| Electroplating industry is one of the three industries with heavy pollution in the global,and the electroplating wastewater has characteristics of massive water amount,great water quality change,complex components,high toxicity and degradation-resistant,etc.Pollutant type in electroplating wastewater includes complex compound,cyanide,surfactant,brightener and other macro-molecular organics,all kinds of heavy metal chromium,cadmium,nickel and lead,so the effect of conventional biological processing technology is not perfect in practice.This study has used technology of electric-flocculation-A/O-DMBR to treat the electroplating wastewater and researched the removal efficiency of this technology to heavy metal(Cr6+,Cd2+,Ni2+and Pb2+),COD and ammonia nitrogen in order to seek for a new type high-efficient electroplating wastewater treatment technology.Based on electroplating wastewater with artificial water distribution as the research object,it is to investigate the utmost tolerance concentration of A/O-DMBR technology to heavy metal.As the results indicate:When the concentration of heavy metal in A/O-DMBR technology reaches 20mg/L,processing efficiency of activated sludge to COD and ammonia nitrogen decreases,meanwhile,activity of activated sludge and MLSS will decrease,sludge viscosity and capillary suction time?CST?will increase.Regarding four factors of HRT,DO,F/M and reflux ratio of mixed liquor as the experimental factors of orthogonal test,it is to confirm influences of each factor's removal effect of A/O-DMBR on treatment of electroplating waste-water pollutant through range analysis and comprehensive balancing method to seek for the optimum operation conditions.The results indicate that:HRT:24h,DO:3-4mg/L,F/M:0.1kg?COD?/kg?MLSS?·d,reflux ratio of mixed liquor:200%.Choosing electric flocculation method as pre-treatment technology,influences of three factors of current density,PH and electrolyte concentration on heavy metal(Cr6+,Cd2+,Ni2+and Pb2+)removal ratio have been researched and response surface method has been adopted to optimize and obtain optimum technology conditions,and the results indicate:Heavy metal removal contribution of each factor shall be current density>pH>electrolyte concentration.The optimum technology condition shall be:Current density,electrolyte concentration and PH shall be relatively 55.62 mA/cm2,4.16mg/L and 4.87.The optimum Cr6+,Cd2+,Ni2+and Pb2+removal ratio shall be relatively 90.09%,76.15%,82.86%and 75.69%.Experimental verification values shall be relatively 89.21%,76.19%,80.66%and 75.24%,which approach to predicated value of model.Through adopting electric-flocculation-A/O-DMBR technology to process electroplating waste water,the removal efficiency of COD,ammonia nitrogen and heavy metal(Cr6+,Cd2+,Ni2+and Pb2+),control of membrane pollution and removal effects of electric flocculation to pollutant have been researched.The results indicate that:rate of inflow is 1L/h,retention time in water is 24h.Under the condition that DO:3-4mg/L,F/M:0.1kg?COD?/kg?MLSS?·d and reflux ratio of mixed liquor is 200%,electric flocculation-A/O-DMBR technology could have good removal effects on COD,ammonia nitrogen and heavy metal,among them,average removal ratio of COD and ammonia nitrogen shall be relatively 92.63%and 89.44%.Average removal ratio of Cr6+,Cd2+,Ni2+and Pb2+shall be 98.08%,99.41%,98.23%and 96.36%.Sludge concentration has obvious influence on membrane pollution resistance Rf and relationship between the two shall be y=0.15637x-791.27444.Pearson coefficient is0.9783.Sludge viscosity and Rf show non-linear relationship,which shall be expressed as y=x14.5+0.61131,R2=0.891.Addition of electric flocculation could effectively delay the rise rate of polysaccharide and protein in sludge mixed liquor.Three-dimensional fluorescence spectrum shows that organic matters in waste water shall be transferred to micro-molecular tryptophan after electric flocculation effect to improve organics treatment efficiency by A/O-DMBR.Figure[19]Table[19]Reference[98]... |
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