Preparation Of Electron Mediator Suspended Carriers And Their Performance Of Enhancing Anaerobic Wastewater Treatment

Anaerobic integrated floating fixed-film and activated sludge(An-IFFAS)and anaerobic moving bed biofilm reactor(AMBBR)combine the advantages of anaerobic activated sludge and fixed biofilm,and show unique potential in the anaerobic treatment of organic wastewater,of which the physical and chemical properties of the biofilm carriers play a key role in organic pollution removal.Nowadays,the conventional suspended biofilm carriers,such as polyethylene(PE),polypropylene(PP)and high-density polyethylene(HDPE),usually have the drawbacks of poor biocompatibility and lacking of functional design.In this study,electron mediator suspended biofilm carriers were prepared through electron-accelerating functional design,which can promote direct interspecies electron transfer(DIET).Then,those novel carriers were applied to An-IFFAS and AMBBR aiming at enahancing the efficiency of anaerobic digestion.The performance of pollutant removal and methane production in An-IFFAS and AMBBR were explored.The main research contents were shown as follows:(1)The graphite electron mediator suspended biofilm carriers were made of HDPE,diatomite,talc and a series of conductive graphite powders(3 wt%,5 wt%and 7 wt%)by blending and screw extrusion technology.And those novel carriers were applied to An-IFFAS process to enhance the treatment of high-concentration organic wastewater.Results showed that comparing with the anaerobic floc reactor and the An-IFFAS reactor with HDPE carriers,An-IFFAS reactors filled with graphite electron mediator suspended biofilm carriers had better organics removal performance and methane production capability at organic loading rates(OLRs)of 5.9-23.7 kg COD/(m~3?d).Besides,the high throughput sequencing results showed that 7 wt%graphite electron mediator suspended biofilm carriers improved approximately4.2%abundance of Geobacter and 7.3%abundance of electrotrophic methanogens(Methanothrix)comparing with that of HDPE carriers,respectively.These results demonstrated that graphite electron mediator suspended biofilm carriers were able to proceed DIET and improve the efficiency of anaerobic digestion.(2)Assisted by diatomite and talc,a certain amount of zero valent iron(ZVI)or graphene had been blended into HDPE granules to develop 4 wt%ZVI modified carriers,10 wt%and 20wt%graphene electron mediator suspended biofilm carriers,of which two kind of graphene electron mediator suspended biofilm carriers were mixed with ZVI modified carriers respectively.And those mixed modified carriers were applied in sequencing batch AMBBR to enhance the treatment of complex organics.Results showed that AMBBR with mixed modified carriers significantly enhanced the treatment of complex organics.Especially,the AMBBR filled with 4 wt%ZVI modified carriers and 20 wt%graphene electron mediator suspended biofilm carriers increased 37.9%methane production rate and 34.4%methane yield comparing with the reactor filled with HDPE carriers at OLR of 8.5 kg COD/(m~3?d).