| Anaerobic Dynamic Membrane Bio-reactor（AnDMBR）combines membrane separation technology and anaerobic bioreactor,which can effectively remove organic matters,retain suspended solids（SS）and refractory macromolecular matters in wastewater,and improve the quality of anaerobic effluent.At present,AnDMBRs are often used nonconductive porous materials as supporting materials and it is mostly used to treat low and medium concentration wastewater,while there are few reports on the treatment of high concentration organic wastewater such as incineration leachate.Direct Interspecies Electrons Transfer（DIET）is a more efficient pathway in anaerobic system.Adding conductive materials and functional microorganism in anaerobic reactor has been proved to be able to promote DIET process,and enhance wastewater treatment efficiency to produce more methane.Therefore,AnDMBR was enhanced by adding conductive materials and functional microorganisms to treat incineration leachate in this paper,and the enhancing performance and mechanisms were also studied.In this paper,firstly,two AnDMBRs were activated with conductive carbon cloth and polyester cloth as the supporting materials,respectively.The study found that carbon cloth AnDMBR had a faster start-up and more stable operation,and had a higher removal efficiency of organic matter（95%vs 90%）.Carbon cloth alleviates the accumulation of VFAs in the anaerobic system,converts more organic matter into methane,and improves the quality of anaerobic effluent.Microorganisms with extracellular electron transfer ability such as Geobacter,Desulfovibrio,Closteidium,Sulfurospirillum and Methanothrix were abundantly enriched on the surface of carbon cloth to form an electroactive cake layer.The relative abundance of Geobacter on the carbon cloth was 23%,which could generate electrons by metabolizing organic matters and transfer them to Methanothrix through the conductive carbon cloth to produce methane.Conductive carbon cloth can be used as a supporting material with good performance in AnDMBR,which can effectively speed up the startup of AnDMBR and improve the processing performance.In view of the high content of SS and refractory macromolecular organic matters in incineration leachate,carbon cloth AnDMBR was used to treat it.The results showed that the carbon cloth reactor had a higher COD removal efficiency（96.5%vs 85.5%）and methane yields（217 vs 169 mmol/d）than the polyester cloth reactor,when the influent COD was 15,000 mg/L.The OLR of carbon cloth AnDMBR was increased by 27.8%（5.129 vs 4.014 kg COD/（m3·d））.AnDMBRs could effectively intercept those organic compounds with molecular weights>4k Da and remove>97%dissolved organic matter（DOM）in leachate,which had good interception efficiency.Additionally,more Syntrophomonas and Methanothrix species was enriched on the carbon cloth surface,which could participate in DIET,and the relative abundance of Methanothrix was more than 76%.The transcription of mtd,fpo D and hdr（ABC）involved in the DIET process in Methanothrix on the carbon cloth were more higher.Syntrophomonas and Methanothrix species used carbon cloth as conductor to perform DIET process in which CO2 was reduced to methane.In order to solve the problems of low organic loading,poor impact resistance and excessively thick of cake layer during operation of carbon cloth AnDMBR treating incineration leachate,granular activated carbon（GAC）was added to the carbon cloth AnDMBR.The results showed that the COD removal efficiency of GAC-carbon cloth reactor was still higher than 90%,when the influent COD concentration was increased to 26,000 mg/L.And the OLR of GAC reactor was increased by about 20.8%,indicating a stronger loading impact resistance.GAC increased the shear force on the membrane surface with biogas cycling,which slowed down the increase of TMP and the accumulation of the cake layer.Compared with the sludge in the control reactor without GAC,the sludge from experimental reactor with GAC had a higher conductivity（13.91 vs 3.34μS/cm）.Electroactive microorganisms such as Syntrophomonas and Desulfovibrio were enriched in the suspended sludge of the GAC reactor,and their relative abundances were higher than those from surface of carbon cloth（12.5%vs 9.8%）.The relative abundance of Methanothrix in the suspended sludge of GAC reactor was about 78%.The addition of GAC further promoted DIET among anaerobic microorganisms and enhanced the methanogenesis via syntroph interaction in the treatment of incineration leachate.In order to further improve the organic loading of AnDMBRs and promote the anaerobic methanogenesis,bioaugmentation technology by adding functional microorganisms Geobacter was used.The results showed that the reactor with Geobacter/GAC had the best treatment performance.The OLR of the anaerobic system was increased by 120%（5.575 vs 12.265 kg COD/（m3·d））,and the COD removal efficiency was still as high as 95%,with the influent COD up to 50,000 mg/L.The content of refractory organics such as aromatics and fulvic-like acids in the anaerobic effluent was significantly reduced.Geobacter species rapidly grew and multiplied in the Geobacter/GAC-carbon cloth AnDMBR,and the relative abundance exceeded 60%.G.anodireducens became the dominant strain,which has better tolerance to high-salt environment.The relative abundance of Methanosarcina was higher than 60%,which is more robust under high loading and can perform DIET with Geobacter.Adding Geobacter can effectively promote the DIET process and improve the methane production efficiency in the treatment of incineration leachate. |
