Qinghua Sun

Bioaugmentation and adsorption treatment of coking wastewater containing pyridine and quinoline using zeolite-biological aerated filters.

Bioaugmented zeolite-biological aerated filters (Z-BAFs), i.e. adding isolated degrading bacteria into the BAFs with zeolite as fillings, were designed to treat coking wastewater containing high concentrations of pyridine and quinoline and to explore the bacterial community of biofilm on the zeolite surface. The investigation was carried out for 91 days of column operation and the treatment of pyridine, quinoline, total organic carbon (TOC), and ammonium was shown to be highly efficient by bioaugmentation and adsorption. Biomass determination and bacterial diversity detection based on 16S rDNA and rRNA techniques supported the treatment data and indicated that bioaugmentation could recover the bacterial richness and diversity from pyridine and quinoline loading shocks. However, bioaugmentation accelerated the shift of the bacterial community structure resulting in a more distinct difference from the starting community. Clone library analysis revealed that pyridine and quinoline were more harmful to Bacterodietes among all ingenious bacteria, and bioaugmentation promoted the growth of Planctomycetes in the biofilm. Moreover, the introduced bacteria did not remain dominant in the bioaugmented biofilm, indicating the indigenous degrading bacteria played the most significant role in the treatment. This bioaugmented Z-BAF method was shown to be an alternative technology for the treatment of wastewater containing pyridine and quinoline or other N-heterocyclic aromatic compounds.

Aerobic biodegradation characteristics and metabolic products of quinoline by a Pseudomonas strain

A bacterial strain, BW003, which utilized quinoline as its sole C, N and energy source, was isolated and identified as Pseudomonas sp. BW003 degraded 192-911 mg/l quinoline within 3-8 h with removal rates ranging from 96% to 98%. The optimum conditions for the degradation were 30 degrees C and pH 8. In the process of biodegradation, at least 43% of quinoline was transformed into 2-hydroxyquinoline, then 0.69% of 2-hydroxyquinoline was transformed into 2,8-dihydroxyquinoline, and then, presumably, into 8-hydroxycoumarin. Meanwhile, at least 48% of the nitrogen in quinoline was directly transformed into ammonia-N. An extra carbon source enhanced the nitrogen transformation from ammonia-N. Further experiments showed that, besides cell synthesis, BW003 transformed less than 6% of ammonia-N into nitrate through heterotrophic nitrification. In addition, BW003 contained a large plasmid, which may be involved in quinoline metabolism. The study indicates that quinoline and its metabolic products can be eliminated from wastewater by controlling the C/N ratio using BW003 as the bioaugmentation inoculum.

Removal of pyridine and quinoline by bio-zeolite composed of mixed degrading bacteria and modified zeolite.

In the process of the biodegradation of pyridine and quinoline, ammonium is often generated because of the transformation of N from pyridine and quinoline. Zeolite has been proven to be an effective sorbent for the removal of the ammonium. The natural zeolite can be modified to be the macroporous carrier in the biological wastewater treatment process. In this study, a specific bio-zeolite composed of mixed bacteria (a pyridine-degrading bacterium and a quinoline-degrading bacterium) and modified zeolite was used for biodegradation and adsorption in two types of wastewater: sterile synthetic and coking wastewater. The experimental results indicated that pyridine and quinoline could be degraded simultaneously by the mixed bacteria. Furthermore, NH(4)(+)-N transformed from pyridine and quinoline could be removed by the modified zeolite. In addition, the bacterial community structures of the coking wastewater and the bio-zeolite were monitored by the amplicon length heterogeneity polymerase-chain reaction (LH-PCR) technique. Both LH-PCR results and scanning electron microscope (SEM) observations indicated that the microorganisms, including BW001 and BW003, could be easily attached on the surface of the modified zeolite and that the bio-zeolite could be used in the treatment of wastewater containing pyridine and/or quinoline.

Quinoline biodegradation and its nitrogen transformation pathway by a Pseudomonas sp. strain

A Pseudomonas sp. strain, which can utilize quinoline as its sole carbon, nitrogen and energy source, was isolated from activated sludge in a coking wastewater treatment plant. Quinoline can be degraded via the 8-hydroxycoumarin pathway. We quantified the first two organic intermediates of the biodegradation, 2-hydroxyquinoline and 2,8-dihydroxyquinoline. We tracked the transformation of the nitrogen in quinoline in two media containing different C/N ratios. At least 40.4% of the nitrogen was finally transformed into ammonium when quinoline was the sole C and N source. But addition of an external carbon source like glucose promoted the transformation of N from NH3 into NO3−, NO2−, and then to N2. The product analysis and gene characteristics indicated that the isolate accomplished heterotrophic nitrification and aerobic denitrification simultaneously. The study also demonstrated that quinoline and its metabolic products can be eliminated if the C/N ratio is properly controlled in the treatment of quinoline-containing wastewater.

