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In this work, we systematically investigated the performance and degradation mechanism of quinoline using a persulfate (PS) or sulfite (S(Ⅳ)) assisted WO 3 /CuFe 2 O 4 /Cu (10WCC) photocatalysis. The experimental results showed the degradation efficiency of quinoline were the best in the PS-photocatalysis system with the catalyst dosage of 3 g/L, the PS dosage of 4 mmol/L and pH of 7, and that were the best in the S(Ⅳ)-photocatalysis system with the catalyst dosage of 2 g/L, the S(Ⅳ) dosage of 5 mmol/L and pH of 7. In addition, the S(Ⅳ)-photocatalysis system (77.2%, 1.43 h−1) had lower degradation efficiency than the PS-photocatalysis system (100%, 11.04 h−1) under visible light irradiation. The main active species in the 10WCC/VIS/PS system were h+ and ·OH, while in the 10WCC/VIS/S(Ⅳ) system they were h+, ·O 2 - and SO 4 ·-. This was likely because the electrons of 10WCC could not be captured by S(Ⅳ), and more electrons were captured by O 2 to form ·O 2 -. Some h+ oxidized S(Ⅳ), resulting in a small amount of ·OH. Thus, ·O 2 - and SO 4 ·- played key roles in presence of S(Ⅳ). Moreover, h+ was most important in both systems, indicating photocatalytic degradation dominated quinoline removal reaction. This study provides some reference for SO 4 ·- coordinated photocatalysis technology. [Display omitted] • WO 3 /CuFe 2 O 4 /Cu Z-scheme catalyst was constructed. • Quinoline was removed by persulfate or sulfite assisted photocatalytic process. • The main active species were different between persulfate system and sulfite system. • Degradation mechanism and pathways of quinoline in two systems were compared. [ABSTRACT FROM AUTHOR]

Sulfaquinoxaline (SQX) is a vital sulfonamide antibiotic for the treatment of livestock infections. Although its degradation has become a research focus in the last few years, its biodegradation process and biometabolic mechanisms were rarely studied. In this research, microbial electrolytic cells (MECs) were used to remove SQX using sodium acetate as a co-substrate. The findings indicated that the maximum removal rate of SQX for a 5-day period in co-substrate reached 94.2%, and SQX exhibited a lower resistance (45.64 Ω) and had a larger double-layer area than a single substrate (95.03 Ω). LC MS/MS analysis suggested that SQX could eventually degrade to 17 byproducts through hydrolysis, hydroxylation, N rearrangement and sulfur reduction. Density flooding theory (DFT) calculations showed that sodium acetate addition weakened the N-C bond and facilitated hydroxylation. Meanwhile, the fluorescence composition of fDOM shifted from protein-like to humic acid-like with co-substrate supplementation. Microbial community analysis showed that Actinobacteria, Proteobacteria, Bacteroidota and Chloroflexi were highly correlated with SQX removal. Analysis of the metabolic pathways showed that key enzymes such as NAT, CAT, DHP and NAD+ were involved in the degradation of SQX. Biotoxicity tests indicated that weak electrical stimulation was beneficial in reducing biotoxicity. These results provide theoretical basis and new insights into the bioelectrochemical degradation of SQX. [Display omitted] • The feasibility of facilitating SQX degradation through MEC was first assessed. • The degradation of SQX was effectively improved with sodium acetate addition. • The main metabolic pathway of SQX was hydroxylation by DFT calculations. • The correlation between SQX degrading bacteria and exoelectrogens was existed. • The NAT and CAT had higher abundance based on the number of genes for key enzymes. [ABSTRACT FROM AUTHOR]

In this study, the attempt was made to enhance the degradation of the typical antibiotics, metronidazole (MNZ) by coupling three-electrode photocatalytic and microbial fuel cell systems (PMFC). The PMFC reactor was constructed, and the photocatalytic bioanode, attached with TiO 2 , was synthesized and characterized using SEM, EDS, XPS methods. The stability of microbial on bioanode was tested during acclimatization process. Electrochemical characteristics, including power density, CV and EIS curve, were analyzed to explore the advantage of power generation and higher electron transfer interaction in the PMFC. Compared with the traditional MFC system, the improved degradation and enhanced mineralization of MNZ were achieved, and the 1.30 and 1.24-fold increase in MNZ and TOC removal were realized, respectively. The three degradation pathways of MNZ were identified by LC-MS in the coupling PMFC, and the intermediates were more easily to further degrade and mineralize. The structure of the microbial community was demonstrated, and the functional species consisted of MNZ degradation bacteria, exoelectrogens, hydrocarbon removal bacterial, and nitrogen removal bacterial, were largely enriched in the PMFC, contributing to the improved electricity production, MNZ degradation and photoelectric effect. Moreover, the photoelectric played the selective role in the enrichment of functional microbial. The study provides a promising and environmentally approach for the treatment of containing antibiotics wastewater in the practical application. [Display omitted] • The PMFC system was developed for the treatment of metronidazole. • The performance of metronidazole degradation and mineralization was strengthened in the PMFC system. • The higher electron transfer reaction was obtained in the PMFC. • Degradation bacterial, exoelectrogens, nitrogen removal bacterial were enriched and coexisted. [ABSTRACT FROM AUTHOR]

