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A packed-bed anaerobic-aerobic reactor (PBAOR) with two anaerobic and two aerobic compartments was constructed to treat manure-free piggery wastewater which was characterized by high ammonium (NH4+-N) and low ratio of chemical oxygen demand (COD) to total nitrogen (TN). Performed for 60 days at the normal atmospheric temperature of 25℃ with a constant hydraulic retention time of 32 h and reflux ratio of 2.0, a stable state in pollutants removal was obtained in the PBAOR. Within the next routine operation process, the removal of COD, NH4+-N and TN was above 85.7%, 98.2% and 85.8%, with a residual less than 81.7, 7.2 and 39.9 mg L-1 in effluent, respectively. Twelve veterinary antibiotics classified into tetracyclines (TCs), sulfonamides (SAs) and fluoroquinolones (FQs) were detected from the piggery wastewater. and the PBAOR was effective in removing TCs and SAs with an average removal of 74.8% and 93.3%, respectively, but presented a negative removal for FQs. Most COD in the piggery wastewater was mainly removed in the first two anaerobic compartments along with an obvious removal of TCs and SAs, while the TN were mainly removed in the last two aerobic compartments with the negative removal of FQs.

The effects of two solid-based hydrogen peroxides sodium percarbonate (SPC) and calcium peroxide (CP) on waste activated sludge (WAS) disintegration were investigated. Both oxidants achieved efficient WAS disintegration for the synergistic effect of alkaline and oxidation. The strong alkaline condition led to the leakage of ammonia and the existence of abundant calcium ions accelerated the fixation of phosphorus via precipitation in CP WAS disintegration process. However, the spongy-like layer and low pH condition retarded the release of gaseous ammonia in SPC group. Hydroxyl radical was the main oxygen reactive species in SPC approaches which were more intense than CP by electron spin resonance (ESR) analysis. CP treated WAS contented more small particle size matter and total suspended solids (TSS) increased dramatically. In conclusion, CP pretreated sludge was more suitable for fertilization, while SPC was in favor of anaerobic digestion. This study clarified the differences between these two oxidants and their intermediates on nutrients release in sludge disintegration.

Mainstream anaerobic wastewater treatment has received increasing attention for the recovery of methane-rich biogas from biodegradable organics, but subsequent mainstream nitrogen and dissolved methane removal at low temperatures remains a critical challenge in practical applications. In this study, granular sludge coupling n-DAMO with Anammox was employed for mainstream nitrogen removal, and the dissolved methane removal potential of granular sludge at low temperatures was investigated. A stable nitrogen removal rate (0.94 kg N m-3 d-1 at 20 °C) was achieved with a high-level effluent quality (

Herein, we report that Co(II)-doped g-C3N4 can efficiently trigger peracetic acid (PAA) oxidation of various sulfonamides (SAs) in a wide pH range. Quite different from the traditional radical-generating or typical nonradical-involved (i.e., singlet oxygenation and mediated electron transfer) catalytic systems, the PAA activation follows a novel nonradical pathway with unprecedented high-valent cobalt-oxo species [Co(IV)] as the dominant reactive species. Our experiments and density functional theory calculations indicate that the Co atom fixated into the nitrogen pots of g-C3N4 serves as the main active site, enabling dissociation of the adsorbed PAA and conversion of the coordinated Co(II) to Co(IV) via a unique two-electron transfer mechanism. Considering Co(IV) to be highly electrophilic in nature, different substituents (i.e., five-membered and six-membered heterocyclic moieties) on the SAs could affect their nucleophilicity, thus leading to the differences in degradation efficiency and transformation pathway. Also, benefiting from the selective oxidation of Co(IV), the established oxidative system exhibits excellent anti-interference capacity and achieves satisfactory decontamination performance under actual water conditions. This study provides a new nonradical approach to degrade SAs by efficiently activating PAA via heterogeneous cobalt-complexed catalysts.

Catalysts/co-catalysts for cathodic oxygen reduction and anodic methanol oxidation reactions (ORR/MOR) play the major roles in promoting the commercialization of direct methanol fuel cells. Herein, bimetallic zeolite-imidazolate-frameworks (CoZn-ZIFs) is used as precursor to synthesize Co3O4@NPC/CuO composites as catalysts for ORR and Pt supports/co-catalysts for MOR. The ORR activity (E1/2 = 0.83 V) and long-term stability (activity retention of 85.5% after 30,000 s) of Co3O4@NPC/CuO-400 (400 °C) dodecahedron are better than those of commercial Pt/C (10 wt%) in alkaline electrolytes. The surface CuO with variable valence states (Cu0 and Cu2+) can be used as both the active component for ORR and the protective layer for Co3O4 to enhance catalytic stability. Partial removal of CoOx from carbon framework promotes the exposure of highly active sites (Co2+) on the Co3O4. For MOR, the mass activity of Pt-Co3O4@NPC/CuO-400 (5 wt%) (1947 mA mgPt−1) is much higher than that of Pt/C (751 mA mgPt−1), mainly attributing to that the Pt active sites are uniformly dispersed on Co3O4@NPC/CuO support. The strong interaction between Pt and CuO can reduce the bond strength of Pt-CO to enhance CO resistance. Co3O4 can activate H2O molecules to provide sufficient OH− species to promote MOR. This study provides a new idea for preparation of active ORR catalysts and MOR co-catalyst from bimetallic ZIFs.

Ammonium (NH4+) oxidation is crucial for nitrogen (N) removal, contributing to regional and global N cycles, but is regarded as limited to a few biological pathways. A novel pathway for NH4+ oxidat...

Swine wastewater is a typical high-strength animal wastewater. For treatment, it often requires combined processes (i.e., integrated units), such as multiple anaerobic reactors and advanced treatments. Microbial electrolysis cells (MECs) are a promising technology for wastewater treatment and simultaneous hydrogen harvesting. In this study, we constructed a MEC powered by an iron-air battery to treat swine wastewater and produce hydrogen efficiently. The performance of iron-air batteries with different electrolyte concentrations was compared in terms of coagulant production and power generation. The highest coagulation performance was obtained with coagulants generated using a battery with 35 g/L NaCl, which achieved 54 % ± 3%, 27 % ± 2%, 49 % ± 1%, and 34 % ± 3% removal of ammonia, chemical oxygen demand (COD), suspended solids (SS) and turbidity, respectively. Powered by the iron-air battery with 35 g/L NaCl, the hydrogen generation rate of MEC reached approximately 6 L/m3·d using raw swine wastewater and 57 L/m3·d using coagulated swine wastewater. The reduction of organics by coagulating helped improve hydrogen production. The total COD removal by the coagulation process integrated with MEC reached 98 % ± 0.2 %. The iron-air battery–MEC system is a promising method for simultaneous hydrogen production and wastewater treatment without any additional energy input.

