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Accurate modeling of methane (CH 4 ) and sulfide (H 2 S) production in sewer systems was constrained by insufficient consideration of microbial processes under dynamic environmental conditions. This study introduces a microbial-guided machine learning (ML) framework (Micro-ML), which integrates microbial process representations from mechanistic models (microbial information) with ML models. Results indicate that Micro-ML model enhanced predictions of CH 4 and H 2 S production, where microbial information provides more information for model optimization. The feature importance of microbial information performed comparable weightings for 58.12 % and 55.16 %, respectively, but their relative significance in influencing Micro-ML model performance varies considerably. The application of Micro-ML performed great potential in reducing CH 4 and H 2 S production (decreased ∼ 80 % and 90 %). The integrated model not only improves the accuracy of CH 4 and H 2 S predictions but also offers a valuable tool for effective management strategies for sewer systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The production of short-chain fatty acids (SCFAs) from sludge is promising, but the efficiency and product quality often vary because of extracellular polymeric substances (EPS) characteristics and pretreatment principles. This study adopted specific EPS disintegration pretreatment to treat different types of sludge. By correlation coefficient matrix analysis and correlation dynamics change resolution, the intrinsic relationships between the nature of EPS and the production of SCFAs from sludge was unveiled. We demonstrate that tight-bound EPS (TB-EPS) is a principal carbon reservoir, positively impacting SCFAs yields, in the fermentation system with EPS as the main fermentation substrate, it can contribute about 29.2 % for SCFAs growth during fermentation. Conversely, TB-EPS exhibits a negative correlation during fermentation due to EPS-SCFAs interconversion, while loosely bound EPS (LB-EPS) correlates positively. Proteins and polysaccharides in TB-EPS, especially proteins, significantly enhance individual SCFAs yields, predominantly acetic, propionic, and isovaleric acids. The findings would provide a theoretical basis for developing pretreatments and process-control technologies aimed at improving SCFAs production efficiency and quality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Carbon disulfide (CS 2 ) is a widely used enzyme inhibitor with cytotoxic properties, commonly employed in viscose fibers and cellophane production due to its non-polar characteristics. In industry, CS 2 is often removed by aeration, however, residual CS 2 may enter the wastewater treatment plants, impacting the performance of nitrifying sludge. Currently, there is a notable dearth of research on the response of nitrifying sludge to CS 2 -induced stress. This study delves into the alterations in the performance of nitrifying sludge under short-term and long-term CS 2 stress, scrutinizes the toxic effects of CS 2 on microbial cells, elucidates the succession of microbial community structure, and delineates changes in microbial metabolic products. The findings from short-term CS 2 stress revealed that low concentrations of CS 2 induced oxidative stress damage, which was subsequently repaired in cells. However, at concentrations of 100-200 mg/L, CS 2 inhibited reactive oxygen species, superoxide dismutase, and catalase, which are associated with metabolic and antioxidant activities. The inhibition of nitrite oxidoreductase activity by high concentrations of CS 2 was attributed to its impact on the enzyme's conformation. Prolonged CS 2 stress resulted in an increase in the secretion of soluble extracellular polymeric substances in sludge, while CS 2 was assimilated into sulfate. The analysis of sludge microbial community structure revealed a decline in the relative abundance of Rhodanobacter, which is associated with nitrification, and an increase in Sinomonas, involved in sulfur oxidation. Metabolite analysis results demonstrated that high concentrations of CS 2 affect pantothenate and CoA biosynthesis, purine metabolism, and glutathione metabolism. This study elucidated the microbial response mechanism of nitrifying sludge under short-term and long-term CS 2 stress. It also clarified the composition and function of microbial ecosystems, and identified key bacterial species and metabolites. It provides a basis for future research to reduce CS 2 inhibition through approaches such as the addition of metal ions, the selection of efficient CS 2 -degrading strains, and the modification of strain metabolic pathways., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

