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• Iron-based carbon redirection enables the transformation of wastewater treatment. • In-situ iron reduction and advanced oxidation synergistically decompose sludge. • Log-Logistic model fits the relationship between iron dosage and electron transfer. • Iron-based sludge enhances carbon recovery through multi-mechanism collaboration. • Iron promotes the construction of high-value product biorefinery consortium. Wastewater treatment plants face significant challenges in transitioning from energy-intensive systems to carbon-neutral, energy-saving systems, and a large amount of chemical energy in wastewater remains untapped. Iron is widely used in modern wastewater treatment. Research shows that leveraging the coupled redox relationship of iron and carbon can redirect this energy (in the form of carbon) towards resource utilization. Therefore, re-examining the application of iron in existing wastewater carbon processes is particularly important. In this review, we investigate the latest research progress on iron for wastewater carbon flow restructuring. During the iron-based chemically enhanced primary treatment (CEPT) process, organic carbon is captured into sludge and its bioavailability is enhanced through iron-based advanced oxidation processes (AOP) pretreatment, further being recovered or upgraded to value-added products in anaerobic biological processes. We discuss the roles and mechanisms of iron in CEPT, AOP, anaerobic biological processes, and biorefining in driving organic carbon conversion. The dosage of iron, as a critical parameter, significantly affects the recovery and utilization of sludge carbon resources, particularly by promoting effective electron transfer. We propose a pathway for beneficial conversion of wastewater organic carbon driven by iron and analyze the benefits of the main products in detail. Through this review, we hope to provide new insights into the application of iron chemicals and current wastewater treatment models. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermochemical technologies are suitable for municipal sludge (MS) recycling. • Hydrothermal methods show a great potential on energy and resource recovery of MS. • Machine learning (ML) guides process optimization, mechanism mining in MS recycling. • Application of ML for thermochemical conversion of MS still remains challenging. • Comprehensive ML models considering successive reaction processes deserve further study. The sustainable disposal of high-moisture municipal sludge (MS) has received increasing attention. Thermochemical conversion technologies can be used to recycle MS into liquid/gas bio-fuel and value-added solid products. In this review, we compared energy recovery potential of common thermochemical technologies (i.e., incineration, pyrolysis, hydrothermal conversion) for MS disposal via statistical methods, which indicated that hydrothermal conversion had a great potential in achieving energy recovery from MS. The application of machine learning (ML) in MS recycling was discussed to decipher complex relationships among MS components, process parameters and physicochemical reactions. Comprehensive ML models should be developed considering successive reaction processes of thermochemical conversion in future studies. Furthermore, challenges and prospects were proposed to improve effectiveness of ML for energizing thermochemical conversion of MS regarding data collection and preprocessing, model optimization and interpretability. This review sheds light on mechanism exploration of MS thermochemical recycling by ML, and provide practical guidance for MS recycling. [ABSTRACT FROM AUTHOR]

The performance of an oxic-settling-anaerobic (OSA) system in terms of sludge reduction was investigated for various anaerobic hydraulic retention times (HRTs) (7 d, 5 d, 3 d, 1 d, 12 h, and 6 h) for a sequencing batch reactor (SBR)-OSA system. Compared to the traditional SBR system, the rates of sludge reduction in the 7d, 5d-1, 5d-2, 3d, and 1d OSA systems were observed to be 66.6, 57.7, 52.5, 50.0, and 48.5%, respectively. In terms of the apparent yield and actual yield of sludge, the OSA systems with longer HRTs exhibited lower sludge yields and better sludge reduction performance. The systems with an HRT > 1 d achieved a considerable increase in sludge reduction, whereas those with an HRT < 1 d did not. The anaerobic HRT was observed to be an important factor in determining the sludge reduction of OSA systems. [ABSTRACT FROM PUBLISHER]

Abstract: Floating beds of canna can remove nitrogen from polluted river water, but the removal efficiency is not very high in a short time, so some enhanced methods must be used to improve nitrogen removal efficiency by the system. Immobilized denitrifying bacteria and aeration were added into the canna floating bed. The experimental results showed that these enhancements substantially improved the nitrogen removal efficiency of the floating beds. With the enhancements, total nitrogen removal was 72.1%, ammonia nitrogen oxidation was 100%, nitrate nitrogen removal was 75.8%, nitrite nitrogen removal was 95.9%, and COD removal was 94.6% in 5 days. Without the enhancements, the canna floating bed system removed only 50.4% of the total nitrogen, 22.4% of the nitrate nitrogen, 5.3% of the nitrite nitrogen and 39.9% of the COD, respectively, in 5 days, but did accomplish 100% oxidation of the ammonia nitrogen. The experimental results provide an improved method for the treatment of polluted river water. [Copyright &y& Elsevier]