Bioaugmentation treatment for coking wastewater containing pyridine and quinoline in a sequencing batch reactor

Two pyridine-degrading bacteria and two quinoline-degrading bacteria were introduced for bioaugmentation to treat the coking wastewater. Sequencing batch reactors (SBRs) were used for a comparative study on the treatment efficiency of pyridine, quinoline, and chemical oxygen demand. Results showed that the treatment efficiency with coking-activated sludge plus a mixture of the four degrading bacteria was much better than that ones with coking-activated sludge only or mixed degrading bacteria only. Moreover, a 52-day continuous operation of the bioaugmented and general SBRs was investigated. The bioaugmented SBR showed better treatment efficiency and stronger capacity to treat high pyridine and quinoline shock loading. The general SBR failed to cope with the shock loading, and the biomass of the activated sludge decreased significantly. In order to monitor the microbial ecological variation during the long-term treatment, the bacterial community in both reactors was monitored by the amplicon length heterogeneity polymerase chain reaction technique. The diversity of the bacterial community decreased in both reactors, but the introduced highly efficient bacteria were dominant in the bioaugmented SBR. Our experiment showed clearly that the use of highly efficient bacteria in SBR process could be a feasible method to treat wastewater containing pyridine or/and quinoline.

Simultaneous biodegradation of pyridine and quinoline by two mixed bacterial strains

Experiments were conducted to provide data on the effectiveness of bioaugmentation in the removal of pyridine and quinoline from different wastewaters. A pyridine-degrading bacterial strain (Paracoccus sp. BW001) and a quinoline-degrading strain (Pseudomonas sp. BW003) were isolated from the activated sludge of a coking wastewater treatment plant. In this study, a consortium of these two bacterial strains was used as inoculum to simultaneously degrade pyridine and quinoline in three types of wastewaters: sterile synthetic, domestic, and industrial. In addition, variation of the bacterial community structures during degradation was monitored by denaturing gradient gel electrophoresis and amplicon length heterogeneity polymerase chain reaction techniques. The results of our experiments indicate that pyridine and quinoline can be removed efficiently using this inoculum but that the degradation process results in the production of ammonium as a by-product. Also, in the two actual wastewaters investigated, we observed that several autochthonous strains of bacteria in both the domestic and industrial wastewater were tolerant of pyridine and quinoline and grew rapidly.

Bacterial diversity in the polluted water of the Dianchi Lakeshore in China

Dianchi Lake is a typical Chinese eutrophic lake. The bacterial community in the polluted water of the Dianchi lakeshore was investigated by cultivation-independent approaches. The amplicon length heterogeneity polymerase-chain reaction (LH-PCR) was used to detect the major differences in bacterial structure among the nine different sampling sites. Cluster analysis shows that the bacterial communities in water blooming sites were similar. Three genes were employed to characterize bacteria in the two parts of Dianchi Lake. The 16S rRNA gene was used to analyze the total bacterial community, the ammonia monooxygenase (amoA) gene for detecting ammonia-oxidizing bacteria, and the nitrous oxide reductase (nosZ) gene for identifying denitrifying bacteria. The clone library results demonstrate that Proteobacteria, Bacteroidetes, and Cyanobacteria were the dominant bacteria in both parts of the lake. The communities of ammonia-oxidizing bacteria were very different in the two parts of the lake and belonged to Nitrospira in the north and Nitrosomonas in the south part, respectively. Denitrifying bacteria in the Dianchi lakeshore were related to several cultured denitrifiers such as Pseudomonas, Paracoccus, Achromobacter, and Rubrivivax.

Analysis of denitrifier community in a bioaugmented sequencing batch reactor for the treatment of coking wastewater containing pyridine and quinoline

The denitrifier community and associated nitrate and nitrite reduction in the bioaugmented and general sequencing batch reactors (SBRs) during the treatment of coking wastewater containing pyridine and quinoline were investigated. The efficiency and stability of nitrate and nitrite reduction in SBR was considerably improved after inoculation with four pyridine- or quinoline-degrading bacterial strains (including three denitrifying strains). Terminal restriction fragment length polymorphism (T-RFLP) based on the nosZ gene revealed that the structures of the denitrifier communities in bioaugmented and non-bioaugmented reactors were distinct and varied during the course of the experiment. Bioaugmentation protected indigenous denitrifiers from disruptions caused by pyridine and quinoline. Clone library analysis showed that one of the added denitrifiers comprised approximately 6% of the denitrifier population in the bioaugmented sludge.

Comparison of denitrifier communities in the biofilms of bioaugmented and non-augmented zeolite–biological aerated filters

The denitrifier communities of a bioaugmented and non-augmented zeolite–biological aerated filter (Z-BAFs) were investigated and compared because the bioaugmented Z-BAF provided better and more stable treatment efficiency for nitrate and nitrite removal. Terminal restriction fragment length polymorphism (T-RFLP) and reverse transcription T-RFLP (RT-T-RFLP) were applied to analyse the denitrifier community diversity in the biofilm collected from each Z-BAF. The results showed that the bioaugmentation technology favourably changed the indigenous denitrifier community and enhanced denitrification under nitrogen loading shocks. The cDNA clone libraries were developed to explore the active denitrifier community structures of both filters. The results showed that the active denitrifiers in both the bioaugmented and non-bioaugmented Z-BAF belonged to α-, β- and γ-proteobacteria. However, the sequence of the introduced denitrifier (Paracoccus sp. BW001) was not found in the clone library of the bioaugmented filter, which implied that the removal of nitrate and nitrite was attributed mainly to the indigenous denitrifiers in the adjusted bacterial community in the bioaugmented Z-BAF.