Study On Treatment Of MBR Effluent From Landfill Leachate By Three-dimensional Electro-fenton

As a kind of heavily polluted wastewater,landfill leachate poses a serious threat to both human health and ecological environment.In the field of landfill leachate treatment,the conventional membrane treatment process can produce more harmful membrane concentrate,while the traditional non-membrane treatment process has the problems of great security hidden trouble and high treatment cost.Therefore,it is urgent to find an efficient and low-consumption landfill leachate treatment method that does not produce concentrated liquid.In this paper,a study on the treatment of MBR effluent from landfill leachate by Three-dimensional electro-Fenton is carried out.The effects of the initial p H value,particle electrode size,particle electrode dosage,electrode plate spacing,aeration intensity,current density and Fe²⁺dosage on the three-dimensional electro-Fenton treatment were studied through single factor influence experiments.Then the RSM was used to determine the optimal process parameters.And under the condition of the optimized process parameters,the efficiency of the Three-dimensional electro-Fenton process was compared and evaluated.The specific reaction process was quantitatively studied by reaction kinetics fitting,free radical shadowing test and H₂O₂ in-situ generation test.Finally,3D-EEM and GC-MS were used to discuss the removal characteristics of organic pollutants in the process.The following results and conclusions are obtained through research:（1）Single-factor experimental research shows that among the selected seven influencing factors,three factors such as p H value,current density,and Fe²⁺dosage have relatively significant effects on the removal of organic pollutants and power consumption of the Three-dimensional electro-Fenton system.（2）The model of COD removal rate established by RSM has high significance and good fitting effect.The significant relationship between the four main influencing factors is as follows:Fe²⁺dosage>H₂O₂（30%）dosage>p H value>current density.The optimal process parameters predicted by the model were as follows:p H=4.04,Fe²⁺dosage=13.62mmol/L,H₂O₂（30%）dosage=9.78m L/L,Current density=14.02m A/cm².The organic pollutant removal effect is good.The removal rates of COD,TOC and UV₂₅₄can reach 86.51%,64.41%and 90.71%,respectively.The B/C value was increased from0.025 to 0.35,and the biodegradability of wastewater was greatly improved.Compared with the Fenton system and the E-Fenton system,the E-GAC-Fenton system has the lowest energy consumption,equivalent to 113.83 kw·h/kg TOC.（3）The comparison of the treatment effects and the quantification of the synergistic effect of each system showed that the E-GAC-Fenton system is the best.And 62.73%of TOC can be removed within 60 minutes of reaction time.The reaction kinetic constant reached 1.67×10^-2min^-1,and the synergy indexes were all greater than 1,indicating a good synergistic effect.It is also found that·OH plays a major role in the degradation of organic pollutants,and contribute up to 52%of UV₂₅₄ removal.At the same time,the H₂O₂gradually accumulated in the reactor.The accumulation can reach 211.50mg/L at 120min.The cumulative current efficiency of H₂O₂ gradually decreases,after 120 minutes of reaction,it drops from 38.87%to 23.82%.（4）The refractory organic pollutants in the MBR effluent of the landfill leachate are mainly humic substances such as fulvic acid（FA）and humic acid（HA）,which account for 56.19%of the dissolved organic matter.After Three-dimensional electro-Fenton treatment,a large number of humus substances were removed,and the total proportion decreased to 43.11%.The proportion of fulvic acid（FA）decreased the most,from 31.5%to 21.13%.The types of organic matter dropped from 65 to 35.Among them,nitrogen-containing organics,sulfur-containing organics,heterocyclics and unsaturated hydrocarbons were removed in large quantities,and the remaining organic pollutants were mainly long-chain alkanes.At the same time,some chlorinated disinfection by-products will be added to the effluent.