Liquid-gas phase transition enables microbial electrolysis and H2-based membrane biofilm hybrid system to degrade organic pollution and achieve effective hydrogenotrophic denitrification of groundwater.

Electron-donor Lacking was the limiting factor for the denitrification of oligotrophic groundwater and hydrogenotrophic denitrification provided an efficient approach without secondary pollution. In this study, a hybrid system with microbial electrolysis cell (MEC) assisted hydrogen-based membrane biofilm reactor (MBfR) was established for advanced groundwater denitrification. The liquid-gas phase transition prevented the potential pollution from organic wastes in MEC to groundwater, while the bubble-free diffusion of MBfR promoted hydrogen utilization efficiency. The negative-pressure extraction from MEC and the positive pressure for gas supply into MBfR increased the hydrogen proportion and current density of MEC, and improved the kinetic constant K of the denitrification reaction in MBfR. With actual groundwater, the MEC-MBfR hybrid system achieved a nitrate reduction of 97.8% with an effluent NO3--N of 2.2 ± 1.0 mg L-1. The hydrogenotrophic denitrifiers of Thauera, Pannonibacter, and Azonexus, dominated the denitrification biofilm on the membrane and elastic filler in MBfR.

Lignocellulose reconstituted shape-controllable self-supporting carbonaceous capacitance-anodes with high electron transfer rates for high-performance microbial electrochemical system.

Natural biomass is a promising candidate for manufacturing an efficient anode in the microbial electrochemical system (MES) for its abundance and low cost. However, the structure and performance of the electrode highly depend on the biomass species. A simple and sustainable method for creating a self-supporting electrode is proposed by freeze-drying and carbonizing a blend of cellulose, lignin, and hemicellulose. This strategy leads to a cork-like structure and improved mechanical strength of the lignocellulose carbon. A power density of 4780 ± 260 mW m-2 (CLX-800) was achieved, which was the highest record for unmodified lignocellulose-based anodes in the microbial fuel cells. The morphological as lamellar multilayer and rich in hydrophilic functional groups could facilitate the formation of thick electroactive biofilms and enrich Geobacter with the highest abundance of 92.3%. The CLX material is expected to be the ideal electrode for high performance and functionally controllability.

Electrosynthesis of H2O2 through a two-electron oxygen reduction reaction by carbon based catalysts: From mechanism, catalyst design to electrode fabrication.

Hydrogen peroxide (H2O2) is an efficient oxidant with multiple uses ranging from chemical synthesis to wastewater treatment. The in-situ H2O2 production via a two-electron oxygen reduction reaction (ORR) will bring H2O2 beyond its current applications. The development of carbon materials offers the hope for obtaining inexpensive and high-performance alternatives to substitute noble-metal catalysts in order to provide a full and comprehensive picture of the current state of the art treatments and inspire new research in this area. Herein, the most up-to-date findings in theoretical predictions, synthetic methodologies, and experimental investigations of carbon-based catalysts are systematically summarized. Various electrode fabrication and modification methods were also introduced and compared, along with our original research on the air-breathing cathode and three-phase interface theory inside a porous electrode. In addition, our current understanding of the challenges, future directions, and suggestions on the carbon-based catalyst designs and electrode fabrication are highlighted.

Engineering the Local Atomic Environments of Indium Single-Atom Catalysts for Efficient Electrochemical Production of Hydrogen Peroxide.

The in-depth understanding of local atomic environment-property relationships of p-block metal single-atom catalysts toward the 2 e- oxygen reduction reaction (ORR) has rarely been reported. Here, guided by first-principles calculations, we develop a heteroatom-modified In-based metal-organic framework-assisted approach to accurately synthesize an optimal catalyst, in which single In atoms are anchored by combined N,S-dual first coordination and B second coordination supported by the hollow carbon rods (In SAs/NSBC). The In SAs/NSBC catalyst exhibits a high H2 O2 selectivity of above 95 % in a wide range of pH. Furthermore, the In SAs/NSBC-modified natural air diffusion electrode exhibits an unprecedented production rate of 6.49 mol peroxide gcatalyst -1 h-1 in 0.1 M KOH electrolyte and 6.71 mol peroxide gcatalyst -1 h-1 in 0.1 M PBS electrolyte. This strategy enables the design of next-generation high-performance single-atom materials, and provides practical guidance for H2 O2 electrosynthesis.

