| Phosphorus in the water environment is a limiting factor for the eutrophication of water bodies.Therefore,it is very important for the deep removal of phosphorus.The traditional water treatment technology mainly relies on biological phosphorus removal and chemical flocculation and phosphorus removal,while chemical phosphorus removal is the main method of advanced treatment,but due to the excessive addition of chemical agents,sludge disposal and secondary pollution,the advanced treatment of phosphorus Faced with challenges.Electrocoagulation(EC)technology is mostly used for the treatment of industrial wastewater.This technology has the characteristics of wide range of pollutant removal,wide range of applicable p H,high electrode utilization efficiency,small amount of mud,and dense sedimentation and clarification effect.EC has gradually become a research hotspot as an electrochemical treatment method.However,due to the limitations of the reaction mechanism,there are problems such as large power consumption and low efficiency of electrode passivation treatment,which limits its widespread application in the field of water treatment.In this study,a new type of air cathode was applied to the electrocoagulation technology and a new reactor configuration was developed.By optimizing the operating parameters of the system,the most important high energy consumption problem in the application process of the traditional electro-coagulation technology was solved,and at the same time,The reactor of the new air cathode electro-coagulation system was optimized.The electrode material and operating parameters were optimized for the system.Basic research and applied basic research were carried out on the performance and characteristics of the actual wastewater treatment process.The application has important practical significance.This study was based on the single-chamber microbial fuel cell(MFC)reactor structure,using the modified new rolling activated carbon stainless steel mesh air cathode to construct the air cathode electro-coagulation system.The roll-type activated carbon stainless steel net air cathode replaces the metal electrode in the traditional electrocoagulation technology,and uses the dissolved oxygen gradient at the gas-liquid interface to reoxygenate and independently "breathe" to avoid the energy consumption required for aeration.Using an aluminum mesh as the sacrificial anode,the process consumes energy of 1.8 k Wh/m3 under the operating conditions of an air cathode with a sacrificial anode electrode spacing of 1.5 cm,a current density of 8 m A/cm2,a treatment time of 4 h,and a static precipitation of 1 hour.The COD effluent concentration was 130 ± 5 mg/L,the removal was 73%,the TSS effluent was 56 ± 4 mg/L,the removal was 72%,the ammonia nitrogen effluent was 0.5 ± 0.02 mg/L,and the removal rate was 99%.The effluent of phosphate concentration was 0.3 ± 0.06 mg/L,with a removal of 99%.The study found that the removal efficiency of the air cathode electro-coagulation system is limited by the effective reaction area of the air cathode,and because of the configuration of the reactor,the resulting precipitate will accumulate at the bottom of the reactor and easily adhere to the surface of the air cathode,resulting in dissolved oxygen content.The phenomenon of short circuit in the electrode was reduced and the result was that the air cathode electro-coagulation system reduced the removal efficiency of nutrients in the sewage as the processing time prolonged.In order to avoid the limitation of the configuration of the single chamber MFC reactor on the electrocoagulation of the air cathode,a new reactor configuration was designed to solve the sacrifice anode consumption caused by the floc deposition in the bottom of the reactor caused by using the cube MFC reactor during the electro-coagulation process.The anode is short-circuited locally,resulting in problems such as large electrode consumption and increased power consumption.Through the redesign of the reactor configuration,a stackable migration electric-field assisted electrocoagulation system(MEAEC)was constructed.This technology uses a graphite inert electrode in combination with an air cathode to apply an additional auxiliary electric field to cause directed charges to move in the liquid phase,form a local concentration gradient difference,and adjust the distance between the electrodes by the electric field.By making the concentration of ions near the sacrificial anode relatively high,by using the pulse energization mode,the phosphorus removal element,which is the target removal material,is further removed from the wastewater in the form of phosphate precipitation,and the energy is reduced during relatively less processing time.Consumption achieves ideal phosphate removal efficiency.Under the constant voltage of 0.5 V,the inert electrode working time is 10 s,the current density of the sacrificial anode is 1 m A/cm2,and the removal time of phosphate is as high as 98% within 15 mins.Compared with the experimental control group(no migration)The application of the electric field is increased by 6%,but the energy consumption of the MEAEC system is only 0.14 k Wh/m3.These results show that the use of the MEAEC system can effectively reduce the power consumption and at the same time shorten the processing time compared with the traditional electrocoagulation technology for removing phosphate from waste water.In order to achieve stable long-term operation and achieve better processing performance,the optimization of the electric field assisted air cathode electro-flocculation system was investigated.By comparing the sacrificial anode material,the feasibility of the inert electrode material was screened from the perspective of engineering application,and the formed precipitated product composition was analyzed.The MEAEC system was used to treat the primary sedimentation tank of the wastewater treatment plant and the secondary sedimentation tank.The titanium plate as an inert electrode finally has stronger durability and corrosion resistance than the graphite plate.As a sacrificial anode material,the iron electrode is cheaper and more environmentally friendly than the aluminum electrode.The iron sacrificial anodes treated the primary sedimentation tank to obtain phosphate removal rate of 98%,the treatment time was 7 mins,and the energy consumption was only 0.039 kwh/m3.The use of the optimized MEAEC system is particularly effective for the removal of low-concentration phosphorus-containing wastewater.After the treated secondary sedimentation pond,the concentration of phosphate meets the requirement of the surface level IV water standard <0.3 mg/L.The introduction of the new MEAEC system has greatly improved the removal efficiency of phosphate in wastewater treatment by electro-flocculation technology,shortened the overall processing time,reduced the consumption of electric energy while ensuring the treatment effect,and maximized the use of sacrificial anode materials.In order to build a new type of electric flocculation technology with low energy consumption,low material consumption and high effluent level,it aims to reduce phosphorus pollution in the water environment and reduce the environmental load,providing new methods and ideas for wastewater treatment.This stackable structure and modular configuration are also more conducive to the promotion of practical engineering applications,making the MEAEC system has a better application prospect in the field of domestic sewage treatment. |
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