Accelerating Biodegradation Of A Monoazo Dye Acid Orange 7 By Using Its Intermediates

Azo dye with one or more azo bonds（-N=N-）is a kind of electron-deficient xenobiotic components.And it usually contains sulfonic（SO₃^-）or other electron-withdrawing groups that generate an electron deficiency make it less susceptible to be biodegraded.To improve efficiency of azo dyes biodegradation,advanced oxidation process coupled biological treatment was proved to be an effective strategy,in order to convert the azo dyes into smaller and much more easily biodegradable intermediates.In fact,the intermediates produced after the pretreatments acted as redox mediators transferred electrons to azo dyes via enzymes during bacterial catabolism.The addition of organic intermediates with available electrons could form a kind of co-substrate acceleration.On the other hand,what was the role of the inorganic intermediates（ions）playing during the azo dye biodegradation?This paper was exactly focusing on the relationship between the inorganic intermediates and the organic intermediates for azo dyes biodegradation.UV radiation was chosen to be the pretreatment in this study.The results showed that 1)the organic intermediates（SA,AN）and inorganic intermediates(NH₄⁺and SO₄^2-)generated by UV radiation reached the maximum concentration at 9,12 and 24 h,respectively;2)the regular of intermediates acceleration effect was All>organic intermediates>inorganic intermediates(NH₄⁺>SO₄^2-);3)NH₄⁺and SO₄^2-could influence the biodegradability.When the concentration of NH₄⁺increased from 0 to 3 mg/L,the BOD₅ and B/C ratio increased gradually.Compared with 0.5 mg/L NH₄⁺added,when 3 mg/L NH₄⁺,BOD₅ increased5 times.The promotion effect of SO₄^2-had showed a positive effect at low concentration（0-1.5 mg/L）and a negative effect at high concentration（1.5-3 mg/L）,and its BOD₅ and B/C ratio reached a peak when 1.5 mg/L SO₄^2-added.Compared with no sulfate added sample,BOD₅ at 1.5 mg/L SO₄^2-was increased by 142%.And SOURx/SOUR₀ analysis suggested the similar regular.SA,AN and NH₄⁺were positive to enhance the metabolic activity,while SO₄^2-had a two-sided effect;4)inorganic intermediates could improve the microbial respiration rate,and had a positive effect on microorganism enzymes and cofactors which improved the whole microorganisms’metabolic activities.