Amplifying anti-flooding electrode to fabricate modular electro-fenton system for degradation of antiviral drug lamivudine in wastewater.

The advanced oxidation based on in-situ hydrogen peroxide production using carbon air cathode is very potential for wastewater treatment. However, catalyst flooding and complex assembly patterns are the bottleneck limiting the air cathode to the long-term and large-scale application. In this work, a novel anti-flooding air-breathing cathode (ABC) was prepared by a simple rolling-spraying method with relatively low price commercial materials. The novel method changed the morphology of gas diffusion layer as well as adjusted the hydrophobicity of air side of the catalyst layer. As a result, water-air distribution management was achieved and TPI disequilibrium was prevented. Compare with traditional ABC, the H2O2 yield and current efficiency (CE) of optimized anti-flooding ABC (ABC0.9) increased by 13.5% (941 ± 10 mg·L-1·h-1 with CE of 84% at 30 mA·cm-2), the material cost and fabrication time decreased by 10.1% (2.32 ¥·dm-2, ~0.36 $·dm-2) and 40%. Amplified ABC coupled with Ti/IrO2 anodes were integrated into a modular electrode used for H2O2generation. When the current density (j) increased from 10 to 30 mA·cm-2, the energy cost increased from 0.19 to 0.43 ¥·mol-1 H2O2 (from 0.03 to 0.07 $·mol-1 H2O2). The modular electrode was utilized in a 2 L pre-pilot scale reactor for antiviral drug lamivudine degradation by electro-Fenton (EF) process. 100% of lamivudine and 78.1% of total organic carbon (TOC) were removed within 60 min at 20 mA·cm-2. The susceptible sites on the lamivudine toward hydroxyl radicals were investigated and transformation products (TP) as well as degradation pathway were studied.

Thermal reduced graphene oxide enhanced in-situ H2O2 generation and electrochemical advanced oxidation performance of air-breathing cathode.

Developing highly efficient catalysts with high ORR activity and H2O2 selectivity is an important challenge for producing H2O2 through 2e- oxygen reduction reaction (ORR). In this work, we tuned the reduction degree of graphene oxide by controlling reducing temperature and prepared graphite-TRGO hybrid air breathing cathodes (ABCs). The H2O2 production rate of TRGO-1100 (with highest reduction degree) modified ABC exhibits highest H2O2 generation rate of 20.4 ± 0.8 mg/cm2/h and current efficiency of 94 ± 2%. The charge transfer resistance of TRGO-1100 decreases by 2.5-fold compared with pure graphite cathode. Unreduced GO shows high H2O2 selectivity and low ORR activity, while TRGO shows lower H2O2 selectivity but higher ORR activity. Though the 2e- ORR selectivity of TRGO decreased TRGO with all reduction degrees, the H2O2 production increased in all forming electrodes. Superior performance of TRGO modified ABCs is attributed to high oxygen adsorption and low charge transfer resistance. TRGO possesses super-hydrophobicity and large surface area for oxygen adsorption. Besides, TRGO provides abundant electrochemically active sites to facilitate the electron transfer and formed more mesopores for H2O2 release. Electro-Fenton using TRGO-1100-ABC exhibited great performance for Persistent Organic Pollutants (POPs) degradation, which removed 66% of tetracycline in 5 min.

Graphene family for hydrogen peroxide production in electrochemical system.