[Display omitted] • Different types of municipal sludge (MS) properties were analysed. • Hydrothermal carbonization (HTC) of MS was modelled by machine learning (ML). • MS properties were more important than HTC parameters for hydrochar HHV. • HTC parameters were more critical than MS properties for carbon and energy recovery. • Primary sludge is an optimal candidate of the four MS as a feedstock of HTC. In the context of advocating carbon neutrality, there are new requirements for sustainable management of municipal sludge (MS). Hydrothermal carbonization (HTC) is a promising technology to deal with high-moisture MS considering its low energy consumption (without drying pretreatment) and value-added products (i.e., hydrochar). This study applied machine learning (ML) methods to conduct a holistic assessment with higher heating value (HHV) of hydrochar, carbon recovery (CR), and energy recovery (ER) as model targets, yielding accurate prediction models with R 2 of 0.983, 0.844 and 0.858, respectively. Furthermore, MS properties showed positive (e.g., carbon content, HHV) and negative (e.g., ash content, O/C, and N/C) influences on the hydrochar HHV. By comparison, HTC parameters play a critical role for CR (51.7%) and ER (52.5%) prediction. The primary sludge was an optimal HTC feedstock while anaerobic digestion sludge had the lowest potential. This study provided a comprehensive reference for sustainable MS treatment and industrial application. [ABSTRACT FROM AUTHOR]

• Electrochemical stimulation accelerated and enhanced antibiotics biodegradation. • Microbial metabolic activity was promoted under electrochemical stimulation. • Desulfobulbus and Geobactor were enriched in biocathode and bioanode biofilm. • Electrochemical stimulation facilitated extracellular electron transfer processes. The presence of antibiotics in wastewater poses significant threat to our ecosystems and health. Traditional biological wastewater treatment technologies have several limitations in treating antibiotic-contaminated wastewaters, such as low removal efficiency and poor process resilience. Here, a novel electrochemical-coupled sulfur-mediated biological system was developed for treating wastewater co-contaminated with several antibiotics (e.g., ciprofloxacin (CIP), sulfamethoxazole (SMX), chloramphenicol (CAP)). Superior removal of CIP, SMX, and CAP with efficiencies ranging from 40.6 ± 2.6 % to 98.4 ± 1.6 % was achieved at high concentrations of 1000 μg/L in the electrochemical-coupled sulfur-mediated biological system, whereas the efficiencies ranged from 30.4 ± 2.3 % to 98.2 ± 1.4 % in the control system (without electrochemical stimulation). The biodegradation rates of CIP, SMX, and CAP increased by 1.5∼1.9-folds under electrochemical stimulation compared to the control. The insights into the role of electrochemical stimulation for multiple antibiotics biodegradation enhancement was elucidated through a combination of metagenomic and electrochemical analyses. Results showed that sustained electrochemical stimulation significantly enriched the sulfate-reducing and electroactive bacteria (e.g., Desulfobulbus, Longilinea , and Lentimicrobiumin on biocathode and Geobactor on bioanode), and boosted the secretion of electron transport mediators (e.g., cytochrome c and extracellular polymeric substances), which facilitated the microbial extracellular electron transfer processes and subsequent antibiotics removal in the sulfur-mediated biological system. Furthermore, under electrochemical stimulation, functional genes associated with sulfur and carbon metabolism and electron transfer were more abundant, and the microbial metabolic processes were enhanced, contributing to antibiotics biodegradation. Our study for the first time demonstrated that the synergistic effects of electrochemical-coupled sulfur-mediated biological system was capable of overcoming the limitations of conventional biological treatment processes. This study shed light on the mechanism of enhanced antibiotics biodegradation via electrochemical stimulation, which could be employed in sulfur-mediated bioprocess for treating antibiotic-contaminated wastewaters. [Display omitted] [ABSTRACT FROM AUTHOR]

Effluent organic matter (EfOM) originating from wastewater treatment plant (WWTP) is of significant concern, as it not only influences the discharge quality of WWTP but also exerts a significant effect on the efficiency of the downstream advanced treatment facilities. Soluble microbial products (SMP) is a major part of EfOM. In order to further understand the relationship between soluble microbial products (SMP) and EfOM, and in turn, to propose measures for EfOM control, the formation of SMP and EfOM in identical activated sludge sequencing batch reactors (SBR) with different feed water was investigated using fluorescence excitation and emission spectroscopy matrix coupled with parallel factor analysis (EEM–PARAFAC) as well as other organic matter quantification tools. Results showed that EfOM contained not only SMP but also a considerable amount of allochthonous organic matter that derived not merely from natural organic matter (NOM). Four components in EfOM/SMP were identified by EEM–PARAFAC. Tyrosine-like substances in EfOM (Component 3, λ ex/em = 270/316 nm) were mainly originated from utilization associated products (UAP) of SMP. Tryptophan-like substances (Component 2, λ ex/em = 280/336 nm) as well as fulvic-like and humic-like substances in EfOM (Component 1, λ ex/em = 240(290)/392 nm and Component 4, λ ex/em = 260(365)/444 nm) were majorly derived from the refractory substances introduced along with the influent, among which Component 2 was stemmed from sources other than NOM. As solid retention time (SRT) increased, Component 2 and polysaccharides in SMP/EfOM decreased, while Component 4 in SMP increased. [ABSTRACT FROM AUTHOR]

