| Azo dye wastewater is the main source of industrial wastewater which is extremely difficult to treat.It not only has deep chromaticity,large emissions,but also has a complex composition and high concentration of organic matters and inorganic salts.In addition,the discharge of azo dye wastewater into the natural waters can cause great harm to environmental ecosystems and human health.Different from traditional azo dye wastewater treatment processes such as physical,chemical or biological methods,the coupling system of bioelectrocatalysis and contact oxidation was adopted in this study,and it is a combination process of bioelectrochemical system(BES)and bio-contact oxidation(BCO).As a novel wastewater treatment reactor,the BES-BCO coupling system has the characteristics of high dye decolorization efficiency,low sludge production,land saving and no secondary pollution.In this study,microbial membranes were applied to BES and BCO units,respectively.The artificially simulated AO7 wastewater was used to the tolerant domestication of dye toxicity and high salinity of BES and BCO,and finally the BES-BCO coupling system was constructed to treat high-salinity wastewater.The decolorization of the dye AO7 was mainly concentrated in the BES portion,and the removal of the organic matters was concentrated in the BCO unit.For the azo dye wastewater with a salt concentration of 50 g/L,AO7 concentration of 150 mg/L and COD concentration of 1100 mg/L,94%dye decolorization rate and 73%COD removal rate were obtained after the treatment by BES-BCO.The results showed that the decolorization rate of dye AO7 can be enhanced with the increase of salinity,but the aerobic removal of organic matter can be inhibited.At the same time,the internal resistance of the reactor was measured by changing the applied voltage.The results showed that the resistance of the reactor was 127.5 Q when the salinity was 0%,and the resistance decreased to 60.6 Q when the salinity increased to 5.0%.Salinity played an important role in regulating the internal resistance of the reactor.Higher salinity would make the internal resistance smaller and the current larger.The decolorization specific energy consumption of dye AO7 was calculated by using the measured data.The effects of hydraulic retention time,external voltage and dissolved oxygen concentration on reactor performance and wastewater treatment effect were investigated by designing the single factor change experiments,and the simulation was carried out by response surface software.According to the analysis,the best operating conditions of BES-BCO coupling system were the applied voltage of 0.37 V,the hydraulic retention time of 24 h and the dissolved oxygen concentration of 2.16 mg/L.94%dye decolorization rate,75%COD removal rate and 978.31 J/g AO7 decolorization specific energy consumption can be achieved.Using high-throughput sequencing technology based on Illumina platform,the microbial community in the reactor was analyzed.It was found that the richness and diversity of microbial community decreased gradually with the decrease of organic concentration in water.At the Phylum level,the microbial community of each biofilm sample in the reactor was relatively small and simple,which was mainly due to the elimination of a large number of microorganisms that were not suitable for the high salinity environment.Among them,the microbial species of each sample were identical,and there were four main bacteria,among which Proteobacteria accounted for the highest proportion.At the Genus level,the optimum salinity of most microorganisms ranges from 2%to 4%,and the salinity environment of 5%in this study has exceeded this range,which inhibited the activity of these microorganisms and was not conducive to the degradation of wastewater by the reactor.The effect of wastewater treatment could be improved by inoculating halophilic bacteria into the reactor,especially the BCO unit. |
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