Analysis of Dominant Microorganisms of Bulking Sludge at Low Dissolved Oxygen Concentration using 16S rRNA Sequences

Maintaining dissolved oxygen(DO) at sufficiently low concentration in the aeration tank at a wastewater treatment plant(WWTP) is essential for reduction of the costs ofoperation and maintenance. On the other hand, the low DO level may result in adverse effect on the integrity of the activated sluge. A typical and disastrous outcome frequently experienced is the outgrowth of filamentous microorganisms, whichi is called as filamentous bulking. In addition to the traditional methods such as sludge settleability and microscopic observation of the culture, molecular techmiques including polymerase chain reaction(PCR) amplification followed by 16S rRNA sequencing were applied to identify filamentous bacteria present in bulking sludge under a condition of low DO concentration. Two morphologically distinct groups, presumably consisting of Sphaerotilus natans, and Eikelboom Type 1701 or Type 1851, were identified through microsecopic observation. They were further confirmed by subsequent 16S rRNA sequecing. Dominant filamentous bacteria identified by the molecular techniques were consisted of three major groups. Sequences of partial 16S rRNA cloned showed that the filamentous bulking organisms were closely related to Eikelboom Type 021N and Eikelboom Type 1701, and Sphaerotilus natans, respectively. Molecular methods were found to possess a strong potential of direct exmination of the microbial community of an activated sludge system.본 연구는 BK21서울대/한양대 사회기반 및 건설기술 인력양성 사업단의 지원과 한국과학재단 목적기초연구(R01-2002-000-00314-0)의 지원으로 수행되었으며, 이에 감사드립니다

Analysis of Dominant Microorganisms of Bulking Sludge at Low Dissolved Oxygen Concentration using 16S rRNA Sequences

Maintaining dissolved oxygen (DO) at sufficiently low concentration in the aeration tank at a wastewater treatment plant (WWTP) is essential for reduction of the costs of operation and maintenance. On the other hand, the low DO level may result in adverse effect on the integrity of the activated sludge. A typical and disastrous outcome frequently experienced is the outgrowth of filamentous microorganisms, which is called as filamentous bulking. In addition to the traditional methods such as sludge settleability and microscopic observation of the culture, molecular techniques including polymerase chain reaction (PCR) amplification followed by 16S rRNA sequencing were applied to identify filamentous bacteria present in bulking sludge under a condition of low DO concentration. Two morphologically distinct groups, presumably consisting of Sphaerotilus natans, and Eikelboom Type 1701 or Type 1851, were identified through microscopic observation. They were further confirmed by subsequent 16S rRNA sequencing. Dominant filamentous bacteria identified by the molecular techniques were consisted of three major groups. Sequences of partial 16S rRNA cloned showed that the filamentous bulking organisms were closely related to Eikelboom Type 021N and Eikelboom Type 1701, and Sphaerotilus natans, respectively. Molecular methods were found to possess a strong potential of direct examination of the microbial community of an activated sludge system.N