[Display omitted] • Emerging contaminants (ECs) removal by biochar was modeled by machine learning (ML) • ML and classical adsorption models were coupled to build models. • Ash content of biochar had most critical influences on the adsorption speed of ECs. • Surface structure of biochar played a dominant role in maximum adsorption capacity. • An interactive Biochar-ECs platform was designed for users based on our ML models. Insights into key properties of biochar with a fast adsorption rate and high adsorption capacity are urgent to design biochar as an adsorbent in pollution emergency treatment. Machine learning (ML) incorporating classical theoretical adsorption models was applied to build prediction models for adsorption kinetics rate (i.e., K) and maximum adsorption capacity (i.e., Q m) of emerging contaminants (ECs) on biochar. Results demonstrated that the prediction performance of adaptive boosting algorithm significantly improved after data preprocessing (i.e., log-transformation) in the small unbalanced datasets with R 2 of 0.865 and 0.874 for K and Q m , respectively. The surface chemistry, primarily led by ash content of biochar significantly influenced the K, while surface porous structure of biochar showed a dominant role in predicting Q m. An interactive platform was deployed for relevant scientists to predict K and Q m of new biochar for ECs. The research provided practical references for future engineered biochar design for ECs removal. [ABSTRACT FROM AUTHOR]

• Over 89 % nitrogen in raw landfill leachate was removed through ESdAD system. • The effluent TN concentration is less than 25 mg-N/L in ESdAD system. • Superior pH modulation and system stability were obtained in ESdAD than SdAD system. • Nitrogen metabolic activity and electron transfer capacity were enhanced under current stimulation. • The coexistence of heterotrophic and autotrophic bacteria contributed to nitrogen removal improvement. The cost-effective and environment-friendly sulfur-driven autotrophic denitrification (SdAD) process has drawn significant attention for advanced nitrogen removal from low carbon-to-nitrogen (C/N) ratio wastewater in recent years. However, achieving efficient nitrogen removal and maintaining system stability of SdAD process in treating low C/N landfill leachate treatment have been a major challenge. In this study, a novel electrochemical-coupled sulfur-driven autotrophic denitrification (ESdAD) system was developed and compared with SdAD system through a long-term continuous study. Superior nitrogen removal performance (removal efficiency of 89.1 ± 2.5 %) was achieved in ESdAD system compared to SdAD process when treating raw landfill leachate (influent total nitrogen (TN) concentration of 241.7 ± 36.3 mg-N/L), and the effluent TN concentration of ESdAD bioreactor was as low as 24.8 ± 5.1 mg-N/L, which meets the discharge standard of China (< 40 mg N/L). Moreover, less sulfate production rate (1.3 ± 0.2 mg SO 4 2 − − S / mg NO x − − N vs 1.7 ± 0.2 mg SO 4 2 − − S / mg NO x − − N) and excellent pH modulation (pH of 6.9 ± 0.2 vs 5.8 ± 0.4) were also achieved in the ESdAD system compared to SdAD system. The improvement of ESdAD system performance was contributed to coexistence and interaction of heterotrophic bacteria (e.g., Rhodanobacter, Thermomonas , etc.), sulfur autotrophic bacteria (e.g., Thiobacillus, Sulfurimonas, Ignavibacterium etc.) and hydrogen autotrophic bacteria (e.g., Thauera, Comamonas, etc.) under current stimulation. In addition, microbial nitrogen metabolic activity, including functional enzyme (e.g., Nar and Nir) activities and electron transfer capacity of extracellular polymeric substances (EPS) and cytochrome c (Cyt-C), were also enhanced during current stimulation, which facilitated the nitrogen removal and maintained system stability. These findings suggested that ESdAD is an effective and eco-friendly process for advanced nitrogen removal for low C/N wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

• A single-chamber up-flow anaerobic bioelectrochemical reactor (UBER) was designed. • The UBER realized biogenic S0 recovery from antibiotic production wastewater. • 0.8 V was the optimal voltage of UBER with the highest operational performance. • The bio-anode was proved to lower energy barrier and enhance electron transfer. • C -type cytochromes served as the crucial electron transfer mediator. The high-concentration sulfate (SO 4 2 −) in the antibiotic production wastewater hinders the anerobic methanogenic process and also proposes possible environmental risk. In this study, a novel single-chamber up-flow anaerobic bioelectrochemical reactor (UBER) was designed to realize simultaneous SO 4 2 − removal and elemental sulfur (S0) recovery. With the carbon felt, the cathode was installed underneath and the anode above to meet the different biological niches for sulfate reducing bacteria (SRB) and sulfur oxidizing bacteria (SOB). The bio-anode UBER (B-UBER) demonstrated a much higher average SO 4 2 − removal rate (SRR) of 113.2 ± 5.7 mg SO 4 2 − − S L−1 d−1 coupled with a S0 production rate (SPR) of 54.4 ± 5.8 mg S0-S L−1 d−1 at the optimal voltage of 0.8 V than that in the abio-anode UBER (control reactor) (SRR = 86.6 ± 13.4 mg SO 4 2 − − S L−1 d−1; SPR = 25.5 ± 9.7 mg S0-S L−1 d−1) under long-term operation. A large amount of biogenic S0 (about 72.2 mg g−1 VSS) was recovered in the B-UBER. The bio-anode, dominated by Thiovirga (SOB genus) and Acinetobacter (electrochemically active bacteria genus), exhibited a higher current density, lower overpotential, and lower internal resistance. C -type cytochromes mainly served as the crucial electron transfer mediator for both direct and indirect electron transfer, so that significantly increasing electron transfer capacity and biogenic S0 recovery. The reaction pathways of the sulfur transformation in the B-UBER were hypothesized that SRB utilized acetate as the main electron donor for SO 4 2 − reduction in the cathode zone and SOB transferred electrons to the anode or oxygen to produce biogenic S0 in the anode zone. This study proved a new pathway for biogenic S0 recovery and sulfate removal from sulfate-laden antibiotic production wastewater using a well-designed single-chamber bioelectrochemical reactor. [ABSTRACT FROM AUTHOR]