Anaerobic fermentation (AF) could achieve simultaneous recovery of short-chain fatty acids (SCFAs) and phosphorus (P) when waste activated sludge (WAS) and meat processing waste (MPW) act as co-substrate. However, long-chain fatty acids, the degradation intermediates of lipids, always inhibit anaerobic microbial activity. Therefore, sodium hydroxide (NaOH) conditioning was applied to improve the lipid-rich AF performance in this study. The results demonstrated that 96% WAS (v/v) with NaOH addition that remaining at pH 7.5 could achieve the maximum SCFAs yield (1180.05 mg/g VS fed) at 12 d, and ortho-P content in the AF liquor (AFL) was much more than that of without NaOH addition. Anaerovibrio and Aminobacterium , one kind of lipolytic and proteolytic bacteria, respectively, became the major genus in the lipid-rich AF system. 86% of P in the AFL from 96% WAS + pH 7.5 reactor was recovered through vivianite crystallization method, with 91% of SCFAs remaining in the post-AFL. Meanwhile, analysis results verified vivianite formation in the P precipitate products. Overall, this study provided a new idea to achieve SCFAs and P simultaneous recovery from WAS and MPW through AF with NaOH conditioning and vivianite crystallization. [Display omitted] • Meat processing waste and activated sludge were treated by anaerobic fermentation. • NaOH conditioning enhanced SCFAs yield and P release from lipid-rich AF. • Maximal SCFAs yield (1180.05 mg/g VS fed) occurred at pH 7.5 with NaOH addition. • Anaerovibrio , one kind of lipolytic bacteria, was stimulated during lipid-rich AF. • Ortho-P release from the fermentation system was favorable for vivianite recovery. [ABSTRACT FROM AUTHOR]

Quinoline is a critical raw material for the dye, metallurgy, pharmaceutical, rubber, and agrochemical industries, and its use poses a serious threat to human health and the ecological environment. Quinoline has carcinogenic, teratogenic and mutagenic effects on the human body through food accumulation. However, due to the steric hindrance of its bicyclic fused structure and its long photooxidation half-life, quinoline is too difficult to decompose naturally. To date, numerous technologies have been used to degrade quinoline, whereas only a few have been reviewed. Therefore, this paper is focused on offering a comprehensive overview of the state of quinoline degradation in an effort to improve its degradation efficiency and fully utilize the carbon and nitrogen within quinoline without causing any damage to the environment. Accordingly, the strains, research progress and mechanisms of various methods for degrading quinoline are explored and elucidated in detail, especially quinoline biodegradation and the combination of these technologies for efficient removal. The state-of-the-art processes and new findings of our team on the biofortification of quinoline degradation are also presented. Finally, research bottlenecks and gaps for future research were identified along with the prospects and resource utilization of quinoline. These discussions facilitate the realization of the zero discharge of quinoline. Unlabelled Image • Research progress and various mechanisms of quinoline biodegradation were elucidated. • Research bottlenecks and gaps for future research were also identified. • State of art processes for biofortification of quinoline degradation are presented. • Efficient open loop methods also need to be further explored. • Future research may focus on the use of C and N in quinoline instead of being removed. [ABSTRACT FROM AUTHOR]

Bioretention has been widely used in urban non-point source (NPS) pollution management for effectively reducing downstream pollution loads and peak flows. However, nitrogen (N) removal in conventional bioretention systems has been uniformly unstable and highly variable due to a lack of anaerobic denitrification. To improve the stability and effectiveness of N removal, two bioretention columns with bilayer media (C1 and C2) were designed. High permeability quartz sand (~2 mm diameter) was used as the upper media, and low permeability modified media (~0.6 mm diameter, adding 5% organic substance) as the lower media. The bilayer media structure formed an anaerobic zone for promoting denitrification processes. The results showed that the retrofitted columns performed well and that the removal efficiencies of various forms of N were considerably enhanced to 76.8%–95.3%, 85.1%–98.3%, and 87.5%–97.4% for TN, NH 4 +-N, and NO 3 −-N, respectively. Additionally, copying numbers of the denitrification functional genes detected via FQ-PCR in the lower media of C1 and C2 were accounted for 46.06% and 44.16% of the 16S rDNA gene, respectively. These results confirmed the presence of anaerobic denitrification processes. Consequently, bilayer media bioretention systems are worth promoting in cities where nitrogen in urban runoff poses a threat to the receiving surface water, due to the systems' remarkable performance in nitrogen removal, simple structure, and easy implementation. Unlabelled Image • Bilayer media bioretention was designed and constructed to improve N removal. • The bilayer media structure increased adsorption capacity, hydraulic retention time. • Ammonia nitrogen was mainly captured by adsorption in the upper layer. • Nitrate nitrogen was largely converted by denitrification in the lower media layer. • The lower media had a high proportion of denitrification genes detected via FQ-PCR. [ABSTRACT FROM AUTHOR]

• A novel 2D/3D Bi 5 O 7 Br/BiOBr was prepared via one-step hydrolysis method. • The Bi 5 O 7 Br/BiOBr exhibited better visible light degrade pharmaceutical activity. • The Bi 5 O 7 Br/BiOBr showed tight contact and superior electron-hole separation rate. • The photocatalytic mechanism of Bi 5 O 7 Br/BiOBr was proposed. BiOBr-based composite photocatalysts had attracted extensive attention for efficient photocatalytic degradation aqueous organic pollutants in the past decade. However, the catalysis ability of photocatalyst is greatly limited by their intrinsic high recombination rate of photo-generated charge carriers. Herein, we solve this problem by constructing a novel 2D/3D Bi 5 O 7 Br/BiOBr heterojunction photocatalyst that was prepared via one-step facile hydrolysis process. The pure Bi 5 O 7 Br and pure BiOBr photocatalysts were also obtained by only adjusting the pH value of the mixed solution. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical and electric property analysis and etc. The results suggested that 2D Bi 5 O 7 Br nanosheets tightly attached to the surface of BiOBr 3D structure with nanoflakes self-assembled microsphere, which could increase the transfer and separation efficiency of photogenerated charges. Furthermore, the 2D/3D Bi 5 O 7 Br/BiOBr heterojunction exhibited superior visible light photocatalytic performance for carbamazepine (CBZ) degradation than pure BiOBr and pure Bi 5 O 7 Br, which owing to the enhanced separation of photoinduced electrons and holes. At last, the underlying photocatalytic mechanism is elucidated based on the band structure and radical scavenging experiments. This work provided a feasible design idea to one-step construct 2D/3D nanocomposite for pharmaceutical wastewater purification. [ABSTRACT FROM AUTHOR]