The development of carbon-based materials to catalyze two-electron (2e-) pathway of oxygen reduction reaction (ORR) offers great potential for hydrogen peroxide (H2O2) production. As a class of novel two-dimensional (2D) carbon materials, graphene and its derivatives have raised increasing attention as excellent noble-metal-free catalysts in 2e ORR due to their unique structure, physical and chemical properties. This review focuses on the synthesis of main graphene family members and graphene based electrodes, as well as their applications for H2O2 generation in electrochemical systems. We describe the functions of the graphene family in electrochemical systems, such as accelerating electron transfer and increasing oxygen transfer for cathodes in electrochemical systems, aiming to reveal the enhancement mechanisms of graphene and its derivatives on H2O2 production. Furthermore, the challenges and prospects for graphene family used as catalyst for H2O2 production in the future are also proposed.

Excessive extracellular polymeric substances induced by organic shocks accelerate electron transfer of oxygen reducing biocathode.

Electrotrophic bacteria on cathodes are promising substitutes to precious metals as oxygen reduction reaction catalysts in bioelectrochemical systems (BESs). Leading the anodic effluent to the biocathode has additional benefits of neutralizing pH and removing residual pollutants. However, the overflow of excessive organic pollutants inhibits the activity of autotrophic biocathodes. Adding glucose as an organic shock, we confirm that the startup time of biocathodes is initially prolonged by 1.2 times with a decrease in current. However, the currents inversely surpass the control in glucose-added BESs when the biofilm is mature, and the maximum current density increase by 5.5 times with a relatively stable performance. This increase is mainly attributed to the production of agglomerates dominated by polysaccharides and proteins as extracellular polymeric substances. These agglomerates wrap additional redox shuttles that accelerated the electron transfer between electrotrophic bacteria and the cathode. This study demonstrates for the first time that organic shocks enhance the electroactivity of autotrophic biocathodes and provides insights into the feedback mechanisms of electrotrophic microbial community to environmental changes.

Graphite accelerate dissimilatory iron reduction and vivianite crystal enlargement.

Biomineralized vivianite induced by dissimilatory iron reduction bacteria (DIRB) has received increasing attention because it alleviates phosphorus crisis and phosphorus pollution simultaneously. However, the relatively small crystal size and low Fe(III) reduction rate restrict the separation and recovery of vivianite. In this study, graphite was selected as additive to enhance vivianite biomineralization with soluble ferric citrate and insoluble hematite as two representative electron acceptors. As soluble ferric citrate provided abundant accessible electron acceptors, relatively inconspicuous increase (lower than 7%) was observed for graphite on vivianite formation while inoculated with raw sewage or DIRB. In contrast, graphite considerably increased vivianite formation efficiency by 23% in insoluble hematite inoculated with raw sewage. The graphite promotion on vivianite formation in hematite batch was magnified to 70% by DIRB. Dosing hematite inhibited the supply of electron acceptors, while conductive graphite promoted the electrical connection between minerals and DIRB, thus improved the Fe(III) reduction rate and efficiency. In addition, secondary minerals in hematite exhibited a larger aspect ratio and tended to aggregate on graphite. Graphite enlarged the vivianite size in hematite from 10 µm to 90 µm due to aggregation. Enhancing dissimilatory iron reduction (DIR) rate of iron oxides and enlarging crystal size provide new insights for vivianite formation and separation during wastewater treatment.

Fenton-based technologies as efficient advanced oxidation processes for microcystin-LR degradation.

In recent years, the safety and ecology threat of cyanobacterial burst has drawn wide concern, especially the release of toxic microcystin-LR (MC-LR). To break through the bottleneck of uncomplete MC-LR degradation by conventional physical-chemistry methods, Fenton-based advanced oxidation processes (AOPs) developed rapidly due to striking degradation efficiency through the potent hydroxyl radicals (HO·) oxidation. Herein, a comprehensive overview is presented on the recent achievements of the various Fenton-based technologies (including conventional Fenton, photo-Fenton, electro-Fenton, ozone-Fenton and sono-Fenton) for MC-LR degradation. In particular, the comparisons between various Fenton-based technologies about advantages and drawbacks are discussed. Based on analyzing the degradation intermediates and pathways, the destruction of Adda chain via hydroxylation was confirmed to be essential for detoxification of MC-LR. Roles of influencing factors such as MC-LR initial concentration, dosages of the catalyst and oxidant, environment alkalinity, natural organic matters (NOMs) as well as other inorganic ions are specifically summarized. This Review also gave special emphasis on technique optimization trends for Fenton application of MC-LR degradation, as well as key challenges and future opportunities in this fast developing field.