As an emerging pollutant, benzalkonium chlorides (BACs) potentially enriched in waste activated sludge (WAS). However, the microbial response mechanism under chronic effects of BACs on acidogenesis and methanogenesis in anaerobic digestion (AD) has not been clearly disclosed. This study investigated the AD (by-)products and microbial evolution under low to high BACs concentrations from bioreactor startup to steady running. It was found that BACs can lead to an increase of WAS hydrolysis and fermentation, but a disturbance to acidogenic bacteria also occurred at low BACs concentration. A noticeable inhibition to methanogenesis occurred when BAC concentration was up to 15 mg/g TSS. Metagenomic analysis revealed the key genes involved in acetic acid (HAc) biosynthesis (i.e. phosphate acetyltransferase, PTA), β-oxidation pathway (acetyl-CoA C-acetyltransferase) and propionic acid (HPr) conversion was slightly promoted compared with control. Furthermore, BACs inhibited the acetotrophic methanogenesis (i.e. acetyl-CoA synthetase), especially BAC concentration was up to 15 mg/g TSS, thereby enhanced short chain fatty acids (SCFAs) accumulation. Overall, chronic stimulation of functional microorganisms with increasing concentrations of BACs impact WAS fermentation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

To recover resource from waste activated sludge (WAS) is of great significance. This study proposed a promising way, i.e., stepwise alkaline treatment coupled with ammonia stripping, to remarkably enhance short-chain fatty acids (SCFAs) production from WAS anaerobic digestion. The maximal production of SCFAs, with the value of 323 mg COD/g volatile suspended solid, was obtained with first initial pH = 10 adjustment followed by second initial pH = 10 adjustment on third day coupled with ammonia stripping. Mechanistic studies showed that solubilization of both extracellular polymeric substances and cells could be accelerated by stepwise initial pH = 10 adjustment. However, without ammonia stripping, the activities of either acidogens or methanogens could be inhibited by free ammonia formed under alkaline conditions; positively, anaerobes related to SCFAs production were enriched with ammonia stripping. Moreover, the proposed strategy can simultaneously achieve nitrogen and carbon recovery, providing some solutions for the carbon-neutral operation of wastewater treatment plants., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Biological foaming (or biofoaming) is a frequently occurring problem in wastewater treatment plants (WWTPs) and is attributed to the overwhelming growth of filamentous bulking and foaming bacteria (BFB). Biological foaming has been intensively investigated, with BFB like Microthrix and Skermania having been identified from WWTPs and implicated in foaming. Nevertheless, studies are still needed to improve our understanding of the microbial diversity of WWTP biofoams and how microbial activities contribute to foaming. In this study, sludge foaming at the Qinghe WWTP of China was monitored, and sludge foams were investigated using culture-dependent and culture-independent microbiological methods. The foam microbiomes exhibited high abundances of Skermania , Mycobacterium, Flavobacteriales , and Kaistella . A previously unknown bacterium, Candidatus Kaistella beijingensis, was cultivated from foams, its genome was sequenced, and it was phenotypically characterized. Ca . K. beijingensis exhibits hydrophobic cell surfaces, produces extracellular polymeric substances (EPS), and metabolizes lipids. Ca . K. beijingensis abundances were proportional to EPS levels in foams. Several proteins encoded by the Ca . K. beijingensis genome were identified from EPS that was extracted from sludge foams. Ca . K. beijingensis populations accounted for 4 to 6% of the total bacterial populations in sludge foam samples within the Qinghe WWTP, although their abundances were higher in spring than in other seasons. Cooccurrence analysis indicated that Ca . K. beijingensis was not a core node among the WWTP community network, but its abundances were negatively correlated with those of the well-studied BFB Skermania piniformis among cross-season Qinghe WWTP communities. IMPORTANCE Biological foaming, also known as scumming, is a sludge separation problem that has become the subject of major concern for long-term stable activated sludge operation in decades. Biological foaming was considered induced by foaming bacteria. However, the occurrence and deterioration of foaming in many WWTPs are still not completely understood. Cultivation and characterization of the enriched bacteria in foaming are critical to understand their genetic, physiological, phylogenetic, and ecological traits, as well as to improve the understanding of their relationships with foaming and performance of WWTPs.