A ternary biochar/vanadium pentoxide/graphite like carbon nitride (BC/V2O5/g-C3N4 denoted BC/VO/CN) composite was prepared by a simple hydrothermal method and its photocatalytic performance was investigated under simulated solar irradiation. The BC/VO/CN was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Within the BC/VO/CN composites VO nanoparticles were highly crystalline and intertwined with the lamellas of CN, resulting in the formation of well-defined Z-type heterostructures. The photocatalytic activity was evaluated using Rhodamine B as a model pollutant. Under simulated solar (230–780 nm) irradiation the as-prepared BC/VO/CN hybrid materials demonstrated highly improved photocatalytic activity compared to CN, VO and VO/CN. The cause of the solar enhancement could be ascribed to the formation of Z-type heterojunctions between VO and CN, which promoted faster electron–hole separation and more efficient charge transfer. BC, as an electron transfer medium, accelerated the transfer of photogenerated charge carriers and inhibited their recombination.

Titanium-based SnO2 with Sb dopant (Ti/Sb-SnO2) was of interest in the field of electro-catalytic oxidation due to its high organic oxidation rates. However, the relatively poor mass transfer performance and short service time limited its practical application. To overcome this problem, Ti/Sb-SnO2 electrode was fabricated on mesh substrate and used as the anode for electrochemical oxidization of phenol. Compared to the anode prepared on planar Ti, the mesh anode with compact and uniform catalyst surface lowered electron transfer resistance and higher Oads content (17.41%), which benefited the generation of hydroxyl radicals (·OH) (increment of 24.5%). In addition, this structure accelerated the fluid perturbation around electrode in microscopic scale as the COMSOL simulation result indicated; the electric potential on mesh anode varied regularly along the undulant terrain of electrode so that the mass transfer coefficient was enhanced by 1.67 times. These structure-dependent characteristics contributed to the superior electro-catalytic performance toward degradation of phenol. Experimental results showed that mesh anode had a higher TOC removal efficiency of 90.6% and mineralization current efficiency of 20.1% at current density of 10 mA cm-2, which was 9.95% and 21.6% higher than the planar anode, and the service lifetime was 1.89 times longer than planar anode. This highly electro-catalytically active and stable Ti/Sb-SnO2 mesh electrode showed a potential application prospect toward electro-catalytic degradation process.

The air cathode of microbial fuel cells (MFCs) facing wastewater is easily coated with microbes to cause catalyst poisoning, resulting in the serious decline of electricity generation and wastewate...

Batch experiments were conducted to study bioelectrochemical enhancement of the anaerobic digestion (AD) of alkaline-pretreated sewage sludge in microbial electrolysis cell (MEC) in the presence or absence of phosphate buffer solution (PBS). Experimental results showed that the maximum methane production rate was increased from 0.18 mL-CH4/(mLreactor·d) (control) to 0.2 mL-CH4/(mLreactor·d) in the presence of PBS and cumulative methane production was 1.4-fold higher than that of control. The initial concentrations of SCOD, protein, polysaccharide and VFAs in the presence of PBS were slightly higher than those of control, suggesting that PBS might facilitate the release of organics into mixed liquor. The microbial community analysis results showed that the microbial community with PBS had higher diversity and Bacteroidetes and Firmicutes were the two most abundant phyla in the communities. Moreover, the PBS addition could enhance the growth of aceticlastic methanogens (Methanosaeta) and inhibit a portion of hydrogenotrophic methanogens (Methanobacterium), possibly due to the different cell wall composition.

Polymeric membranes are widely applied in water and wastewater treatment. During membrane filtration, membrane hydrophilicity is essential for both membrane flux and fouling resistance, and sufficient mechanical strength is also critical for enduring various operational condition. In the last 10 years, mussel-inspired chemicals have become a promising strategy for membrane modification due to their universality and versatility. Simply immersing membranes into a basic dopamine solution can induce a hydrophilic PDA layer on the membrane surface. Both the mechanical properties and the hydrophilicity of polymeric membranes are altered via this adhesion procedure. This review aims to expand the general vision on controlling PDA based hydrophilic modification, including influential factors of dopamine self-polymerization and the deposition behavior on different types of membranes. In addition, advanced dopamine-based hydrophilic modification is also reviewed where PDA serves as a filler or an intermediate layer to optimize the membrane separation performance. Finally, some critical unsolved challenges are discussed, and possible directions of further research on mussel-inspired PDA modification of polymeric membranes are proposed.

Alum sludge produced by drinking water plants needs to be conditioned and dewatered before final disposal. In this study, a novel ferrous iron/peroxymonosulfate (PMS) oxidation process was employed to enhance alum sludge dewaterability The effect of oxidative sulfate radicals generated by Fe2+ activated HSO5− on alum sludge was studied. The results showed that the optimal conditioning conditions for addition of Fe2+ and PMS were 0.5 g/g and 0.1 g/g TSS, respectively. Meanwhile, the capillary suction time (CST) and specific resistance to filtration (SRF) of alum sludge was reduced by 66% and 88%. Also found was that the absolute value of the zeta potential increased and the particle size decreased in alum sludge after Fe2+-PMS conditioning, which indicated that oxidative sulfate radicals destroyed the floc structure of alum sludge and smaller particles were generated. At the same time, the water contained in sludge flocs was released and enhanced sludge dewaterability, while leaching of aluminum ions also characterized decomposition of alum sludge.

The growing applications of carbon nanomaterials (CNMs) are speculated to exert potential risks to aquatic ecosystems. However, little is known about the response of aquatic microalgae to surface modified nanodiamonds (NDs), which could limit the safer design and scientific assessment for further application. Here, we comprehensively integrated phenotypic and transcriptional analyses to investigate the response of Chlorella pyrenoidosa to both graphitized nanodiamonds (GNDs) and oxidized nanodiamonds (ONDs). Results indicated that 50 mg L−1 GNDs could induce higher growth inhibition with severe organelle damage and oxidative stress than the OND treatment. Intriguingly, extracellular polymeric substances (EPSs) stimulated by OND exposure alleviated the adverse effects. Meanwhile, the conventional global molecular response to surface modified NDs was meticulously disclosed to fill in the knowledge gap. Additionally, the photosynthetic mechanism, amino acid synthesis, protein synthesis and protein export were further investigated under OND treatment, confirming a positive correlation for the crucial strategy to mitigate the negative effect. The underlying mechanism response to GNDs/ONDs has been thoroughly and completely revealed, providing a novel insight for the estimation of ND surface modification and the apperception of aquatic environmental risk.

In lignocellulose-to-hydrogen bioconversion, reducing the concentration of chemical agents in pretreatment is of great interest. In this study, rice straw (RS) pretreated at reduced NaOH and urea (NU) concentrations was evaluated. Results showed that the composition of RS exhibited excellent pretreatment performance at a reduced concentration of NU. When the concentration of NaOH was decreased to 3 wt% in combination with 6 wt% urea, the lignin was reduced by 59.52% with a cellulose and hemicellulose loss of less than 17%. Moreover, extending the pretreatment time at a low concentration of NU could effectively promote the biodegradability of RS. Upon fermentation by Thermoanaerobacterium thermosaccharolyticum M18 for H2 production, the H2 production increased up to 213.06 mL/g with a substrate treated by 3 wt% NaOH/6 wt% urea at low solid loading for 15 d, which was 16.31% higher than the counterpart subjected to a 7 wt% NaOH/12 wt% urea pretreatment. The present results suggest the NU pretreatment can be carried out at low concentrations to improve the conversion of RS into bio-H2 production.