A highly sensitive bioelectrochemical toxicity sensor and its evaluation using immediate current attenuation.

Electroactive biofilm (EAB) sensor had shown great potential in the field of early warning of toxicants in water because of the low-cost and broad-spectrum. However, the traditional calculation of sensitivity strongly relied on the time and concentration gradient which weakened time-efficiency of the sensor. Moreover, the sensitivity could be further improved to respond trace concentrations. Here EAB sensors with different substrate concentrations were formed to respond different concentrations formaldehyde ranging from 1 ppm to 50 ppm and immediate current attenuation (ICA) was induced to evaluate the sensitivity. The ICA (~70 s) exhibited a shorter time than that calculated by calculable sensitivity (CS) and current attenuation (CA), which not only achieved the response of trace concentration but also improved the time-efficiency of the sensor. The EAB formed with 0.1 g/L acetate (EAB-0.1) had a 380% higher sensitivity than that formed with 1.0 g/L acetate (EAB-1.0), leading to a significant electrochemical toxicity response to 1 ppm of formaldehyde. The results of electrochemical response coefficient confirmed that EAB-0.1 was 1.5-6.3 times of that formed with acetate from 0.2 to 1.0 g/L, which was related with microbial community and component of EAB as described in our previous study. Our findings demonstrated that calculation of sensitivity could be optimized to reflect time-efficiency and EAB with limit acetate could be applied in trace toxicant detection.

Revealing Decay Mechanisms of H2O2-Based Electrochemical Advanced Oxidation Processes after Long-Term Operation for Phenol Degradation.

Hydrogen peroxide (H2O2)-based electrochemical advanced oxidation processes (EAOPs) have been widely attempted for various wastewater treatments. So far, stability tests of EAOPs are rarely addressed and the decay mechanism is still unclear. Here, three H2O2-based EAOP systems (electro-Fenton, photoelectro-Fenton, and photo+ electro-generated H2O2) were built for phenol degradation. More than 97% phenol was removed in all three EAOPs in 1 h at 10 mA·cm-2. As a key component in EAOPs, the cathodic H2O2 productivity is directly related to the performance of the system. We for the first time systematically investigated the decay mechanisms of the active cathode by operating the cathodes under multiple conditions over 200 h. Compared with the fresh cathode (H2O2 yield of 312 ± 22 mg·L-1·h-1 with a current efficiency of 84 ± 5% at 10 mA·cm-2), the performance of the cathode for H2O2 synthesis alone decayed by only 17.8%, whereas the H2O2 yields of cathodes operated in photoelectro-generated H2O2, electro-Fenton, and photoelectro-Fenton systems decayed by 60.0, 90.1, and 89.6%, respectively, with the synergistic effect of salt precipitation, •OH erosion, organic contamination, and optional Fe contamination. The lower current decay of 16.1-32.3% in the electrochemical tests manifested that the cathodes did not lose activity severely. Therefore, the significant decrease of H2O2 yield was because the active sites were altered to catalyze the four-electron oxygen reduction reaction, which was induced by the long-term erosion of •OH. Our findings provided new insights into cathode performance decay, offering significant information for the improvement of cathodic longevity in the future.

Geobacter Autogenically Secretes Fulvic Acid to Facilitate the Dissimilated Iron Reduction and Vivianite Recovery.

