• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.329-334
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• 2009

Bacterial numbers, such as endospore-formers, and treatment efficiencies were investigated for Rotating Activated Bacillus Contactors (RABC) and other advanced wastewater treatment processes including anaerobic-anoxic-oxic (A2O), sequencing batch reactor (SBR) and biological aerated filter (BAF). Endospore-forming bacterial numbers in the RABC showed 129-fold higher levels than those of the existing advanced systems. RABC process demonstrated the highest bacterial numbers in its bioreactors (paired t-test, p<0.01). RBC biofilms and aeration tanks of the RABC system showed 131- and 476-fold higher than other existing advanced processes, respectively. Mean treatment efficiencies of the existing systems were 83.5% for chemical oxygen demand (COD), 59.1% for total nitrogen (TN) and 76.8% for total phosphorus (TP). However, RABC process removed 96.9% for COD, 96.9% for TN and 91.9% for TP for highly concentrated food wastewater (COD>1,500 mg/L, TN>150 mg/L, TP>50 mg/L). Treatment efficiency was significantly reduced when the numbers of Bacillus genus in the bioreactors decreased below $10^6CFU/mL$. The automated RABC (A-RABC), in which dissolved oxygen concentrations are automatically controlled, showed higher treatment efficiencies compared to the RABC process. The RABC system maintained sufficient bacterial numbers for the effective treatment of highly concentrated food wastewater. Moreover, final effluent was in agreement to water quality standards.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1221-1228
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• 2005

Carbon electrode was applied to a wastewater treatment system as biofilm media. The spatial distribution of heterotrophic bacteria in aerobic wastewater biofilm grown on carbon electrode was investigated by scanning electron microscopy, atomic force microscopy, and biomass measurement. Five volts of electric oxidation and reduction potential were charged to the carbon anode and cathode of the bioelectrochemical system, respectively, but were not charged to electrodes of a conventional system. To correlate the biofilm architecture of bacterial populations with their activity, the bacterial treatment efficiency of organic carbons was measured in the bioelectrochemical system and compared with that in the conventional system. In the SEM image, the biofilm on the anodic medium of the bioelectrochemical system looked intact and active; however, that on the carbon medium of the conventional system appeared to be shrinking or damaging. In the AFM image, the thickness of biofilm formed on the carbon medium was about two times of those on the anodic medium. The bacterial treatment efficiency of organic carbons in the bioelectrochemical system was about 1.5 times higher than that in the conventional system. Some denitrifying bacteria can metabolically oxidize $H_{2}$, coupled to reduction of $NO_{3}^{-}\;to\;N_{2}$. $H_{2}$ was produced from the cathode in the bioelectrochemical system by electrolysis of water but was not so in the conventional system. The denitrification efficiency was less than $22\%$ in the conventional system and more than $77\%$ in the bioelectrochemical system. From these results, we found that the electrochemical coupling reactions between aerobic and anaerobic reactors may be a useful tool for improvement of wastewater treatment and denitrification efficiency, without special manipulations such as bacterial growth condition control, C/N ratio (the ratio of carbon to nitrogen) control, MLSS returning, or biofilm refreshing.

• KSBB Journal
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• v.28 no.2
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• pp.80-85
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• 2013

The bacterial community structure in a biological reactor fed influent from a wastewater treatment system was investigated by denaturing gradient gel electrophoresis (DGGE) and in situ hybridization. Sludges were collected from three biological reactors (aerobic, oxic, and anoxic tanks) at the M wastewater treatment facility (WTF). The influent of the MWTF consisted of mixed tannery wastewater (40~65%) and seafood wastewater (35~60%). The treatment processes resulted in a removal efficiency for BOD (biochemical oxygen demand) and COD (chemical oxygen demand) of 83.6~98.2% and 72.8~84.6%, respectively for tannery wastewater than for seafood wastewater resulted in greater survival of biomass in the biological reactors and a higher removal of BOD, COD, and T-N of about 8~18%. In contrast, addition of greater amounts of seafood wastewater decreased the amount of biomass in the bioreactors due to the increasing concentration of chromium from that wastewater and it also. The dominant bacterial species during the high seafood wastewater input period were Burkholderia cepacia (JX901049) and an uncultured bacterium (JF247555), while Pseudomonas geniculata (HQ256559) was dominant during the high tannery wastewater input period. Flavobacteriumsp. BF.107 (FM173271) and Hyphomicrobium zavarzinii (Y14306) were dominant under anoxic conditions.