• Bio-foaming seemed to be caused by the accumulation of volatile fatty acids. • CH 4 yield was increased by 2.5–11.3% after Fe0 dosing at a loading rate of 7.5 kgVS/m3/d. • Addition of Fe0 decreased the degree of effluent surface active by 49.7–59.2%. • Fe0 dosing was assessed by comparison with commercial antifoam agents. Bio-foaming during the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) is a major cause of unstable reactor operations, especially under high organic loading rates (OLRs). Here, we used two 40-liter anaerobic reactors to deal with the actual organic fraction of municipal solid waste at OLRs of 5 and 7.5 kgVS/m3/d and tried to inhibit bio-foam generation by dosing with Fe0. One of reactors had 400 g of Fe0 added before operation and additional 200 g of Fe0 was added when the operating conditions changed; the other one was the control reactor with no Fe0 dosing. The results show that bio-foam was generated in the control reactor at an organic shock loading of 10 kgVS/m3/d and re-startup at 5 kgVS/m3/d, while the reactor containing Fe0 operated normally. Due to the surfactant attributes of volatile fatty acids (VFAs), the probability of bio-foam generation was positively correlated with the effluent's degree of surface activity (SA) induced by VFAs, which is a parameter representing the foaming potential. Because VFA biodegradation was enhanced in the reactor with added Fe0, at the position of Fe0 accumulation, the SA was decreased by 49.7–59.2%. Furthermore, the effect of Fe0 dosing on inhibiting bio-foam was evaluated by comparison with traditional commercial anti-foam agents. The results suggest possible reasons for bio-foam generation in OFMSW AD and suggest the reasonable usage of Fe0 to inhibit bio-foam formation. [ABSTRACT FROM AUTHOR]

• 150 mgN/L of nitrate photolysis improved SCFAs production from WAS. • Nitrate increase (150∼375 mgN/L) has no significant promotion on SCFAs in photolysis. • ROS contributed more than RNS on WAS solubilization, hydrolysis and acidification. • Both AFB and NRB enriched for the high SCFAs production and complete denitrification. • Genes related to glycolysis, amino acid, acetate and nitrogen metabolism were enhanced. Nitrate photolysis has become an efficient, low-cost and promising technology for emerging contaminants removal, while its performance and mechanism for waste activated sludge (WAS) treatment is still unknown. This study innovatively introduced nitrate photolysis for WAS disintegration, and investigated the effect of nitrate addition (150–375 mg N/L) for short-chain fatty acids (SCFAs) production during anaerobic fermentation (AF). The results showed that nitrate photolysis significantly promoted the SCFAs production from WAS, and peaked at 280.7 mg/g VSS with 7-d fermentation with 150 mg N/L addition (150N-UV), which increased by 8.8–35.0 % and 10.7–23.3 % compared with other photolysis groups and sole nitrate groups. Effective release of the soluble organics was observed in the nitrate photolysis groups during AF, especially soluble proteins, reaching 1505.4 mg COD/L at 9 d in 150N-UV group, promoted by 7.0∼15.7 % than nitrate/nitrate photolysis groups. The model compounds simulation experiment further demonstrated the positive effect of nitrate photolysis on organics hydrolysis and SCFAs accumulation. The result of the radical capture and quenching verified the reactive oxygen species contributed more compared with reactive nitrogen species. Functional group analysis confirmed the effective bioconversion of the macromolecular organics during the fermentation. Moreover, the nitrate photolysis enhanced the enrichment of the functional consortia, including anaerobic fermentation bacteria (AFB), e.g., Fnoticella, Romboutsia, Gracilibacter and Sedimentibacter , and nitrate reducing bacteria (NRB), e.g., Acinerobacter and Ahniella. The macrogenetic analysis further revealed that glycolysis, amino acid metabolism, acetate metabolism and nitrogen metabolism were the dominating metabolic pathways during fermentation, and the abundance of the relevant genes were enhanced in 150N-UV group. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyrolytic carbon from waste tire pyrolysis was used to boost the AD performance. • Pyrolysis temperature for pyrolytic carbon used in AD should be higher than 800 °C. • The conductivity of pyrolytic carbon at 1000 °C is (12.5–25.2) × 104 S/m. • The hydrolysis of vinegar residue is enhanced and the VFA content is 3330 mg/L. • The maximal CH 4 yield is 454.53 mL CH 4 /gVS, representing an increase of 104.4%. Random disposal of waste tires and vinegar residues is deleterious to the environment; these materials can be sufficiently treated using pyrolysis and anaerobic digestion, respectively. In this study, pyrolytic carbon was used to enhance the performance of the anaerobic digestion of vinegar residues, which is a much more economic method comparing with dosing commercial-level carbon based materials. The conductivity of pyrolytic carbon at 1000 °C is much higher than that of commercial activated carbon. At a dosage of 10 g per 29 g of vinegar residues, the maximum volatile fatty acid production was 4225.4 mg COD/L in the reactor (effective volume of 400 mL) with inoculum to substrate ratio (ISR) of 1:1, representing an increase of 50.3% from that of the control reactor. A sufficient dosage is necessary to improve methane yield. The maximum methane yield was obtained at a pyrolytic carbon dosage, obtained at 1000 °C, of 12 g per 29 g of vinegar residues. The results indicated that the differences in the microbial communities of the control and experimental reactors correlated with the performance; however, the deep microbial mechanism of pyrolytic carbon boosting anaerobic digestion performance must be explored in further studies. [ABSTRACT FROM AUTHOR]

