| One bacterial strain with high degradation capacity for the dye- C.I. Direct Black19 (DB19) was isolated from anaerobic sludge in an Internal Circulation (IC) anaerobic reactor of a paper and pulp wasterwater treatment plant. The bacterium, which is named Pf-6, was primarily identified as Pseudomonas fluorescens through analysis results of its morphological, physiological and biochemical performances and 16S rDNA genetical sequence test. By batch experiments, the effect of zero-valent iron (Fe~0) on the biodegradation of DB19,C.I. Reactive Blue4 (X-BR or RB4),C.I. Reactive Red2 (X-3B or RR2) and mixed pollutant composed of above three dyes, and kinetics of their decolorization in the Fe~0/Pf-6 combined system were investigated under the condition of mesophilic temperature 35±2℃. The decolorization process and intermediate products of these dyes in the Fe~0/Pf-6 combined system were preliminarily analysed by means of some methods such as UV-vis, FT-IR.(1) Compared with pure Pf-6 and single Fe~0 treatment systems, the decolorization effect of DB19 was significantly improved in the Fe~0/Pf-6 combined system. Under the anaerobic condition, the decolorization process of DB19 obeyed the first-order reaction dynamics in above three treatment systems. The dynamical constants k1 in the Fe~0/Pf-6 combined, pure Pf-6 and single Fe~0 systems were 55.4×10~3 h~1, 35.7×10~3 h~1 and 14.3×10~3 h~1 respectively.(2) When intial DB19 concentration was 100 mg/L, the optimum conditions of oxygen supplied,pH, Fe~0 dosage and Pf-6 inoculation volume for its decolorization in the Fe~0/Pf-6 combined system were facultative anaerobic, 7.0, 500mg/L and 5% respectively. Otherwise, the k1 decreased from 63.8×10~3 h~1 to 22.4×10~3 h~1 with increasing of initial DB19 concentration from 100 mg/L to 1500 mg/L.(3) When initial X-BR concentration and HRT were 100 mg/L and 71 h respectively, its decolorization rate was about 90% in the Fe~0/Pf-6 combined system under the facultative anaerobic condition, which were 30% and 40% higher than that in the pure Pf-6 and single Fe~0 systems respectively. However, the decolorization rate of X-3B in the Fe~0/Pf-6 combined system could also reach about 90% with initial dye concentration and HRT of 100 mg/L and 55 h respectively, which was 60% higher than that in the pure Pf-6 and single Fe~0 systems. Otherwise, both of the decolorization processes of X-BR and X-3B obeyed the first-order reaction dynamics and theirs dynamical constants k1 were 31.1×10~3 h~1 and 35.6×10~3 h~1 respectively in the combined system.(4) After these dyes– DB19, X-BR and X-3B were decolozied under the facultative anaerobic condition, the values of 2,3,5-triphenyl tetrazoliumchloride dehydrogenase activity (TTC-DHA) in the Fe~0/Pf-6 combined system could reach up to 40.98, 37.07, 45.26μgTF/(mL·h) respectively, while they were only 16.53, 12.23, 19.80μgTF/(mL·h) respectively in the pure Pf-6 system. It showed that, Fe~0 could effectively improve dehydrogenase activity under the facultative anaerpbic condition, which was benefit to promote dye decolorization in the Fe~0/Pf-6 combined system.(5) Based on analysis results of UV-vis and FT-IR, it indicated that, in the Fe~0/Pf-6 combined system, the decolorization of DB19, X-3B and X-BR were achieved mainly through fracture of azo bond and damage of anthraquinone conjugate structure respectively. Otherwise, some intermediate products with the structure of naphthalene ring and benzene during these dyes decolorization could also be partially degraded in the combined system.(6) During treatment of mixed dye wasterwater composed of DB19,X-BR and X-3B, certain decolorization effect could be obtained in the Fe~0/Pf-6 combined system. When initial each dye concentration and HRT were 40 mg/L and 55 h respectively, the decolorization rates of DB19, X-BR and X-3B were 80%, 75% and 47% respectively under the optimum conditions.
|
PDF Full Text Request