Research Of Enhancing Dye Wastewater Disposal In A Biocatalyzed Electrolysis-Aerobic Process Coupled System

Due to the low efficiency in the anaerobic stage of the traditional anaerobic-aerobic dye treatment process, this study aims to utilize the biocatalyzed electrolysismethod to improve the removal performance of dye wastewater treatment. Especially,an up-flow biocatalyzed electrolysis reactor (UBER)-contact oxidation process coupledsystem was established to treat the wastewater containing azo dyes (Alizarin Yellow R,AYR).Firstly, the decolorize performance of UBER was explored. The results showedthat the decolorization of AYR mainly occurred at the cathode of UBER, which is acombined effect of electrochemical system and anaerobic microorganisms. Moreover,electrochemical reaction played a mainly role. The biological anode contributed tocolor removal, as well. Then, the structure and operating conditions of UBER werefurther optimized. The result showed the best operating conditions as follows: cathodeand anode volume ratio is2:1, the HRT equal to4h. At this condition, the chrominanceof the effluent of UBER was80times, decolorization rate equal to86.2%. Thechrominance of the effluent can reach the secondary standard of the textile industrypollutant discharge standard (GB4287-92). Then, UBER coupled with contactoxidation reactor under this condition later.Secondly, the coupled system of UBER-contact oxidation reactor was establishedto remove AYR in water and to explore the treatment effect after having launched thecontact oxidation reactor successfully. The result showed that the most color removaloccurred in the UBER, resulting in the improved biodegradability of the influent ofcontact oxidation reactor, as well. Meanwhile, there was a certain contribution to theremoval of COD since organic substrate consumed in the anode. At the same time, theremoval of COD and decolorized products of AYR mainly occurred in contactoxidation reactor, while with low color removal efficiency. The analysis of thetransmission mechanism of AYR in the coupled system demonstrated that the twostable products of AYR was p-phenylenediamine and5-aminosalicylic acid in UBER.While in contact oxidation reactor the two decolorized products firstly converted top-aminophenol, and then p-aminophenol converted to succinic acid and acetic acidthrough open looping, deamination and carbon strand breaking after further oxidation, which enter the TCA cycle of aerobic microorganisms and mineralized completely inthe end.Finally, the operating conditions of the coupled system were optimized byadjusting the coupled system HRT. The result indicated that with the UBER at a HRTof3h and the contact oxidation reactor at a HRT of4.5h, the coupled system reachedthe optimal conditions with the effluent chrominance of64times, decolorization rateof94.2%, COD of54.9mg/L, COD removal rate of of93.4%, the content ofp-phenylenediamine of0.26mg/L and5-aminosalicylic acid of0.09mg/L,respectively. These indexes of water quality of the effluent can reach the secondarystandard of GB4287-92. And the effluent of coupled system can be discharged into theIV, V standard waters in GB3838and the third standard waters in GB3097. Comparingthe performance of coupled system at this condition with other anaerobic-aerobicprocess, we found that the coupled systems in this study can be achieving higherdecolorization and COD removal at a shorter HRT.