• The "capture" of ciprofloxacin by P. bifermentans is examined by QCM-D and AFM. • Single P. bifermentans cell exhibits adhesive force to ciprofloxacin molecules. • Extracellular proteins are crucial for P. bifermentans to "capture" ciprofloxacin. • Transferase-related signaling molecules manipulate the "capture" process. The extensive exploration of antibiotic biodegradation by antibiotic-degrading bacteria in biological wastewater treatment processes has left a notable gap in understanding the behavior of these bacteria when exposed to antibiotics and the initiation of biodegradation processes. This study, therefore, delves into the adhesive behavior of Paraclostridium bifermentans , isolated from a bioreactor treating ciprofloxacin-laden wastewater, towards ciprofloxacin molecules. For the first time, this behavior is observed and characterized through quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy. The investigation further extends to identify key regulatory factors and mechanisms governing this adhesive behavior through a comparative proteomics analysis. The results reveal the dominance of extracellular proteins, particularly those involved in nucleotide binding, hydrolase, and transferase, in the adhesion process. These proteins play pivotal roles through direct chemical binding and the regulation of signaling molecule. Furthermore, QCM-D measurements provide evidence that transferase-related signaling molecules, especially tyrosine, augment the binding between ciprofloxacin and transferases, resulting in enhance ciprofloxacin removal by P. bifermentans (increased by ∼1.2-fold). This suggests a role for transferase-related signaling molecules in manipulating the adhesive behavior of P. bifermentans towards ciprofloxacin. These findings contribute to a new understanding of the prerequisites for antibiotic biodegradation and offer potential strategies for improving the application of antibiotic-degrading bacteria in the treatment of antibiotics-laden wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • MNB ozonation is highly effective for OTC removal (>99 % in 60 min) in wastewater. • MNB ozonation improves subsequent AD performance vs. conventional ozonation. • 30 min of MNB ozonation enhances CH 4 production by 51 % vs. conventional ozonation. • MNB ozonation leads to reduced VFA accumulation during AD. • OTC and its OBPs significantly shift the sludge microbial community structure. This study investigated the potential of micro-nano bubble (MNB) ozonation pretreatment to eliminate oxytetracycline (OTC) from wastewater and improve subsequent anaerobic digestion (AD) performance. The findings revealed that MNB ozonation achieved efficient OTC oxidation (>99 % in 60 min), and significantly enhanced methane production by 51 % compared to conventional ozonation (under 30 min of pretreatment). Additionally, MNB ozonation resulted in a decrease in the soluble chemical oxygen demand and reduced volatile fatty acid accumulation compared to conventional ozonation. Furthermore, the study sheds light on the profound impact of OTC and its oxidation by-products on the sludge microbiome. Exposure to OTC and its oxidation by-products resulted in alterations in extracellular polymeric substances composition and led to significant shifts in microbial community structure. This study highlights the promise of MNB ozonation as an effective approach for pharmaceutical pollutant removal and the optimization of AD performance in wastewater treatment, with implications for improved environmental sustainability. [ABSTRACT FROM AUTHOR]

• The SRB-enriched sludge was highly resistant and tolerant to SMX toxicity. • The SRB-enriched sludge eliminates the toxicity of SMX via biodegradation. • All TPs except TP6 and TP7 exhibited lower toxicity than SMX. • Efflux pump and inactivation play an important role in microbial self-defense. Incomplete mineralization of sulfamethoxazole (SMX) in wastewater treatment systems poses a threat to ecological health. The toxicity and environmental risk associated with SMX biodegradation in the sulfur-mediated biological process were examined for the first time through a long-term (180 days) bioreactor study and a series of bioassays. The results indicated that the sulfur-mediated biological system was highly resistant and tolerant to SMX toxicity, as evidenced by the enrichment of sulfate-reducing bacteria (SRB), the improved microbial metabolic activity, and the excellent performance on pollutants removal under long-term SMX exposure. SMX can be effectively biodegraded by the cleavage and rearrangement of the isoxazole ring, hydrogenation and hydroxylation reactions in sulfur-mediated biological wastewater system. These biodegradation pathways effectively reduced the acute toxicity, antibacterial activity, and ecotoxicities of SMX and its biotransformation products (TPs) in the effluent of the sulfur-mediated biological system. The TPs produced via hydrogenation (TP1), hydroxylation, and isoxazole ring cleavage (TP3, TP4, TP5, TP8, and TP9) exhibited lower toxicity than SMX. Under SMX stress, although the abundance of sulfonamide resistance genes increased, the total abundance of ARGs decreased due to the extrusion of some intracellular SMX by the efflux pump genes and the inactivation of some SMX through the biodegradation process. Efflux pump and inactivation, as the main resistance mechanisms of antibiotics in the sulfur-mediated biological system, play a crucial role in microbial self-defense. The findings of this study demonstrate the great potential of the sulfur-mediated biological system in SMX removal, detoxication, and ARGs environmental risk reduction. [Display omitted] [ABSTRACT FROM AUTHOR]