• Journal of Microbiology and Biotechnology
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• v.20 no.3
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• pp.447-459
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• 2010

Bacterial diversity of two distinct wastewater treatment systems, conventional activated sludge (CAS) and membrane bioreactor (MBR), of petroleum refineries were investigated through 16S rRNA gene libraries. Sequencing and phylogenetic analysis showed that the bacterial community composition of sludge samples was distinct between the two wastewater treatment systems. MBR clones belonged predominantly to Class Betaproteobacteria, represented mainly by genera Thiobacillus and Thauera, whereas CAS clones were mostly related to Class Alphaproteobacteria, represented by uncultured bacteria related to Order Parvularculales. Richness estimators ACE and Chao revealed that the diversity observed in both libraries at the species level is an underestimate of the total bacterial diversity present in the environment and further sampling would yield an increased observed diversity. Shannon and Simpson diversity indices were different between the libraries and revealed greater bacterial diversity for the MBR library, considering an evolutionary distance of 0.03. LIBSHUFF analyses revealed that MBR and CAS communities were significantly different at the 95% confidence level ($P{\leq}0.05$) for distances $0{\leq}D{\leq}0.20$. This work described, qualitatively and quantitatively, the structure of bacterial communities in industrial-scale MBR and CAS processes of the wastewater treatment system from petroleum refineries and demonstrated clearly differentiated communities responsible for the stable performance of wastewater treatment plants.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.847-854
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• 2011

To deal with issues from global climate changes, renewable bioenergy has become important. Algae have been regarded as a good resource for biorefinery and bioenergy, and also have potential capability to remove nutrient and non-decompositional pollutants for wastewater advanced treatment. Although algal-bacterial ecological interaction would be a crucially important factor in using algae for wastewater advanced treatment and resource recovery from wastewater, very little is known about ecological interaction between algae and bacteria in a real wastewater environment. In this study, under a real municipal wastewater condition, we characterized wastewater pollutant treatability and bacterial communities in response to growth of Ankistrodesmus gracilis SAG278-2, which can grow in wastewater and has a high lipid contents. The growth of algal population using the wastewater was inhibited by increase in wastewater bacteria while bacterial survival and cellular decay rate were not influenced by the algal growth. Removals of recalcitrant organic matters and total nitrogen were improved in the presence of algal growth. According to T-RFLP and statistical analysis, algal growth affected time-course changes in bacterial community structures. The following 16S rRNA gene amplicon, cloning results showed that the algal growth changes in bacterial community structure, and that bacterial populations belonging to Sediminibacterium, Sphingobacterium, Mucilaginibacter genera were identified as cooperative with the algal growth in the wastewater.

• Journal of Microbiology and Biotechnology
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• v.26 no.5
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• pp.900-908
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• 2016

The effects of algal inoculation on chemical oxygen demand (COD) and total nitrogen (TN) removal, and indigenous bacterial dynamics were investigated in municipal wastewater. Experiments were conducted with municipal wastewater inoculated with either Chlorella vulgaris AG10032, Selenastrum gracile UTEX 325, or Scenedesmus quadricauda AG 10308. C. vulgaris and S. gracile as fast growing algae in municipal wastewater, performed high COD and TN removal in contrast to Sc. quadricauda. The indigenous bacterial dynamics revealed by 16S rRNA gene amplification showed different bacterial shifts in response to different algal inoculations. The dominant bacterial genera of either algal case were characterized as heterotrophic nitrifying bacteria. Our results suggest that selection of indigenous bacteria that symbiotically interact with algal species is important for better performance of wastewater treatment.