Biosynthetic organic matters, such as humus, play important roles in iron and phosphorus cycling in soil and aquatic systems. As an important member of humus, fulvic acid (FA) is ubiquitous in different environmental media, such as water, soil, and sediments. In this study, we fabricated the network among phosphate supply, metabolism pathway of FA, iron reduction, and vivianite recovery at the batch scale. Both the vivianite recovery performance and the content of biosynthetic FA were positively related to the phosphorus dosage. The highest vivianite formation efficiency of 53% was obtained in the Fe/P = 1 batch, accompanied with the maximal iron reduction rate of 2.29 mM·day-1, which was 2.66 times higher than that of the Fe/P = 3 batch. Simultaneously, the highest content of FA was detected in extracellular polymeric substances (EPS) of the Fe/P = 1 batch. Metabolome analysis revealed that FA biosynthesis was mainly relevant to tricarboxylic acid (TCA) cycle, amino acid metabolism, and purine metabolism, with glutamate and aspartate as the precursors. Sufficient phosphate stimulated the FA biosynthesis by modulating the biosynthesis and transformation of glutamate and aspartate. After adding 10 mg L-1 FA in Fe/P = 1 batch, the maximal iron reduction rate increase by 35%, as well as 12% improvement of the vivianite formation efficiency. Transcriptome revealed that FA promotes iron reduction and vivianite recovery by upregulating the expression of metal ion binding-, flagella-, and electron transfer activity-related genes.

Acetate limitation selects Geobacter from mixed inoculum and reduces polysaccharide in electroactive biofilm.

Bioelectrochemical systems (BESs) are widely investigated as a promising technology to recover bioenergy or synthesize value-added products from wastewaters. The performance of BES depends on the activity of electroactive biofilm (EAB). As the core of BES, it is still unclear how the EAB is formed from mixed inoculum, and how exoelectrogens compete with non-exoelectrogens. Here we confirmed that microbial community composition and the morphology of EAB on the electrode including the thickness and porosity of the biofilm are critical for the performance of BES, and these properties can be simply controlled by the substrate concentration during EAB formation. The EAB formed with 0.1 g/L of acetate (EAB-0.1) exhibited a 90% higher current density than that formed with 1.0 g/L acetate (EAB-1.0). EAB-0.1 had a 50% higher electroactivity per biomass and a 20% thinner thickness than EAB-1.0, which was partly due to the 54% decrease of insulative polysaccharide in biofilm. Limited acetate also imposed a selective pressure to enrich Geobacter up to 88% compared to 72% when acetate was abundant. Our findings demonstrate that a highly active EAB can be formed by limiting substrate concentration, providing a broader understanding of the EAB formation process, the ecology of interspecies competitions and potential applications for bioenergy recovery and trace toxicant detection in the future.

Unignorable toxicity of formaldehyde on electroactive bacteria in bioelectrochemical systems.

Formaldehyde poses significant threats to the ecosystem and is widely used as a toxicity indicator to obtain electrical signal feedback in electroactive biofilm (EAB)-based sensors. Although many optimizations have been adopted to improve the performance of EAB to formaldehyde, nearly no studies have discussed the toxicity of formaldehyde to EAB. Here, EABs were acclimated with a stable current density (8.9 ± 0.2 A/m2) and then injected with formaldehyde. The current density decreased by 27% and 98% after the injection of 1 and 10 ppm formaldehyde, respectively, compared with that in the control. The ecotoxicity of formaldehyde caused the irreversible loss of current with 3% (1 ppm) and 81% (10 ppm). Confocal laser scanning microscopy and scanning electron microscopy results showed that the redox activity was inhibited by formaldehyde, and the number of dead/broken cells increased from 2% to 40% (1 ppm) and 91% (10 ppm). The contents of the total protein and extracellular polymer substances decreased by more than 28% (1 ppm) and 75% (10 ppm) because of the cleavage reaction caused by formaldehyde. Bacterial community analysis showed that the proportion of Geobacter decreased from 81% to 53% (1 ppm) and 24% (10 ppm). As a result, the current production was significantly impaired, and the irreversible loss increased. Toxicological analysis demonstrated that formaldehyde disturbed the physiological indices of cells, thereby inducing apoptosis. These findings fill the gap of ecotoxicology of toxicants to EAB in a bioelectrochemical system.