Quaternary ammonium compounds have gained widespread attention due to their extensive enrichment in waste activated sludge (WAS) and potentially adverse effect to anaerobes. This study selected benzalkonium chlorides (BACs) as model to reveal the responses of anaerobic digestion of WAS to long-term stress of BACs. Results showed that the solubilization enhancement of WAS contributed by BACs was the acceleration of cell lysis, rather than the disruption of extracellular polymeric substances, and the accumulation improvement of short chain fatty acids (SCFAs) attributed to hydrolysis improvement and methanogenesis inhibition at either medium -or high level of BACs. In addition, a low level had no significant effect on the production of methane compared to control, with averages of 0.059 and 0.055 m 3 /(m 3 ·d), respectively, whereas a medium level reduced methane production to 20% of control, and a high level almost completely inhibited methanogenesis. Correspondingly, BACs could shift microbial communities related to SCFAs and methane productions. For the bacterial community, a high level of BACs led to abundance reductions of Firmicutes, Bacteroidetes, Acidobacteria and Chloroflexi, but Synergistetes was increased to 10.5%, which was almost not detected either in control or at a low level of BACs. And for dominant archaeal community, they tended to be shifted from acetotrophic to hydrogenotrophic methanogens with BACs increasing from low to high level. These findings provided some new insights for the role of BACs in anaerobic digestion, as well as resource recovery from WAS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The plastic products have large consumption over last decades, resulting in a serious microplastics (MPs) pollution. Specially, the main removal way of MPs from wastewater is to transfer MPs from liquid to solid phase, leading to its enrichment in waste activated sludge (WAS). Anaerobic digestion has been served as the most potential technique to achieve both resource recovery and sludge reduction, herein this review provides current information on occurrence, effect, and fate of MPs in anaerobic digestion of WAS. The effects of MPs on WAS anaerobic digestion are greatly related to forms, particles sizes, contents, compositions and leachates of MPs. Also, the presence of MPs not only can change the effects of other pollutants on anaerobic digestion of WAS, but also can affect the fates of them. Besides, the future perspectives focused on the fate, effect and final removal of MPs during WAS anaerobic digestion process are outlined., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study was conducted to investigate the effects of residual ferric ions (FI), released from iron or its oxides for wastewater or waste activated sludge (WAS) treatment, on anaerobic digestion of WAS. Herein it was found that the anaerobic digestion process was greatly affected by FI dosages as well as FI distributions. The responses of performance and microorganism suggested that a low FI (e.g., 0.125 mmol/g volatile suspended solid (VSS)) enhanced methane production by 29.3%, and a medium FI (e.g., 0.3 mmol/g VSS) promoted short chain fatty acids accumulation to reach the maximum of 247 mg chemical oxygen demand /g VSS, conversely, a high FI (e.g., 0.9 mmol/g VSS) led to severe inhibition on acidogenesis and methanogenesis. The findings may provide some new insights for mechanism understanding on anaerobic digestion process influenced by iron or its oxides, as well as the disposal of WAS contained FI., (Copyright © 2020. Published by Elsevier Ltd.)

