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Biological conversion of gaseous compounds (e.g., H 2 /CO 2 ) into valuable liquid fuels or chemicals using mixed culture is a promising technology, which could be effectively and efficiently implemented in a membrane biofilm reactor (MBfR) with gas being supplied from inside of membranes. In this study, a model integrating multiple production pathways of fatty acids (including acetate, butyrate, and caproate) was developed and tested using reported mixed culture experimental data from a lab-scale MBfR fed with 60% H 2 and 40% CO 2 . The uncertainty of the four estimated model parameters was explored by a sensitivity analysis. With the developed model, the impacts of key process parameters (i.e., gas supply and hydraulic retention time (HRT)) on the performance of the MBfR converting H 2 /CO 2 to fatty acids were then investigated. The results show that a high HRT is imperative for chain elongation to produce a higher proportion of caproate with a higher added value. A proper gas supply should be provided to favour the speciation of biological gas conversion products as well as to fully exploit the conversion capacity of the MBfR. The findings of this work provide useful information for a better understanding and further applications of this MBfR technology for mixed culture syngas fermentation. [ABSTRACT FROM AUTHOR]

Mathematical models for nitrous oxide (N 2 O) production by ammonia oxidizing bacteria (AOB) based on a single pathway have been proposed to support the design and operation of wastewater treatment plants (WWTPs). However, the boundary conditions for each of these models have not been established to date. This study tests the predictive ability of two single-pathway models based on the AOB denitrification pathway and the hydroxylamine (NH 2 OH) oxidation pathway, respectively, to describe the N 2 O data generated by a N 2 O model that incorporates both pathways, and provides theoretical guidance on how to use these two single-pathway models as well as the two-pathway model under various conditions. The model based on the AOB denitrification pathway can be used under the condition of a constant dissolved oxygen (DO) concentration, applied either at a low DO concentration (<∼0.5 mg O 2 /L) with any non-inhibitory nitrite (NO 2 − ) concentrations or at higher DO (⩾∼0.5 mg O 2 /L) with relatively high NO 2 − (⩾∼1.0 mg N/L) but non-inhibitory concentrations. The model based on the NH 2 OH oxidation pathway can be applied under the condition of relatively high DO concentrations (⩾∼1.5 mg O 2 /L), being either constant or time-varying, with any non-inhibitory NO 2 − concentrations. Under other conditions, the two-pathway model should be applied. [ABSTRACT FROM AUTHOR]

Abstract: In this study, an integrated dynamic model was developed through combining a mechanistic model, a neural network (NN) model and a genetic algorithm approach, in order to simulate the performance of a full-scale municipal wastewater treatment plant (WWTP) with substantial influent fluctuations. As the base of the integrated model, the mechanistic model was initially established based on the activated sludge model 3 and the EAWAG bio-P module, and was used to generate the residuals for the NN model. The NN model was employed to build the relationship between the input and output variables. The network weights of the NN model were optimized with a genetic algorithm approach. The resulting integrated model was applied to simulate the 5-month performance of a full-scale WWTP with significant influent fluctuations, and the simulation results matched the measured ones of the WWTP well even under influent disturbance conditions. Compared with the individual mechanistic model and NN model, the integrated model was able to capture sufficient residual information to compensate for the inaccuracy of the mechanistic model and improve the extrapolative capability of the NN model. This model established in our work is demonstrated to be an effective and useful tool to simulate the performance of WWTPs. [Copyright &y& Elsevier]

Abstract: In this work, an extension of the Activated Sludge Model No. 3 (ASM3) is presented which takes oxygen transfer, microbial maintenance, and biomass decay into account, in order to describe the heterotrophic storage and growth processes in activated sludge. The sensitivity of the effluent chemical oxygen demand and oxygen uptake rate to the stoichiometric and kinetic coefficients was analyzed. Model calibration was successfully performed by comparing measured and predicted values for model components. Thereafter, the model was evaluated with the experimental results of four independent case studies. Results show that the established model is able to better and mechanistically describe the heterotrophic storage and growth processes in activated sludge. [Copyright &y& Elsevier]

The dissolved oxygen (DO) concentration is known to be one of the most important factors affecting nitrous oxide (N 2 O) production, which might weaken the advantages of nitrogen removal in completely autotrophic nitrogen removal biofilm process. In this work, a mathematical model is applied to study the N 2 O production in a biofilm reactor performing nitritation followed by anaerobic ammonium oxidation (Anammox) for nitrogen removal. The nitrifier denitrification pathway through utilization of nitrite as the terminal electron acceptor under oxygen limiting conditions is used to predict N 2 O production. Simulations explicitly show that a large number of N 2 O is produced under conditions of low DO concentration for high nitrogen removal. A low ammonium concentration (<50 mg N L −1 ) and a suitable DO level (at around 0.5 mg O 2 L −1 ) could lead to high total nitrogen (TN) removal with a low N 2 O production. Biofilm has to be controlled to be in the optimal thickness (1000 μm under the simulating conditions of this study), which allows relatively high TN removal, avoiding higher thickness that favors N 2 O production. [ABSTRACT FROM AUTHOR]