Superhydrophobic Air-Breathing Cathode for Efficient Hydrogen Peroxide Generation through Two-Electron Pathway Oxygen Reduction Reaction.

Electrochemical catalysis of carbon-based material via two-electron pathway oxygen reduction reaction (ORR) offers great potential for in situ hydrogen peroxide (H2O2) production. In this work, we tuned catalyst mesostructure and hydrophilicity/hydrophobicity by adjusting polytetrafluoroethylene (PTFE) content in graphite/carbon black/PTFE hybrid catalyst layer (CL), aimed to improving the two-electron ORR activity for efficient H2O2 generation. As the only superhydrophobic CL with initiating contact angles of 141.11°, PTFE0.57 obtained the highest H2O2 yield of 3005 ± 58 mg L-1 h-1 (at 25 mA cm-2) and highest current efficiency (CE) of 84% (at 20 mA cm-2). Rotating ring disk electrode (RRDE) results demonstrated that less PTFE content in CLs results in less electrons transferred and better selectivity toward two-electron ORR. Though the highest H2 concentration (2 µmol L-1 at 25 mA cm-2) was monitored from PTFE0.57 which contained the lowest PTFE, the CE decreased inversely with increasing content of PTFE, which proved that the H2O2 decomposition reaction was the major side reaction. Higher PTFE content increased the hydrophilicity of CL for excessive H+ and insufficient O2 diffusion, which induced H2O2 decomposition into H2O. Simultaneously, the electroactive surface area of CLs decreased with higher PTFE content, from 0.0041 m2 g-1 of PTFE0.57 to 0.0019 m2 g-1 of PTFE4.56. Besides, higher PTFE content in CL leads to the increase of total impedance (from 14.5 Ω of PTFE0.57 to 18.3 Ω of PTFE4.56), which further hinders the electron transfer and ORR activity.

Highly efficient electro-generation of H2O2 by adjusting liquid-gas-solid three phase interfaces of porous carbonaceous cathode during oxygen reduction reaction.

Equilibrium of three reactants (oxygen, proton and electron) in oxygen reduction reaction at large current flux is necessary for highly efficient electro-generation of H2O2. In this work, we investigated reactants equilibrium and H2O2 electrochemical production in liquid-gas-solid three phase interfaces on rolling cathodes with high electroactive area. Electrocatalytic reaction accelerated the electrolyte intrusion into hydrophobic porous catalyst layer for higher electroactive surface area, resulting in a 21% increase of H2O2 yield at 15 mA cm-2. Air aerated cathode submerged in air/O2 aeration solution was unable to produce H2O2 efficiently due to the lack of O2 in three phase interfaces (TPIs), especially at current density > 2.5 mA cm-2. For air breathing cathode, stable TPIs inside the active sites was created by addition of gas diffusion layer, to increase H2O2 production from 11 ±â€¯2 to 172 ±â€¯11 mg L-1 h-1 at 15 mA cm-2. Pressurized air flow application enhanced both oxygen supply and H2O2 departure transfer to obtain a high H2O2 production of 461 ±â€¯11 mg L-1 h-1 with CE of 89 ±â€¯2% at 35 mA cm-2, 45% higher than passive gas transfer systems. Our findings provided a new insight of carbonaceous air cathode performance in producing H2O2, providing important information for the practical application and amplification of cathodes in the future.

Heterotopic formaldehyde biodegradation through UV/H2 O2 system with biosynthetic H2 O2.

