| China is a big industrial country.With the increasing demand for paper products,the amount of wastewater is also increasing.The wastewater generated is the third largest in China.Because papermaking wastewater contains a large amount of cellulose,lignin and its derivatives,wastewater has high COD,large chroma and poor biodegradability.How to effectively treat papermaking wastewater has always been a difficult point in the field of water treatment.With the rapid development of the economy,water environment problems restrict the development of industry.Therefore,it is imperative to find an efficient treatment method to make the papermaking wastewater meet the standard discharge and resource utilization.The electroflocculation method is favored by scholars at home and abroad because of its high efficiency,low pollution and easy operation,and small footprint.The hydrolysis acidification process can greatly improve the biodegradability of wastewater and realize sewage.The treatment of wastewater industry has a place in the treatment of mud;the dynamic membrane bioreactor(DMBR)has the advantages of small footprint,large amount of effluent water and less residual sludge.The advantages of low cost of membrane substrate and good water quality have become a popular means of sewage treatment.In this paper,electro-flocculation-hydrolysis acidification-DMBR combined process was used to treat papermaking wastewater.The main researches were carried out on the removal of COD and chroma in papermaking wastewater,the migration and transformation of dissolved organic matter and the delay control of membrane fouling.A new type of energy-efficient papermaking wastewater treatment technology also provides a reliable method and theoretical basis for delaying membrane fouling.In this study,the papermaking wastewater was used as the research object,and the low-quality nylon cloth(300 mesh)was used as the film substrate.The effects of three conditions of HRT,SRT and DO on the removal of COD and chromaticity in wastewater were compared.The optimum process parameters are HRT=24h,SRT=35d,DO=2~3mg/L.Electro-flocculation was used as the pretreatment process to investigate the effects of electrolysis time,plate spacing and current density on COD removal.Based on single factor data,the response surface method was used to optimize the values of various factors and the relative magnitude of impact.The experimental results show that the contribution of three factors to the COD removal rate is: current density > plate spacing > electrolysis time.Finally,the best process conditions were obtained: electrolysis time was 73.2 min,electrolysis plate spacing was 3.92 cm,current density was 39 mA/cm2,and the COD removal rate was 76.35%.The removal rate of COD was verified to be 74.19%.The model has a high degree of credibility.Under the best working conditions,the efficiency of pollutant removal,the migration and transformation of dissolved organic matter and the delay of membrane fouling were studied by electroflocculation-hydrolysis acidification-DMBR combined process.The experimental results show that the removal rate of COD in wastewater can reach 94.06%~99.36% and the removal rate of chroma can reach 96.4%~90.4%.The contents and changes of protein,polysaccharide and EPS in the two reactors were observed for 30 days.The addition of pretreatment process can reduce the growth rate of protein,polysaccharide and EPS.The LB-EPS in the EPS is positively correlated with the viscosity in the mixed solution,and the addition of electroflocculation can effectively reduce the growth rate and content of the viscosity of the mixed solution.By comparing the SEM images of the original film,the pretreated film and the film without pretreatment,it can be seen that the surface of the contaminated film is covered with a layer of pollutants,but the surface of the film added with electroflocculation is loose and the surface of the membrane that was not completely covered,but not pretreated,was completely covered by contaminants and was difficult to wash.Fourier infrared spectroscopy can further prove that proteins and polysaccharides are the main factors causing membrane fouling.Finally,the addition of electroflocculation as a pretreatment process can effectively delay membrane fouling. |
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