This work provided a novel anaerobic fermentation paradigm of inoculating yeast to internally generate ethanol from FW as ED for subsequent MCFAs production. [Display omitted] • High MCFAs production from FW was achieved with self-produced ethanol instead of external electron donor. • Ethanol was on-site generated from FW by the inoculation of yeast. • A coordinated metabolic route related to MCFAs production from FW was established. • This novel biotechnology does not require major changes to existing anaerobic fermentation infrastructure but reduce the cost. As food waste (FW) is a largely available and carbon-rich feedstock, bulk production of medium-chain fatty acids (MCFAs) via chain elongation (CE) from FW is of great interest to biotechnology. However, the development of this emerging biotechnology is limited by the high cost from external electron donor (ED) input. To solve this bottleneck, replacing external ED input with self-produced ED in the system is a key. Therefore, this study provided a novel anaerobic fermentation paradigm of inoculating yeast to internally generate ethanol from FW as ED for subsequent MCFAs production. Batch experimental results demonstrated that cumulative 1540 mg COD/L of MCFAs was produced from FW with endogenous ethanol when inoculating 4.50 × 107 cells/ml-FW Saccharomyces cerevisiae in the fermenter over 20 days. In contrast, only a very small amount of MCFAs were detected in the control (58.98 mg COD/L). In continuous operation over 61 days, around 1300 mg COD/L of MCFAs was steadily obtained in the long-term fermenter with yeast assisted, which was almost 1.49 times higher than that from the control. The enriching S. cerevisiae responsible for on-site ethanol generation and chain-elongating bacteria including Caproiciproducens and Oscillibacter jointly promoted FW-derived MCFAs productions. Higher abundance of genes encoding substrate degradation, ethanol biosynthesis and CE further ensured the higher MCFAs production in the yeast-assisted system. This biotechnology does not require major changes to the design and operation of existing anaerobic fermentation infrastructure. Instead, the utilization of FW was enlarged through producing high-value MCFAs while waiving the cost of external ED by using inexpensive cheap yeast. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multiple mediators function as electron shuttles to promote anammox process; • The EET capability of anammox bacteria can be facilitated by external mediators; • The concurrent presence of mediators triggered the activation of essential enzymes; • The application perspective should focus on the EET-enhanced anammox optimization. The anaerobic ammonium oxidation (anammox) process, transforming ammonia into nitrogen gas in oxygen-free environments using nitrite as an electron acceptor, is increasingly recognized for its potential in treating ammonium-rich wastewater. A major challenge for widespread application of this technology is the limited presence of nitrite in most wastewaters. The intrinsic electroactivity of anammox bacteria implies that the introduction of exogenous additives through the extracellular electron transfer (EET) process could effectively stimulate ammonia oxidation even in the absence of nitrite. This comprehensive review consolidates various approaches to enhance EET-dependent anammox, including the utilization of carbonaceous materials, metal ions, and humic substances. Molecular mechanisms involved in enhancing nitrogen removal performance based on extracellular electron transfer capacity are expounded. The co-occurrence of electron acceptors and exogenous electron shuttles is proposed to increase the activity of c-type cytochromes (c -Cyts) and N-acyl-homoserine lactones (AHLs) in extracellular polymeric substances (EPS), as well as enzymes such as hydrazine synthase (HZS) and hydrazine dehydrogenase (HDH), leading to stable a nitrogen removal performance. This review presents novel insights into the engineering of the EET-enhanced anammox process, providing a theoretical framework for its advancement and optimization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low concentrations (less than 5 mM) of EDTA improved nitrate removal rate. • High concentrations of EDTA hindered TN removal, leading to N 2 O accumulation. • EDTA increased the redox potential of pyrite, resulting in the improvement of pyrite oxidation. • Ferric iron as product of denitrification could facilitate the conversion of solid pyrite into S0. • Fe(II)/Fe(III) cycle was a critical biological process driving the bioleaching of pyrite. Pyrite autotrophic denitrification (PAD) is crucial for removing nitrate in groundwater and advanced wastewater treatment. While disulfide is typically seen as the electron donor, the role of iron in pyrite oxidation is often ignored. In this study, Ethylene Diamine Tetraacetic Acid (EDTA) had been proven to have the potential to facilitate pyrite oxidation by promoting the solubility of iron in solution, thereby enhancing the kinetics of pyrite autotrophic denitrification. Firstly, EDTA could improve PAD performance, i.e. the nitrate removal rate at EDTA addition of 5 mM was 0.69 mg N/L•h and twice that of the control. However, high concentrations of EDTA inhibited the activity of the nitrous oxide reductase, resulting in the maximum accumulation of N 2 O reaching 13.26 mg N/L with an EDTA concentration of 15 mM. Furthermore, the X-ray Photoelectron Spectroscopy (XPS) result indicated that the EDTA addition promoted the production of bioavailable sulfur, with the concentration of S0 at 15 mM EDTA being more than twice higher than that of the control. Transmission electron microscopy (TEM) analysis indicated that EDTA could relieve the damage of iron encrustation on cell activity because it was difficult for EDTA-chelated ferrous iron to penetrate the cell membrane. Microbial community analyses showed an increase abundance of iron oxidizing bacteria, suggesting that EDTA addition promoted the bioavailability of iron for Fe(II) autotrophic denitrification. Overall, this study will provide insights into the understanding of oxidation mechanism of PAD process and the practical application for efficient nitrogen removal and N 2 O mitigation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The modification of biochar enhances its ability to remove ECs. • Characteristics and evaluation of different modification methods. • ECs adsorbed by modified biochar based on several adsorption mechanisms. • Modified biochar acts as catalyzer to induce the degradation of ECs. • Establishing a unified evaluation standard is the goal for the future. The increasing concern over emerging contaminants (ECs) in aqueous solutions is driven by their potential risks to public health. Handling ECs becomes an urgent mission in the world. Biochar has been applied for ECs removal in wastewater for its low cost and satisfactory efficiency, while its practical applications are hindered by the limited adsorption capacity. To improve the removal efficiency of biochar on ECs, diverse techniques (acid-base modification, metal compound modification, steam activation, magnetization, heteroatom doping, and ball milling) have been applied to modify biochar and imbue it with a range of physicochemical attributes. This leads to unique adsorption outcomes, behaviors, and mechanisms. Herein, effective modification methods, effects and mechanisms of modified biochar on the removal of typical ECs including per- and polyfluoroalkyl substances (PFASs), antibiotics and antibiotic resistance genes (ARGs), micro(nano)plastics, and endocrine disrupting compounds (EDCs) in aqueous solution have been systematically discussed. Modified biochar has upgraded removal performance towards ECs, and the removal mechanisms generally follow two pathways: adsorption and catalytic degradation. Future efforts should focus on establishing standardized evaluation criteria for cost, effectiveness, and environmental risk, and leverage artificial intelligence to broaden the applications of modified biochar in ECs removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Various nitrogen removal pathways are exhibited by different species of GAOs. • The denitrification capacity of GAOs enables their potential synergy with anammox. • EPD offers a dependable and effective alternative for a nitrite supply. • EPDA process extends anammox-based application combined with PN and DPR processes. • Control strategies and functional microbial interaction mechanisms are imperative. The recently proposed glycogen accumulating organisms (GAOs)-driven anammox process, which terminates nitrate (NO 3 –) reduction to nitrite (NO 2 –) without external carbon source addition, has emerged as a promising alternative for supplying NO 2 – to anammox bacteria. The endogenous partial denitrification anammox (EPDA) process demonstrates superior nitrogen elimination efficiency, cost-effectiveness, and operational stability in low C/N wastewater treatment, concurrently mitigating greenhouse gas releases. This comprehensive review presents and discusses an in-depth analysis of the notable progress in EPDA, covering the physiology and biochemistry of diverse GAO-lineages under specified conditions, intricate microbial interactions and metabolic pathways shared between GAOs and anammox bacteria, and appropriate process modifications. Strategies for sludge morphology, carbon content, and spatial distribution of functional bacteria are discussed in detail to regulate the metabolic activity of EPDA. Future research needs to focus on balancing the competitiveness between functional consortia such as GAOs, phosphorus accumulating organisms (PAOs) and anammox bacteria in the synergetic system, and countermeasures to deal with the effects of adverse conditions on nutrient removal performance of the EPDA-based processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • US-enhanced PAA pretreatment remarkably improved SCFAs yields from WAS. • US-enhanced PAA oxidation accelerated sludge disruption and organic matter release. • US-enhanced PAA pretreatment altered protein secondary structure. • 1O 2 was the dominant reactive species during US-enhanced PAA oxidation. • Acidogenic microorganisms were enriched by US-enhanced PAA pretreatment. This study proposed a new technology, i.e. , ultrasound (US)-enhanced peracetic acid (PAA) pretreatment, to enhance resource recovery from anaerobic sludge fermentation. Results show that the optimum operation condition was achieved with US-enhanced 10 mg PAA/g TSS (total suspended solids), leading to a remarkable 31.72-fold increase in short-chain fatty acids (SCFAs) production compared to the control group (with PAA contribution in SCFAs deducted). Mechanism explorations prove that US-enhanced PAA pretreatment significantly promoted sludge disruption and organic matter release, creating a substantial amount of soluble substances (i.e. , tyrosine-like and tryptophan-like substances) for subsequent fermentation. Fourier transform infrared (FTIR) analysis indicates that US-enhanced PAA pretreatment induced alterations in the protein secondary structure and facilitated its transformation. Quenching experiments imply that the contribution of reactive species during sludge oxidation followed the order: 1O 2 > OH > CH 3 C(O)O /CH 3 C(O)OO. These reactive species played essential roles in the inherent mechanisms responsible for sludge disintegration and organic conversion. On the other hand, the analysis of key enzyme activities reveals a severe inhibition of the enzymes associated with SCFAs consumption. Further microbial community investigation confirms the enrichment of acidogenic microorganisms, such as Clostridium_sensu_stricto_10 sp. , norank_f__norank_o__Bacteroidales sp. , etc. Overall, US-enhanced PAA pretreatment can facilitate energy recovery and enhance the efficiency of anaerobic fermentation, offering significant benefits in sustainable sludge management. [ABSTRACT FROM AUTHOR]

[Display omitted] • The study firstly reviews MCFAs production from sewage sludge fermentation. • MCFAs synthesis can be suppressed by competitive metabolisms and sludge hydrolysis. • Competition and cooperation among microbes co-exist in sludge CE system. • Pretreatments and semi-/conductive materials are the main reinforcement strategies. • Pretreatments are efficient to impede byproducts formation and avoid BES dosing. Huge sludge volumes and increased energy demands are the main challenges faced by wastewater treatment plants (WWTPs) currently, while it stimulates organics transformation and carbon recovery from sludge treatment process. Due to higher energy density and greater hydrophobicity, medium-chain fatty acids (MCFAs) exhibit easier extraction and more widespread application than traditional short-chain fatty acids (SCFAs). Therefore, MCFAs synthesis from sewage sludge via chain elongation (CE) has recently attracted growing attention in anaerobic open culture fermentation. Nevertheless, a comprehensive and systematic review focused on MCFAs synthesis from sludge is not available so far. This study provides a critical review on sewage sludge-derived MCFAs synthesis. The metabolic pathways, potential influencing factors, and cooperative and competitive relationships among various microorganisms are first elucidated to understand the mechanisms, limitations, and microbial interactions involved in MCFAs production via open culture fermentation of sludge. Unfortunately, MCFAs synthesis from sewage sludge is mainly hampered by low organics accessibility, inferior electron transfer efficiency and presence of competitive microbes. To foster sludge degradation and high-value MCFAs production, various techniques based on pretreatment and facilitation of electron transfer have recently been proposed, which are comprehensively reviewed with the corresponding mechanisms meticulously discussed. Ultimately, knowledge gaps and new opportunities for sludge-derived MCFAs production are prospected. This review will offer theoretical and technological guidelines for the subsequent investigations and future engineering applications of MCFAs production from sewage sludge. [ABSTRACT FROM AUTHOR]

[Display omitted] • Impacts of NH 2 OH and N 2 H 4 on the SDAD process were studied. • NH 2 OH and N 2 H 4 showed different potential for NO 2 − and N 2 O accumulation. • NIR/N 2 OR were sensitive to NH 2 OH inhibition, while N 2 H 4 primarily suppressed N 2 OR. Hydroxylamine (NH 2 OH) and hydrazine (N 2 H 4) are crucial intermediates in biological nitrogen removal processes, but their potential effects on the nitrogen-related metabolic pathway during the sulfur-driven autotrophic denitrification (SDAD) process remain unclear and were thus explored in this work. The results of dedicated batch tests indicated that the accumulation ratio of NO 2 − was positively correlated with the NH 2 OH concentration, reaching 86.2 ± 2.6% at the NH 2 OH concentration of 2.0 mg-N/L, while it was barely affected by the N 2 H 4 concentration. Furthermore, the joint inhibition of NH 2 OH and free nitrous acid led to the substantial accumulation of N 2 O (up to 32.9 ± 1.3%) during the NO 2 − reduction phase. In contrast, N 2 H 4 exhibited great potential for facilitating N 2 O accumulation in both the NO 3 − reduction and NO 2 − reduction phases with an accumulation ratio of 13.0 ± 0.3% and 27.5 ± 1.5%, respectively, at the N 2 H 4 concentration of 2.0 mg-N/L. Total enzyme activity analyses revealed that the presence of NH 2 OH inhibited the activity expression of all denitrifying enzymes, with the downstream enzymes (such as NO 2 − reductase and N 2 O reductase) being more susceptible to NH 2 OH. The addition of N 2 H 4 did not cause a significant decrease in the activity of NO 3 − reductase and NO 2 − reductase, but notably curbed the activity of N 2 O reductase. Based on the responses of the SDAD-related nitrogen metabolic pathway to NH 2 OH/N 2 H 4 , this work provided effective technical means for i) the promotion of NO 2 − accumulation which might enable the coupling of SDAD with Anammox and ii) the efficient recovery of N 2 O via the SDAD process. [ABSTRACT FROM AUTHOR]

