Organic chemical wastewater has the characteristics of poor biodegradability and high biological toxicity,which pose a serious threat to the ecological environment and human health and safety.It is essential to carry out economical and efficient wastewater treatment technology research.In order to overcome the problems of low bioactivity,poor stability,large dosage of electron donor/receptor and long startup time in the treatment of organic chemical wastewater by traditional biotechnology,efficient and stable light-excited semiconductors were synthesized to enhance biodegradation in this paper.The efficient degradation of organic pollutants and mineralization could be realized with photoelectron/hole as electron donor/acceptor acceleratcing biological degradation process.The electron transfer pathways between semiconductor and microbes were supplemented by optimizing the semiconductor-microbe interfaces structure.Improved semiconductor structure enhanced photocharge generation and drived faster electron transfer between semiconductor and microbes.In view of the slow biodegradation of pyridine and the lack of electron acceptors in biodegradation system,a Bi VO4/Fe OOH light-excited semiconductor was synthesized to enhance the biodegradation of pyridine.The results showed that the semiconductor significantly promoted the biodegradation of pyridine under light without the need of additional electron acceptor/donor.The effects of key parameters(pyridine concentration,p H,organic electron donor,and light intensity)on bio-photodegradation system were explored,and the electron transport system activity,photocurrent,and electrochemical impedance characterization were performed to explore the electron transfer between semiconductors and microbes.The results showed that light-excited semiconductors could significantly promote the pyridine biodegradation without additional electron acceptor/donor.Under the optimal conditions,the removal load of pyridine reached 2.34 mol m-3 d-1,which was better than traditional biological treatment.Meanwhile,the energy consumption of semiconductor-microbe interfaces was only2.3 k Wh mol-1,which is much lower than that of physical and chemical treatment of pyridine.The microbial activity at the semiconductor-microbe interface was significantly improved,and the electron transfer process between the semiconductor and the microbe was significantly accelerated.The microbial community structure of the semiconduction-microbe interface was optimized,and the species associated with pyridine degradation(Shewanella,Bacillus and Lysinibacillus)and the electroactive species(Shewanella and Tsierella)were enriched.Photogenerated holes were the main reactive species in the degradation of pyridine at the semiconductor-microbe interface.Photogenerated holes could be used as electron acceptors for accelerating the biological reaction during the biodegradation of pyridine.In view of the high biological toxicity and difficult biodegradability of chlorophenol wastewater,Cd S/g-C3N4 composite semiconductors and conductive graphite felts(GF)were used to construct 3D semiconductor-microbe interfaces to enhance the degradation of p-chlorophenol(p-CP).The excellent degradation performance of the 3D semiconductor-microbe interfaces indicated that GF could provide more reactive sites for microbes to carry out electron transfer.Superoxide radical(·O2-)and photogenerated hole(h+)were the main reactive species in the degradation of p-CP by composite semiconductor.The composite semiconductor could also continuously produce H2 during p-CP degradation,which could help to promote electron transfer between microbes and semiconductors.The 3D semiconductor-microbe interfaces selectively enriched functional species such as p-CP degradation related species(Chryseobacterium,Stenotrophomonas and Rhodopseudomonas),electroactive species(Stenotrophomonas,Hydrogenophaga and Cupriavidus)and hydrooxidizing species(Hydrogenophaga and Cupriavidus).The results of PICRUSt2 showed that the genes involved in p-CP degradation(dha A、MVD、pan D、spe A/D and hem E),denitrification(hyf E/F and hyp X)and extracellular electron transfer(pil A、men E/G and rib A)were remarkably enriched at the3D semiconductor-microbe interfaces.The synergistic effect between different functional species and semiconductor is the key to enhance p-CP degradation and mineralization.The 3D semiconductor-microbe interfaces could degrade p-CP stably and efficiently for a long time without additional electron donors,and the microbial community structure tended to be stable during this period.In order to explore the electron transfer mechanism between microbes and semiconductors with different heterostructures,Cd S/g-C3N4 composite semiconductors with direct Z-scheme heterostructure and type II heterostructure were prepared by simple ionic deposition and photodeposition,respectively.The reduction decolorization of acid orange 7(AO7)was enhanced by constructing semiconductor-microbobe interfaces with electroactive bacteria Shewanella oneidensis MR-1 and composite semiconductors.The results of UV-vis diffuse reflection and photoluminescence analysis indicated that the direct Z-scheme heterostructure had a stronger photoelectron-hole separation ability.Riboflavin-mediated indirect electron transport was crucial for the enhancement of AO7 decolorization at the semiconductor-microbe interfaces.Compared with the type II heterostructure,the direct Z-scheme heterostructure could not only promote the electron transfer at the semiconductor-microbe interfaces more quickly,but also provide a stronger reduction driving force for the decolorization of AO7.The direct Z-scheme heterostructure accelerated the intracellular NAD+/NADH cycle of Shewanella oneidensis MR-1,which was beneficial for AO7 reduction by Shewanella oneidensis MR-1.Transcriptomic results showed that the Mtr pathway and conducting pili of Shewanella oneidensis MR-1 were stimulated to accelerate the extracellular electron transport process due to the unique direct Z-scheme heterostructure of CSCN1.Suitable heterostructure and electron transfer medium are important factors affecting the performance of semiconductor-microbe interface.Aiming at the problems of high photoelectron-hole recombination rate of semiconductor and high nitrogen content in pyridine wastewater,an electricity assisted bio-photodegradation system(EBPS)for enhanced pyridine removal and simultaneous denitrification has been developed.Reactor performance and microbial structure analysis showed that photoelectrical stimulation played a key role in pyridine degradation and microbial population structure optimization.By optimizing the system parameters(pyridine concentration,recirculation ratio and photoanode potential),it is found that the EBPS performance is the best when the photoanode potential was 400 m V vs.Ag/Ag Cl,the hydraulic retention time(HRT)was 60 h,the recirculation ratio was 300%.The removal rate of pyridine reached 0.50 kg m-3 d-1 without additional electron donor or acceptor,and the nitrogen removal rate reached 97.87±0.01%.Photoelectrical stimulation could promote the dominant growth of pyridine biodegradation species(Rhodococcus,Hydrogenophaga,Truepera and Thermovirga),denitrification species(Thiobacillus,Thioalkalispira and Rhodococcus)and electroactive species(Thiobacillus,Thermovirga,Hydrogenophaga,Thioalkalispira and Rhodococcus)in the cathode biofilm.The results of PICRUSt2 showed that the genes involved in pyridine degradation(chn B,amh X,gab D,sad and ALDH5A1),denitrification(nar G/H/I,nap A/B,nir K,nor C and nos Z)and extracellular electron transfer(mtr A/C,fcc A,men C/G and rib A)were remarkably enriched with photoelectrical stimulation.The EBPS has a broad application prospect in the enhanced degradation and simultaneous denitrification of pyridine wastewater. |