%). Diaphorobacter and Acidovorax constituted 52.75% of the identified genera which were denitrifying bacteria.