An increasing interest is devoted to combined microbial electrolysis cell-anaerobic digestion (MEC-AD) system which could convert waste activated sludge into biogas. In this study series tests were initially conducted to study the effect of alkaline pretreatment on AD system and the results showed that alkaline pretreatment could promote the dissolution of organic matters in the sludge and thus improve the methane production. Then, the methane production in combined MEC-AD system fed with alkaline-pretreated sludge was investigated. The results indicated that the methane productions increased by 37% and 42% when applied voltage was 0.5 V and 0.8 V. The microbial electrochemical system strongly promoted the growth of Euryarchaeota (Methanosaeta and Methanobacterium). Meanwhile, the abundance of Paraclostridium increased from 17.9% to 38.5% when applied voltage was 0.8 V, suggesting an enhanced fermentation and acetogenesis process. The results of energy balance estimation indicated that MEC-AD system at 0.5 V could achieve higher net energy output., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Microorganisms in wastewater treatment plants (WWTPs) play a key role in the removal of pollutants from municipal and industrial wastewaters. A recent study estimated that activated sludge from global municipal WWTPs harbors 1 × 10 9 to 2 × 10 9 microbial species, the majority of which have not yet been cultivated, and 28 core taxa were identified as "most-wanted" ones (L. Wu, D. Ning, B. Zhang, Y. Li, et al., Nat Microbiol 4:1183-1195, 2019, https://doi.org/10.1038/s41564-019-0426-5). Cultivation and characterization of the "most-wanted" core bacteria are critical to understand their genetic, physiological, phylogenetic, and ecological traits, as well as to improve the performance of WWTPs. In this study, we isolated a bacterial strain, designated SJ-1, that represents a novel cluster within Betaproteobacteria and corresponds to OTU_16 within the 28 core taxa in the "most-wanted" list. Strain SJ-1 was identified and nominated as Casimicrobium huifangae gen. nov., sp. nov., of a novel family, Casimicrobiaceae. C. huifangae is ubiquitously distributed and is metabolically versatile. In addition to mineralizing various carbon sources (including carbohydrates, aromatic compounds, and short-chain fatty acids), C. huifangae is capable of nitrate reduction and phosphorus accumulation. The population of C. huifangae accounted for more than 1% of the bacterial population of the activated sludge microbiome from the Qinghe WWTP, which showed seasonal dynamic changes. Cooccurrence analysis suggested that C. huifangae was an important module hub in the bacterial network of Qinghe WWTP. IMPORTANCE The activated sludge process is the most widely applied biotechnology and is one of the best ecosystems to address microbial ecological principles. Yet, the cultivation of core bacteria and the exploration of their physiology and ecology are limited. In this study, the core and novel bacterial taxon C. huifangae was cultivated and characterized. This study revealed that C. huifangae functioned as an important module hub in the activated sludge microbiome, and it potentially plays an important role in municipal wastewater treatment plants., (Copyright © 2020 American Society for Microbiology.)

This study reported an efficient approach, i.e., alkaline followed by potassium ferrate (PF) pretreatment, to enhance short chain fatty acids (SCFAs) production from waste activated sludge anaerobic fermentation process. The optimum condition was initial pH of 10.0 and PF dosage of 28 mg Fe(VI)/g total suspended solid, with the highest SCFAs production of 382 mg chemical oxygen demand/g volatile suspended solid, which was 2.03 and 2.06 times higher than that of corresponding sole treatments. It was found that the alkaline + PF treatment could provide more soluble substrates for subsequent acidification process by accelerating disruption of both microbial cells and extracellular polymeric substances. And the alkaline + PF treatment also benefited to the activity promotion of specific hydrolases and inhibition of methanogens. Besides, the abundances of microorganisms related to SCFAs production, such as Proteiniclasticum and Macellibacteroides, were increased greatly, whereas the main SCFAs consumer, Proteobacteria, was decreased from 29.1% to 14.4%., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Volatile chlorinated hydrocarbons (VCHs) are often found as a type of persistent and ubiquitous contaminant in groundwater. The feasibility, characteristics and microbial mechanism of acclimation of biodiversity-rich inoculation source for bioelectrochemical stimulated VCH dechlorination remain poorly understood. Here, the superior bioelectrochemical catalytic activities were observed for tetrachloroethylene (0.26 mM d -1 ) and 1,2-dichloroethane (2.20 mM d -1 ) dechlorination in anaerobic sludge-acclimated biocathodes with an optimal potential of -0.5 V, averaging 1.60-2.71 times higher than those reported in previous works on biocathodes. When the cathode was applied as the sole electron donor for dechlorination, columbic efficiencies reached the values greater than 80%. Tetrachloroethylene dechlorination showed a metabolic pathway with cis-1,2-dichloroethene as the main product, whereas 1,2-dichloroethane was dechlorinated entirely to the nontoxic ethene. The cathodic biofilms were highly abundant with the dechlorination and electro-active genera, while significant bacterial consortium variation was observed in response to the different VCH types and changes in cathodic potential. Bacillus, Pseudomonas and Lactococcus were mostly enriched for tetrachloroethylene dechlorination, and pceA, tceA and omcX were highly expressed. Geobacter was the most predominant during 1,2-dichloroethane dechlorination with rdhA, tceA and omcX highly expressed. In addition, although the impact of cathodic potentials was weaker than that of VCH types, the lower cathodic potentials, the more abundant of the electrode respiring populations and the higher expression of extracellular electron transfer related gene. This study demonstrated the great potential of acclimation of anaerobic sludge by electrical stimulation for accelerating VCH remediations and gave insights into its working molecular mechanisms., (Copyright © 2019. Published by Elsevier Ltd.)