• Zn(II) inhibited the performance of SDM and multiple antibiotic biodegradation. • Zn(II) intervention promoted protein release in the DOM of EPS. • ZnuA and zipB can provide abundant sites to bind Zn(II) and antibiotics. • The effect of Zn(II) stress on ARGs was higher than that of antibiotics. • The abundances of MGEs, Zn-RGs, and ARGs were positively correlated. High-strength nitrogen and antibiotics-containing wastewater can be efficiently eliminated by simultaneous denitrification and methanogenesis (SDM). Heavy metals and antibiotics are two critical factors that can lead to horizontal transfer of antibiotic resistance genes (ARGs), which can be simultaneously detected in wastewater. Unfortunately, the impacts of heavy metals on SDM and antibiotic biodegradation have not been fully elucidated. Herein, the effects of SDM and multiple antibiotics biodegradation, extracellular polymeric substances (EPSs) and protein response mechanisms, and ARG fate under Zn(II) stress were comprehensively evaluated. The results indicated that a high level of Zn(II) (≥5 mg/L) stress significantly decreased the degradation rate of multiple antibiotics and suppressed denitrification and methanogenesis. In addition, Zn(II) exposure prompted the liberation of proteins from microbes into the EPSs, and the combination of EPSs with small molecules quenched the original fluorescent components and destroyed the protein structure. The dominant proteins can bind to both Zn(II) and multiple antibiotics through several types of chemical interactions, including metallic and hydrogen bonds, hydrophobic interactions, and salt bridges, relieving the toxicity of harmful substances. Moreover, metagenomic sequencing revealed that the abundance of zinc resistance genes (Zn-RGs), ARGs (mainly tetracyclines), and mobile genetic elements (MGEs) increased under Zn(II) stress. Mantel test illustrated that the ARGs mecD, tetT, and tetB(60) were most affected by MGEs. Moreover, molecular network analysis revealed that several MGEs can bridge metal resistance genes (MRGs) and ARGs, facilitating the horizontal transfer of ARGs. This study provides theoretical guidance for the environmental risk control of antibiotics-containing wastewater treated by an SDM system. [Display omitted] [ABSTRACT FROM AUTHOR]

Exploration of value-added products from wastewater treatment plants (WWTPs) was promising for its sustainable development. This study simultaneously addressed the possibility of volatile fatty acids (VFAs) production boost and cellulosic components recovery from fine-sieving fractions (FSF) under initial alkaline conditions. The step utilization of FSF was relatively untapped in similar literatures. The effect of different initial pH values with 8.5, 9.5 and 10.5 (defined as F-8.5, F-9.5 and F-10.5) on fermentation performance were investigated. Then, the fermentation residues were collected to evaluate the changes in chemical structure and thermodynamic properties by fourier transform infrared spectroscopy (FTIR) and thermo-gravimetric (TG) analysis. Furthermore, analysis of the changes in microbial community structure and the interaction between functional genus and performance parameters were undertaken by high throughput sequencing and canonical correspondence analysis (CCA). Results showed that F-10.5 obtained the highest VFAs yields of 234 mg/g VSS, due to efficient polysaccharides release and inhibited methane production. However, high alkaline intensity caused proteins denaturation. Acidogenesis kinetics suggested that the fermentation rate was chemical-dominated. Although crystalline structure was more disordered with increasing alkalinity, the weight loss was lower than 2.5%, making it possible to recover cellulose from fermented residues. Interaction between functional genus and performance parameters revealed the microbial mechanism during the alkaline fermentation. Consequently, the initial-alkaline motivated fermentation was proved to be a promising technology in value-added products recovery to be cost economic, energy positive and environmental friendly. [Display omitted] • VFAs production was accelerated due to efficient chemical-dominated hydrolysis. • Change in cellulose structure was detected with less weight loss after fermentation. • Alkaline fermentation significantly affected the microbial community structure. • The process was evaluated to be cost effective, energy and environmental positive. [ABSTRACT FROM AUTHOR]

Environment-friendly nano-catalysts capable of activating peroxymonosulfate (PMS) have received increasing attention recently. Nevertheless, traditional nano-catalysts are generally well dispersed and difficult to be separated from reaction system, so it is particularly important to develop nano-catalysts with both good catalytic activity and excellent recycling efficiency. In this work, magnetically recoverable Fe 3 O 4 -modified ternary CoFeCu-layered double hydroxides (Fe 3 O 4 /CoFeCu-LDHs) was prepared by a simple co-precipitation method and initially applied to activate PMS for the degradation of Rhodamine B (RhB). X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET), and vibrating sample magnetometer (VSM) were applied to characterize morphology, structure, specific surface area and magnetism. In addition, the effects of several key parameters were evaluated. The Fe 3 O 4 /CoFeCu-LDHs exhibited high catalytic activity, and RhB degradation efficiency could reach 100% within 20 min by adding 0.2 g/L of catalyst and 1 mmol/L of PMS into 50 mg/L of RhB solution under a wide pH condition (3.0-7.0). Notably, the Fe 3 O 4 /CoFeCu-LDHs showed good super-paramagnetism and excellent stability, which could be effectively and quickly recovered under magnetic condition, and the degradation efficiency after ten cycles could still maintain 98.95%. Both radicals quenching tests and electron spin resonance (ESR) identified both HO• and SO 4 •− were involved and SO 4 •− played a dominant role on the RhB degradation. Finally, the chemical states of the sample's surface elements were measured by X-ray photoelectron spectroscopy (XPS), and the possible activation mechanism in Fe 3 O 4 /CoFeCu-LDHs/PMS system was proposed according to comprehensive analysis. [Display omitted] [ABSTRACT FROM AUTHOR]