A rapid and efficient magnetic solid phase extraction (MSPE) method, based on Fe3O4@β-cyclodextrin–lipid bilayer nanocomposites (Fe3O4@β-CD–LB), was built. The MSPE method coupled with GC-QTOF-MS has been designed for the trace detection of nine organochlorine pesticides (OCPs) in soil samples. The Fe3O4@β-CD–LB was successfully synthesized and characterized by vibrating sample magnetometry, Fourier transform infrared spectrometry, transmission electron microscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. In this experiment, the OCPs in the soil samples were firstly extracted with n-hexane/dichloromethane (v/v 1 : 1) at high pressure and temperature, and then subjected to MSPE for adsorption and purification. Considering the synergy effect between host–guest inclusion complexation and hydrophobic interaction in the adsorption mechanism, the bi-functionalized magnetic nanocomposites exhibited excellent adsorption properties for the OCPs and natural resistance to interference by macromolecules. Under the optimum experimental conditions, the method showed wide linear ranges with low limits of detection (4.5 to 34 pg g−1). The results showed that the mean recoveries of the OCPs in the soil samples were 78–107% with 3.0–6.1% intra-day relative standard deviation (RSD) and 3.5–6.9% inter-day RSD. The method has been applied for the determination of the OCPs in actual samples, and ΣOCPs ranged between 0 and 2.3 ng g−1 in seven soil samples.

Protecting active species from aggregation and corrosion may be feasible to obtain stable catalytic activities for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, bamboo-shaped N-doped carbon nanotubes (hollow BS-NCNTs as shells) are self-generated to in situ wrap the Co/CoOx schottky junctions (cores) to obtain the Co/CoOx@BS-NCNTs as bifunctional ORR/OER catalysts by using the Co-chelated melamine precursor. For ORR, Co/CoOx@BS-NCNTs (700 °C) exhibits more positive peak (0.822 V vs. RHE) and half-wave (0.842 V vs. RHE) potential than those of commercial Pt/C (10 wt%). Superior ORR activity is mainly attributed to the enriched coordination-unsaturated Co2+ (tetrahedral CoTd2+) in the CoOx wrapped in the tubular structure of BS-NCNTs featuring high electrical conductivity and active N species. Moreover, the π-π bonds of CNTs are activated by N substitution, which provides a stunning electron capture and transmission capability for enhancing ORR activity. For OER, Co/CoOx@BS-NCNTs (700 °C) obtains a smaller potential (1.590 V vs. RHE) than that of RuO2/C at 10 mA cm−2. The outstanding OER activity and durability of Co/CoOx@BS-NCNTs (700 °C) originates from strong interactions between C-skeleton and Co species, and efficient Co3+/Co4+ (Co4+OOH as active sites) transition protected by the externally-grown CNTs. Furthermore, abundant oxygen vacancies on CoOx surface can facilitate the adsorption of OH−/or OER-related intermediates to improve OER activity. Therefore, this study provides a promising strategy to develop NCNTs-wrapped Co species with high catalytic activity and stability for energy conversion.

Chlorination has been intensively investigated for use in water disinfection and pollutant elimination due to its efficacy and convenience; however, the generation and transportation of chlorine and hypochlorite are energy-consuming and complicated. In this study, a novel binary photosensitizer consisting of anthraquinone-2-sulfonate (AQ2S) and graphene was synthesized via a π-π stack adsorption method; this compound could allow for the chlorination of organic pollutants using on-site chlorine generation. In this photosensitive degradation process, sulfapyridine (SPY) was selected as a model pollutant and was decomposed by the reactive species (Cl2•-, Cl• and O2•-) generated during the photosensitive oxidation of chloride. The synthesized AQ2S/graphene exhibited superior activity, and the degradation rate of SPY was over 90 % after 12 h of visible light irradiation with a kinetic constant of 0.2034h−1. Results show that 20 mg AQ2S/GR at a 21 % weight percentage of AQ2S in a pH 7 SPY solution with 1 mol/L Cl− achieved the highest kinetics rate at 0.353 h−1. Free radical trapping experiments demonstrated that Cl2•- and O2•- were the dominant species involved in SPY decomposition under solar light. The reusability and stability of this composite were verified by conducting a cycle experiment over five successive runs. The capacity of photodegradation still remained over 90 % after these 5 runs. The current study provides an energy-efficient and simple-operational approach for water phase SPY control.

Methane, a potent greenhouse gas of global importance, has traditionally been considered as an end product of microbial methanogenesis of organic matter. Paradoxically, growing evidence has shown that some microbes, such as cyanobacteria, algae, fungi, purple non-sulfur bacteria, and cryptogamic covers, produce methane in oxygen-saturated aquatic and terrestrial ecosystems. The non-methanogenesis process could be an important potential contributor to methane emissions. This systematic review summarizes the knowledge of microorganisms involved in the non-methanogenesis process and the possible mechanisms of methane formation. Cyanobacteria-derived methane production may be attributed to either demethylation of methyl phosphonates or linked to light-driven primary productivity, while algae produce methane by utilizing methylated sulfur compounds as possible carbon precursors. In addition, fungi produce methane by utilizing methionine as a possible carbon precursor, and purple non‐sulfur bacteria reduce carbon dioxide to methane by nitrogenase. The microbial methane distribution from the non-methanogenesis processes in aquatic and terrestrial environments and its environmental significance to global methane emissions, possible mechanisms of methane production in each open water, water-to-air methane fluxes, and the impact of climate change on microorganisms are also discussed. Finally, future perspectives are highlighted, such as establishing more in-situ experiments, quantifying methane flux through optimizing empirical models, distinguishing individual methane sources, and investigating nitrogenase-like enzyme systems to improve our understanding of microbial methane emission from the non-methanogenesis process.

In the last few decades, anthraquinone and its derivatives (AQs) have been intensively applied to electrochemical, textile and dye, and photovoltaic industries. This has increased the levels of AQs in the natural environment and threatens human health. To remove AQs from the aqueous phase and recover these multi-functional molecules, a binary magnetic adsorbent, reduced graphene/Fe3O4 (rGO/Fe3O4), was synthesized via a hydrothermal method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectra, and thermogravimetric analysis (TGA) were then used to characterize the samples. The adsorption capacities of rGO/Fe3O4 to AQs were investigated by selecting anthraquinone-2-sulfonate (AQ2S) as a model molecule. The adsorption process followed the Langmuir adsorption isotherm and the second-order kinetics. The regeneration of adsorbents and the recycling of AQ2S and solvent were simultaneously achieved by Soxhlet extraction and rotary evaporation. These results confirm the high adsorption efficiency of rGO/Fe3O4 for removing AQs from water and provide a promising approach to recover the valuable molecules from the aqueous phase.

The fate of antibiotics in activated sludge has attracted increasing interests. However, the focus needs to shift from concerning removal efficiencies to understanding mechanisms and sludge responding to antibiotic toxicity. Herein, we operated two anaerobic sequencing batch reactors (ASBRs) for 200 days with sulfadiazine (SDZ) and sulfamethoxazole (SMX) added. The removal efficiency of SMX was higher than that of SDZ. SDZ was removed via adsorption (9.91-21.18%) and biodegradation (10.20-16.00%), while biodegradation (65.44-86.26%) was dominant for SMX removal. The mechanisms involved in adsorption and biodegradation were investigated, including adsorption strength, adsorption sites and the roles of enzymes. Protein-like substance (tryptophan) functioned vitally in adsorption by forming complexes with sulfonamides. P450 enzymes may catalyze sulfonamides degradation via hydroxylation and desulfurization. Activated sludge showed distinct responses to different sulfonamides, reflected in the changes of microbial communities and functions. These responses were related to sulfonamides removal, corresponding to the stronger adsorption capacity of activated sludge in ASBR-SDZ and degradation capacity in ASBR-SMX. Furthermore, the reasons for different removal efficiencies of sulfonamides were analyzed according to steric and electronic effects. These findings propose insights into antibiotic removal and broaden the knowledge for self-protection mechanisms of activated sludge under chronic toxicities of antibiotics.