A potentially practical technology based on ferrate (VI), i.e. potassium ferrate (PF), pretreatment integrated into waste activated sludge (WAS) anaerobic fermentation has been presented to greatly enhance short-chain fatty acids (SCFAs) production with a shortened fermentation time. The maximum production of SCFAs, 343mg chemical oxygen demand/g volatile suspended solid with acetic acid proportion of 48.2%, was obtained with PF dosage of 56mg Fe(VI)/g total suspended solid within 5days, which was increased to 5.72times compared to that of control. The mechanism study showed that PF accelerated the release rate of both intracellular and extracellular constituents. And the activities of key hydrolytic enzymes were much improved with PF addition. Moreover, PF positively enriched the abundance of microorganisms responsible for WAS hydrolysis and SCFAs production, especially acetic acid-forming characteristic genera such as Petrimonas, Fusibacter and Acetoanaerobium. Besides, the incubation time of acidogenesis and methanogenesis were separated by PF., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

To characterize the impact of influent loading on elemental sulfur (S 0 ) recovery during the denitrifying and sulfide oxidation process, three identical, lab-scale UASB reactors (30cm in length) were established in parallel under different influent acetate/nitrate/sulfide loadings, and the reactor performance and functional community structure were investigated. The highest S 0 recovery was achieved at 77.9% when the acetate/nitrate/sulfide loading was set to 1.9/1.6/0.7kgd -1 m -3 . Under this condition, the genera Thauera, Sulfurimonas, and Azoarcus were predominant at 0-30, 0-10 and 20-30cm, respectively; meanwhile, the sqr gene was highly expressed at 0-30cm. However, as the influent loading was halved and doubled, S 0 recovery was decreased to 27.9% and 45.1%, respectively. As the loading was halved, the bacterial distribution became heterogeneous, and certain autotrophic sulfide oxidation genera, such as Thiobacillus, dominated, especially at 20-30cm. As the loading doubled, the bacterial distribution was relatively homogeneous with Thauera and Azoarcus being predominant, and the nirK and sox genes were highly expressed. The study verified the importance of influent loading to regulate S 0 recovery, which could be achieved as Thauera and Sulfurimonas dominated. An influent loading that was too low or too high gave rise to insufficient oxidation or over-oxidation of the sulfide and low S 0 recovery performance., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This study aimed to clarify phosphorus (P) fractions in waste activated sludge (WAS) and explore release performance and enhancement mechanism of different P species related to pH. Results showed that inorganic P (IP) was the major P fraction in raw sludge (87.86% of total solid P), and non-apatite inorganic P (NAIP), the most labile P forms, occupied 81.30% of IP, suggesting that WAS could be selected as potential substitution of phosphate rock. The optimized acid and alkaline conditions were pH=4 and pH=12 for molybdate reactive P accumulation, increased by 311.20mg/L and 479.18mg/L compared to raw sludge, which were 3.80 and 5.84 times higher than that of control, respectively. The mechanism study demonstrated that high pH promoted NAIP release, and apatite P was sensitive to low pH. Moreover, the releasable and recoverable P depended on both fractions of different P species in sludge and pH adjustment for sludge treatment., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

