| Nitrobenzene is one kind of widely used recalcitrant organic compounds, it is of great harm for its toxicity, mutagenicity, carcinogenicity. Nitrobenzene was listed as the priority pollutant by America last century and now our country also makes it on this list. Nitrobenzene is a kind of important organic synthetic intermediate, mainly used for synthesis of aniline, and is the raw material for dyes manufacture and dye intermediates. It has wide applications in many industries such as medicines, pesticides and spices. The waste water, waste gas of the Chemical plants and dye factory are the main sources of nitrobenzene in the environment, especially the sewage of aniline dye factory contains a lot of nitrobenzene. Our country developed a corresponding standard to control emissions of nitrobenzene concentration based on this serious situation.At present, there are lots of methods for nitrobenzene wastewater treatment, the efficiency of traditional methods of physical, chemical and biological is lower, and there are more studies about the combinations of physical and chemical and biological processing of which the effect are better. Such as coupling ozone oxidation and biological technology, coupling Fenton oxidation with biological, iron(Fe/C) carbon reduction-biological coupling technology and membrane bioreactor.In this paper, we combine the physicochemical method and the biological methods to treat the nitrobenzene wastewater. It is the technology of UV coupled with biological degradation that is used to disposal the nitrobenzene. We discussed the removal efficiency of the different combination means of UV and biology. Then studied the matrix effect on nitrobenzene removal under the anaerobic conditions, getting the following results.(1) The removal rate of nitrobenzene by single UV is lower than single biological degradation(B), ultraviolet coupling with biological sequentially(P+B) and the simultaneously ultraviolet coupling with biological(P&B), so the single ultraviolet method does not apply to the degradation of nitrobenzene. We compared the removal rate by the fractional-order kinetics among the B, P + B and P&B, and knowing that k(P&B)>k(B)> k(P+B).(2) The products from UV photolysis are nitrophenol and oxalic acid. The experimental results support that NP slowed NB biodegradation, but OA accelerated its biodegradation, and its impact on nitrobenzene biodegradation rate depends on the adding amount when adding the nitrophenol and oxalic acid at the same time.(3) With intimate coupling, the photolysis product NP did not accumulation to a concentration high enough to inhibit NB biotransformation. Instead, more OA was generated by means of photolysis, and it accelerated biotransformation of NB and NP by its co-substrate effect on the initial mono-oxygenation and N-reduction reactions. Short UV illumination could minimize the inhibitory effects of NP inhibition with sequential photolysis and biodegradation, but the best NB removal was with P&B, which accentuated the co-substrate benefit of OA. Intimate coupling allowed the immediate oxidation of oxalic acid, which increased the rate of NB biodegradation and prevented the accumulation of inhibitory levels of nitrophenol.(4) A certain amount of common metabolic substances will promote the anaerobic biodegradation of nitrobenzene, and with the same amount, or the same concentration of the COD value of matrix material, pyruvate metabolism substance is the most effective compared with other substances. Pyruvic acid addition amount have great influence on the rate of the degradation of nitrobenzene, in a certain concentration range, the nitrobenzene biodegradation rate increases with the increasing of pyruvic acid adding amount, but if the amount is too large, it can inhibit the nitrobenzene degradation.(6) In our experiments, under both aerobic and anaerobic degradation situation, the mineralization degree of nitrobenzene were positively related to the rate of the degradation of nitrobenzene. |
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