• Journal of Environmental Science International
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• v.28 no.10
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• pp.899-905
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• 2019

Recently, an innovative method for wastewater treatment and nutrient removal was developed by combining the sequence batch reactor and membrane bioreactor to overcome pollution caused by shipboard sewage. This system is a modified form of the activated sludge process and involves repeated cycles of mixing and aeration. In the present study, the bacterial diversity and dominant microbial community in this wastewater treatment system were studied using the MACROGEN next generation sequencing technique. A high diversity of bacteria was observed in anaerobic and aerobic bioreactors, with approximately 486 species. Microbial diversity and the presence of beneficial species are crucial for an effective biological shipboard wastewater treatment system. The Arcobacter genus was dominant in the anaerobic tank, which mainly contained Arcobacter lanthieri (8.24%), followed by Acinetobacter jahnsonii (5.81%). However, the dominant bacterial species in the aerobic bioreactor were Terrimonas lutea (7.24%) and Rubrivivax gelatinosus (4.95%).

• Korean Journal of Microbiology
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• v.46 no.4
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• pp.352-358
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• 2010

Bacterial community composition in activated sludge wastewater treatment bioreactors were analyzed using 16S rRNA gene-based pyrosequencing for the four different wastewater treatment processes. Sequences within the orders Rhodocyclales, Burkholderiales, Sphingobacteriales, Myxococcales, Xanthomonadales, Acidobacteria group 4, Anaerolineales, Methylococcales, Nitrospirales, and Planctomycetales constituted 54-68% of total sequences retrieved in the activated sludge samples, which demonstrated that a few taxa constituted majority of the activated sludge bacterial community. The relative ratio of the order members was different for each treatment process, which was assumed to be affected by different operational and environmental conditions of each treatment process. In addition, activated sludge had very diverse bacterial species (Chao1 richness estimate: 1,374-2,902 operational taxonomic units), and the diversity was mainly originated from rare species. Particularly, the bacterial diversity was higher in membrane bioreactor than conventional treatment processes, and the long solids retention time of the operational strategy of the membrane bioreactor appeared to be appropriate for sustaining diverse slow growing bacteria. This study investigating bacterial communities in different activated sludge processes using a high-throughput pyrosequencing technology would be helpful for understanding microbial ecology in activated sludge and for improving wastewater treatment in the future.

• Journal of Microbiology and Biotechnology
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• v.19 no.4
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• pp.346-350
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• 2009

Although salt is known to influence the performance of nitrification significantly, it has not been well reported on how salt affects ammonia-oxidizing bacterial(AOB) community compositions and dynamics in wastewater treatment bioreactors. In this study, these questions were evaluated in a full-scale bioreactor treating saline wastewater. Clone library analysis for the ammonia monooxygenase subunit A gene revealed that AOB belonging to the Nitrosomonas europaea and the N. oligotropha lineages inhabited in the bioreactor. Terminal restriction fragment length polymorphism analysis for monthly samples demonstrated a fluctuation pattern among AOB populations, although AOB within the N. europaea lineage were dominant during the test period. Correlation analysis between patterns of terminal restriction fragments and environmental variables suggested that sodium, chloride, and sulfate were less important; rather, temperature was the most significant factor affecting the AOB community in the bioreactor.

• Journal of Microbiology and Biotechnology
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• v.13 no.1
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• pp.15-21
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• 2003

Two microbial communities of activated sludge in the same municipal wastewater, but treated with different systems, were studied and compared using molecular microbiological approaches. The bacterial 16S rDNA sequences from 124 clones were analyzed, however, the majority of them were not closely related to any known species, and found to belong to 8 different phylogenetic groups and 3 different unidentified groups. The relative frequencies of each group were similar between the two microbial communities. Fingerprinting using terminal restriction fragment length polymorphism (T-RFLP) showed that the putative Nitrospira-related populations were more diverse and quantitatively higher in the KNR process system than in the other system using a conventional activated sludge process. The relationship between the bacterial community composition and the higher removal efficiency of nitrogen and phosphorus in the KNR process is discussed.