Biodegradation was regarded an environmentally benign and cost-effective technology for formaldehyde (CH2 O) removal. However, the biotoxicity of CH2 O inhibited microbial activity and decreased removal performance. We developed a novel heterotopic CH2 O biodegradation process that combined bioelectrochemical system (BES) and UV/H2 O2 . Instead of exogenous addition, H2 O2 was biosynthesized with electron transferred from electrochemically active bacteria. Heterotopic biodegradation of CH2 O was more efficient and faster than in situ biodegradation, as confirmed by 69%-308% higher removal efficiency and 98% shorter degradation time. Operated under optimal conditions for 30 min, which are optical distance of 2 cm, initial H2 O2 concentration of 102 mg/L, and pH 3, heterotopic biodegradation removed 78%, 73%, 49%, and 30% of CH2 O with 6, 8, 10, and 20 mg/L initial concentration. Mild formation of hydroxyl radicals from UV/H2 O2 is beneficial to sustainable CH2 O degradation and efficient H2 O2 utilization. Heterotopic biodegradation is a promising technology for efficient degradation of other organic compounds with biological toxicity. PRACTITIONER POINTS: H2 O2 biosynthesis through electrochemically active bacteria (EAB) served as source of ·OH for CH2 O removal in UV/H2 O2 . Heterotopic CH2 O biodegradation avoided the biotoxicity of CH2 O. Heterotopic biodegradation of CH2 O saved 98% time than in-situ biodegradation. Heterotopic CH2 O biodegradation improved 69%-308% efficiency than in-situ.

A novel electro-coagulation-Fenton for energy efficient cyanobacteria and cyanotoxins removal without chemical addition.

Harmful cyanobacterial bloom is a serious threat to global aquatic ecology and drinking water safety. Electro-Fenton (EF) has emerged as an efficient process for cyanobacteria and cyanotoxins removal, but high consumption of energy and chemicals remain a major bottleneck. This study presents a novel convertible three-electrodes Electro-Coagulation-Fenton process for cyanobacteria and cyanotoxins removal with low energy consumption and no chemicals addition. We for the first time demonstrated the freely alternating between Electrocoagulation (EC) and EF by switching electrodes. The optimal aerated EC was operated at pH 8 and 100 mA to remove 91 ± 2% of cyanobaterial cells and 15% of Microcystins (MCs). Coagulants generated in EC were adsorbed on cyanobacterial cells to form a protect layer against algae disruption and cyanotoxins releasing. Residual MCs and cyanobaterial cells were completely mineralized by EF at 28 mA with iron ions and H2O2 generated in-situ. Compare to traditional EF, the optimal Electro-Coagulation-Fenton process increased total organic carbon (TOC) removal efficiency by 30%, yet energy consumption reduced up to 92%. The novel Electro-Coagulation-Fenton process is a promising technology for the efficient treatment of the mixture of suspended solid pollutants and persistent organic pollutants in one system with low energy consumption.

Phosphorus Competition in Bioinduced Vivianite Recovery from Wastewater.

Phosphorus undergoes a one-way flow from minerals to soil to water, which creates a phosphorus crisis as well as aquatic eutrophication. Dissimilatory metal reduction bacterial (DMRB)-induced vivianite recovery from wastewater is a promising route to solve these problems synthetically. In this study, phosphorus competition between biomass growth and bioinduced vivianite mineralization was investigated at the batch scale. Biomass growth leads to phosphorus utilization over vivianite mineralization. Geobacter was selected as the main functional microorganism and presented higher vivianite recovery rates (20-48%) than sewage biomass (7-33%). An optimal Fe/P stoichiometric ratio of 1:1 was observed for both sewage biomass and Geobacter-inoculated batches. The highest vivianite yield of 4.3 mM was obtained in Geobacter-inoculated batches at a Fe:P of 1:1, with values 59% higher than those at a Fe:P of 1:0.67 (equal to the Fe/P molar ratio in vivianite). Sufficient PO43- stimulated cell growth and yielded a higher Fe3+ reduction rate and vivianite yield. Nevertheless, excessive PO43- facilitated the precipitation of KFe3 (PO4)2(OH)·8H2O and Fe7 (PO4)6, which inhibited vivianite synthesis. In the optimal Geobacter batch, the µ -S curve indicated a mixed order reaction (0 < x < 1) for both vivianite formation and biomass growth. The vivianite growth series proceeded as follows: tiny blue particles, plain pieces, dark blue nodules, and large spherical crystals.