Fabrication of easily recyclable photocatalyst with excellent photocatalytic activity for degradation of organic pollutants in wastewater is highly desirable for practical application. In this study, a novel ternary magnetic photocatalyst BiVO4/Fe3O4/reduced graphene oxide (BiVO4/Fe3O4/rGO) was synthesized via a facile hydrothermal strategy. The BiVO4/Fe3O4 with 0.5 wt% of rGO (BiVO4/Fe3O4/0.5% rGO) exhibited superior activity, degrading greater than 99% Rhodamine B (RhB) after 120 min solar light radiation. The surface morphology and chemical composition of BiVO4/Fe3O4/rGO were studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The free radicals scavenging experiments demonstrated that hole (h+) and superoxide radical (O2•−) were the dominant species for RhB degradation over BiVO4/Fe3O4/rGO under solar light. The reusability of this composite catalyst was also investigated after five successive runs under an external magnetic field. The BiVO4/Fe3O4/rGO composite was easily separated, and the recycled catalyst retained high photocatalytic activity. This study demonstrates that catalyst BiVO4/Fe3O4/rGO possessed high dye removal efficiency in water treatment with excellent recyclability from water after use. The current study provides a possibility for more practical and sustainable photocatalytic process.

Biological phosphorus removal (BPR) is an economical and sustainable processes for the removal of phosphorus (P) from wastewater, achieved by recirculating activated sludge through anaerobic and aerobic (An/Ae) processes. However, few studies have systematically analyzed the optimal hydraulic retention times (HRTs) in anaerobic and aerobic reactions, or whether these are the most appropriate control strategies. In this study, a novel optimization methodology using an improved Q-learning (QL) algorithm was developed, to optimize An/Ae HRTs in a BPR system. A framework for QL-based BPR control strategies was established and the improved Q function, Q t + 1 ( s t , s t + 1 ) = Q t ( s t , s t + 1 ) + k · [ R ( s t , s t + 1 ) + γ · max a t Q t ( s t , s t + 1 ) − Q t ( s t , s t + 1 ) ] was derived. Based on the improved Q function and the state transition matrices obtained under different HRT step-lengths, the optimum combinations of HRTs in An/Ae processes in any BPR system could be obtained, in terms of the ordered pair combinations of the . Model verification was performed by applying six different influent chemical oxygen demand (COD) concentrations, varying from 150 to 600 mg L−1 and influent P concentrations, varying from 12 to 30 mg L−1. Superior and stable effluent qualities were observed with the optimal control strategies. This indicates that the proposed novel QL-based BPR model performed properly and the derived Q functions successfully realized real-time modelling, with stable optimal control strategies under fluctuant influent loads during wastewater treatment processes.

Bio-H2, produced from lignocellulosic biomass or organic wastewater, is an ideal future energy candidate due to its feature of renewability and sustainability. In order to uncover the mechanisms of the reducing agent of l -cysteine in bio-H2 production process, effects of l -cysteine on oxidation–reduction potential (ORP), cell growth, H2 yield by Ethanoligenens harbinense were investigated. Meanwhile, effects of l -cysteine on the expression of genes such as [FeFe]-hydrogenase (hydA), acetate kinase (AK), alcohol dehydrogenase (ADH), and lactate dehydrogenase (LDH) were analysed by quantitative reverse transcription PCR (qRT-PCR). The maximum H2 yield of 1.88 mol-H2/mol-glucose and dry cell weight of 0.92 g/L, which were about 1.57 and 1.51 folds of that of negative control, were obtained with supplementation of 800 mg/L l -cysteine. The experimental results indicated that the supplementation of l -cysteine at a suitable dosage (

Background Microalgae as a viable biodiesel feedstock show great potential to approach the challenges of energy shortage and environment pollution, but their economic feasibility was seriously hampered by high production cost. Thus, it is in urgent need to reduce the cost of cultivation and improve the biomass and lipid production of microalgae. In this work, anaerobic digestion effluent from cattle manure combined with municipal wastewater was used as a cost-effective medium for cultivating microalgae and expected to obtain high biomass. The pretreatment of anaerobic digested effluent containing dilution rate, sterilization and nutrient optimization was investigated. Then, initial pH and light intensity for algal growth, lipid production and wastewater purification were optimized in this study. Results Scenedesmus sp. could grow rapidly in 10% anaerobic digestion effluent from cattle manure combined with secondary sedimentation tank effluent without sterilization. Optimum nutrient additives for higher biomass were as follows: glucose 10 g/L, NaNO3 0.3 g/L, K2HPO4·3H2O 0.01 g/L, MgSO4·7H2O 0.075 g/L and trace element A5 solution 1 mL/L. Biomass of 4.65 g/L and lipid productivity of 81.90 mg/L/day were achieved during 7-day cultivation accompanying over 90% of COD, NO3−-N, NH4+-N, and 79–88% of PO43−-P removal with optimized initial pH of 7.0 and light intensity of 5000 l×. The FAME profile in ADEC growth medium consisted in saturated (39.48%) and monounsaturated (60.52%) fatty acids with the 16- to 18-chain-length fatty acids constituting over 98% of total FAME. Conclusions This study proves the potential of anaerobic digested effluent combined with municipal wastewater for microalgae culture, and provides an effective avenue for simultaneous microalgal lipid production and treatment of two kinds of wastewater.

To enhance photo-fermentative hydrogen production (PFHP), biofilm reactor (BR) was employed as an ideal strategy with optimization on key factors of acetate concentration and carriers in this work. Optimal conditions for hydrogen production were acetate concentration of 4 g/L and carriers (silicon sheet) of 10 cm × 1 cm at amount of 1 piece. Biofilm formed on silicon sheet strongly improved hydrogen production compared with control reactor (CR). Cumulative hydrogen volume was enhanced about 20% from 2850 ± 130 mL/L of CR to 3349 ± 153 mL/L of BR and hydrogen yield was increased 20% from 2.61 ± 0.13 mol H2/mol acetate of CR to 3.06 ± 0.15 mol H2/mol acetate of BR at 4 g/L acetate. Protein and deoxyribonucleic acid (DNA) were important components to form the biofilm and they occupied 90% of extracellular polymeric substances (EPS). In particular, DNA, nearly 50% content of EPS, likely indicated a substantial contribution to biofilm formation and bacterial communication. Moreover, it suggested biofilm could regulate free cells to decline EPS secretion for improved hydrogen production. This work indicates BR could be a promising and economic strategy to enhance hydrogen production by photo-fermentation.