• PHA yield from fermented food waste and sludge achieved 0.60–0.69 g COD PHA /g COD S. • A synthesis of SCL/MCL-PHAs pathway was identified through metagenomic analysis. • The bacterial structure shifting along with feedstock complexity was revealed. • Dominant bacteria were significantly changed in response to feedstock shifts. • Unreported PHA producers subsisting on municipal organic wastes were characterized. The microbial community of a sequencing batch reactor operated under feast and famine conditions for production of polyhydroxyalkanoates (PHAs) was characterized through high-throughput sequencing and metagenomic analysis. The fermented food waste and chemically-enhanced primary sludge was fed in this bioreactor. After acclimation, the PHA yield achieved as high as 0.60–0.69 g COD PHA /g COD S. The complete changes of microbial community structure were found during shifts of feedstock. A synthesis of SCL/MCL-PHAs pathway was established for PHA-producing bioreactor in this mixed-culture system. The structure-performance relationship of PHA-producing microbial community and feedstock composition was investigated. The results showed that microbial community tends to be decentralized and prefer team work for PHA synthesis to consume the multiple substrates and digest inevitable non-VFA contents in fermented liquor. This study also discovered unreported potential PHA producers (e.g., genera Tabrizicola, Nannocystis, Ga0077539, Ga0077559, JOSHI-001, SNC69–320 and UBA2334) subsisting on municipal organic wastes and expands the current knowledge about mixed-culture system that the PHA synthesis pathway is widely existed in activated sludge. [Display omitted] [ABSTRACT FROM AUTHOR]

The poor reusability of catalysts and secondary pollution are critical issues for sulfur-containing volatile organic compounds (S-VOCs) removal. In this paper, a three-dimensional (3D) hierarchical porous sludge-derived carbon supported on silicon carbide foams (SiC) has been fabricated for deep decomposition of S-VOCs under ambient conditions. The sludge-derived Fenton-like catalyst has been confirmed to be hierarchical 3D porous structure based on detailed characterization by scanning electron microscopy (SEM), X-ray diffraction (XRD), Nitrogen adsorption-desorption measurements and Raman spectroscopy. Significantly, the catalyst after KOH activation (SC FeK -SiC) shows excellent catalytic decomposition of methyl mercaptan (CH 3 SH) with almost complete CH 3 SH oxidation into sulfate using hydrogen peroxide as an oxidant under ambient conditions. This catalyst also possesses relative low iron dissolution and excellent cycling performance. The efficient catalytic ability of SC FeK -SiC can be attributed to SiC foam functioned as a stable 3D macroporous skeleton, in which the porous sludge-derived carbon immobilizes the active iron species and promotes the efficient capture of gaseous CH 3 SH, thus facilitating the decomposition of CH 3 SH by generating reactive species, specifically ·OH. The reaction mechanism was systematically investigated. Herein, the design of the porous sludge-derived carbonaceous Fenton-like catalyst paves an avenue for efficient VOCs treatment and rational sludge disposal. [ABSTRACT FROM AUTHOR]

The extraction of phosphorus (P) from iron-rich sludge is a critical step for P recovery process. The acidogenic phosphorus release (APR) process was proved as a cost-effective and environmental-friendly method to separate and release Fe–P from iron-rich sludge, including primary sludge and activated sludge. However, the role of bacteria in this microbial-driven metal reductive dissolution approach was not clear. This study aimed to reveal the mechanism of microbial cooperation during APR process. The P release fraction could achieve as high as 63.2% from iron-rich primary sludge. High-throughput sequencing of 16S rRNA gene amplicon was conducted to characterize the functional microorganisms participating in APR process, including hydrolytic bacteria Prevotella , acidogens Selenomonas , Bacteroides, Lactococcus , Tolumonas , and iron-reducing bacteria Aeromonas and Sulfurospirillum. Microbial iron reduction and acidogenic fermentation were identified as two critical biological reactions in APR process. A two-phase temporal succession of bacterial community was characterized in batch APR process. The strong positive relationship between iron-reducing bacteria and acidogens was revealed by network analysis. This study successfully proved that bacteria-mediating metal reductive dissolution approach could efficiently release the reducible metal compounds (such as Fe–P) from complex mixture, which can be extended to many other scenarios regarding resource extraction and recovery. [Display omitted] • Bacteria-mediating metal reductive dissolution approach was applied for P release. • Functional bacteria playing important roles in acidogenic P release were characterized. • The two-phase temporal succession of bacterial community was revealed. • Relationship of iron-reducing bacteria and fermentative bacteria was deciphered. [ABSTRACT FROM AUTHOR]