[Display omitted] • CaO 2 mediated microalgal-bacterial consortium (MBC) system was first proposed. • CaO 2 enhanced SCFAs production from anaerobic fermentation for MBC system. • CaO 2 effectively promoted the breakdown of MBC sludge cells for organics releasing. • Phosphorus and COD removal of MBC system were promoted. Microalgal-bacterial consortium (MBC) is an effective way to meet increasingly stringent standards in wastewater treatment, with advantages in nutrient removal, resource recovery, and energy conservation. The efficient and stable operation of the MBC sewage treatment system is generally limited by the insufficient and unstable carbon source in the influent. In this study, a calcium peroxide-mediated anaerobic fermenter was configured to transfer the MBC sludge into the preferred carbon source, short-chain fatty acids (SCFAs) in-situ, to alleviate the limitations. Experimental results showed that after 4-day 0.15 g/g VS calcium peroxide mediated anaerobic fermentation, the production of SCFAs and the proportion of acetic acid reached 514.8 mg COD/g VS and 59 %, respectively. Scanning electron microscopy, COD mass balance analysis, and lactate dehydrogenase assays jointly showed that calcium peroxide effectively promoted the breakdown of MBC sludge cells, which led to the release of large amounts of organic matter and could be attributed to the released OH–, ·OH and ·O 2 – from calcium peroxide, thereby providing more bioavailable substrates for SCFAs production. Microbial community analysis indicated that the anaerobes associated with hydrolysis and degradation of refractory organic matters were enriched in the mediated fermenter and had positive correlation with SCFAs production. Using such fermentation liquid as an additional carbon source for influent sewage, the MBC process performance was significantly promoted, with phosphorus and COD removal and sludge settleability reaching 84.7 %, 96.1 %, and 33 %, respectively. Configuring calcium peroxide-mediated anaerobic fermentation may thus become a sustainable strategy to strengthen the MBC sewage treatment system, thus providing new ideas for wastewater treatment to reduce inputs and improve performance. [ABSTRACT FROM AUTHOR]

• Photocatalytic conversion of biomass to biofuels is firstly and comprehensively reviewed. • Long-chain hydrocarbons can be produced from photocatalytic C-C coupling of biomass-derived compounds. • Photocatalytic decarboxylation reactions are concluded for the generation of diesel-like biofuels. • Photocatalytic (trans)esterification processes are reviewed for the production of biodiesels. • Photocatalytic conversion of biomass to produce syngas or H 2 energy is reviewed. Biofuels derived from abundant biomass are promising alternatives to fossil fuels, which are considered to be green, renewable, and sustainable. Great efforts have been made to explore efficient strategies for converting biomass to biofuels. Although thermal catalytic methods are frequently studied, but the harsh reaction conditions and high energy consumption limit their applications. Alternatively, the solar energy-driven photocatalytic approaches are considered as mild, eco-friendly and energy-saving processes, and recent achievements in the photocatalytic biomass-to-biofuels conversion significantly improve the sustainable development of biofuels. Lignocellulosic biomass and non-edible oil are seen as promising source of materials for future biofuels. In this review, photocatalytic processes for producing liquid biofuels from diverse biomass are systematically concluded, including the C-C coupling of biomass-derived platform compounds to produce diesel-like biofuels, decarboxylation reactions to produce diesel-like biofuels, and (trans)esterification of crude bio-oil to produce biodiesels. Moreover, photocatalytic conversion of biomass to produce gas biofuels is also discussed including the production of hydrogen, carbon monoxide, and syngas. The advances in photocatalysts are emphasized, and efficient photocatalysts for specific reactions and the factors influencing the catalytic performance are outlined. Moreover, perspectives for the photo-reforming of biomass to biofuels are proposed to guide further development of biofuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrodynamics affect vivianite precipitation and agglomeration processes. • Stirring improved crystal growth over aeration by offering homogeneous mixing. • Higher shear rates in stirring systems yield larger crystals and improved settling. • Particle Imaging Velocimetry characterizes vivianite crystals in turbulent flows. • Hydrodynamic-vivianite correlations inform phosphorus recovery optimization. Hydrodynamic conditions have an essential influence on the precipitation and agglomeration processes of crystals. However, the influence of hydrodynamics under different operating conditions on vivianite crystallization is commonly ignored in the phosphorus recovery process. To this purpose, the effects of hydrodynamics on vivianite properties in stirring and aeration systems were investigated with the aid of particle image velocimetry (PIV). Hydrodynamic parameters of shear rate (G), flow velocity, Kolmogorov microscale (η), turbulent dissipation rate (ε), and turbulent kinetic energy (k) were calculated, and the generated vivianite properties were recorded. The analysis of flow field distribution showed that the mixing state under the stirring system was more homogeneous and formed a smaller hydraulic dead zone, which may be more favorable for the formation and growth of crystals. Compared with the aeration system at the same G , the stirring system has higher hydrodynamic parameters, producing stronger turbulent intensity and higher shear rate. The higher recovery efficiency, as well as larger crystal size in the stirring system, demonstrated that higher shear rates (95–309 s−1) increased the crystallization rate, ultimately improving the crystal size and settling performance. Significant relationships between hydrodynamic parameters and the harvested crystal size showed that the flow velocity, η , ε , and k were suitable hydrodynamic parameters for evaluating the growth of vivianite. This work is expected to provide the theoretical basis and technical support for the design and operation of vivianite recovery reactors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Food waste-derived MCFAs was synthesised predominantly at pH 5. • Chain elongators were enriched maximally at pH 5. • Chain elongation pathways were improved at pH 5. • Restricted EEO limited the ethanol loss during MCFAs production. Using food waste (FW) as a sustainable feedstock for the production of valuable medium-chain fatty acids (MCFAs) would alleviate greenhouse gas emissions while allowing the efficient recovery of carbon contained in this biowaste. The fermentation pH is a crucial factor controlling the type and yields of the MCFAs derived from FW-fed fermentation by steering the biological reactions involved. However, the mechanism shifts that occur at varying pH values are not well understood. Therefore, this study assessed the potential role of fermentation pH (i.e., 5, 7, and 10) on the carbon recovery from FW as MCFAs and the associated mechanisms. Predominantly MCFAs (5.52 g COD/L) were synthesized at pH 5 with caproate formed as the main high-value product. Abundant but a bit fewer MCFAs (1.08 g COD/L) were yielded at pH 7, in which caproate also was the prevalent MCFAs. However, no obvious MCFAs were synthesized under pH 10. The pH also drove the change of key microbial communities that served as chain elongators, which were maximally enriched at pH 5 but were scarce at pH 10. More importantly, mildly acidic pH (i.e., 5) drove less ethanol oxidization, ensuring the effective usage of electron donor for higher MCFAs yield. This study revealed how pH steers the metabolic pathways of MCFAs production from FW in open-culture anaerobic fermentation from a metagenomic viewpoint. [ABSTRACT FROM AUTHOR]