An innovative approach is developed to utilize the frass of mealworms (Tenebrio molitor Linnaeus 1758) for producing dye-removal biochar. Agricultural waste wheat straw (WS) was tested as feedstock versus wheat bran (WB) to rear mealworms for the production of insect biomass. Mealworms on WS grew at a slightly slower rate than those grown on WB for 32 days with ∼40% lignin removed at 25 °C. Biochars were generated using the frass of mealworms via pyrolysis. The best adsorption performance for three dyes, especially malachite green, a cationic dye, was the biochar of WS frass at 800 °C; it had better capacity (1738.6 mg/g) compared with the frass fed with bran, raw WS and raw WB as well as those reported in the literature. Adsorption of malachite green fits the Langmuir isotherm and the pseudo second order kinetic model, mainly due to chemisorption and electrostatic interaction. Our results demonstrated that the WS can be utilized to rear mealworms, and that frass of mealworms is an excellent raw material for generating high-efficiency bioadsorbents.

Biochars are low-cost and environmental-friendly materials, which are promising in wastewater treatment. In this study, biochars were manufactured from C-phycocyanin extracted (C-CP) Spirulina residue (SDBC) via thermal pyrolysis. Simultaneously, N-doping was also achieved from the protein in the algae for obtaining a high-performance carbocatalyst for peroxydisulfate (PDS) activation. The SDBC yielded large specific surface areas, nitrogen loading, and good conductivity, which demonstrated excellent oxidation efficiencies toward a wide array of aqueous microcontaminants. An in-depth mechanistic study was performed by integrating selective radical scavenging, solvent exchange (H2O to D2O), diverse organic probes, and electrochemical measurement, unveiling that SDBC/PDS did not rely on free radicals or singlet oxygen but a nonradical pathway. PDS intimately was bonded with a biochar (SDBC 900-acid, pyrolysis at 900 °C) to form a surface reactive complex that subsequently attacked an organic sulfamethoxazole (SMX) adsorbed on the biochar via an electron-transfer regime. During this process, the SDBC 900-acid played versatile roles in PDS activation, organic accumulation and mediating the electron shuttle from SMX to PDS. This nonradical system can maintain a superior oxidation efficiency in complicated water matrix and long-term stable operation. More importantly, the nonradical species in SDBC 900-acid/PDS system were capable of inactivating the bacteria (Escherichia coli) in wastewater. Therefore, the biochar based nonradical system can provide a mild and high-efficiency strategy for disinfection in waste and drinking water by green carbocatalysis. This study provides not only a value-added biochar catalyst for wastewater purification but also the first insight into the bacteria inactivation via nonradical oxidation.

The performance and microbial community succession of a 36 L working volume plug flow reactor was evaluated for treated cattle manure at an organic loading rate of 2.67 g-TS/L/day, a temperature of 38 °C ± 1 °C, and a hydraulic retention time of 18 days. A reflux of acidizing fluid effectively enhanced anaerobic digestion performance and promoted optimization of microbial community structure. The average biogas volume production rate was 1.08 L biogas/L reactor, which was 116.5% higher than the control without reflux of acidizing fluid. The specific qmethane production yield and methane content reached 0.204 L/g VS and 70%. Moreover, methane yield achieved 0.34 m3/kg removal COD with a COD removal of about 70.56%. The bacteria genera Christensenellaceae, Bacteroidales, vadinBC27, Ruminococcaceae and Treponema_2 were further enriched. Methanosarcina became the dominant methanogen in the whole PFR operation process. This study offers new opportunities for producing renewable energy from enhanced cattle manure biodegradability.

Hydraulic retention time (HRT) is the main process parameter for biohydrogen production by anaerobic fermentation. This paper investigated the effect of the different HRT on the hydrogen production of the ethanol-type fermentation process in two kinds of CSTR reactors (horizontal continuous stirred-tank reactor and vertical continuous stirred-tank reactor) with molasses as a substrate. Two kinds of CSTR reactors operated with the organic loading rates (OLR) of 12kgCOD/m3•d under the initial HRT of the 8 h condition, and then OLR was adjusted as 6kgCOD/m3•d when the pH drops rapidly. The VCSTR and HCSTR have reached the stable ethanol-type fermentation process within 21 days and 24 days respectively. Among the five HRTs settled in the range of 2–8 h, the maximum hydrogen production rate of 3.7LH2/Ld and 5.1LH2/Ld were investigated respectively in the VCSTR and HCSTR. At that time the COD concentration and HRT were 8000 mg/L and 5 h for VCSTR, while 10000 mg/L and 4 h for HCSTR respectively. Through the analysis on the composition of the liquid fermentation product and biomass under the different HRT condition in the two kinds of CSTR, it can found that the ethanol-type fermentation process in the HCSTR is more stable than VCSTR due to enhancing biomass retention of HCSTR at the short HTR.

Heteroatoms-doped carbon-based materials (with non-precious metals or no metals) with porous structure have already shown high catalytic activities for oxygen reduction reaction (ORR), especially in microbial fuel cells (MFCs). Here, we use pectin extracted from pomelo peels as carbon source to prepare metal-free and sulphur/nitrogen co-doped partially-graphitized carbon (HP-SN-PGCs) by using silica nanospheres as sacrificial templates. Single-chamber MFC (SC-MFC) with HP-SN-PGC-0.5 (0.5 g of silica) cathode has the shortest start-up time (45 h) and lowest charge transfer resistance (19.3 Ω). The maximum power density of HP-SN-PGC-0.5 (1161.34 mW m−2) cathode is higher than that of Pt/C (1116.90 mW m−2) at the initial cycle. After 75 d operation, power density of HP-SN-PGC-0.5 cathode only declines 4.6%, which is more stable than that of Pt/C (37.69%). HP-SN-PGC-0.5 has a highly porous structure (869.25 m2 g−1) by removal of templates and Fe species (as the graphitization catalyst) to facilitate exposure of active sites and diffusion of ORR-related intermediates (OH− and HO2−, etc) to accessible active sites. N and S species provide highly active sites to enhance OH− generation to conduct the 4e− ORR process. Thus, this study presents a viable ORR catalyst with high activity and long-term stability for bio-electricity generation from organic wastewater in SC-MFCs.

Background H2–ethanol-coproducing bacteria, as primary fermenters, play important roles in the microbiome of bioreactors for bioenergy production from organic wastewater or solid wastes. Ethanoligenens harbinense YUAN-3 is an anaerobic ethanol–H2-fermenting bacterium. Ethanol is one of the main end-products of strain YUAN-3 that influence its fermentative process. Until recently, the molecular mechanism of metabolic regulation in strain YUAN-3 during ethanol accumulation has still been unclear. This study aims to elucidate the metabolic regulation mechanisms in strain YUAN-3, which contributes to effectively shape the microbiome for biofuel and bioenergy production from waste stream. Results This study reports that ethanol stress altered the distribution of end-product yields in the H2–ethanol-coproducing Ethanoligenens harbinense strain YUAN-3. Decreasing trends of hydrogen yield from 1888.6 ± 45.8 to 837 ± 64.7 mL L−1 and acetic acid yield from 1767.7 ± 45 to 160.6 ± 44.7 mg L−1 were observed in strain YUAN-3 with increasing exogenous ethanol (0 mM–200 mM). However, the ethanol yield of strain YUAN-3 increased by 15.1%, 30.1%, and 27.4% in 50 mM, 100 mM, and 200 mM ethanol stress, respectively. The endogenous ethanol accounted for 96.1% (w/w) in liquid end-products when exogenous ethanol of 200 mM was added. The molar ratio of ethanol to acetic acid increased 14 times (exogenous ethanol of 200 mM) compared to the control. iTRAQ-based quantitative proteomic analysis indicated that 263 proteins of strain YUAN-3 were differentially expressed in 50 mM, 100 mM, and 200 mM of exogenous ethanol. These proteins are mainly involved in amino acid transport and metabolism, central carbon metabolism, and oxidative stress response. Conclusion These differentially expressed proteins play important roles in metabolic changes necessary for growth and survival of strain YUAN-3 during ethanol stress. The up-regulation of bifunctional acetaldehyde-CoA/alcohol dehydrogenase (ADHE) was the main reason why ethanol production was enhanced, while hydrogen gas and acetic acid yields declined in strain YUAN-3 during ethanol stress. This study also provides a new approach for the enhancement of ethanologenesis by H2–ethanol-coproducing bacteria through exogenous ethanol addition.

