| Bioelectrochemical system(BES)is a new wastewater treatment technology developed in recent years.The technology can not only degrade pollutants,but also realize the generation of electric energy,and the electricity generation capacity of BES bioanode is controlled by the cathode catalytic performance.Although the power generation of BES is limited,it can generate electricity from pollutants,and drive and catalyze the self-clarification of wastewater.The research of BES has great achievements both at home and abroad,but BES still has some problems to be solved,such as poor effluent quality,expensive material,the promotion of the power production value and other problems.The study tries to expand the functions of new electrode membrane,which is used not only as the cathode of BES,but also as the filter medium of MBR.While reducing the cost of the system,it can realize the wastewater self-clarification and self control of the membrane fouling driven by the biological electricity production and the autogenic electric field.In this study,two different carbon fiber based catalytic electrode membranes were prepared from the development of a new type of electrode materials.The performance of the pollutants removal and electricity generation were studied in the new BES.Proton exchange membrane was replaced by a narrow chamber packed with quartz sand,or manganese sand and activated carbon to lower the cost of equipment for sewage treatment,and the passive interface re-oxygenation was used for increasing dissolved oxygen level in wastewater,reducing the energy consumption in aeration.An aluminum anode and thus induced electric flocculation was used to improve the treatment and effluent quality.The specific research contents are as follows:(1)Catalytic electrode based on PVDF/GO membrane was prepared,by firstly phase inversion method using carbon fiber cloth as the substrate,that graphene(GO)was dispersed in the PVDF casting solution.GO in PVDF/GO membrane was reduced by hydroiodic acid(HI),then oxidized by the introduced potassium permanganate(KMnO4),that formed the composite load of manganese dioxide(MnO2)and GO in PVDF.The characterization results of the membrane confirmed that the catalyst MnO2 could be prepared in-situ on the membrane surface.The conductivity of carbon fiber based MnO2 catalytic electrode membrane increased from 4.9 × 10-5 S cm-1 to 2.4 x 10-4 S cm-1,when GO ratio increased from 0.5 wt%to 1 wt%,and the conductivity increased by nearly 5 times.In the MFC/MBR coupled BES,catalytic electrode membrane was used to test the electrochemical performance,the internal resistance was 752 ?.When the hydraulic retention time(HRT)of the BES was 8 h,the COD removal efficiency was above 97%,the maximum power density was 228 mW m-3,the corresponding current density was 9.59 mA m-2,the coulombic efficiency(CE)was 9.5%,and the clear water flux of the electrode membrane was 437 L m-2 d-1.The concentration of extracellular polymeric substances(EPS)was decreased by 28.9%compared with the control group,which LB-EPS and TB-EPS were decreased by 32.9%and 51.3%,respectively.(2)To reduce aeration energy consumption,air contact oxidation bed(ACOB)was coupled to BES which allow passive DO increase without energy consumption.To improve the effluent quality of BES,Trickle filtration(TF)and ACOB were embedded between the anode chamber and cathode chamber of BES for continuous enhanced biological treatment of wastewater.DO in the cathode chamber was effected by ACOB.the contribution rate was 25%,the optimal aeration rate was 100 mL min-1.PEM was replaced by quartz sand chamber(QSC)in the BES.The open circuit voltage(OCV)was 0.686 V.the volume power density was 111 mW m-3,and the corresponding current density was 13.7 mA m-2.The COD,NH4+-N and TP removal efficiencies of the novel BES were 97%,93%and 50%;microbial sequencing results in BES showed that there were Nitrosomonas sp.(6.31%),Comamonas sp.(4.53%)and Candidatus Kuenenia(0.80%)in the ACOB biofilm.From the typical microorganism,simultaneous nitrification and denitrification existed in the BES.(3)To improve the membrane surface conductivity and enhance the antifouling performance of the catalytic electrode membrane.Fe/Mn/C/F/O carbon fiber based catalytic electrode membrane was in-situ prepared by adding reduced iron in the casting solution.The pore size of the electrode membrane material was about 2-7 nm the measured clear water flux was 240 L m-2 h-1,and the conductivity of electrode membrane doped with 15 wt%reduced iron was 9.141 × 10-1 S cm-1.BES power density using Fe/Mn/C/F/O carbon fiber based catalytic electrode membrane was 446 mW m-3,corresponding to the current density of 6.70 mA m-2,and the OCV was 0.80 V.The removal efficiencies of COD,NH4+-N and TP were 97.4%,96.7%and 98%,respectively.The electrode membrane cost(315 cm2)was only$0.46;the total material cost of BES was lower than $47,and the cost efficiency of BES was 969.6 mW $-1.(4)For realizing the low cost and high quality treatment of high load wastewater by BES,one sacrificed aluminum anode was adopted,and active carbon and graphite particles were used as the electrode of biological anode.Micro-electrolysis and Electro-flocculation were coupled into BES.The aluminum ions released from aluminum anode by micro-electrolysis could achieve high efficiency flocculation of pollutants in wastewater.The COD removal efficiency of BES was 99.4%,the COD of effluent was less than 7.7 mg L-1,the NH4+-N removal efficiency was over 98.7%,the NH4+-N concentration in effluent was lower than 0.6 mg L-1,Meanwhile,the removal efficiency of TP was above 98.6%,and the TP concentration in effluent was less than 0.5 mg L-1.The power density of the system reached 365.1 mW m-3,and the maximum output voltage of closed operation was 0.97 V.The micro-electric field generated by BES enhanced the antifouling effect of the electrode membrane.Compared with the control group,the LB-EPS and TB-EPS were reduced by 66.5%and 29.9%,respectively.PEM was replaced by MMC in the novel BES.When the volume ratio of quartz sand to activated carbon was 1:1,the internal resistance of BES was only 490 ?,the output voltage increased by nearly 60%compared with QSC. |
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