Xiaoxu Sun

Iron–carbon micro-electrolysis and combined processes were used to treat simulated dyeing wastewater containing direct Big Red 4BE dye (concentration of 1500 mg/L, chromaticity of 80,000 times, and salt content of 20 g/L). Through single-factor experiments, the optimal reaction conditions were determined as follows: reaction time of 110 min, initial pH of 5, and iron and carbon mass ratio of 1:2. Under the optimal conditions, the concentration was reduced to 14.51 mg/L, the chromaticity was reduced to 3000 times, and the decolorization rate reached 99.03%. In order to further decrease the wastewater chromaticity, coagulation and Fenton oxidation were respectively employed for in-depth treatment after iron–carbon micro-electrolysis. The total decolorization rate of the dye wastewater exceeded 99.7%, with the treated effluent meeting the specified chromaticity discharge standard (80-fold). The integrated processes of iron–carbon micro-electrolysis combined with either coagulation sedimentation or Fenton oxidation demonstrated superior performance in treating direct Big Red 4BE dye wastewater.

IIron-carbon micro-electrolysis and combined process were used to treat printing and dyeing wastewater, which was formulated with direct Big Red 4BE dye (concentration of 1500mg/L, chromaticity of 80,000 times, and salt content of 20g/L). The optimal conditions were determined by one-factor experiments, with a reaction time of 110 min, an initial pH of 5, and an iron and carbon mass ratio of 1:2. Under the optimal conditions, the concentration was reduced to 14.51mg/L, the chromaticity was reduced to 3,000 times, and the decolourization rate reached 99.03%. In order to further reduce the chromaticity of the wastewater, coagulation and Fenton oxidation were used to treat the wastewater in depth after the iron-carbon micro-electrolysis, respectively. The total decolorization rate of the dye wastewater reached more than 99.7%, and the treated wastewater met the emission standard of 80 times the chromaticity in the "Discharge Standard of Water Pollutants for Textile Dyeing and Finishing Industry" (GB4287-2012). The combination of iron-carbon micro-electrolysis and coagulation sedimentation or Fenton oxidation had a good effect on the treatment of direct Big Red 4BE dye wastewater.

Controlling the concentration of free radicals in polymerization systems is advantageous for preparing cationic polyacrylamide (CPAM) with a high molecular weight and acceptable dissolvability. In this study, a novel ultraviolet (UVA)-initiated system characterized by an adjustable light intensity and a redox-azo complex initiator was used to synthesize a CPAM flocculant named NP. Comparatively, another CPAM flocculant named SP with a stable UVA light intensity and a single initiator was prepared. Their chemical structure, morphology, and thermal stability were analyzed through instrumental analysis. ¹H NMR indicated that NP was successfully prepared, and a small fraction of a cationic homopolymer was mixed in the product. Polymerization conditions of NP were optimized, and polymerization mechanism was determined by investigating the effects of various parameters on intrinsic viscosity, conversion, and dissolvability. Results showed that the best performance was obtained at indices of 0.45 wt‰ redox initiator concentration, 0.2 wt‰ azo initiator concentration, 40.0 wt% cationic monomer, 3 wt‰ urea, and first- and second-stage light intensities of 8.5 and 13 mW/cm², respectively. The sludge conditioning performances of NP and SP were comparatively evaluated, and the mechanism was determined by examining sedimentation behavior and floc size distribution. High intrinsic viscosity, porous morphology structure, and mixed NP cationic homopolymer contributed to the improvement of sludge conditioning performance.

To control eutrophication caused by agricultural non-point sources, integrated riparian wetlands were constructed and operated to intercept and treat the polluted water flowing into the Fuxian Lake. The influent and effluent mass loadings of total nitrogen (TN), total phosphorus (TP), suspended solid (SS), and chemical oxygen demand (COD) of riparian wetland systems were monitored for nearly one year. In addition, influent and effluent samples of each riparian wetland treatment unit were collected and analyzed for nitrogen (nitrate, nitrite, ammonia, and organic nitrogen) and phosphorus (organic phosphorus and phosphate). Results showed that the wetland systems removed various pollutants. There was a little seasonal change on the COD, SS, TN, and TP removal efficiency. There was no flow in the wetland during the winter. Therefore, the pollutant removal efficiency could not be determined. The nitrogen analysis results showed that ammonia nitrogen and nitrate nitrogen were the main nitrogen species present in the influent and effluent of each wetland functioning unit. Information obtained from this study is helpful in providing a design basis for similar wetland systems to control agricultural non-point source pollution.