Sluggish kinetics of oxygen reduction reaction (ORR) on air-cathode of microbial fuel cells (AC-MFCs) is one of the main obstacles for energy loss. In this study, nitrogen-doped Fe3Se4/FeSe/partially-graphitized carbon (Fe3Se4/FeSe/NPGC) composites as non-precious-metal air-cathode (ORR) catalysts are obtained using waste biomass (cornstalk cores) as raw material. As carbonization temperature increases (800–950 °C), the crystalline phase transition between Fe3Se4 and FeSe is strengthened to form the Fe3Se4/FeSe heterojunctions. The highest power density (1003 mW m−2) and durability (decline of 7.8% after 105 d operation) are obtained by Fe3Se4/FeSe/NPGC (850 °C) cathode in AC-MFCs, which are higher than those of Pt/C (840 mW m−2, 52.4%). The high ORR activity of Fe3Se4/FeSe/NPGC (850 °C) is partly attributed to the large specific surface area (356.68 m2 g−1) and porous structure. Doped N atoms (pyridinic N, pyrrolic N and graphitic N) in carbon skeleton enhance the charge delocalization of C atoms to reduce the electron loss to enhance the electron utilization via a four-electron (4e−) ORR pathway. Fe3Se4/FeSe heterojunctions should greatly promote the charge transfer and oxygen dissociation efficiencies. The highly-conductive NPGC skeleton also contributes to the efficient charge transfer. The good long-term durability of AC-MFCs with Fe3Se4/FeSe/NPGC (850 °C) cathode is mainly ascribed to its fast ORR kinetics, which still generates a small amount (below 10.0%) of H2O2 (•OH and •O2−) intermediate to inhibit the electrogenic microbe growth on cathode surface. This work not only provides the fundamental studies on carbon-supported transition-metal selenides for ORR, but also provides a new kind of promising alternatives for precious metal-based electrodes for AC-MFCs.

Concentration and fraction distribution of organics and heavy metals in municipal sludge treated by modified phosphogypsum and acetic acid (signed as MPG/HAC) were studied. The results showed that MPG/HAC conditioning significantly produce synergistic enhancement effect to dissolution of unstable heavy metals wrapped in the stable colloid network. Simultaneously, after conditioning, about 45.16% of organics such as proteins, polysaccharides and humic acid in supernatant was degraded, thus dissociating large amount of active group which accelerated immobilization of dissolved heavy metals and weaken its toxicity. In addition, MPG with a porous structure could adsorb unstable heavy metals and transform them into residual fraction, leading to a considerable decrease in their mobility risk level. Besides, linear regression models showed that a strong oxidizability of sludge, and destruction of colloidal network could greatly promote dissolution of unstable heavy metals. Simultaneously, sludge oxidizability and organics degradation rate, and disintegration of extracellular polymeric substances (EPS) layer highly accelerate immobilization of unstable metals. Excepting Cd, environmental risk of Cr, Cu, Pb, Zn, Ni and As can be effectively weakened after conditioning. Additionally, MPG/HAC conditioning might be appropriate for stabilization of Cd, Cr and Zn in water supply sludge, especially for Zn.

In this study, the biochar (BC)-induced Fe(III) reduction for persulfate (PS) activation system was used for the first time in sulfamethoxazole (SMX) degradation. The apparent rate constant of the BC/Fe(III)/PS system was 31.3 and 8.2 times that of BC/PS system and Fe(III)/PS system, respectively. The carbon-centered persistent free radicals contained in BC acted as electron donors. Electron transfer occurred between the BC surface and Fe(III) successfully. Fe(II) was thus generated and played a key role for the subsequent PS activation. Scavenger quenching experiments and electron spin resonance spectrometry confirmed the presence of sulfate ( SO 4 · - ) and hydroxyl radicals ( HO · ), which brought about the efficient SMX degradation in the BC/Fe(III)/PS system. Furthermore, the frontier molecular orbital (FMO) theory and dual descriptor (DD) method were employed in predicting radical attacking sites of SMX. According to the results of theoretical computations and the experimental detection, degradation pathways of SMX in the BC/Fe(III)/PS system were deduced accurately. This study gives new insight into the possible mediatory roles of biochar in PS activation by transition metal ions. The BC/Fe(III)/PS system is a promising process for groundwater and soil remediation.

Glucose and xylose co-fermentation is crucial to maximize hydrogen yield from waste lignocellulose. In this study, cell growth, sugar consumption, and hydrogen production profiles of Thermoanaerobacter thermosaccharolyticum W16 feeding with a range of glucose and xylose were experimental investigated coupled with kinetic analysis. Results showed although T. thermosaccharolyticum W16 could use both glucose and xylose for hydrogen production, a maximum cell growth rate of 0.27 g/L/h and hydrogen production rate of 14.53 mmol/L/h was found with glucose as sole substrate, the value was 92.8% and 49.8% higher than using xylose as the only carbon source. Further interpolation analysis and experimental demonstration suggested when glucose content in the mixed substrate higher than 58.2%, the inhibitory effect on xylose utilization was increased, but when glucose concentration fell below 21.7%, its utilization will be subject to a certain degree of feedback inhibition. Coupling experimental results with kinetic analysis in this study provides a powerful evidence to further develop the potential of T. thermosaccharolyticum W16 as a biocatalyst for hydrogen production from lignocellulosic biomass.

The enhancement of the degradability and dewaterability of waste activated sludge (WAS) is important scientific and engineering topics because sludge treatment has strict environmental regulations due to increased urbanization. The impact of three co-treatments (alkali combined with ultrasonication, potassium ferrate (K2FeO4) combined with ultrasonication, and potassium ferrate combined with alkali) on the degradability and dewaterability of sewage sludge and the nutrient release during the co-treatment was investigated. The soluble chemical oxygen demand (SCOD) and disintegration degree (DDSCOD) increased sharply after the co-treatment and the increase in the DDSCOD was almost 40% for the potassium ferrate combined with an ultrasonication treatment after 90 min. The decreased dewaterability observed for the alkaline and potassium ferrate pretreatments was further lowered when combined with ultrasonication based on the increase in the capillary suction time (CST) from 26.4 ± 1.8 s to 1614.1 ± 131 s. The ultrasonication treatment produced a high proportion of colloidal solids (d (0.9) = 6.492) and eluted soluble extracellular polymeric substances (EPS), which are detrimental to the filterability of the WAS. Fe (III) was highly flocculated in the solution and re-coagulated the small particles formed during the ultrasonic crushing process. The evidences regarding the soluble EPS, total organic carbon, total nitrogen, total phosphorus, and volatile suspended solids indicated that the co-treatment of potassium ferrate and ultrasonication was effective for disintegrating WAS, and provided a new way for WAS pretreatment.