High value-added utilization of industrial waste is important for environmental protection and sustainability. The objective of this study was to recycle industrial wastes, silica fume (SF) and aluminium ash (AA) as raw materials to substitute chemicals for sustainable and low-cost SUZ-4 zeolite (L-SUZ-4) synthesis in one pot. The synthesis parameters to obtain pure L-SUZ-4 were optimized as x KOH(x = 7.84–9.33): y Al 2 O 3 (y = 0.81–1.10):2.6TEAOH:21.2SiO 2 : z H 2 O(z = 330.72–712.32) at 150 °C for 96 h. The notably high yield of L-SUZ-4 (up to 85%) indicated that silicon and aluminium species in SF and AA are not only easy to be activated but also liable to be incorporated into the zeolitic framework. Exploration of L-SUZ-4 synthesis process by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) characterizations indicated that the synthesis follows the liquid phase transition mechanism. It can also be observed that the complete dissolution of SF is the rate-determing step during the induction period. Meanwhile, the adsorption ability of L-SUZ-4 for Cd2+ in water was first investigated. A notably maximized adsorption amount (q max = 263.68 mg/g) of L-SUZ-4 for Cd2+ was obtained, which is higher than the other adsorbents investigated in this work or those described in the literature. The sustainable production and outstanding adsorption performance of L-SUZ-4 make it a very promising adsorbent for heavy metal removal with practical application prospects, which is the typical case of "waste to treat waste". [Display omitted] • SUZ-4 zeolite is first prepared using silica fume and aluminum ash by one-pot. • The formation mechanism of the low-cost SUZ-4 zeolite is expatiated. • The low-cost SUZ-4 zeolite displays high adsorption capacity for Cd2+. • The low-cost SUZ-4 is a very promising adsorbent from the practical application. [ABSTRACT FROM AUTHOR]

Waste activated sludge (WAS) is a promising phosphorus (P) source for fertilizer production; however, it is mainly enmeshed inside microbial cells or extracellular polymeric matrixes. Thus, efficient P release is a key goal. This study provided an effective route to simultaneously release organic P (OP) and harvest hydrogen from WAS via bio-electrolysis assisted with prefermentation system (AD_MEC). The clarification of P fractions in both solid and liquid phases and the underlying mechanism in this cascading system were explored. Free nitrous acid (FNA) was employed to enhance WAS hydrolysis. The results showed that hydrogen generation was effectively accelerated: 0.54 mL per gram sludge (in volatile suspended solids (VSS)) was produced from raw WAS (AD_MEC_RWAS), which increased to 1.27 mL/g VSS from FNA-pretreated WAS (AD_MEC_FWAS). The limited OP release by prefermentation was enhanced via MECs; additionally, it was further promoted by FNA, and the treatment time was also shortened. The maximum OP release efficiency reached 54.6% at 112 h (AD_MEC_FWAS). Additionally, non-apatite and inorganic apatite P may regenerate in MECs due to the localized decrease in pH caused by hydrogen generation. This work may provide a scientific basis to enhance P and hydrogen co-recovery from WAS in forthcoming implementation. Image 1 • H 2 recovery and P release from WAS was achieved in cascading conversion system. • The limited OP release in prefermentation was accelerated via bio-electrolysis. • FNA played a positive effect on H 2 recovery and OP release from WAS. • Underlying mechanism of cascading conversion system for P release was explored. [ABSTRACT FROM AUTHOR]

• A novel upflow microaerobic sludge reactor was constructed. • The removal efficiencies of NH 4 +-N and TN reached 90.53% and 80.77%, respectively. • AOB, NOB, anammox, autotrophic and heterotrophic denitrifiers cooperated in UMSR. • Partial denitrification/anammox was dominant nitrogen conversion pathway. • The small height waterfall was applicable to treat low strength NH 4 +-N wastewater. A novel falling water aeration-external reflux upflow microaerobic sludge reactor (UMSR) was designed to treat wastewater with the low chemical oxygen demand (COD) to total nitrogen (TN) ratio. The result showed the concentration of dissolved oxygen (DO) in the reactor could be accurately controlled by adjusting the reflux ratio of oxygenated water. The higher aeration efficiency in pollutant removal could be obtained by the reoxygenation mode of the small height falling water. At the reflux ratio of 5:1, the ammonium, nitrite and nitrate nitrogen concentrations in the effluent of UMSR were 6.0, 0.4 and 6.1 mg/L on average, respectively. The removal efficiency of ammonium nitrogen and total nitrogen reached 90.53% and 80.77%, respectively with the influent COD/TN as being 1.0. The structure of the microbial community confirmed the existence of partial-denitrification/anaerobic ammonium oxidation (anammox) bacteria, autotrophic and heterotrophic denitrifiers contributed to nitrogen and carbon removal in UMSR. [ABSTRACT FROM AUTHOR]

