Characterisation of microorganisms responsible for EBPR in a sequencing batch reactor by using the 16S rDNA-DGGE method
Analysis of the bacterial community in the biological phosphorus removal system is propitious to study the phosphorus-removal mechanism. The activated sludge was acclimated through a repeated anaerobic-aerobic process with glucose as carbon source for 2 months and a stable EBPR was established in an SBR. Total phosphate of the wastewater decreased by 12.43 mgE.-1 after 4 h aerobic treatment while total P uptake in the raw sludge was 0.57 mgE.-1 under the same conditions, and the phosphate content of the sludge increased from 1.83% to 6.79%. The protozoa and dominant bacteria of the two sludges were observed by optical and electron microscope. The genomic DNA of samples was extracted as the template and the 16S rDNA genes (V3 region) were amplified; denaturing gradient gel electrophoresis (DGGE) separated these amplified DNA fragments with the denaturant from 35% to 70%. The DGGE profiles showed that the raw sludge, acclimated sludge and dominant bacteria in the acclimated sludge had different band patterns. The results indicated that micro-organisms were selected by the repeated anaerobic-aerobic process and some non-phosphorus accumulating organisms were eliminated. The cultured strains obtained from acclimated sludges were purified and their DNA was amplified using F27 and R1522 to 1.5 kb; the gene sequences were located on the GenBank and they were identified as Acidovorax sp.BSB421 and Sphingomonas sp.SA-3.