| Recently, more and more additives have been developed and applied for the textile production, which results in the increase amount of refractory organic matter of printing and dyeing in the water body. The most effective methods to remove dyeing waste water are the advanced oxidation processes (AOPs), which could produce the free radicals. The technique of non-thermal plasma(ATP) is a kind of new AOP, which could generate radical species, free electrons, ions,UV radiation, shock waves to oxidize or deoxygenize the dyes and to remove the color and CODcr.In this paper, the typical azo dyes-reactive brilliant red X-3B was chosen as the target pollutant to be removed from the aqueous solution by the designed dielectric barrier discharge reactor. The optimal condition and the best catalyst for the degradation of the X-3B were investigated. In addition, the degradation mechanism, the biodegradability and the acute toxicity of the degradation products was explored by different analysis methods. Furthermore, the treatment of actual printing and dyeing wastewater by the hybrid process of dielectric barrier discharge and SBR was studied. By a comparison of treatment efficiency and energy efficiency, the optimal combination style between the two methods was found.The results will provide reliable theory for the treatment of dyeing wastewater.The main results are summarized as following:(1)The degradation ratio of the X-3B increased with the increase of the input power and the water flow rate. However, the air flow rate, water conductivity and the initial pH had little influence on the degradation of the red X-3B.There is slightly higher degradation ratio under the acidic condition than under the alkaline condition.(2)The existence of SO42-and Cl-have little effect on the degradation of the X-3B.The low concentrations of CO32-could promote the degradation of the X-3B,but high concentrations of CO32-could lead to the inhibition. The continuing addition of H2O2can catalyze the X-3B degradation with firstly increasing and then decreasing catalytic effect.(3)Cu2+can enhance the degradation rate of the X-3B.And Fe3+and Fe2+also have positive catalytic effect, with the trend of higher concentration, lower catalytic effect. But the addition of Mn2+could lead to the inhibition of the degradation. Fe2+has the best catalytic effect.(4)After21-minutes the decolorization efficiency of100mg/L X-3B was97.90%, but the removal rates of TOC and CODcr was only38.64%and56.39%respectively. During the reaction, the pH dropped dramatically in the first three minutes, while the conductivity was increasing all the time. By various analyses, it could be found that H2O2hydroxyl radicals and ozone played major roles during the degradation process.(5)The toxicity to Vibrio Qinhaiensis sp.-Q67of the X-3B declined with the degradation no matter with pH adjusting or not. However, the toxicity to Vibrio Qinhaiensis sp.-Q67of real printing and dyeing wastewater without pH adjusting is increasing with the degradation by NTP, while with pH adjusting,the toxicity decreased.(6)With the process of reaction, the CODcr of dyeing wastewater is declining all the time, but BOD5firstly decreased and then increased.This result made the B/C to change with the same trend. But after21minutes of treatment, B/C is still lower than the origin of the dyeing wastewater.(7)Degradation of real dyeing wastewater by NTP alone, was compared with the biological technique.It was found that the degradation of dyeing wastewater by biological treatment had higher removal ratio of TOC. It was found that it was better to use plasma technology to treat the wastewater after the biological treatment instead of as the pretreatment method.(8)Analysis of energy efficiency proves that under high energy density, plasma technology can improve biodegradability of wastewater as the pretreatment unit. But under low energy density, plasma technology is more suitable for the advanced treatment unit but for pretreatment one. |
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