Graphical Abstract Highlights • First investigated the high COD/NO 3 −-N ratio of indole wastewater in mixed culture. • Through nitrate to observe the denitrification and methanogenesis co-existence. • Nitrate was found to facilitate indole degradation and inhibit methane formation. • The metabolites were identified based on 13C-indole isotope analysis. • A dynamic community analysis was presented to study the microbial structures. Abstract Batch experiments were conducted to investigate the effect of nitrate on indole degradation characteristics and methanogenesis under mixed denitrification and methanogenesis culture for the first time. The degradation characteristics were studied under various nitrate concentrations. Nitrate was found to facilitate indole degradation and inhibit methane formation, and the optimum concentration was 50 mg L−1 (COD/NO 3 −-N = 12). Balance analyses showed that nitrate mainly affected indole-C, which generated a higher degree of indole mineralization under NO 3 −-N treatment than in the control. Furthermore, GC–MS combined with 13C-isotope analyses conclusively identified the intermediate metabolites, which included the hydroxylated compounds oxindole and isatin, and the methylated compound 3-methylindole. The results indicated that oxindole did not accumulate and was quickly reduced when nitrate was added, but 3-methylinole, as a recalcitrant material, accumulated without reduction. High-throughput sequencing technology was used to analyse the dynamic microbial community. Results showed that the denitrifying bacterial genera Acinetobacter , Candidimonas and Longilinea accumulated in denitrification stage and decreased in methanogenesis stage, whereas the fermentation genera Alcaligenes and Thermogutta increased in methanogenesis stage. The genera Methanosphaerula and Methanothrix constituted the dominant archaeal communities. The findings obtained in this work may provide a theoretical basis for treatment with N-heterocyclic compounds under mixed culture. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel up-flow microaerobic granular sludge reactor was constructed. • NH 4 +-N and TN removal averaged 92.35% and 90.41%, respectively, at a low C/N ratio. • Nitrifiers, denitrifiers, and anammox bacteria thrived in the microaerobic system. • An ecological nitrogen conversion model of granule sludge was proposed. Abstract In this study, a novel upflow microaerobic sludge reactor (UMSR) was constructed to conduct anaerobic digestion of municipal wastewater with low carbon and nitrogen ratio (C/N). Oxygen in the UMSR was supplied by falling water and external recirculation. Excellent nitrogen removal performance was obtained in the UMSR for treating wastewater with low C/N ratio at a temperature of 25 °C and a hydraulic retention time of 24 h. Ammonium and total nitrogen removal efficiencies averaged 92.35% and 90.41%, respectively, and sludge granulation occurred during acclimation. The inferred metabolism of nitrogen removal and ecological positions of functional microbe were integrated into a granule model by scanning electron microscopy. Additionally, the analysis of microbial community indicated that aerobic nitrifying bacteria and heterotrophic bacteria survived on the surface of sludge floc and granules while the anaerobic autotrophic, heterotrophic denitrifying, and anaerobic ammonia oxidation bacteria were present in the inner layer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wastepaper-flora slow-release carbon was prepared for in-situ fermentation. • The prepared carbon source had self-adaptability to NO 3 –-N concentration. • A stable layered microbial structure was formed by the prepared carbon source. • The presence of the carbon source limited the growth of polysaccharides in sludge. Using wastepaper as external carbon sources is an optional way to achieve total nitrogen removal faced with low carbon to nitrogen ratio municipal sewage. Most of studies have primarily focused on using cellulose-rich wastes establishing the separate denitrification units to achieve in-situ fermentation, which can cause blockages and prolong the process chain. In response, a novel in-situ fermentation wastepaper-flora slow-release carbon source (IF-WF) was proposed using in the original denitrification unit. IF-WF could be efficiently utilized in situ and the denitrification rate increased with the increase of nitrate nitrogen. The fermentation products were highly available, but internal acidification of IF-WF inhibited fermentation. Moreover, IF-WF limited the growth of polysaccharides in the extracellular polymeric substances of denitrified sludge. IF-WF finally formed the structure dominated by nitrate-reduction bacteria outside and cellulose-degrading bacteria inside. These results provide guidance for understanding the mechanism of IF-WF for in-situ fermentation to promote nitrogen removal. [ABSTRACT FROM AUTHOR]

Zero valent iron (ZVI) is a low-cost, earth-abundant reactive metal, and it has a strong reducing ability with a standard redox potential of − 0.44 V. Therefore, it is an effective and widely used reducing agent for pollutant degradation. Since nanoscale zero valent iron (nZVI) shows a larger specific surface area which leads to the faster reaction rate and higher conversion efficiency, it has been widely used in NO 3 − nitrogen reduction reaction, however, it shows disadvantages of poor chemical stability, narrow applicable pH, and low total nitrogen (TN) removal efficiency. To solve these problems, in this paper, the nZVI nanoparticles were deposited on the g-C 3 N 4 /rGO composite, and its NO 3 − removal efficiency under visible light irradiation was investigated. The effects of nZVI loading, initial pH of solution, catalyst dosage and initial NO 3 − concentration on NO 3 − reduction performance were studied. The results showed that the g-C 3 N 4 /rGO/nZVI material achieved 100% of NO 3 − reduction efficiency in 60 min. And the TN removal efficiency of g-C 3 N 4 /rGO/nZVI was 82.8%, superior to nZVI and g-C 3 N 4 /nZVI (13.3% and 38.2%, respectively). Finally, the denitrification mechanism of g-C 3 N 4 /rGO/nZVI was proposed as follows: Under light irradiation, the photogenerated electrons on g-C 3 N 4 transferred via rGO to the nZVI surface, thus improving the reactivity and stability of nZVI. The photogenerated electrons and active electrons on the surface of nZVI reduced NO 3 − to N 2 , NH 4 +, and other products, while the photogenerated holes further oxidized part of NH 4 + to N 2 and other gaseous products. During this process, the rGO material could inhibit the oxidation of nZVI by the photogenerated holes from g-C 3 N 4. [Display omitted] • g-C 3 N 4 /rGO serves as a support for nZVI to enhance its stability and activity. • The rGO in g-C 3 N 4 /rGO hindered the oxidation of nZVI by photogenerated holes. • The NO 3 − reduction mechanism was explored and the reduction products were analyzed. • NO 3 − was completely removed and the selectivity of gaseous products were 82.8%. [ABSTRACT FROM AUTHOR]

Deposition of bimetals on Z-scheme photocatalysts has been reported to improve the nitrate nitrogen (NO 3 −) reduction properties. However, it is not clear whether bimetal deposition possesses advantage over single metal deposition and what is the different reaction mechanisms. In this work, the g-C 3 N 4 (Pd-Cu)/rGO/TiO 2 and g-C 3 N 4 (Ag)/rGO/TiO 2 composites with bimetallic Pd-Cu and single metal Ag deposited on the graphitic carbon nitride/reduced graphene oxide/titanium dioxide (g-C 3 N 4 /rGO/TiO 2) Z-scheme photocatalyst were prepared, and their photocatalytic NO 3 − reduction properties and the mechanisms under visible light irradiation were studied. The results showed that the NO 3 − and total nitrogen (TN) removal efficiencies of g-C 3 N 4 (Pd-Cu)/rGO/TiO 2 were 57.78% and 20.1%, respectively, 1.15 and 1.72 times higher than those of g-C 3 N 4 (Ag)/rGO/TiO 2. This can be ascribed to that Pd-Cu enriched more electrons and absorbed more NO 3 − molecules due to the different charge densities, and the NO 3 − reduction process were enhanced by the staged NO 3 −→NO 2 − and NO 2 −→N 2 /NH 4 + processes on Cu and Pd. The effects of reductive species were demonstrated to be photogenerated electrons > ·OH (·CO 2 −) > ·O 2 − in g-C 3 N 4 (Ag)/rGO/TiO 2 , while it was photogenerated electrons > ·O 2 − > ·OH (·CO 2 −) in g-C 3 N 4 (Pd-Cu)/rGO/TiO 2 , which may be caused by the better O 2 reduction property of the latter. Finally, the cyclic experiment proved the good stability of both materials. This work provided some reference for design of metal deposited Z-scheme photocatalysts for various reduction reactions. [Display omitted] • The g-C 3 N 4 (Cu-Pd)/rGO/TiO 2 and g-C 3 N 4 (Ag)/rGO/TiO 2 composites were prepared. • The NO 3 − reduction performances and mechanisms were studied and compared. • The reductive species in g-C 3 N 4 (Ag)/rGO/TiO 2 were e– > ·OH (·CO 2 −) > ·O 2 −. • The reductive species in g-C 3 N 4 (Cu-Pd)/rGO/TiO 2 were e– > ·O 2 − > ·OH (·CO 2 −). [ABSTRACT FROM AUTHOR]