This study investigated the role of extracellular polymeric substances (EPSs) in enhanced performance of phosphorus (P) release from waste activated sludge (WAS) by adding rhamnolipid (RL). Results showed that compared to WAS without pretreatment, the released PO4(3-)-P increased with RL addition from 0 to 0.2 g/gTSS (total suspended solid), and increased by 208% under the optimal condition (0.1 g RL/g TSS and 72-h fermentation time). The cumulative PO4(3-)-P was better fitted with pseudo-first-order kinetic model. Moreover, the contents of metal ions increased in liquid but decreased in EPSs linearly with RL addition increasing, and WAS solubilizations were positively correlated with the released metal ions. The enhanced total dissolved P mainly came from cells and others (69.39%, 2.27-fold higher than that from EPSs), and PO4(3-)-P was the main species in both liquid and loosely bound EPSs, but organic P should be non-negligible in tightly bound EPSs., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In this study, two lab-scale UASB reactors were established to testify S(0) recovery efficiency, and one of which (M-UASB) was improved from the previous T-UASB by shortening reactor height once S(2-) over oxidation was observed. After the height was shortened from 60 to 30cm, S(0) recovery rate was improved from 7.4% to 78.8%, and while, complete removal of acetate, nitrate and S(2-) was simultaneously maintained. Meanwhile, bacterial community distribution was homogenous throughout the reactor, with denitrifying sulfide oxidization bacteria predominant, such as Thauera and Azoarcus spp., indicating the optimized condition for S(0) recovery. The effective control of working height/volume in reactors plays important roles for the efficient regulation of S(0) recovery during DSR process., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This paper presents the effects of different concentrations of citric acid (CA) and ethylene diamine tetra-acetic acid (EDTA) when used as additive reagents for the treatment of sewage sludge for agricultural use. Herein, both the retention of nutrients and removal of metals from the sewage sludge are examined. The average removal rate for the metals after treatment by CA decreased in the order Cu>Pb>Cd>Cr>Zn, while the rates after treatment by EDTA decreased in the order of Pb>Cu>Cr>Cd>Zn. After treatment with CA and EDTA, total nitrogen and total phosphorus concentrations in the sludge decreased, while the content of available nitrogen and Olsen-P increased. In addition, a multi-criteria analysis model-fuzzy analytic network process method (with 3 main factors and 12 assessment sub-factors) was adopted to evaluate the effectiveness of different treatment methods. The results showed that the optimal CA and EDTA concentrations for sewage sludge treatment were 0.60 and 0.125 mol/L, respectively., (Copyright © 2015. Published by Elsevier Ltd.)

The challenge of energy generation from biodegradation of recalcitrant organics in microbial fuel cells (MFCs) is mainly attributed to their persistence to degradation under anaerobic condition in anode chamber of MFCs. In this work, we demonstrated that electricity generation from aniline, a typical recalcitrant organic matter under anaerobic condition was remarkably facilitated by employing oxygen into bioanode of MFCs. By exposing bioanode to air, electrons of 47.2 ± 6.9 C were recovered with aniline removal efficiency of 91.2 ± 2.2% in 144 h. Limited oxygen supply (the anodic headspace was initially filled with air and then closed) resulted in the decrease of electrons recovery and aniline removal efficiency by 52.5 ± 9.4% and 74.2 ± 2.1%, respectively, and further decline by respective 64.3 ± 4.5% and 82.7 ± 1.0% occurred under anaerobic condition. Community analysis showed that anode biofilm was predominated by several aerobic aniline degrading bacteria (AADB) and anode-respiration bacteria (ARB), which likely cooperated with each other and finally featured the energy recovery from aniline. Cyclic voltammetry indicated that anodic bacteria transferred electrons to anode mainly through electron shuttle. This study provided a new sight to acquaint us with the positive role of oxygen in biodegradation of recalcitrant organics on anode as well as electricity generation., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

