Evaluation of long term stability of seeded bacteria in a bio-enhanced activated carbon filter used for treating drinking water

A bio-enhanced activated carbon (BEAC) filter immobilized with 5 bacteria was operated for 180 days to investigate the seeded bacterial stability. The TOC and ammonium removal efficiency of the filter was analyzed continuously every day. The biofilm, bioactivity and bacterial community structure was evaluated by SEM, ATP test and DGGE respectively. At the initial stage (0 day), low abundance of the bacteria led to low bioactivity (202.97 ng ATP g−1 carbon), which resulted in low TOC and ammonium removal efficiency (63.98% and 30.68%). On the 120th day, The TOC and ammonium removal efficiency improved with the increase of bioactivity (increased to 1436.8 ng ATP g−1 carbon) and climbed to 81.47% and 51.97%, respectively. DGGE results showed that from day 0-120 of the BEAC operation, 5 seeded bacteria were stable with little change. On the 180th day, there were 4 indigenous bacteria appeared in DGGE profiles, which affected TOC removal efficiency and bioactivity. Fluorescence in situ hybridization results showed that, on the 180th day, the seeded bacteria were 92.98% of total count of bacteria, which were dominant in BEAC filter. In this study, BEAC with relatively stable seeded bacteria is a promising approach to maintain performance of the filter.