| description |
Ultrasonication is a common process to dislodge microbes from granular activated carbon (GAC). GAC was sampled from an actual advanced drinking water treatment facility. Effects of ultrasonication (0-396 J•cm-3) and agitation (30 min at 250 rpm) on bacterial DNA and community recovery from GAC were investigated, using real-time PCR and pyrosequencing of the 16S rRNA gene, respectively. Carbon fines, produced from GAC during ultrasonication process, were linearly increased with the energy inputs. Ultrasonication alone exhibited no negative effect on population recovery at ≤66 J•cm-3, but a strong adverse effect at >66 J•cm-3. Agitation showed a strongly positive effect on DNA recovery at ≤40 J•cm-3 but an adverse effect at >40 J•cm-3. An experiment with E. coli revealed that the presence of more than 50 mg carbon fine efficiently blocked the DNA extraction. Pyrosequencing results (0, 20 and 30 J•cm-3 with agitation or not) showed that ultrasonication increased the community richness and diversity, indicating its efficient detachment of bacteria from GAC. Canonical correspondence analysis indicated that delivered energy inputs were significantly correlated with the bacterial community composition (p<0.05), but not agitation. Consistently, correspondence analysis revealed that the 6 communities were grouped by the energy inputs but not by agitation. Collectively, ultrasonication affected both bacterial DNA recovery and community structure while agitation influenced the DNA recovery. |