Current studies have employed various chemicals for disintegrating and hydrolyzing microbial cells in waste activated sludge (WAS). However, a comprehensive process assessment over the whole anaerobic digestion process has seldom been proposed. Besides, the characterization of microbial community responses to these chemicals is not well understood. In this study, the effects of five typical chemicals: solubilizer (β-cyclodextrin, CD), alkaline (NaOH), peroxide (peracetic-acid, PA), biological (rhamnolipid, RL) and chemical (sodium dodecylsulphate, SDS) surfactants on WAS digestion were examined. Higher efficiencies of WAS solubilization, hydrolysis and acidification were achieved by CD treatment, followed by RL and SDS. Methanogenesis was also strongly chemicals-dependent. Shifts in microbial community structure were observed in all chemical-pretreated WAS. The community in RL, CD and PA was dominated by microorganisms that anaerobically hydrolyze organics to acids, while that in NaOH and SDS was mainly associated to biogas production. This study proved that the overall performance of WAS digestion was substantially depended on the initial chemical pretreatments, which in turn influenced and was related to the microbial community structures. Although the economic advantage might not be clear yet, the findings obtained in this work may provide a scientific basis for the potential implementation of chemicals for WAS treatment. [ABSTRACT FROM AUTHOR]

The investigation into the degradation of alkylphenol pollutants (APs) has become a hotspot due to their harmful effects on the environment and human health. In this study, microbial electrolysis cells (MECs) were used to degrade nonylphenol (NP) and 4- tert -octylphenol (4- tert -OP). The study found that the degradation rates of NP and 4- tert -OP for a 6-day period were 83.6% and 96.3%, respectively, which were 30.53% and 26.7% higher than those of the group without applied voltage. The double layer area in the degradation of 4- tert -OP was larger than that of NP, and the resistance exhibited by 4- tert -OP (87.47 Ω) in MEC was lower than that of NP (99.42 Ω). Meanwhile, NP had a greater effect on the bioenzyme activity than 4- tert -OP. GC-MS analysis showed that the degradation pathways of both pollutants mainly included oxidation and hydroxylation reactions. Furthermore, the microbial community analysis indicated that the main functional bacteria in NP degradation were Citrobacter , Desulfovibrio and Advenella , and those in 4- tert -OP degradation were Stenotrophomonas , Chryseobacterium , Dokdonella , and the key microbiomes underlying the cooperative relationship. The biotoxicity test indicated that the toxicity of residual substances was significantly reduced. Therefore, the MEC system is efficient and environmentally friendly and has broad application prospects in phenol refractory organics. [Display omitted] • Degradation ability of NP/4- tert -OP as the sole carbon source in MECs was first evaluated. • The degradation rate of NP and 4- tert -OP was effectively improved by weak electrical stimulation. • 4- tert -OP showed superior electrochemical performance and low impact on bioenzyme activity. • The main metabolic pathways of NP and 4- tert -OP were oxidation and hydroxylation reactions. • The correlation between aromatic compounds degrading bacteria and exoelectrogens was existed. [ABSTRACT FROM AUTHOR]

The effects of chemosynthetic and biological surfactants on accelerating hydrogen generation from waste activated sludge (WAS) is investigated in a short-cut fermentation-bioelectrochemical system. The specific experiments are conducted in a series of completely stirred tank reactors (CSTRs) and single-chamber microbial electrolysis cells (MECs). Results shows that rhamnolipid (RL) lead to a VFAs yield 1.16-fold and 3.63-fold higher over with sodium dodecylsulphate (SDS) and sodium dodecyl benzene sulfonate (SDBS) treatments in CSTRs on 72 h. By contrast, the corresponding conversion efficiency of methanogenesis is inhibited (0.18 ± 0.03% versus 1.89 ± 0.15% (SDS) and 6.63 ± 0.77% (SDBS)), which is beneficial for subsequent hydrogen production in MECs. The distribution of the acidogenesis metabolites is also affected by the types of surfactants, reflected on cascade changing of hydrogen production. Highest hydrogen yield is 12.90 mg H 2 g −1 VSS in RL-MECs, which is larger than all values that have been reported for fermentation and single-chamber MECs. Current and electrochemical impedance spectroscopy clearly demonstrate the important role of RL treatment in electron/proton transfer and the internal resistance decrease. This study demonstrate the sustainability and attractiveness of WAS short-cut fermentation-elelctrohydrogenesis, providing a sound basis for sludge stabilization and bioenergy recovery. [ABSTRACT FROM AUTHOR]