In the present work, with corn stover hydrolysate as the substrate, an efficient hydrogen-producing thermophile, Thermoanaerobacterium thermosaccharolyticum W16, was added to three kinds of seed sludge (rotten corn stover (RCS), cow dung compost (CDC), and sludge from anaerobic digestion (SAD)) to investigate the effect of bioaugmentation on thermophilic hydrogen production. Batch test results indicate that the bioaugmentation with a small amount of the strain T. thermosaccharolyticum W16 (5% of total microbes) increased the hydrogen yield to varying degrees (RCS: from 8.78 to 9.90 mmol H2/g utilized sugar; CDC: from 8.18 to 8.42 mmol H2/g utilized sugar; SAD: from 8.55 to 9.17 mmol H2/g utilized sugar). The bioaugmentation process also influenced the soluble metabolites composition towards more acetate and less butyrate production for RCS, and more acetate and less ethanol accumulation for SAD. Microbial community analysis indicates that Thermoanaerobacterium spp. and Clostridium spp. dominated microbial community in all situations and might be mainly responsible for thermophilic hydrogen generation. For RCS and SAD, the bioaugmentation obviously increased the relative abundance of the strain T. thermosaccharolyticum W16 in microbial community, which might be the main reason for the improvement of hydrogen production in these cases.

Luminescent bacteria can emit visible light at 450–490 nm, and its luminous intensity decreases with the increase of the concentration of toxic substances in test solution. The method using luminescent bacteria is widely used in acute toxicity analysis of water quality because it is a simple, rapid and low-cost way. In recent years, biosensors based on luminescent bacteria have attracted more and more attention, and the reports of bioluminescence biosensors based on microfluidic systems are increasing day by day. Based on the characteristics and mechanism of luminescent bacteria, this paper introduces their applications in the environmental monitoring, and summarizes several new bioluminescence sensors.

In this study, sludge-derived biochar (SDBC) was prepared and applied in peroxydisulfate (PDS) activation for sulfamethoxazole (SMX) degradation. Compared to the slight adsorption (16.5%) by SDBC alone and low direct oxidation (10.1%) by PDS alone, the SMX degradation rate was drastically increased to 94.6% in the combined SDBC/PDS system, suggesting that SDBC can successfully and efficiently activate PDS. The observed rate constant of the combined SDBC/PDS system was 48.3 times those of both PDS alone and SDBC alone processes. Material characterization and comparative experiments showed nitrogen doping and iron loading into the carbon layer might be the important active sites of the graphene-like SDBC material in PDS activation for SMX degradation. More importantly, singlet oxygen (1O2), instead of traditional sulfate radicals or hydroxyl radicals, was the predominant reactive species of the SDBC/PDS system, which involved a new nonradical oxidation method for PDS activation by SDBC. The SMX degradation pathways by the nonradical 1O2 oxidation were first studied by combining density functional theory (DFT) calculations with experimental results. Different from the well-known pathways of SMX through the cleavage of the sulfanilamide bond by the attack of radicals, the 1O2 was likely to attack the aniline ring of SMX to initiate and accelerate the decomposition process. Finally, the energy cost analysis of the SDBC/PDS system further demonstrated the possible and economic application of the SDBC/PDS technique for SMX degradation. Thus, this study proposed a novel and economic method for PDS activation through a new nonradical oxidation pathway predominated by 1O2, which also promoted the safe and efficient transformation of antibiotics or other contaminants by PDS activation processes.

© 2018 Elsevier B.V. Energy uncoupling technology was applied to the membrane process to control the problem of bio-fouling. Different dosages of uncoupler (2,4‑dinitrophenol, DNP) were added to the activated sludge, and a short-term ultrafiltration test was systematically investigated for analyzing membrane fouling potential and underlying mechanisms. Ultrafiltration membrane was used and made of polyether-sulfone with a molecular weight cut off (MWCO) of 150 kDa. Results indicated that low DNP concentration (15–30 mg/g VSS) aggravated membrane fouling because more soluble microbial products were released and then rejected by the membrane, which significantly increased cake layer resistance compared with the control. Conversely, a high dosage of DNP (45 mg/g VSS) retarded membrane fouling owing to the high inhibition of extracellular polymeric substances (proteins and polysaccharides) of the sludge, which effectively prevented the formation of cake layer on the membrane surface. Furthermore, analyses of fouling model revealed that a high dosage of DNP delayed the fouling model from pore blocking transition to cake filtration, whereas this transition process was accelerated in the low dosage scenario.

The inherent properties of hydrophilicity and environmental preferability of cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) make them great candidates for application in water-treatment membranes. In this study, the antifouling properties of CNCs and CNFs, modified ultrafiltration (UF) membranes, were directly compared. A facile modification method was conducted by coating CNCs and CNFs on the surface of polyethersulfone (PES) membranes to prepare CNC-coating membranes and the CNF-coating membranes. Membrane surface morphology was characterized by atomic force microscopy (AFM), and the results showed that the CNF-coating membranes exhibited greater surface roughness than the CNC-coating membranes. Pure water flux measurements demonstrated that the flux of the CNC-coating membranes was slightly lower than that of the CNF-coating membranes. Antifouling properties were evaluated and compared for the two types of membranes by filtration of NOM foulant models, humic acid (HA) and bovine serum albumin (BSA). The results showed that the antifouling properties of the modified membranes were enhanced through the coating of either CNCs or CNFs to a control PES membrane. The CNC-coating membranes outperformed the CNF-coating membranes in alleviating both reversible fouling and irreversible fouling caused by HA and BSA. In addition, the antifouling performance of the coating membranes was enhanced with increased coating content.

In this study, cellulose nanocrystals (CNCs) were incorporated into a polyamide (PA) layer to prepare novel thin film composite (TFC) nanofiltration membranes (CNC-TFC-Ms). Scanning electron microscopy (SEM) results revealed differences in the surface morphologies of the CNC-TFC-Ms compared with that of a control membrane (TFC-control-M). The pore size distribution (PSD) results showed that the CNC-TFC-Ms exhibited smaller pore sizes and narrower PSD curves as the CNC content in the PA layer increased. Continuous potential measurements showed that the negativity of the surface charge of the CNC-TFC-Ms decreased as the CNC concentration increased. The CNC-TFC-Ms showed great rejection performance for divalent salts with rejection rates over 98.0% and 97.5% for Na2SO4 and MgSO4, respectively. Meanwhile, the filtration flux of salts was dramatically enhanced compared with that of TFC-control-M. Additionally, the permeate flux and rejection of NaCl were simultaneously enhanced as the CNC content increased, demonstrating that CNC-TFC-Ms can overcome the trade-off limitation. In addition, the NaCl/Na2SO4 selectivity of the CNC-TFC-Ms reached as high as 60, suggesting their distinguished divalent/monovalent separation characteristics. The CNC-TFC-Ms exhibited greater dye removal for both anionic and cationic dyes due to their decreased negative charge and smaller pore size than the control membrane.

