Experimental Study On Treatment Electroplating Wastewater By Microelectrolysis-DMBR

With the rapid development of the national economy,the electroplating industry has become an important processing industry in China.As a result,the amount of wastewater discharged has increased year by year.The wastewater generated by the electroplating industry contains a large amount of toxic and harmful pollutants such as heavy metal ions,surfactants,brighteners,etc.The common biological treatment technology is difficult to meet the discharge standards of electroplating wastewater.Therefore,how to treat electroplating wastewater efficiently and economically is becoming an urgent problem.The micro-electrolysis method is favored by many scholars because of its high processing efficiency,low cost and convenient operation.Compared with the traditional reactor,DMBR has larger effluent,better removal of polluents and stronger impact load resistance.In this paper,the micro-electrolysis-DMBR combination process is used to treat electroplating wastewater.The removal efficiency of heavy metals(Cr6+?Ni2+),COD and ammonia nitrogen in electroplating wastewater is studied.The migration and transformation of dissolved organic matter and its effect on membrane fouling are also explored.It is hoped that a new,efficient and inexpensive electroplating wastewater treatment technology can be explored to improve the electroplating wastewater treatment process.The DMBR process water is simulated by electroplating wastewater,and the optimum process conditions(HRT,DO,reflux ratio)and treatment efficiency of DMBR system are studied.The optimum process conditions for DMBR are: hydraulic retention time(HRT)of 18 h,dissolved oxygen(DO)of 3 mg/L,and reflux ratio of 200%.Under the optimal process conditions,the heavy metal impact load test was carried out on the DMBR system to study the removal of pollutants.The experimental results show that with the increase of heavy metal concentration,the removal effect of COD and ammonia nitrogen in DMBR process is obviously reduced.When the concentration of Cr6+ and Ni2+ was 20 mg/L,the average removal rates of COD and ammonia nitrogen were 76.32% and 47.34%,respectively.Therefore,the use of micro-electrolysis for pretreatment to attenuate the effects of Cr6+ and Ni2+ heavy metals on microbial activity in DMBR systems,and to enhance the impact load performance of DMBR process as an entry point for further exploration.The micro-electrolysis method was used to treat Cr6+ and Ni2+ in wastewater.The optimum initial p H,iron carbon dosage,aeration and reaction time were investigated.The kinetics of removal of Cr6+ and Ni2+ by micro-electrolysis was analyzed.The optimal experimental parameters were obtained by single factor experiment: the iron carbon dosage was 240 g,the residence time was 60 min,the aeration was 0.2m3/h,and the p H was 5.Through the orthogonal test range analysis,it can be determined that the most important factor affecting the removal efficiency of Cr6+ and Ni2+ in the wastewater treated by micro-electrolysis is the iron-carbon dosage.The reaction process of removing iron and carbon micro-electrolysis to remove Cr6+ and Ni2+ can better meet the first-order power.Under the condition that the iron carbon dosage is 240 g,the aeration volume is 0.2m3/h,and the p H value is 5,the relationship between the concentration of Cr6+ and time is,which between the concentration of Ni2+ and time is.The correlation curves of the fitting curves are 0.92949 and 0.91395 respectively,which indicates that micro-electrolysis plays a key role in the removal of Cr6+ and Ni2+ in the process of treating Cr6+ and Ni2+ wastewater,and verifies the rationality of the experimental scheme.Under the optimal process conditions,the combined process was used to treat electroplating wastewater,and the removal effect of pollutants,the migration and transformation of organic matter,the concentration change of sludge EPS and the apparent morphology of membrane modules were studied.The electrolysis-containing DMBR process was used to treat electroplating wastewater.The average removal rates of Cr6+ and Ni2+ heavy metal ions were 99.34% and 99.14%,respectively.The average removal rates of COD and ammonia nitrogen were 94.75% and 90.22%,respectively.The process has a good removal effect on heavy metal ions and COD,and the effluent reaches the "Electroplating Pollutant Emission Standard"(GB21900-2008).UV-vis spectroscopy indicated that the large molecular weight DOM substance in electroplating wastewater degraded into small molecular weight DOM with wastewater treatment process.The three-dimensional fluorescence spectrum analysis showed that there was peak A(high excitation wavelength tryptophan)and peak B(low excitation)in DOM.Fluorescence peaks of four kinds of substances: wavelength tryptophan),peak C(ultraviolet fulvic acid)and peak D(humic acid).The fluorescence parameters analysis showed that the DOM biological source increased and the microbial activity was active during the treatment of electroplating wastewater.Pretreatment with microelectrolysis can effectively reduce the EPS content of the DMBR system and delay the membrane fouling rate.