Excessive acidification and low methane (CH 4) percentage are technical challenges restricting anaerobic digestion (AD) of kitchen waste, especially under high organic loading rate (OLR) conditions. Although the contribution of Fe0 powder to excessive acidification elimination and CH 4 yield improvement in mesophilic AD (MAD) has been extensively reported, its impact on the thermophilic AD (TAD) process with more frequent excessive acidification problem is rarely studied. Moreover, the difference in microbial interactions and metabolic pathways between MAD and TAD reactors under Fe0 regulation was still unclear. In this study, we compared the performance of Fe0 dosing on excessive acidification elimination and biogas upgrading quality in both MAD and TAD reactors at different OLRs. The results showed that compared with excessive acidification or low CH 4 percentage (less than 70%) in control reactors without Fe0 addition, the CH 4 yield of MAD and TAD reactors with addition of Fe0 at OLR of 35 gVS/L were 470.88 mLCH 4 /gVS and 270.40 mLCH 4 /gVS, with higher CH 4 composition of 81.32%–82.23% and 83.68%–88.48% respectively. Microbial diversity analysis showed a sharp distinction between MAD and TAD reactors with addition of Fe0. Analyses of co-occurrence networks and metabolic pathway presented hydrogenotrophic methanogenic pathway, in addition to acetoclastic methanogenesis, was dominant in MAD reactors as results of enhanced interspecies hydrogen transfer between Methanoculleus and some hydrogen producers, especially under high OLR condition. In contrast, syntrophilic acetate oxidization - hydrogenotrophic methanogenesis, which dominated by Methanothermobacter and Alkaliphilus or Pelotomaculum , was the sole methanogenic pathway in TAD reactors. The results will shed lights on the regulation mechanisms of Fe0 in AD of kitchen waste under mesophilic and thermophilic conditions, offering new insight into development of more efficient waste to energy conversion technologies. [Display omitted] • Fe0 in-situ upgraded CH 4 percentage around 85% in both MAD and TAD reactors. • At OLR of 35 gVS/L, CH 4 yields of MAD and TAD reactors were 470.88 and 270.40 mLCH 4 /gVS. • Fe0 played more important role in determining microbial consortia in MAD than TAD. • Methanoculleus and Methanothermobacter produced CH 4 in MAD and TAD respectively. • IHT was key pathway for eliminating acidification in MAD, but it is SAO-HM in TAD. [ABSTRACT FROM AUTHOR]

The effects of three widely-used surfactants on waste activated sludge (WAS) fermentation and microbial community structures were investigated. Rhamnolipid bio-surfactants (RL) showed more positive effects on WAS hydrolysis and acidification compared to chemosynthetic surfactants, such as sodium dodecylsulphate (SDS) and sodium dodecyl benzene sulfonate (SDBS). The highest SCOD and VFAs concentrations obtained with RL were 1.15-fold and 1.16-fold that of SDS, and up to 1.73 and 3.63 times higher than those obtained with SDBS. Pyrosequencing analysis showed that an evident reduction in bacterial diversity in surfactant-treated WAS. Moreover, acid-producing bacteria (such as Megasphaera and Oscillibacter ), detected with RL, were (6.8% and 6.4% in proportion) more abundant than with SDS, and were rarely found in SDBS and the control. The results also revealed that RL allowed efficient hydrolysis enhancement and was favorable to functional microorganisms for further acidification during WAS fermentation. [ABSTRACT FROM AUTHOR]

To improve anaerobic digestibility of waste activated sludge (WAS), a novel treatment was explored by a plant-derived biosurfactant (saponin biosurfactant (SB)). SB showed positive effects on WAS hydrolysis and acidogenesis with increasing concentration, but was insignificant at dosage >0.20 g SB/g total suspended solids (TSS). Soluble protein and carbohydrate concentrations reached 2029 ± 28 and 343 ± 52 mg chemical oxygen demand (COD)/L (0.20 g SB/g TSS, 48 h), which were 4.77-fold and 5.87-fold higher than that without treatment. Volatile fatty acids (VFAs) bioproduction showed a 3.51-fold increase in 72 h. Moreover, acetic acid increased already after 2 h with SB treatment, but after 8 h in the control, indicating that SB accelerated syntrophic acetogenesis from butyric acid degradation to acetic acid. Additionally, methane production was enhanced at lower dosage (<0.05 g SB/g TSS) and inhibited at higher dosage (>0.10 g SB/g TSS), with 63.0 and 20.3 mL/g volatile suspended solids (VSS), respectively, while it was 46.5 mL/g VSS in the control. The results obtained are in good agreement with previous ones obtained with chemosynthetic surfactants. Moreover, SB has advantages of easy production and sustainability of supply, which should promote the implementation for WAS treatment. [ABSTRACT FROM AUTHOR]

Antibiotics in waste activated sludge (WAS) has drawn increasing attention because of their persistent and bioaccumulation characteristics. Most study illustrated the role of antibiotics in anaerobic fermentation from WAS, but lacking the analysis at microbial level as well as the possible interaction between them. This study investigated the effect of three sulfonamide antibiotics (sulfamethoxazole (SMX), sulfaquinoxaline (SQX), and sulfadiazine (SD)) on WAS fermentation and explored its microbiological mechanism. Results indicated that the production of short-chain fatty acids (SCFAs) was significantly improved by 1.9 folds with a peak value at 4626.1 mg COD L−1 in the existence of SD. This was attributed to the promoted release of soluble proteins and polysaccharides with the existence of sulfonamide antibiotics (SAs) as revealed by the excitation-emission matrix (EEM) spectrum. Analysis of microbial community structure showed that the total abundance of the fermenters in groups with SAs was1.2–1.6 times of that in Control. Specifically, the acid-forming genus Tissierella in SMX and SQX increased by 12.1%–15.0% compared with the Control, while the proteolytic genus Proteinivorax dominated in SD with 39.5%. Molecular ecological networks (MENs) analysis further revealed the potential cooperative relationships among different fermenters. This study was anticipated to provide some valuable information for the behavior of antibiotics in WAS fermentation. [Display omitted] • The existence of SMX, SQX and SD facilitated SCFAs production from WAS anaerobic fermentation. • The presence of SMX, SQX and SD enhanced the solubility and biodegradability of proteins and polysaccharides. • The abundance of fermenters was increased in fermentation systems containing SMX, SQX and SD. • The potential cooperative relationships were established among the key microbial community. [ABSTRACT FROM AUTHOR]