[Display omitted] • The recyclable composite of CoFe-LDH with NF for PMS activation. • Complete MMH removal can be achieved with TOC removal efficiency of 80%. • 1O 2 species and electron transfer pathways were dominant for MMH decomposition. • DFT and XPS analysis elucidated momentous active species of Co and Ni in catalysis. • The sustainability of Co/Fe-LDH/NF was verified in terms of stability, reusability and metal leaching. The growing application of rocket propellants (e.g., monomethylhydrazine (MMH)) leads to awful water pollution, and thus it is urgent to develop efficient remediation methods to remove it from wastewater. Although persulfate-based catalytic technologies are promising for refractory organic compounds decomposition, the undesired aggregations, high cost and troublesome separation of powder catalysts still limit their wide-applications. To address these issues, we prepared Co-Fe layered double hydroxides (CoFe-LDH)/Ni foam (NF) composite as a recyclable peroxymonosulfate (PMS) activator to decontaminate MMH with high robustness to the high-strength co-existing pollutants within a wide pH range. The interfacial synergism between CoFe-LDH and NF could promote the charge transfer in the catalysis. DFT and XPS analysis elucidated the introduction of Ni and Co greatly facilitate charge transfer from LDH/NF to PMS. This work offers profound insights propellant-containing wastewater via non-radical (1O 2 and electron transfer) pathway in the presence of PMS with reclamation of cost-effective heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Calcium peroxide affected hydrogen production in fermentation system. • Calcium peroxide facilitated solubilization and release of biodegradable organics. • Calcium peroxide inhibited methanogenesis process. • Contributions of ingredients were in the order of alkali > O 2 − > OH. Abstract Calcium peroxide (CaO 2), one of versatile and harmless inorganic peroxy compounds, has been recently used as a highly effective oxidant to degrade pollutants in sludge and a method to achieve sludge resource utilization. However, its impact on hydrogen production has never been studied before. This investigation therefore aims to fill this knowledge gap. Results indicated that with CaO 2 increased from 0.05 to 0.25 g/g VSS (volatile suspended solids), the maximum hydrogen yield increased from 0.77 to 10.55 mL/g VSS. The mechanism studies revealed that CaO 2 accelerated the breakage and death of sludge cells. Excitation emission matrix (EEM) analyses further indicated that CaO 2 increased the biodegradability of the released substances, which could provide more biodegradable organics for the following reactions. Although CaO 2 caused inhibitions to some extents to all the tested microbes, its inhibition to hydrogen consumers was much severer than that to hydrolytic microbes and hydrogen producers. The enzyme analyses also demonstrated that the suppression of calcium peroxide to the activities of enzymes related to hydrogen consumption process was much severer than that to the activities of the activities of enzymes related to hydrogen production process. Further investigations exhibited that alkali, O 2 − and OH radicals, were the major intermediate products of CaO 2 decomposition. All of them were verified to contribute the increased hydrogen production, and their contributions were in the order of alkali > O 2 − > OH. This is the first work demonstrating that CaO 2 can enhance hydrogen production from WAS. The findings reported in our paper not only expand the application field of CaO 2 but also deepen the understanding of the CaO 2 -involved sludge fermentation process. [ABSTRACT FROM AUTHOR]

This study proposed a novel zero valent iron (ZVI) technology to enhance anaerobic methane production from primary sludge in the anaerobic digester and to improve the dewaterability of digested sludge for the first time. Compared to the control test without ZVI, the anaerobic digester with ZVI at all levels (1, 4 and 20 g/L) played a driving role in anaerobic methane production from primary sludge. The maximal biochemical methane production of 439 ± 5 L CH 4 /kg VS was achieved at ZVI of 4 g/L, while only 345 ± 2 L CH 4 /kg VS (volatile solids) was produced in the case of no-ZVI dosage, representing a relative increase of 26.9 ± 0.1%. It was also found that ZVI addition would produce an anaerobically digested sludge with a better dewaterability, as indicated by the decrease of the normalized capillary suction time from 100 to 63 ∼ 89 s, respectively. Model based analysis revealed that the enhanced methane production from primary sludge was due to an increase in both hydrolysis rate and biochemical methane potential of primary sludge. Economic analysis demonstrated that ZVI technology was economically favorable. [ABSTRACT FROM AUTHOR]

[Display omitted] • Manganese ore addition significantly increased PAHs removal in CW. • Microbial degradation was the dominant removal mechanism to remove PAHs in CW. • Manganese ore enhanced electron transfer capacity in CW by altered EPS and Mn cycle. • Manganese ore changed microbial community and microbial metabolic expression in CW. • Root length and microbial diversity were two driven factors affecting PAHs removal. Substrates are vital to efficiently remove polycyclic aromatic hydrocarbons (PAHs) in constructed wetlands (CW). However, the critical role of the substrate in the system is still not fully understood due to the unclear PAHs removal mechanism and particularly the main driving factor affecting PAHs removal. In this study, four vertical-flow CWs with different typical substrate types (A: quartz sand, B: quartz sand + granular activated carbon, C: quartz sand + ceramsite, and D: quartz sand + manganese ore) were established to investigate the treatment performance and mechanism of CW systems. Satisfactory and stabilized PAHs removal was achieved in CW-D during the operation period of 120 days, which significantly increased the removal of PAHs by 23.80%–31.18% compared with control group. Microbial degradation was revealed to dominate PAHs removal in CWs, and the enhanced proportion of microbial degradation (21.12%-35.43%) in CW-D led to the higher PAHs removal compared with other CWs. Further analysis showed that altered extracellular polymeric substances and Mn cycle improved the electron transfer capacity, and strengthened the interaction between plants and microorganisms in CW-D. Microbial analysis showed that the abundance of key PAH-degrading microorganisms and microbial metabolic gene expression were enhanced in CW-D, which supported the increased microbial degradation of PAHs. Additionally, root length and microbial diversity were two driving factors affecting PAHs removal rather than specific surface area based on the structural equation modeling analysis. This study provides comprehensive insights into the key role of suitable substrates for PAHs removal as well as the related mechanism and driving factors of PAHs removal in CWs. [ABSTRACT FROM AUTHOR]

• Amorphous Fe-doped NiB outperforms crystalline and undoped counterparts for UOR. • Urine electrolyzer attained 46 times higher H 2 yield than the water electrolyzer. • Crystallinity-dependent structure self-reconstruction process during UOR. • Fe regulates catalyst's electronic structure and forms bimetallic sites for UOR. Designing transition metal-based catalysts for efficient urea oxidation reaction (UOR) is important for realizing energy-saving hydrogen production via urea-rich (waste)water electrolysis. Herein, we have developed an iron-doped amorphous nickel boride electrocatalyst (aFe-NiB) for UOR. Compared with the undoped and crystalline counterparts, aFe-NiB exhibits a higher activity and the benchmark current density of 10 mA cm−2 can be attained at 1.298 V vs. reversible hydrogen electrode (RHE). Coupled with an efficient hydrogen evolution catalyst, the aFe-NiB-assisted urine electrolyzer can attain a 46 times higher H 2 production rate than the water electrolyzer at 1.50 V. Further study reveals a crystallinity-dependent structure self-reconstruction process during UOR. aFe-NiB attains complete phase evolution from boride to electroactive Fe-doped NiOOH. In addition, density functional theory calculations imply that Fe dopants can improve intrinsic catalytic activity via electronic structure regulation of the self-evolved NiOOH and forming heterogeneous bimetallic active sites for UOR. This study provides meaningful insights into the crystallinity-dependent UOR performance and effective strategies to develop efficient UOR (pre)catalysts with dual active sites. Significantly, the demonstrated direct wastewater (urine) electrolysis paves the way for net zero buildings -targeted human waste reutilization. [ABSTRACT FROM AUTHOR]

Perchlorate (ClO 4 − ) is recognized as an important contaminant in surface water and groundwater, which would pose health risks at very low concentrations. A methane-based membrane biofilm reactor (MBfR) has been successfully demonstrated for perchlorate reduction, which provided an alternative solution for perchlorate remediation with low cost. In this work, a multispecies biofilm model was developed to evaluate perchlorate reduction in the methane-based MBfR under different operational conditions. The model was calibrated and validated using the experimental data from the long-term operation of the MBfR at seven distinct stages. The results suggested that the developed model could satisfactorily describe perchlorate reduction and denitrification performances in the MBfR (R 2 > 0.9). The modeling results provided insight into the microbial community distribution in the biofilm, with aerobic methanotrophs and perchlorate reduction bacteria being mainly located at the membrane side (∼60%) and heterotrophic bacteria being situated near the liquid side (∼50%). The model simulations indicated that over 80% of perchlorate removal efficiency could be achieved through controlling the optimal combinations of methane pressure (P CH4 ) and perchlorate loading (L ClO4 ) (e.g., applying a P CH4 of 30 kPa at a L ClO4 of 0.08 g Cl/m 2 /d). In addition, the perchlorate reduction would be inhibited by the presence of nitrate and nitrite in the MBfR, which should be appropriately controlled during the future practical application of the promising process. [ABSTRACT FROM AUTHOR]

