Study On Azo Dye Degradation By AMBR And Membrane Fouling

This paper investigated the application of anaerobic MBR(AMBR) for synthetic azo dye wastewater treatment. The genetic engineering bacteria E coli JM109 was effective biodegradation bacteria for azo dyes and inoculated in the AMBR. Due to membrane rejection, the bacteria concentration was kept at high level in AMBR and the bio-decoloration performance of azo dye Acid Red B was enhanced. In addition. Recolored mechanism of azo dyes discolored products and the mineralization possibility at aerobic condition were also explored. Furthermore, the biofouling of tubular membrane for high concentration bacteria filtration in AMBR was also studied.The bacteria applied in this work was genetic engineering bacteria E coli JM109, it was built by Dalian university of technology (DLUT) for azo dye acid red B decoloration and stored in environmental bioengineering laboratory School of environmental engineering and technology, DLUT. In this study, the anaerobic MBR combined with E coli JM109 was operated more than 200 days and the concentration of E coli JM109 reached 20g/L (dry weight).The batch test with bacteria from AMBR was also carried out to study the bacteria concentration effect on the decoloration performance of acid red B. Anaerobic shaking bottle experiments showed the decoloration efficiency of acid red B was enhanced with the increase of bacteria concentration. The azo dye could be discolored in 1 hour at the bacteria concentration 3g/L to 4g/L. With membrane rejection, the concentration of bacteria retained in AMBR could be up to 20g/L, therefore, the decoloration efficiency was much more enhanced. Meanwhile, COD removal was also improved.The discolored products of acid red B could be recolored as they were exposed to oxygen. The analysis result by HPLC showed peak area of acid red B dropped from 87.01% to 9.94% during the anaerobic degradation. The new peaks at retention time 19.1min and 31.8 min may attribute to the intermediate products of discolored process. These intermediate products had the structure of indophenols, which were produced by the reaction of intermediate products with oxygen. The colored substance with this structure showed nacarat in acid liquor and turned cyan in alkali liquor. With the analysis by LC-MS, two possible recolored passway were assumed.Due to the recalcitrant property of recolored producted, to the total mineralization of azo dye was very difficult in A/O process. At sub-and super-critical flux, the fouling intensities to the tubular membrane were different. The membrane fouling at super-critical flux showed distinct two stages, with the TMP fast increase, followed by a slow increase, the membrane fouling at sub-critical flux indicated three stages, which were TMP slow increase, TMP quick jump and a slow TMP increase. at both sub-or super-critical flux, the shearing flow velocity was able to mitigate membrane fouling. The analysis results of EPS attached on the membrane surface showed the ratio of polysaccharide/protein were varying. With the permeate flux increase, the percentage of polysaccharide decrased and the percentage of protein increased. However, the main portion of foulant on the membrane was polysaccharide.