Four different types of fibers including rice straw, wheat straw, rubber leaf and nylon were added into wood sawdust to prepare renewable biomass pellets (BPs) at room temperature. The effects of these fiber natures on the physical properties of BPs were investigated by characterizing the elongation, particle density, abrasive resistance and impact resistant index. Experimental results showed that the addition of rice straw and rubber leaf possessed a positive effect on the physical properties of BPs while the addition of wheat straw and nylon had a negative effect. The positive effect of the former can be attributed to the strengthened bonds in the BPs by the intertwining action of a “solid bridge” between these linear hydrophilic fibers and wood sawdust. The negative effect of the latter is due to the repelling role between the hydrophobic fiber and hydrophilic wood sawdust to arrest the formation of their “solid bridge”. Therefore, the added fiber natures highly influenced the formation of a “solid bridge” that determined the physical properties of BPs derived from wood sawdust. [ABSTRACT FROM AUTHOR]

[Display omitted] • MB- and NB-aeration improves gas mass transfer compared to conventional aeration. • Latest advances on applications of MB- and NB-aeration to ASP are discussed. • MB- and NB-aeration is promising for upgrading the performance of conventional ASP. • MB- and NB-aeration largely shifts the microbial community composition in ASP. • Future research directions for MB- and NB-aeration are proposed. The activated sludge process (ASP) is widely used for wastewater treatment, and the aeration efficiency is crucial to the operation of wastewater treatment plants. Recently, microbubble (MB)- and nanobubble (NB)-aeration has attracted much attention as there is growing evidence that it holds a great promise for upgrading the process efficiency of current ASP under conventional macro-bubble-aeration. However, a comprehensive review to elucidate the potential application of MB- and NB-aeration in ASP is still lacking. Therefore, this review will provide a systematic introduction to MB- and NB-aeration (including the unique properties and generation methods of MBs and NBs), and gain mechanistic insights on how MB- and NB-aeration improve gas–liquid mass transfer. The recent advances in MB- and NB-aeration applications to ASP and the resultant effects are also highlighted and discussed in-depth. The review concludes with a brief consideration of future research interests. [ABSTRACT FROM AUTHOR]

• PET-MPs improved the performance of sulfur-mediated biological process. • The exposure of PET-MPs stimulated microbial metabolic activity. • PET-MPs promoted production of EPS and Cyt C and their electron transfer capacity. • Desulfobacter and Geobacter were significantly enriched under PET-MPs exposure. Microplastics are ubiquitous in estuaries, coasts, sewage and wastewater treatment plants (WWTPs), which could arouse unexpected effects on critical microbial processes in wastewater treatment. In this study, polyethylene terephthalate microplastics (PET-MPs) were selected to investigate the mechanism of its influence on the performance of sulfur-mediated biological process from the perspective of microbial metabolic activity, electron transfer capacity and microbial community. The results indicated that the exposure of 50 particles/L PET-MPs improved the chemical oxygen demand (COD) and sulfate removal efficiencies by 6.6 ± 0.5% and 4.5 ± 0.3%, respectively, due to the stimulation of microbial metabolic activity and the enrichment of sulfate-reducing bacteria (SRB) species, such as Desulfobacter. In addition, we found that the PET-MPs promoted Cytochrome C (Cyt C) production and improved the direct electron transfer (DET) capacity mediated by Cyt C. The long-term presence of PET-MPs stimulated the secretion of extracellular polymeric substance (EPS), especially the proteins and humic substances, which have been verified to be electroactive polymers to act as electron shuttles to promote the interspecies electron transfer pathway in sulfur-mediated biological process. Meanwhile, the transformation products (bis-(2-hydroxyethyl) terephthalate (BHET) and Mono (2-hydroxyethyl) terephthalic acid (MHET) of PET-MPs were detected in sulfur-mediated biological process. These findings indicate that the sulfur-mediated biological process has good adaptability to the toxicity of PET-MPs, which strengthens a deeper understanding of the dual function of microplastics in WWTPs. [Display omitted] [ABSTRACT FROM AUTHOR]