The mainstream anaerobic ammonium oxidation (anammox) has attracted extensive attention recently, particularly due to its potential of transforming current wastewater treatment plants from energy consuming to energy neutral or positive. However, the presence of biodegradable chemical oxygen demanding (COD, 20–80 mg COD L −1 ) in the mainstream anammox reactor stimulates the growth of heterotrophic bacteria, which would compete for oxygen with ammonia-oxidizing bacteria (AOB) and for nitrite with anammox bacteria, thus interfering with the autotrophic nitrogen removal process. In the present work, with consideration of granule size distribution, a one-dimensional model describing the mainstream simultaneous partial nitrification, anammox and denitrification (SNAD) in a granule-based reactor was established, calibrated and validated, based on the long-term experimental results. Through applying the verified model, simulation studies were conducted and the results showed that the effluent total nitrogen concentration of <5 mg N L −1 could be achieved at C/N ratio of 0.2–0.6, DO concentration of 0.2–0.4 mg L −1 and granule radius of 300–600 μm. The combined effects indicated that the SNAD process with TN removal efficiency >90% was obtained at C/N ratio and DO concentration of 0.2–1.0 and 0.2–0.4 mg O 2 L −1 respectively. Finally, the various granule size distribution patterns were simulated, which confirmed that the size distribution needed to be incorporated in the model to accurately describe the granular anammox system, considering a model based on a uniform granule size does not reflect the real situations. These results provide guides to optimize the operation of mainstream granular autotrophic nitrogen removal process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A SNAD model aimed to recover N 2 O from Fe(II)EDTA-NO was developed and evaluated. • Impacts of key operational conditions on N 2 O recovery were studied. • S/N mass ratio of ∼ 1.0 and high gas/liquid volumetric ratios favoured N 2 O recovery. • N 2 O recovery efficiency of up to 80.2%−84.9% was reached within 3.1 h–3.5 h. Instead of the conventional perception of nitrous oxide (N 2 O) as a potent greenhouse gas whose production should be minimized, this work aimed to assess N 2 O recovery as a potential energy source from nitric oxide (NO) in the form of Fe(II)EDTA-NO through element sulfur (S0) or thiosulfate (S 2 O 3 2−)-driven NO-based autotrophic denitrification (SNAD S0 or SNAD S2O3). A mathematical model was proposed to describe substrate dynamics related to N 2 O production and reduction and was successfully calibrated and validated using batch experimental data from lab-scale SNAD S0 and SNAD S2O3 systems under different substrates conditions. The model was subsequently employed to assess the potential of N 2 O accumulation and recovery by altering the S/N mass ratio and the ratio of gas volume to liquid volume of the system. The simulation results suggested that with a S/N mass ratio of nearly 1.0, high-purity N 2 O could be more rapidly and efficiently recovered from Fe(II)EDTA-NO in the SNAD S0 and SNAD S2O3 systems with a higher ratio of gas volume to liquid volume (i.e., a N 2 O recovery efficiency of up to 80.2%−84.9% reached within 3.1 h−3.5 h under the studied conditions). Comparatively, the SNAD S0 process showed an economic and viable advantage for practical applications to the efficient treatment and resource utilization of NO-containing flue gas. [ABSTRACT FROM AUTHOR]

A biofilm model was developed to evaluate the key mechanisms including microbially-mediated ClO 4 − , NO 3 − , and SO 4 2− reduction in the H 2 -based membrane biofilm reactor (MBfR). Sensitivity analysis indicated that the maximum growth rate of H 2 -based denitrification ( μ 1 ) and maximum growth rate of H 2 -based SO 4 2− reduction ( μ 3 ) could be reliably estimated by fitting the model predictions to the experimental measurements. The model was first calibrated using the experimental data of a single-stage H 2 -based MBfR fed with different combinations of ClO 4 − , NO 3 − , and/or SO 4 2− together with a constant dissolved oxygen (DO) concentration at three operating stages. μ 1 and μ 3 were determined at 0.133 h −1 and 0.0062 h −1 , respectively, with a good level of identifiability. The model and the parameter values were further validated based on the experimental data of a two-stage H 2 -based MBfR system fed with ClO 4 − , NO 3 − , SO 4 2− , and DO simultaneously but at different feeding rates during two running phases. The validated model was then applied to evaluate the quantitative and systematic effects of key operating conditions on the reduction of ClO 4 − , NO 3 − , and SO 4 2− as well as the steady-state microbial structure in the biofilm of a single-stage H 2 -based MBfR. The results showed that i) a higher influent ClO 4 − concentration led to a higher ClO 4 − removal efficiency, compensated by a slightly decreasing SO 4 2− removal; ii) the H 2 loading should be properly managed at certain critical level to maximize the ClO 4 − and NO 3 − removal while limiting the growth of sulfate reducing bacteria which would occur in the case of excessive H 2 supply; and iii) a moderate hydraulic retention time and a relatively thin biofilm were required to maintain high-level removal of ClO 4 − and NO 3 − but restrict the SO 4 2− reduction. [ABSTRACT FROM AUTHOR]

Biodegradation of β-blocker atenolol was investigated using an enriched nitrifying culture at controlled ammonium concentration and without ammonium addition. Analysis of the kinetics and structural elucidation of biodegradation products showed that atenolol biodegradation was found to be linked to the activity of nitrifying bacteria in the presence of ammonium. Atenolol was degraded cometabolically by ammonia-oxidizing bacteria (AOB), likely due to a broad substrate range of ammonia monooxygenase (AMO). Four products were formed during atenolol biodegradation with ammonia oxidation, including P267 (atenolol acid) and three new products P117 (1-isopropylamino-2-propanol), P167 (1-amino-3-phenoxy-2-propanol), and an unknown product P227 with a nominal molecular mass of 227. In comparison, only P267 and P227 were identified during atenolol biodegradation without ammonia oxidation. Follow-up experiments using atenolol acid as the parent compound indicated the formation of products P117, P167 and P227 in the presence of ammonium. Based on the products identified, a tentative biodegradation pathway of atenolol is suggested, which involves two steps independent of the presence of ammonium: i) microbial amide-bond hydrolysis to carboxyl group and formation of P267 (atenolol acid) and ii) a possible formation of P227 with its unidentified structure and other two cometabolically induced reactions: iii) breakage of ether bond in the alkyl side chain and formation of P117 and iv) a minor pathway through N-dealkylation and loss of acetamide moiety from the aromatic ring, yielding P167. This study provided an important insight regarding the biotransformation pathways under different metabolic conditions. [ABSTRACT FROM AUTHOR]

Sulfide removal from wastewater is essential, in view of the toxic, malodor and corrosive property of sulfide. The oxidation of sulfide by chemolithotrophic sulfide oxidation bacteria can produce elemental sulfur, an important chemical material. A membrane aerated biofilm reactor (MABR) has been successfully implemented and demonstrated for enhanced sulfide oxidation and sulfur production, owning to its counter-diffusion design of oxygen supply. In this work, a mathematical model was developed to evaluate the sulfide oxidation and sulfur production in the MABR in the presence of residual organics in the influent. The model was calibrated and validated using the experimental data from the long-term operation of the sulfide-oxidation MABR at different operational stages. The results suggested that the developed model could satisfactorily describe sulfide oxidation, sulfur production, sulfate accumulation and organics conversion in the MABR. The modelling results indicated that with the optimal combinations of sulfide loading and oxygen pressure, over 90% of sulfide removal and over 75% of sulfur recovery could be achieved. The sulfide oxidation and sulfur production would also be affected by the biofilm area to reactor volume (A/V) ratio in the MABR, with high A/V ratio might deteriorate the sulfur production efficiency depending on the oxygen pressure applied. Further, the increase of volatile fatty acids in the wastewater would not affect the sulfide oxidation efficiency but could enhance the sulfur production efficiency by decreasing the amount of sulfur oxidized to sulfate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrochar was applied to capture PVC-MPs or PVC-NPs in the AGS systems. • Hydrochar alleviated the PVC-NPs inhibition more clearly than that of PVC-MPs. • Hydrochar induced more EPS release to against PVC-MPs or PVC-NPs toxicity. • Hydrochar possessed greater adsorption capability for PVC-MPs/NPs than AGS. The exposure to microplastics (MPs) and nanoplastics (NPs) has been confirmed to exhibit significant inhibitory effects on anaerobic granular sludge (AGS) for wastewater treatment, with effective mitigation strategies being accordingly imperative. Herein, this study innovatively proposed a strategy for mitigating inhibitory effects of MPs/NPs on AGS system based on coconut shell-derived hydrochar through efficiently capturing the existing polyvinyl chloride microplastics and nanoplastics (PVC-MPs and PVC-NPs) from AGS. The hydrochar increased methane production of AGS from 69.4% to 76.2% and from 65.6% to 91.4% of control when the AGSs were exposed to PVC-MPs and PVC-NPs, respectively. More extracellular polymeric substance (EPS) was secreted with the existence of hydrochar, which enhanced the protective capabilities AGS held to against the negative effects from the external toxicity of PVC-MPs and PVC-NPs, thus maintaining better AGS integrity regarding granule size and cell viability (especially for the PVC-NPs affected AGS). The hydrochar showed stronger adsorption capability to PVC-MPs and PVC-NPs than AGS, confirmed by their characteristics and adsorption kinetic tests. As a result, less plastic particles would attach AGS, inducing less oxidative stress to the microbes. Specially, it would also be less likely for PVC-NPs to penetrate through AGS surface and enter the internal core, retaining better richness of bacteria such as Bacteroidales and Syntrophobacterales in AGS. This work demonstrated hydrochar effectively alleviated the suppression on AGS caused by PVC-MPs and PVC-NPs, providing a novel strategy for improving the wastewater treatment performance under the stress of MPs and NPs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metabolic pathways for producing LCAs are presented. • Competitive reactions for producing LCAs are introduced. • Suitable operational conditions for enhancing desired products are discussed. • Challenges and strategies to improve LCAs productions are evaluated. The continuously rising energy prices and the growth in petroleum consumption have induced the pertinent pursuit of producing alternative fuels. Utilizing long-chain alcohols (LCAs) yielded from anaerobic bioprocess as renewable energy is a promising strategy to achieve the sustainable production of biofuels. Anaerobic fermentation is a sustainable process for reclaiming biodiesel from the organic wastes, which has received increasing attention due to its potential in producing renewable energy. Open-culture fermentation is preferred over single-species fermentation to yield the said alcohols because of its lower operating and capital costs. To better explore the LCAs productions from open-culture fermentation, a comprehensive understanding of this subject is currently needed but not available yet. To this end, the formations of LCAs and their possible precursors, medium-chain fatty acids (MCFAs), were systematically evaluated at first time with the focus on metabolic platforms, interspecies interactions, and competing microbial reactions. Suitable operational conditions and challenges were then synthesized, followed by the discussion on the viability of adopting current strategies towards higher alcohols productivities. The potential opportunities for enhancing LCAs outputs via biological processes were then suggested based on the review. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lattice doping of Zn boosts the number of OVs in Co 3 O 4 NCs. • BPA degradation rate constant correlates linearly with the OVs content. • OVs promote the combination of PDS onto the catalyst surface. • Surface-activated complex deprive electrons from electron-rich pollutants. • OVs are constructed on MOFs-derived catalysts with preserving original morphology. The presence of oxygen vacancies (OVs) promotes persulfate activation. However, rational modulation of OVs without compromising the inherent structure of catalysts is challenging. Herein, novel OVs-enriched hollow ZnCo 2 O 4 nanocages are synthesized based on a bimetallic ZIF-67@ZIF-8 precursor for efficient peroxydisulfate (PDS) activation. The incorporation of Zn into the lattice of Co 3 O 4 boosts the number of OVs in the catalysts while preserving the morphology of Co 3 O 4 nanocages derived from metal-organic framework (MOFs) templates. As a result, the degradation rate of organic pollutants such as bisphenol A is improved by over 20 times in the developed PDS activation system. OVs promote the formation of a surface-activated complex from PDS onto the catalyst surface, which can subsequently deprive electrons from pollutants. The developed PDS activation system is resistant to Cl−, NO 3 − and humic acid at environmental concentrations. This system adapts to selectively degrade organic pollutants with low ionic potential, and shows applicable potential in practical packaging wastewater treatment. The decreased catalytic performance of catalysts during utilization can be recovered with a facile thermal treatment. Our work constructs OV active sites on Co 3 O 4 nanocages while preserving their original structural superiorities, providing a new strategy to functionalize MOF-derived materials. [ABSTRACT FROM AUTHOR]