The synergies between transition metal oxides (bimetallic oxides) play important roles in determining the bifunctional catalytic activity for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. This study uses a facile hydrothermal method for uniformly coating CeO2 shells on the surfaces of ZIF-67-derived porous Co3O4@Z67-NT (T-temperature, 500–900 °C) cores. Co3O4@Z67-N700@CeO2 exhibits excellent bifunctional (ORR/OER) catalytic activity with a ΔE [Ej=10(OER) − E1/2(ORR)] of 0.70 V. For ORR, Co3O4@Z67-N700@CeO2 exhibits a higher half-wave potential of 0.88 V (vs. RHE) than that of commercial Pt/C (0.87 V), which is attributed to the synergies between CeO2 (Ce3+) and Co3O4 (Co2+). The oxygen vacancies on CeO2 can enhance O2 adsorption on the interfaces to promote the activation of adsorbed O2 to O2−, and can alleviate O2 deficiency during ORR, thereby improving ORR activity. For OER, Co3O4@Z67-N700@CeO2 has a lower overpotential of 350 mV at 10 mA cm−2 and a higher Faraday efficiency of 92.2% than those of RuO2. An effective valence transition between Ce3+ and Ce4+ endows CeO2 with high electrical conductivity and oxygen storage capacity, which greatly promote charge transfer and the generation/smooth transport of highly active species (O22−/O−). Moreover, the interactions between CeO2 (Ce3+/Ce4+ and oxygen vacancies) and Co3O4 (Co3+/CoOOH) provide more electrochemically active sites for OER. This study provides a new strategy for constructing the stable core@shell structure based on MOF derivatives to improve the ORR/OER performance.

Due to the characteristics of renewable and carbon-neutral, lignocellulose is considered to be one of the most potential, feasible, and ample resources for biofuel production on the Earth. However, the low energy conversion capacity of microorganisms is the primary bottleneck for utilizing lignocellulosic biomass to produce biofuel. In the present study, a mesophilic bacterial strain Cel10 identified as Clostridium lentocellum, according to 16S rRNA sequence homology, which can produce hydrogen from lignocellulose was isolated and characterized. The optimal conditions of hydrogen production from carboxymethylcellulose (CMC) are 37 °C, pH 7.0, and 5.0 g L−1. The H2 production peaked at 5.419 mmol H2 g−1 CMC under these conditions, which is relatively high compared to the other reported mesophilic bacteria that use cellulose as a substrate. Moreover, the H2-producing performance of strain Cel10 using cassava residues, a type of natural lignocellulosic feedstock, was also investigated. The results show that the hydrogen production peaked at 4.08 mmol H2 g−1 after 72 h of incubation, which is almost 1.2–3.8 times higher than the production of other mesophilic and thermophilic strains, while the highest cassava residues degradation rate reached 45.43%. The results validate that Clostridium lentocellum strain Cel10, newly isolated from Ailuropoda melanoleuca excrement, can offer a new method for directly converting lignocellulosic biomass to bio-hydrogen.

The lipid production and nutrients removal of Scenedesmus sp. in non-sterile domestic wastewater were investigated in the present study. Compared with secondary effluent, primary effluent was more appropriate substrate for algal growth, and the biomass concentration and lipid yield reached 0.69 ± 0.02 g L−1 and 166.7 ± 8.3 mg L−1, respectively. Ultrasonic exposure significantly enhanced the lipid yield and wastewater treatment performance. The biomass and lipid accumulation increased to 1.56 ± 0.07 g L−1 and 240 ± 9.2 mg L−1 at the optimum ultrasonic treatment frequency of 18 Hz, power of 20 W and time of 10 min. The maximum TN and TP removal rates reached 96.8% and 97.7%, respectively. Microbial community analysis revealed that the ultrasonic treatment markedly affected the microbial communities, which can accelerate the formation of favorable microbial community structure. Gemmobacter and Porphyrobacter were identified as key bacteria under ultrasonic condition, and their relative abundances were 38.7% and 19.1%, respectively. This research showed the efficiency of ultrasonic treatment in promoting algal lipid yield and domestic wastewater treatment.

A Fe-N-C catalyst is supposed to drive commercialization of microbial fuel cells (MFCs) because of its remarkable catalytic performance on oxygen reduction reaction (ORR). However, the catalyst suffers from unclear active site structure and unknown responses of the cathodic microbial community. Here, we prepared a mesoporous core-shell structure catalyst with a nitrogen doped matrix carbon shell, and a Fe3O4 core (Fe3O4@N-mC) as efficient cathode catalysts for the oxygen reduction reaction (ORR). The resulting hybrid electrocatalyst (Fe3O4@N-mC) showed higher limiting current density (2.94 mA cm−2), lower H2O2 yield (7.2–12.7%), and a higher electron transfer number (3.74–3.85) for ORR activity than its intermediates, including Fe3O4, polyaniline (PANI), nitrogen doped carbon (N-C), and magnetic polyaniline composite (Fe3O4@PANI). In MFC tests, Fe3O4@N-mC produced a power density of 0.73 W m−2, which was 2.14 times of N-C (0.34 W m−2), 3.84 times of Fe3O4@PANI (0.19 W m−2), and more than four times of Fe3O4 (4.29, 0.17 W m−2) and PANI (4.87, 0.15 W m−2). Illumina sequencing of 16S rRNA gene amplicons and non-metric multi-dimensional scaling (NMDS) indicated distinct separation of the cathode biofilm bacterial communities between MFCs with different cathodic catalysts. MFCs with the Fe3O4@N-mC cathode facilitated the enrichment of putative exoelectrogenic Dietzia. Our findings suggest that enhancing ORR performance of Fe3O4@N-mC in MFCs can be attributed to the co-effects of Fe and N, the core-mesoporous shell structure, and various nitrogen functionalities.

In this study, a novel, single-chamber bioelectrochemical system (BES) with stacked modules was developed to improve azo dye decolorization. The decolorization extent of BES with three modules (80.3 ± 3.1%) was about 15% and 33% higher than that with two modules (65.6 ± 4.5%) and one module (47.1 ± 3.9%) at an influent Acid Orange 7 (AO7) loading rate of 250 g m−3 d−1, demonstrating the feasibility of enhanced decolorization in scale-up BES through increasing the number of stacked modules. Moreover, the contribution of each module to dye decolorization, chemical oxygen demand (COD) removal and volatile fatty acids (VFAs) changes, showed the sequential utilization of pollutants in the stacked BES. Furthermore, analysis of the microbial communities showed that Pseudomonas, Geobacter, Comamonas, Meniscus, Bellilinea, Achromobacter, and Paludibacter were significantly enriched and resulted in the specific microbial community structures of the biocathode, meanwhile Geobacter and Acinetobacter were enriched in the microbial community of the bioanode, which mainly contributed to the electron transfer and/or azo dye decolorization. The results of this study demonstrate the potential of stacked BES for the accelerated deployment of large-scale BES applications for the treatment of refractory waste streams such as azo dye-bearing wastewater.