Study On Modification And Application Of Iron-carbon Micro-electrolysis Reactor

Wastewater with high concentration of nitrobenzenes is one of the toughest wastewater to be treated in industry owing to its toxicicity,chemical stability,and poor biodegradability.Iron-carbon micro-electrolysis as an industrial wastewater pretreatment technique has been widely used for pretreatment of high concentration of refractory wastewater due to its characteristics of decrease toxicity and improvement biodegradability of wastewater.However,the stability and efficency of Iron-carbon micro-electrolysis equipment for pretreatment of practical nitrobenzene wastewater are much lower than that of expected.In order to overcome the shortcomings of Iron-carbon micro-electrolysis technique,a typical Iron-carbon micro-electrolysis reactor of one wastewater treatment plant was studied.First of all,the aeration structure and packing model of reactant in reactor were modified,and the computational fluid dynamics of reactor was simulated with Fluent software to illustrate the validity of the modified reactor.Secondly,the optimum conditions of modified reactor were obtained from orthogonal experiments,and the stability and efficency of modified reactor were investigated by treating high concentration of nitrobenzene wastewater continuous for a period of 15 days.Finally,based on the advantages and practicability of the modified reactor,an idea to optimize and omit parts of process for treatment of high concentration of nitrobenzene wastewater was put forward,and the experiments were performed in laboratory scale.The main results of the thesis are as follows:(1)In order to overcome the shortages of the existed reactor,such as,inactivation and hardening of reactant,and the time dependence of pollutant removal ratio in wastewater,the aeration structure and packing model of reactant in reactor were modified,and the simulated results verified that the modified reactor meet the expected objectives.(2)The influence factors of iron-carbon micro-electrolysis unit on removal ratio of nitrobenzene were investigated when it was applied to pretreat industrial nitrobenzene wastewater,and optimal operation parameters from orthogonal experiment were pH = 1,the ratio of solid to liquid 3%(0.03 g/m L),retension time 5 h.(3)The experimental data from running the modified reactor continuous at optimal conditions for 15 days revealed that there were advantages,for instance,the nitrobenzene removal ratio was very high,the average removal ratio reached 82.97%;the removal ratio of pollutants was very stable,the nitrobenzene removal ratio was 87.28%~80.40%,the COD removal ratio was 27.38%~17.96%,and most importantly,the removal ratio of pollutants was not time denpendent.On the contrary,when the same wastewater was treated with the existed reactor,the nitrobenzene removal ratio was not very high,the average removal ratio was 65.64%;the removal ratio of pollutants was unstable,the nitrobenzene removal ratio was 73.26% ~ 60.26%,the COD removal ratio was 21.32% ~ 12.62%,and the removal ratio of pollutants decreased as running time of reactor increased.(4)The operation cost will save about 236375 yuan per year if the modified reactor is applied to treat 500m3 of nitrobenzene wastewater per day owing to merits of modified reactor.(5)Based on the advantages and practicability of the modified reactor,the supposed process of wastewater treatment without the second Fenton catalytic oxidation was tested,and the experimental data suggeted that the treated wastewater well meet the emission standard of our county,the index of emission water is colorless,pH = 7.2,and CODCr = 64.4,that means,the supposed process for treatment of industrial nitrobenze wastewater is feasible,which lay a foundation for technical innovation of the enterprise in the future.