Recent discovery of ammonia-oxidizing archaea (AOA) not only substantially improved our understanding of the global nitrogen cycle, but also provided new possibilities for nitrogen removal from wastewater. In particular, compared to ammonia-oxidizing bacteria (AOB), the high ammonia oxidation under oxygen-limited conditions driven by AOA is potentially more suitable for autotrophic nitrogen removal in a single-stage membrane aerated biofilm reactor (MABR) through coupling with anaerobic ammonia oxidation (Anammox). In this work, mathematical modeling is applied to assess the system performance and associated microbial community structure of an AOA–Anammox MABR under low- (30 mg N L −1 ) and high-strength (500 mg N L −1 ) ammonium conditions, with a side-by-side comparison to an AOB–Anammox MABR system under the same conditions. Results demonstrate that both ammonium surface loading (or hydraulic retention time) and oxygen surface loading significantly affect the system performance. In contrast to AOB–Anammox system, the AOA–Anammox MABR shows higher total nitrogen (TN) removal and lower oxygen supply, with much better repression of NOB and substantially wider operating window for high-level TN removal (>80%) in terms of varied oxygen and ammonium loadings. These results provide first insights and useful information for design and operation of this novel AOA–Anammox MABR system in its potential future applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanisms of EF and fundamentals/necessity of cathode modification. • Current cathode modification methods with reported performances in removing POPs. • Pros/cons and perspectives of cathode modification for EF degradation of POPs. The Electro-Fenton (EF) technology has received significant research attention because of its efficacy in the degradation of persistent organic pollutants (POPs), which mainly relies on the in-situ generation of H 2 O 2 via the 2-electron oxygen reduction reaction and the subsequent formation of •OH. However, the practical application of the EF technology still needs to deal with shortcomings such as the limited performance of the traditional heterogeneous catalyst and the restricted generation of •OH that could be overcome by performing modification on the cathode. This work reviewed the reported cathode modification methods including thermal and (electro)chemical treatment and modification based on materials such as metals, graphene, carbon nanotubes, and polymers. Furthermore, the documented performances of the EF systems with differently modified cathodes in degrading specific POPs were presented. Finally, the advantages and limitations of these cathode modification methods were discussed, and some research perspectives were proposed to improve the practicability and feasibility of the EF technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZVI enhanced sludge degradation and nitrogen release in aerobic sludge digestion. • ZVI induced both chemical and biological denitrification for nitrogen removal. • ZVI enriched functional microbes for organic degradation and nitrogen removal. • ZVI improved the dewaterability of digested sludge by disrupting the sludge flocs. Zero-valent iron (ZVI), a low-cost metallic material, has been previously applied in effectively enhancing sewage sludge anaerobic digestion. However, the potential role of ZVI on aerobic digestion of sludge, a completely different sludge treatment method from anaerobic digestion, is still unknown. Herein, the effects of ZVI on the performance of aerobic sludge digestion were systematically studied, focusing on the sludge degradation, nitrogen removal and sludge dewaterability. Results showed ZVI greatly increased the volatile solids (VS) destruction from 27.0 ± 1.3% to 50.0 ± 1.0% and significantly enhanced the TCOD removal from 26.0 ± 1.2% to 47.9 ± 0.9% in aerobic digesters with different ZVI levels (0–20 g/L). The metabolic intermediate transformation steps of solubilization, hydrolysis and catabolism processes in aerobic digestion were all revealed to be enhanced by ZVI. More importantly, the aerobic digesters with higher ZVI levels achieved higher inorganic nitrogen removal, even with higher sludge degradation for ammonium release, due to the occurrence of both chemical and biological denitrification induced by ZVI. Correspondingly, the microbial compositions in the digesters with ZVI shifted towards the direction that was conducive to sludge degradation and nitrogen removal (e.g., aerobic denitrification) compared to control. Further, the dewaterability of the aerobically digested sludge was also improved with ZVI addition, supported by the reducing capillary suction time (CST) and negative surface potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • A SPANADA process was first established in a continuous flow air-lift bioreactor. • Effluent TIN of 8.6 mg/L was achieved in low C/N real wastewater with NH 4 +-N of 100 mg/L. • Anammox was the dominant nitrogen removal pathway in SPANADA system. • Meta-omics revealed the undergoing microbial interaction for nitrogen transformation. • Nitrogen conversion flux was evaluated based on kinetic and stoichiometric parameters. This study describes the development of an air-lift internal circulation reactor that integrates partial nitrification, anammox and denitratation (SPANADA) into a single stage bioprocess for the treatment of low C/N coal gasification wastewater. During 245 days of operation, the compartmental fluidized bed reactor achieved a total inorganic nitrogen (TIN) removal efficiency of 91.4%. Reads-based metatranscriptomic analysis found the expression of the amoA and hao genes essential for nitritation and the hzsA and hdh genes essential for anammox increased dramatically as reactor performance improved and stabilized. Another notable trend was that the total expression of the napA and narG genes, essential for denitratation, was 3-fold higher than the combined reads for nirK and nirS whose products, nitrite reductases, would lower nitrite levels reducing available substrate for anammox. Analysis of metagenome-assembled genomes revealed members of Nitrosomonas and Candidatus Brocadia, were the dominant genera of ammonium-oxidizing bacteria and anammox bacteria, respectively, and accounted for 5.5% and 10.0% of the total reads in the transcriptome. For denitratation, Thiolinea , whose only relevant gene involved in N-metabolism is narG , accounted for 8.5% of the total reads in the transcriptome and, remarkably, 84.1% of narG expression. Mass balance confirmed anammox was the dominant nitrogen removal pathway, accounting for 67.0% of the TIN removed. Nitritation and denitratation accounted for 82.7% and 17.3% of the nitrite production, respectively. The analysis reported demonstrates the development of a novel and effective one-stage nitrogen removal alternative for low C/N wastewater treatment and also helps gain insight into the underlying microbial interactions. [ABSTRACT FROM AUTHOR]

