| The printing wastewater is one of the refractory wastewater because its distinctive characteristics of high pollutant level, difficulty to discoloration, water quality fluctuation and difficult to degradation. How to dispose the printing wastewater with economical and effective processing technology has become a universal problem concerned by the environmental protection field today. The article elaborated the status quo of the dye wastewater treatment from home and abroad, introducing various physical, chemical and biological treatment technologies at present. Since the iron chipping micro-electrolysis method has the problems of rust, easy to harden in treating dyeing wastewater and the shortcomings of acidification, low removal rate of color using anaerobic biological methods, we put forward the process of the built-in zero valent rion (ZVI)-anaerobic treatment and studied the treatment effect and degradation mechanism of this process when it was employed to treat the simulative dying wastewater with different COD and X-3B concentrations. We also researched the effects of treating the actual dying wastewater and microbial populations of the reactor to comprehensively comparing and measuring the feasibility of this technology. According to the experimental study and theoretical analysis, we can draw the following conclusions:1. The decolorization and COD removal efficiencies were perfect and the reactor was stable with built-in iron ZVI-UASB (R1) treating reactive red X-3B dye wastewater, while the UASB (R2) reactor was less effective compared to R1. When the X-3B concentration was less than 200mg/L, the COD and color removal rate were 51.1% and 96.2% respectively, higher than the R2 reactor which was 42.5% and 68.7%, and the pH of effluent was stable. The COD removal rate was still 85% with high X-3B concentration of wastewater in the R1, however, the treatment of dye wastewater wasn't effextive in the R2 reactor and the effluent pH was 4.9 which mean serious acidification. The R1 maiatained more than 90% color removal rate with high influent COD concentration, higher than the 75% in the R2, and the anaerobic environment of the reactor system was stable, ORP value was also lower. The COD and color removal rate was 91.7% and 53% respectively, higher than the R2 43.8% and 32% with the influent COD concentration of 1500mg/L and X-3B concentration of 100mg/L. X-3B structure has been effectively destroyed because the characteristic absorption peak of the effluent was significantly decreased or disappeared by UV spectroscopy. 2. Comparing the effects of treating the actual dye wastewater, the COD and color removal rate were increased by 22% and 21%, reaching to 82% and 63% by adding iron clip and carbon to the UASB. At the same time, the BOD5/COD of effluent increased to 0.28, compared with 0.16 of the R2 which is conducive to aerobic biological treatment in the next step. It was found that the surface of the internal iron clip was obvious no rust and had metallic luster which indicated that the addition of iron to the anaerobic reactor can effectively maintain the environment. On the other hand, the analysis of microbial communities in the sludge using fluorescence in situ hybridization (FISH) method showed that the methanogens in the R1 was more than R2, while the acidogens was less than R2 which also proves the above conclude. The built-in ZVI-UASB process has better capacity and could effectively inhibit the acidification with parameter changes of different hydraulic remain time and reflux ratio.
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