Study On Enhanced Biological Reduction Treatment Technology Of 2,4-Dinitroanisole By Zero-valent Iron

A coupled zero-valent iron (ZVI)/anaerobic sludge treatment system was adopted for the reduction of DNAN waste water to enhance the anaerobic treatment efficiency, and the single anaerobic system and ZVI system were established to compare treatment effects of various systems and explore the coupling effect of zero-valent iron and biology. The mechanisms of ZVI-enhanced anaerobic digestion of DNAN were investigated using the batch and continuous flow experiment.For the batch experiments in DNAN concentration of 40 mg/L, the sludge concentration 5 g MLVSS/L and ZVI lg/L, ZVI/anaerobic sludge coupling system could completely degrade DNAN within 4 hours.2-A-4NAN was the main intermediate reduction product in the process. The DAAN, which was the final reduction product of the reaction process, could be up to 27.69 mg/L with intermediate and final product quality balance more than 98%. The final product DAAN of alone anaerobic sludge system was only 3.88 mg/L. Alone ZVI system produces substantially had no DAAN, which primarily stays in 2-A-4NAN reduction generation phase. Gas, generating in coupling system and alone system of anaerobic sludge mainly was CH4 and the maximum cumulative amount were approximately 1.0599 mmol and 0.0289 mmol. The coupling system is much larger than individual anaerobic sludge system on the gas production. The eventually oxidation-reduction potential (ORP) of coupling system was-265.0 mV, which significantly lower than the two separate systems and provided a more suitable anaerobic environment for anaerobic microorganisms.For the continuous flow experiment at a concentration of influent DNAN 120 ppm, COD 2500 ppm, the coupled ZVI/UASB process had a stable removal efficiency of COD(>85%) and completely degradable of DNAN. Meanwhile, the ZVI/UASB coupled system was less influenced by change of the hydraulic retention time (HRT) and the salinity of solution, which has a stronger ability to resist impact load and the pH (6.4-7.0) of it was stable compared to the control experiments, coupled system created a more favorable anaerobic environment for microorganism.The surface of ZVI in the reactor had a variety of iron corrosion products, which reacted with H+of the reactor to maintain the pH stabilized. Meanwhile they eased the ZVI passivation and maintained ZVI activity in the reactor, which reflected the coupling effect ZVI and organisms. Coupling system sludge particle had clear-cut surface and stable structure and a double structure compared to conventional UASB system, which provided favorable conditions for growth and reproduction of the inner methanogens. The results of high-throughput sequencing technology showed the microbial communities within the coupling system, compared to traditional systems, were more diverse and abundant. As a result, the coupling system had a stronger ability to resist impact load to ensure stable operation of the system.