• FeAsS catalyst was prepared by an environment-friendly mechanical milling process. • The As and S co-etching leads to a self-optimized FeAsS@α-FeOOH heterostructure. • in situ interfacial engineering was achieved via dual-anion etching of arsenopyrite. • The electronic coupling effect between α-FeOOH and FeAsS enhances the OER activity. Designing novel catalysts for oxygen evolution reaction (OER) with high cost-effectiveness plays a central role in sustainably driving renewable energy conversion and storage. Here we demonstrate the in situ interfacial engineering for constructing efficient OER catalysts based on the electrochemical dual-anion etching of natural arsenopyrite. The OER catalyst (FeAsS) prepared from natural arsenopyrite via an environment-friendly ball milling approach achieves a current density of 10 mA cm−2 at an overpotential of 200 mV, outperforming many state-of-the-art catalysts. The in-depth study indicates that the co-etching of lattice As and S under the OER conditions triggers the in situ surface self-reconstruction, and a self-optimized catalytic active and stable FeAsS/α-FeOOH interface has been developed. Computational studies further confirm that the strong electronic coupling effect between α-FeOOH and FeAsS significantly tunes the binding energy between reaction intermediates and active sites, finally leading to an enhanced OER activity. The dual-anion etching of precatalysts induced in situ interfacial engineering demonstrated here expands the way of exploring other multiple nonmetallic elements involved nanomaterials as efficient OER precatalysts. This study also stimulates further study on the eco-design of electroactive materials for advanced energy conversion/storage applications from earth-abundance natural resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • A FFI-Net model based on deep learning was developed to analyze 3D-EEM. • The numbers of fluorescent components were accurately classified. • The maps of fluorescent components were rapidly generated and predicted. • A user-friendly interface was established for facilitating practical applications. Three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy has been widely applied to detect the fluorescent components in samples from natural water bodies to wastewater treatment processes. Data interpretation methods such as parallel factor analysis (PARAFAC) are required to decompose the overlapped fluorescent signals in the 3D-EEM spectra. However, strict requirements of data and complicated procedures of the PARAFAC limit the online monitoring and analysis of samples. Here we develop a fast fluorescent identification network (FFI-Net) model based on the deep learning approach to fast predict the numbers and maps of fluorescent components by simply inputting a single 3D-EEM spectrum. Two types of convolutional neural networks (CNN) are trained to classify the numbers of fluorescent components with an accuracy of 0.956 and predict the maps of fluorescent components with the min mean absolute error of 8.9 × 10-4. We demonstrate that the accuracy of the FFI-Net model will be further improved when more 3D-EEM data are available as a training dataset. Meanwhile, a user-friendly interface is designed to facilitate practical applications. Our approach gives a robust way to overcome the shortage of the PARAFAC and provides a new platform for online analysis of the fluorescent components in water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The enhanced nutrients removal from wastewater by ZVI is reviewed. • The impact of ZVI on sulfate removal from wastewater is discussed. • The improved methane production from sludge by ZVI is summarized. • The stimulated vivianite formation in sludge by ZVI is outlined. • The effective sludge reduction and dewatering by ZVI is analyzed. In quest of meeting the requirements of sustainable development, coupling zero valent iron (ZVI) with microorganisms has attracted extensive attentions for enhancing biological wastewater and sludge treatment in terms of microbial growth, nutrients removal, and resources recovery. Given to the significant role of ZVI playing in biological wastewater and sludge treatment, a thorough evaluation of the associated interactions among ZVI and microorganisms is necessary to further scale-up the application of ZVI-based biotechnologies. To this end, this review comprehensively summarizes the mechanisms of ZVI for enhancing nutrients removal (i.e., C, N, S and P) in several typical biological wastewater treatment processes, discusses the role of ZVI in improving the excess sludge reduction by dewatering or anaerobic digestion for methane production, and analyzes the feasibility of recovering phosphorus from anaerobic sludge digestion system in the form of vivianite through using ZVI. Knowledge gaps regarding the application of ZVI in sludge or wastewater treatment are also identified in this review to facilitate the further development of the ZVI-based biological technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkaline pre-fermentation (AF) enhanced polyacrylamide (PAM) degradation to 80.1%. • AF accelerated the hydrolysis and acidification of PAM-flocculated sludge (PFS). • Biochemical methane potential of PFS was improved by ~230% through AF. • AF broke the large firm "PAM-sludge" floccules and decreased PAM molecular weight. • Petrimonas and Sedimentibacter and Methanosaeta were enriched in AF-digester. The residual Polyacrylamide (PAM) in sewage sludge might cause severe disturbance in anaerobic digestion, and appropriate solutions to alleviate such situation are urgently required. In present study, alkaline pre-fermentation was proposed for PAM-flocculated sewage sludge (PFS) pretreatment, by which both PFS methane production and PAM degradation were remarkably enhanced. Under the optimal alkaline pre-fermentation condition (pH 10 for 12 d), the biochemical methane potential of PFS (12 g PAM/kg TS) increased from 107.2 to 246.6 mL/g VS, the hydrolysis rate increased from 0.109 to 0.197 d−1, and the degradation efficiency of PAM increased from 30.6% to 80.1%. Mechanism analysis indicated that the alkaline pre-fermentation broke the large "PAM-sludge" floccules, decreased the molecular weight of PAM, which alleviated the disturbance situation of PAM-present digester and made PAM more available for microbes to be biodegraded. Moreover, PFS hydrolysis and acidification were simultaneously accelerated by alkaline pre-fermentation, thereby providing more bioavailable carbon substrates for subsequent methane producing and PAM co-metabolism. Microbial community analysis demonstrated syntrophic bacteria such as Petrimonas and Sedimentibacter , which had ability to degrade an extensive range of various types of organics including carbohydrates and PAM, were enriched in alkaline pre-fermenter, and the acetotrophic methanogen Methanosaeta , were elevated in anaerobic digester. This work provides an effective microbial based strategy to improve the efficiency of anaerobic digestion of PFS. [ABSTRACT FROM AUTHOR]

[Display omitted] • TCS was partially degraded in anaerobic fermentation process. • TCS inhibited hydrogen production from anaerobic fermentation of sludge. • The presence of TCS inhibited acidogenesis process. • High level of TCS changed the relative abundances of functional microbes. Triclosan (TCS), a widely used antibacterial agent, was accumulated at significant levels in waste activated sludge (WAS). To date, however, the interaction between TCS and sludge anaerobic fermentation was rarely reported. Hence, this work aimed to deeply understanding the degradation of TCS in sludge anaerobic fermentation and its impact on hydrogen production. Experimental results showed that ~ 45% of TCS was degraded in long-term anaerobic fermentation, with 2,4-dichlorophenol as its main intermediate. Based on the information from high performance liquid chromatography–mass spectrometry analysis, three pathways i.e., dechlorination, hydroxylation, and cleavage of ether bonds, were proposed for TCS degradation. It was found that the maximum hydrogen yield decreased from 18.6 to 12.8 mL/g VSS with the increase of TCS from 12 to 487 mg/kg TSS. One possible reason for the decreased hydrogen yield was that a part of hydrogen generated might serve as electron donors for TCS dechlorination. Besides, the presence of TCS significantly suppressed acidogenesis (an important step responsible for hydrogen generation). This inhibition to acidogenesis is likely due to that the high-affinity functional groups of TCS such as hydroxyl groups could bind to the active sites of acetate kinase (AK, a key enzyme in acidogenesis), which reduced the active sites available for original fermentation substrates. Microbial analysis revealed that TCS increased the relative abundances of potential contaminant decomposers such as Guggeheimella but inhibited the populations of hydrogen producers such as Proteiniborus , which was consistent with the results obtained by chemical analyses. [ABSTRACT FROM AUTHOR]

• The coagulation removal and photocatalytic degradation of MPs in urban water are reviewed. • The mechanisms of coagulation and photocatalysis removal are summarized. • The conditions and characteristics of MPs can significantly affect coagulation removal. • The knowledge gaps and prospect of coagulation and photocatalytic removal are given. The global concerns to the environmental pollution and health risks by microplastics (MPs) urgently require action to develop effective and sustainable processes to deal with this problem. Coagulation removal and photocatalytic degradation, considered as cost- and energy-effective techniques, have attracted growing attention to remove MPs from urban waters. However, its removal behavior and degradation mechanism have not been systematically summarized. Therefore, the recent progress on coagulation and photocatalysis for MPs removal was comprehensively reviewed in this study. Particularly, the effects of parameters (e.g., type and dosage of coagulant, environmental conditions, characteristics of MPs and catalyst type, etc) and removal mechanisms were commendably discussed. Moreover, the challenges of current techniques application process and the potential coping strategies were also put forward. This review will not only help to deeply understand the detailed processes and mechanisms for removing MPs by coagulation and photocatalysis but also provide constructive information and useful data for future researches relevant to the enhanced removal of MPs from urban waters. [ABSTRACT FROM AUTHOR]

• Pretreatment with 0.1 g/g TSS KMnO 4 increased SCFAs yield from WAS to 7.4 times. • KMnO 4 pretreatment promoted the degradation of humus and lignocellulose. • KMnO 4 reduced the species and total detection frequency of organic contaminants. • KMnO 4 pretreatment enhanced the inactivation of the fecal coliforms. Potassium permanganate (KMnO 4), one typical strong oxidant, is used extensively in various applications. However, its impact on anaerobic fermentation of waste activated sludge is unknown. This paper therefore aims to investigate its effect on generation of short-chain fatty acids (SCFAs) and qualities of fermentation liquor and fermented solid sludge. Experimental results showed that when KMnO 4 increased from 0 to 0.1 g/TSS, the highest SCFAs production enhanced from 33.9 to 251.8 mg COD/g VSS. The mechanism analysis revealed that KMnO 4 addition increased the disintegration of sludge cells and the degradation of substantial recalcitrant organics in sludge such as humus and lignocellulose, thereby provided more substances for SCFAs generation. Ultraviolet absorption spectroscopy analysis showed that KMnO 4 addition destroyed unsaturated conjugated bonds and decreased organics aromaticity, thereby promoting humus and lignocellulose degradation. GC/MS analyses showed that several micro-molecular substances (e.g., acid-like, alkane-like, and alcohol-like organics) were generated from KMnO 4 pretreated humus and lignocellulose, and some of them were demonstrated to serve as substrates to produce SCFAs. The enzyme activity and model-based analyses showed that although KMnO 4 restrained all the microorganisms to some extends, the activities of SCFAs generators were much higher than those of SCFAs consumers. In addition, the sludge mixture was separated into liquid and solid fraction after anaerobic fermentation, and the components in fermentation liquid and solid sludge were tested. It was found that the addition of KMnO 4 effectively reduced the categories and total detected frequency of refractory organic pollutants in fermentation liquid, which improved the quality of the produced SCFAs. KMnO 4 addition also increased the inactivation of fecal coliforms and degradation of emerging contaminants in fermented sludge, which were helpful to its final disposal. [ABSTRACT FROM AUTHOR]

