Analysis of bacterial community structure in vermifiltration for sludge reduction by nested PCR-DGGE method

Vermifiltration was a innovative process to sludge reduction. The relationship of earthworm and bacterial community was not conclusive in the treatment. The techniques of polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) was used to analyze the bacterial community structure in vermifiltration column in the paper. Results showed bacterial diversity index (H) in the middle layer was 1.87 and 3.19, and subsequently in the lower layer was 1.24 and 1.58. H in the upper layer was lowest (0.67 and 1.07). 11 bacterial organism were identified in the columns, demonstrated that richness and complexity of bacterial ecology. The important factors to determine bacterial community structure in vermifiltration was likely to be earthworm predation and cast, rather than bacterial community of raw sludge. Earthworm biomass reduced gradually in the depth distribution. The possible reasons were possible to be food sources and dissolved oxygen.