| Dyeing wastewater is one of the most harmful industrial wastewater because of its large discharge, complicated composition, low biodegradability and toxicity. The inappropriate disposal of dyeing wastewater poses a great threat to aquatic environment and human health. As a traditiona l biological treatment process, hydrolysis acidification(HA) process can not only improve the biodegradability of dye ing wastewater, but also have the ability of decolorization. Therefore, it is wide ly used in the treatment of dyeing wastewater. However, the treatment efficiency of HA process is low, and its effluent cannot meet the discharge standard, which can be improved greatly. In order to improve the efficiency of HA process for dyeing wastewater treatment, it is essential to choose suitable methods on the base of understanding the relationship among microorganisms in HA process. This is a research subject of exploration significance and development prospect.In present study, simulated dyeing wastewater was used as the treatment object. Firstly, an HA reactor was constructed for dyeing wastewater treatment. The treatment effect and microbia l community structure were investigated in the start-up period. Secondly, by changing the structures and concentrations of dyes in simulated dyeing wastewater, the effects of different dyes on performance and microbia l community structure of HA process were studied, as well as the relationship between them. Finally, co-substrates and mixed flora were added into the HA reactor to improve its treatment efficiency of dyeing wastewater, respectively. The variation of microbia l community structure and dominant species were analyzed during the augmentation process. The main research works in this study are listed as following:1) Start-up of HA reactorA HA reactor was constructed for dyeing wastewater treatment. During start-up period, the physicochemical characteristics of influent and effluent of HA reactor were monitored to reflect the treatment effect. PCR-DGGE(Polymerase chain reaction-denaturing gradient ge l electrophoresis) analysis was performed to trace the changes of microbia l community structure in HA reactor. The results showed that approximately 65% decolorization rate and 50% COD removal rate were achieved by HA process after 100 days treatment. The biodegradability of simulated dyeing wastewater was improved as well. DGGE profile exhibited that the microbia l community structure varied significantly. Phylogenetic analysis indicated that the dominant species was related to Bacteroidetes group, which might be the main functional bacteria related to dyeing wastewater degradation in this HA process.2) Effect of different dyes on HA process for dyeing wastewater treatmentAfter entering the stable phase, the operation condition of HA process was divided into two stages based on dyes with different structures. Stage 1(the dye used was Reactive Black 5, RB5, azo dye): the concentration of RB5 increased from 10 mg/L to 200 mg/L gradua lly; stage 2(the dye used was Remazol Brilliant Blue R, RBBR, anthraquinone dye): the concentration of RBBR increased from 10 mg/L to 200 mg/L gradually. During the whole period, the physicochemical characteristics were investigated to reveal the effects of different dyes on the performance of HA process. Fourier transform infrared spectroscopy(FTIR) and gas chromatography-mass spectrometry(GC-MS) were introduced to detect the degradation products in HA process. Illumina MiSeq sequencing together with PCR-DGGE analysis was performed to reveal the variation of microbia l community influenced by different dyes. The results indicated that decolorization rate and COD removal rate of HA reactor were better in stage 1 than that in stage 2. The results of FTIR and GC-MS analysis confirmed the biodegradation of RB5 and RBBR by HA process, and RB5 was easier to be degraded than RBBR. PCR-DGGE analysis revealed that significant difference of microbia l community structures existed between stage 1 and 2. Compared with the concentration of dyes, the structure of dyes had more significant influence on microbia l community structure. The results of Illumina MiSeq sequencing analysis revealed that dyes with different structures had significant influence on the microbial community structure in HA reactor on different taxonomic levels(from phylum to genus). The genera Klebsiella sp., Lactococcus sp., and Desulfovibrio sp. might play important roles in degradation of both RB5 and RBBR under HA condition, while Dysgonomonas sp. and Prevotella sp. had potential biodegradation ability of RB5 and RBBR, respectively.3) Effect of different co-substrates on HA process for dyeing wastewater treatmentDifferent co-substrates were added into the HA reactor, respectively, in order to improve the treatment effects of dyeing wastewater. Co-substrates used in this study included starch, glucose, sucrose, peptone and yeast extract(YE). Physicochemical characteristics were detected to reveal the changes of the performance of HA process under different co-substrates conditions. Overall microbia l community structure was analyzed using PCR-DGGE followed by band sequencing, as well as Illumina MiSeq sequencing. The influence of co-substrates on microbial community composition and structure were also discussed. The results showed that the highest decolorization rate(about 50.64%) and COD removal rate(about 60.73%) were obtained with sucrose as co-substrate. Carbon sources included starch, glucose and sucrose exhibited better decolorization and COD removal efficiency than nitrogen sources included YE and peptone. The results of Illumina MiSeq sequencing and PCR-DGGE analyses revealed that co-substrates had significant influence on the community structure and microbial diversity in HA process. Sequence analyses by them both showed that Bacteroidetes, Proteobacteria and Firmicutes were the dominant phyla in a ll samples, despite of the change of co-substrates. Sucrose was considered to be the suitable co-substrate in this HA process, because it could not only obta in the best effect on the performance of HA process, but also stimulate some species(Raoultella sp., Desulfovibrio sp., Tolumonas sp., Clostridium sp., etc.) which might capable of dyes degradation.4) Bioaugmentation with mixed flora for HA treatment of dyeing wastewaterMixed flora FF who has high efficiency of dye degradation was fed into the HA reactor to enhance the treatment effect of simulated dyeing wastewater, which was reflected by decoloriza iton rate, COD removal rate, B/C value and the production of VFAs. The results showed that after bioaugmentation with mixed flora, decoloriza iton rate and COD removal rate in HA process were enhanced with approximately 15% and 20%, respectively. The biodegradability of simulated dyeing wastewater was improved as well. PCR-DGGE was performed to analyze the microbia l community diversity and structure in HA reactor before and after bioaugmentation. The results suggested that after bioaugmentation with mixed flora, Shannon Weaver index(H) increased from 2.17 to 2.56, which indicated an increase of species richness. DGGE Profile revealed that the structure of microbia l community changed largely. Phylogenetic analysis indicated that species belonged to Bacteroidetes kept its dominant position despite of the bioaugmentation. At the same time, species belonged to Proteobacteria and Firmicutes were enhanced as well.The organic composition of dyeing wastewater is complex, which is diff icult to deal with. It is difficult to achieve the expect treatment effect by the traditiona l HA process. In this study, co-substrates and mixed flora were used to enhance the performance of HA process for dyeing wastewater treatment, and achieved good effects. This study provided a theoretical reference for augmentation of actual HA process. |
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