• A granule model embedding metabolisms of DAMO microbes and AnAOB was proposed. • The model predictions matched experimental data from two granular sludge reactors. • The estimated parameter values indicated a stimulated growth of DAMO archaea. • The model managed to simulate the microbial abundance and stratified distribution. • Short HRT and small granule size increased DAMO archaea but reduced DAMO bacteria. The granular bioreactor, characterized by excellent settling velocity, high rate and low cost is an ideal choice for achieving coupled nitrate/nitrite dependent denitrifying anaerobic methane oxidation (n-DAMO) and anaerobic ammonium oxidation (Anammox) process. To fundamentally understand its underlining mechanisms and provide suggestions for process optimization, a granule-based model framework was developed to describe simultaneous anaerobic methane and ammonium oxidation by functional microbes. The proposed model was evaluated based on long-term experimental data from two membrane granular sludge reactors (MGSRs) with different operational conditions. The model possessed of good predictive ability to reproduce removal rates and effluent concentrations of nitrogen species. The predicted biomass abundance in two MGSRs and stratified microbial distribution along granule depth were consistent with experimental observations. The estimated parameter values, with good identifiability and reliability indicated a stimulated growth of DAMO archaea in MGSRs. Both hydraulic retention times (HRTs) and granule sizes have influences on microbial abundance in the MGSR and community distribution inside granules. Within the investigated HRTs from 1.4 h to 20 h and granule sizes from 500 μm to 2900 μm, it was revealed that a proper control of relatively short HRTs and small granule sizes resulted in an increased fraction of DAMO archaea and a reduced DAMO bacteria abundance with AnAOB less impacted, which would lower the required nitrite nitrogen to ammonium nitrogen ratio in the nitritation reactor (prior unit) and thus minimize operational cost in sidestream treatment lines. [ABSTRACT FROM AUTHOR]

• Magnetic AN-SA copolymer was produced by oxidative copolymerization. • The adsorbent exhibited remarkably simultaneous removal of Cr(VI) and 2,4-DCP. • Aqueous Cr(VI) was adsorbed and reduced by –NH–/–NH 2 groups to Cr(III). • 2,4-DCP was removed due to n-π EDA interaction, π-π stacking, and hydrogen bond. • Bridge interactions of 2,4-DCP and chromium induced the adsorbance enhancement. The common coexistence of heavy metal ions (HMIs) and toxic organic matters (OMs) arouses public concerns for their combined toxicity and carcinogenicity. The magnetic poly[aniline(AN)- co -5-sulfo-2-anisidine(SA)] (AN-SA/Fe 3 O 4) was synthesized by an oxidative copolymerization method for the highly-effectively simultaneous removal of Cr(VI) and 2,4-dichlorophenol (2,4-DCP) from aqueous solution. The novel adsorbent exhibited ultra-strong adsorption capacities for sole Cr(VI) and sole 2,4-DCP. The mechanism studies revealed that Cr(VI) species (HCrO 4 − and Cr 2 O 7 2− in solution pH as 5) were reduced to Cr(III) by the –NH–/–NH 2 groups after attaching to the protonated binding sites of AN-SA/Fe 3 O 4 through electrostatic attraction. By contrast, multiple reactions involving the n-π electron donor-acceptor (EDA) interaction, π-π stacking and hydrogen bond contributed to the elimination of 2,4-DCP. In binary system, the coexistent Cr(VI) and 2,4-DCP elevated mutual adsorption capacities by 88.1% and 102.1%, respectively. Specially, 2,4-DCP can form bridge interactions with both Cr(VI) and Cr(III) due to conjugate effect. This property enabled Cr(VI) to additionally link to the hydrophobic sites, except for the hydrophilic sites, via 2,4-DCP bridges. Moreover, the produced Cr(III) can forcefully captured 2,4-DCP with the electron-rich groups (i.e., NH , N , SO 3 H, OCH 3) on AN-SA/Fe 3 O 4 to form the multi-components complexes. The bridge interactions (i.e., n-π EDA interaction, complexation) created the newly available sites for Cr(VI) and 2,4-DCP, resulting in enlarged adsorbance and synchronous removal on AN-SA/Fe 3 O 4 in coexisting system. In addition, the high proportion of N groups generated by Cr(VI) oxidation also devoted to the uptake enhancement due to its strong affinity for 2,4-DCP. Overall, the high-performance and synergistic removal qualified AN-SA/Fe 3 O 4 as a multifunctional adsorbent for the integrated treatment of HIMs-OMs hybrid pollutants. [ABSTRACT FROM AUTHOR]

• Freezing activated nitrite pretreatment (FN) enhanced anaerobic digestion from WAS. • FN benefited WAS disintegration and the biodegradable of organics released. • FN benefited the dewaterability or pathogens inactivation of digested sludge. • Freezing induced reactive derivatives from nitrite were the major contributors. • FN was economically and environmentally attractive. Nitrite-based pretreatment was demonstrated to effectively improve anaerobic digestion of waste activated sludge. It was found in this work that the freezing activated nitrite pretreatment could further enhance the performances. With the increase of nitrite addition from 0 to 600 mg NO 2 −-N/L during freezing process, the biochemical methane potential of pretreated-sludge gradually increased from 191.3 ± 8.0 to 233.2 ± 10.6 mL per gram volatile solid (VS), while only 178.6 ± 7.3 mL/g VS was obtained in the raw sludge. Mechanism explorations revealed that the freezing activated nitrite pretreatment remarkably facilitated the disintegration of sludge. Excitation emission matrix and fluorescence regional integration analyses further revealed that nitrite addition during freezing process promoted the proportion of biodegradable organics released, thereby providing more bio-available substrates for subsequent anaerobic digestion. Freezing condition induced reactive derivatives from nitrite (e.g., free nitrite acid, NO 2 , N 2 O 3) were assumed to be the major contributors to the enhanced sludge disintegration and recalcitrant organics (e.g., humic acid-like substances) degradation. It was also found that 600 mg NO 2 −-N/L addition activated by freezing pretreatment produced an anaerobically digested sludge with an improved dewaterability, as indicated by the decrease of the specific resistance to filterability and moisture content of dewatered cake. Moreover, 600 mg NO 2 −-N/L addition activated by freezing pretreatment and subsequent anaerobic digestion largely inactivated the pathogens to the levels below Class A biosolids requirements. Considering that nitrite can be in-situ produced in wastewater treatment plants through nitritation of the digestion liquid, this nitrite-based freezing process for sludge pretreatment was environmental-friendly and economically attractive. [ABSTRACT FROM AUTHOR]

• Novel K 2 W 4 O 13 nanowires were synthesized for highly-efficient Pb2+ removal. • K 2 W 4 O 13 showed huge, fast uptake and acid-resistance toward Pb2+ removal. • Pb2+ uptake was a spontaneous, exothermic, and film diffusion limited chemisorption. • Both ion-exchange and complexation contributed to about 50% of Pb2+ uptake. • Pb favored to complex with equatorial oxygen than axial oxygen based on DFT. As one of the most toxic heavy metals, lead ions (Pb2+) contamination arouses increasing public concern for high carcinogenicity and neurotoxicity. In this study, a modified hydrothermal method was designed to fabricate novel hexagonal K 2 W 4 O 13 nanowires to achieve highly-efficient Pb2+ removal from water. Attractively, the as-prepared K 2 W 4 O 13 exhibited large uptake capacity (228.83 mg/g), fast kinetic (141.67 mg/g in 30 min), superior acid-resistance (75% of removal at pH = 2) and excellent reusability (over 95% of removal after 5 runs) toward Pb2+ adsorption. The Langmuir isotherm and pseudo-second-order kinetic model gave a better fit to the adsorption experimental data. The Pb2+ adsorption process on K 2 W 4 O 13 was revealed to be a spontaneous, exothermic, film diffusion limited chemisorption reaction. The mechanism studied elucidated that both ion-exchange and complexation were involved in Pb2+ adsorption, with each accounting for approximate 50% of Pb2+ elimination. Through density functional theory (DFT) calculation, the equatorial oxygen was found to be more accessible for Pb attachment than the axial corner oxygen from [WO 6 octahedra. Electron pairs from the adjacent O atoms would transfer to the empty orbitals of Pb atoms after adsorption, causing the Pb2+ removal via metal-ligand complexation. [ABSTRACT FROM AUTHOR]