• Metagenomics analysis was applied to investigate the impacts of ciprofloxacin on sulfate-reducing bioprocess. • Ciprofloxacin induced microbial SOS responses such as activating efflux pump and DNA repair systems. • Functional genes involved in C, S and amino acid metabolisms were up-regulated. • Ciprofloxacin promoted the cooperation between microbes. • Species with a high complementarity index played pivotal roles against ciprofloxacin exposure. The fate and removal of ciprofloxacin, a class of fluoroquinolone antibiotic, during sulfur-mediated biological wastewater treatment has been recently well documented. However, little is known regarding the genetic response of microorganisms to ciprofloxacin. Here, a lab-scale anaerobic sulfate-reducing bioreactor was continuously operated over a long term for ciprofloxacin-contaminated wastewater treatment to investigate the response of the microorganisms to ciprofloxacin by adopting a metagenomics approach. It was found that total organic carbon (TOC) removal and sulfate reduction were promoted by approximately 10% under ciprofloxacin stress, along with the enrichment of functional genera (e.g., Desulfobacter, Geobacter) involved in carbon and sulfur metabolism. The metagenomic analytical results demonstrated that ciprofloxacin triggered the microbial SOS response, as demonstrated by the up-regulation of the multidrug efflux pump genes (8–125-fold higher than that of the control) and ciprofloxacin-degrading genes (4–33-fold higher than that of the control). Moreover, the contents of ATP, NADH, and cytochrome C, as well as related functional genes (including genes involved in energy generation, electron transport, carbon metabolism, and sulfur metabolism) were markedly increased under ciprofloxacin stress. This demonstrated that the carbon and sulfur metabolisms were enhanced for energy (ATP) generation and electron transport in response to ciprofloxacin-induced stress. Interestingly, the microbes tended to cooperate while being subjected exposure to exogenous ciprofloxacin according to the reconstructed metabolic network using the NetSeed model. Particularly, the species with higher complementarity indices played more pivotal roles in strengthening microbial metabolism and the SOS response under long-term ciprofloxacin stress. This study characterized the response mechanisms of microorganisms to ciprofloxacin at the genetic level in sulfur-mediated biological wastewater treatment. These new understandings will contribute the scientific basis for improving and optimizing the sulfur-mediated bioprocess for antibiotics-laden wastewater treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

• SRB consortia can gradually adapt to and resist to high levels of PE microplastics. • SRB consortia produced EPS to protect them against exposure to PE microplastics. • Leaching additives from PE microplastics did not affect the activity of SRB sludge. • The presence of PE microplastics shifted the community structure of SRB consortia. The stress responses of sulfate-reducing bacteria (SRB) sludge to polyethylene (PE) microplastic exposure were revealed for the first time. In this study, a lab-scale sulfate-reducing up-flow sludge bed reactor was continuously operated with different concentrations of PE microplastics in the feed (20, 100, and 500 microplastic particles (MPs)/L). Exposure to low levels of PE microplastics (i.e., 20 MPs/L) had a limited effect on SRB consortia, whereas higher levels of PE microplastics imposed apparent physiological stresses on SRB consortia. Despite this, the overall reactor performance, i.e., chemical oxygen demand removal and sulfate conversion, was less affected by prolonged exposure to PE microplastics. Moreover, as the concentration of PE microplastics increased, the SRB consortia promoted the production of extracellular polymeric substances to a greater extent, especially the secretion of proteins. As a result, protective effects against the cytotoxicity of PE microplastics were provided. Batch experiments further demonstrated that leaching additives from PE microplastics (including acetyl tri-n‑butyl citrate and bisphenol A, concentrations up to 5 μg/g sludge) exerted only a minor effect on the activity of SRB consortia. Additionally, microbial community analysis revealed active and potentially efficient sulfate reducers at different operational stages. Our results provide insight into the stress responses of SRB sludge under PE microplastic exposure and suggested that SRB consortia can gradually adapt to and resist high levels of PE microplastics. These findings may promote a better understanding of the stable operation of SRB sludge systems under specific environmental stimuli for practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • This study provides novel insight into stability improvement of co-digestion. • Recalcitrant substrates support highly diverse and stable community. • Labile substrates result in enrichment of monopoly taxon and less stable community. • High co-digestion efficiency depend on community redundancy and enriched lineages. This study investigated the temporal dynamics of digestion efficiency and community stability in digesters fed with waste activated sludge (WAS), straw (STR-AD), food waste (FW-AD) and mixture of straw-and-food waste (STR-FW-AD). Results showed that carbon removals of recalcitrant substrates (i.e., 48.2 ± 3.9% in WAS-AD and 57.8 ± 4.9% in STR-AD) were lower than that of labile substrates (i.e., 70.7 ± 4.0% in FW-AD). Nonetheless, carbon removal of recalcitrant substrates was largely improved through co-digestion (70.3 ± 3.2% in STR-FW-AD). In contrast to monopoly communities (e.g., the highly enriched Paludibacter) fed with the labile substrates, recalcitrant substrates supported highly diverse communities. Accordingly, the medians of negative/positive cohesions of communities in WAS-AD, STR-AD, STR-FW-AD and FW-AD decreased from 0.86 to 0.63, suggesting their decreasing community stability. Microbial source tracking analyses showed the major contribution of the STR-AD community to the co-digestion community. This study provided unprecedented mechanistic insight into stability improvement of substrate co-digestion on the methanogenic digestion microbiome. [ABSTRACT FROM AUTHOR]

