Study On Electrocoagulation Of Strongly Alkline Wastewater In Commercial Concrete Mixing Plant

The wastewater generated during the cleaning of mixing tank trucks and pump trucks in commercial concrete mixing plant and the cleaning of the plant area is characterized by complex components,high hardness,and strong alkalinity.Reasonable and effective disposal,purification,and recycling of wastewater are the key to protect the environment of the plant area,save water resources,and support the construction of green commercial concrete mixing plant.Based on the principle of electrochemistry,this thesis carried out a study on enhancing the coagulation and clarification effect of wastewater in commercial concrete mixing plant by electrocoagulation.With the turbidity of the above clear liquid as the index,the influences of electrode and combination,electrode spacing,operating voltage,electrolytic time,electrode configuration mode and initial p H value on the clarifying effect of electrocoagulation sedimentation of strong alkaline wastewater in commercial concrete mixing plant were investigated by single factor exploration,response surface analysis and orthogonal experiment.The effects of electrode configuration mode,operating voltage,and electrolysis time on the floc size in electrocoagulation were investigated using FBRM;The chemical composition of the flocs formed during electrocoagulation were characterized and analyzed using IR.(1)Physical and chemical analysis and on-site investigation indicate that the mineral and chemical composition of the solid components in the wastewater from the commercial mixing station are very complex;Suspended solid particles are fine and carry strong negative charges,which are not conducive to natural settlement;The ionic composition of wastewater is complex,with a high content of calcium and magnesium ions,and the p H value is as high as 12;The composition,concentration,and flow rate of wastewater in commercial concrete mixing plant are influenced by the grade of concrete,the source of raw material,and the operating habits of drivers,etc.,and have great temporal variability.(2)Comparing different electrode combinations,electrode distance and initial p H values,when selecting an Al-Al electrode combination with an electrode distance of20 mm and maintaining the intrinsic p H value of wastewater,the electrocoagulation treatment effect is the best;Moreover,with the extension of electrolysis time and the increase of operating voltage,the treatment effect of electrocoagulation tends to improve,but when they increase to a certain extent,the degree of improvement in settlement clarifying effect decreases.(3)The significance of key factors in the treatment of wastewater by electrocoagulation was evaluated through orthogonal experiment: working voltage>electrode configuration mode>electrolysis time;The interaction between key factors in the treatment of wastewater by electrocoagulation was analyzed through response surface experiment:the interaction between operating voltage and electrolysis time,as well as between working voltage and electrode configuration mode,was significant,while the interaction between electrolysis time and electrode configuration mode was not significant(4)By analyzing the monitoring results of the chord length changes of flocs in three electrode configuration modes: monopolar-serial,monopolar-parallel,and bipolar-serial using FBRM,it can be concluded that the flocs generated in MP-P mode have a larger scale and stronger resistance to fragmentation;The changes in the chord length of flocs under different operating voltages indicate that the scale and anti-crushing ability of flocs increase with the increase of voltage;The changes in the chord length of flocs at different electrolysis times indicate that although the difference brought about by electrolysis time is smaller than that of electrolysis configuration mode and working voltage,the scale and anti-crushing ability of flocs gradually increase with the extension of electrolysis time;According to the changes in the chord length of flocs measured by FBRM and the difference in turbidity of the supernatant,it is found that there is a good correlation between them.(5)Through IR analysis on the flocs produced by electrocoagulation,it is concluded that in the process of electrocoagulation treatment of wastewater in commercial concrete mixing plant,what plays a role is the aluminum hydroxide hydrolyzed by aluminum ions produced by electrolysis of aluminum electrodes in water.In other words,the bridge and net effect of inorganic macromolecules are the main factors that enhance the coagulation effect of wastewater from commercial mixing station.(6)Designed and built an integrated experimental device for continuous feeding of electrocoagulation and sedimentation,and evaluated its sedimentation and clarification effect.This thesis has 50 figures,14 tables and 83 references.