• The influence of ibuprofen (IBU) on biological sludge systems and ecosystem were evaluated. • The anaerobic sludges were less effective in IBU removal. • IBU affected organics removal and sludge settling in activated sludge (AS) system. • The transformation products in AS system possessed higher acute toxicity than IBU. • The effluent IBU residue could impose chronic toxicity to aquatic organisms. Ibuprofen (IBU) is one of the frequently detected non-steroidal anti-inflammatory drugs (NSAIDs) in wastewater treatment plants (WWTPs) and aquatic environment. However, little is known about the effect of IBU and its biotransformation products (TPs) on different biological sludge systems and aquatic environment. The effects and toxicity of IBU and TPs on three biological sludge systems (i.e., activated sludge (AS), sulfate-reducing bacteria (SRB)-enriched sludge and anaerobic methanogenic (AnM) sludge systems) and aquatic environment were comprehensively evaluated through a long-term operation of three bioreactors and a series of batch experiments. Both of the SRB-enriched sludge and AnM sludge systems were not affected under a long-term exposure to IBU, based on removing organic carbon and sulfur and producing methane. This could be attributed to the high tolerance of functional microbes in the SRB-enriched sludge (e.g., genus Desulfobacter) and AnM sludge systems (e.g., genus Candidatus Methanomethylicus) for IBU. In contrast, IBU had some apparently inhibitory effects on the AS system, such as reduced organic removal efficiency and poor sludge settling. The analysis on microbial community revealed that IBU significantly inhibited the genera involved in organic degradation (e.g., genus Candidatus Competibacter) and also stimulated those genera (e.g., genus Brachymonas) to secret excess extracellular polymeric substances (EPS), which thus caused sludge bulking in the AS system. The toxicity of IBU and its TPs in the effluent of the AS system was also investigated with Vibrio fischeri bioluminescence inhibition tests and quantitative structure activity relationship (QSAR) analysis by ecological structure-activity relationship (ECOSAR) program. The results indicated that the AS system could effectively eliminate the acute toxicity of both IBU and TPs, but a potential chronic toxicity of IBU could still existed, which could be more harmful to aquatic organisms than that of its TPs. These findings provide an insight into the toxic effects of IBU and its TPs on biological sludge systems and ecosystem. [ABSTRACT FROM AUTHOR]

• Thermal-alkaline pretreatment synergistically release DOM from sludge EPS and cells. • The maximum attainable carbon removal efficiency achieved ~65% in sludge digestion. • Pretreatment-derived DOM as the key parameter in shaping sludge communities. • Digestion communities consists of both common and pretreatment-specific lineages. In this study, temporal impacts of thermal, alkaline/acid and thermal-alkaline sludge pre-treatments on digestion performance and microbiome were investigated and compared in methanogenic sludge digesters. Results showed that thermal and alkaline/acid pre-treatments were efficient in releasing intracellular and EPS organic matter, respectively. The thermal-alkaline pre-treatment showed synergistic impacts of both thermal and alkaline/acid pre-treatments by releasing the major portion of sludge organic matter from solid- to liquid-phase, which result in 60–65% organic carbon removal in subsequent sludge digestion and further optimizing digestion temperature had negligible improvement. The 16S rRNA gene-based analyses suggested that organic matter released from sludge pre-treatments is a major deterministic parameter in shaping sludge microbiome. Pre-treatment specific lineages were identified in different sludge digesters, whereas several taxa were identified as common functionally active populations in sludge digestion. This study provided mechanistic insights into impacts of pre-treatments on digestion performance and microbiome in methanogenic sludge digesters. [ABSTRACT FROM AUTHOR]

• A new APAD process was developed for methane generation from WAS. • Carbon removal achieved 52.8 ± 1.7% in APAD. • Pre-treatment changed community composition, function and microbial interaction patterns. • APAD had comparable environmental impact with thermal-AD and control-AD. Anaerobic sludge digesters are biorefineries for energy recovery from waste activated sludge (WAS) via methane production, in which disintegration of floc structure and microbial cells is a major challenge in releasing extracellular polymeric substances (EPS) and cytoplasmic macromolecules for subsequent hydrolysis and fermentation. Here, we developed a new process combining alkaline/acid pre-treatments and anaerobic digestion (APAD) to improve sludge digestion. Both alkaline and acid pre-treatments effectively disintegrated the floc structure and microbial cells to release sludge organic contents. Under the optimized alkaline/acid pre-treatment condition, carbon removal achieved 52.8 ± 1.7% in APAD digesters, in contrast to 30.9 ± 2.2% and 42.4 ± 1.6% in anaerobic digesters fed with fresh WAS (control-AD) and thermal pre-treated sludge (thermal-AD), respectively. Both alkaline/acid and thermal pre-treatments largely shifted sludge community composition and function, but in distinct ways, possibly due to their different sludge constitutes (i.e., dissolved organic matter and NaCl). Correspondingly, microbial network analysis identified three modules with varied keystone taxa and interaction patterns in the three digesters. Life cycle assessment showed the comparable environmental impacts of APAD, thermal-AD and control-AD. In all, this study provided a new solution for WAS treatment and insights into impact of sludge pre-treatments on sludge digestion microbiome. [ABSTRACT FROM AUTHOR]