A Gram-staining-negative, rod-shaped, motile and facultatively anaerobic bacterial strain, designated X2(T), was isolated from the sludge of an anaerobic, denitrifying, sulfide-removal bioreactor, and found to oxidize sulfide anaerobically with nitrate as electron acceptor. The strain grew at salinities of 0-3% (w/v) NaCl (optimum, 0-1%). Growth occurred at pH 6.0-10.0 (optimum, pH 8.0) and 10-37 °C (optimum, 30 °C). The genomic DNA G+C content was 59 mol%. Q-8 and Q-9 were detected as the respiratory quinones. The major fatty acids (>10 %) were C16:1ω7c and/or C16: 1ω6c, C18: 1ω7c and C16:0. The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and one unidentified phospholipid. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain X2(T) formed a novel clade within the family Pseudomonadaceae, with the highest sequence similarity to Pseudomonas caeni KCTC 22292(T) (93.5%). On the basis of phenotypic, chemotaxonomic and phylogenetic characteristics, it is proposed that this strain represents novel genus and species within the family Pseudomonadaceae, for which the name Thiopseudomonas denitrificans gen. nov., sp. nov. is proposed. The type strain is X2(T) ( =CCTCC M 2013362(T) =DSM 28679(T) = KCTC 42076(T))., (© 2015 IUMS.)

Significant progress has been achieved in China for biohydrogen production from organic wastes, particularly wastewater and agricultural residues, which are abundantly available in China. This progress is reviewed with a focus on hydrogen-producing bacteria, fermentation processes, and bioreactor configurations. Although dark fermentation is more efficient for hydrogen production, by-products generated during the fermentation not only compromise hydrogen production yield but also inhibit the bacteria. Two strategies, combination of dark fermentation and photofermentation and coupling of dark fermentation with a microbial electrolysis cell, are expected to address this issue and improve hydrogen production as well as substrate utilization, which are also discussed. Finally, challenges and perspectives for biohydrogen production are highlighted.

A mathematical model of carbon, nitrogen and sulfur removal (C-N-S) from industrial wastewater was constructed considering the interactions of sulfate-reducing bacteria (SRB), sulfide-oxidizing bacteria (SOB), nitrate-reducing bacteria (NRB), facultative bacteria (FB), and methane producing archaea (MPA). For the kinetic network, the bioconversion of C-N by heterotrophic denitrifiers (NO 3 − → NO 2 − → N 2 ), and that of C-S by SRB (SO 4 2− → S 2− ) and SOB (S 2− → S 0 ) was proposed and calibrated based on batch experimental data. The model closely predicted the profiles of nitrate, nitrite, sulfate, sulfide, lactate, acetate, methane and oxygen under both anaerobic and micro-aerobic conditions. The best-fit kinetic parameters had small 95% confidence regions with mean values approximately at the center. The model was further validated using independent data sets generated under different operating conditions. This work was the first successful mathematical modeling of simultaneous C-N-S removal from industrial wastewater and more importantly, the proposed model was proven feasible to simulate other relevant processes, such as sulfate-reducing, sulfide-oxidizing process (SR-SO) and denitrifying sulfide removal (DSR) process. The model developed is expected to enhance our ability to predict the treatment of carbon-nitrogen-sulfur contaminated industrial wastewater. [ABSTRACT FROM AUTHOR]

• RONCs transformation and ammonification is the key step for total nitrogen removal. • The cleavage of C-N bond limited the transformation of electrophilic RONCs to NH 4 +. • Electrostimulation enhances the anaerobic reduction of RONCs into aromatic amines. • Micro-aeration enhances the aerobic oxidation of amine products into NH 4 +. • Regulating microbial redox reactions facilitates the transformation of RONCs. Biotechnology for wastewater treatment is mainstream and effective depending upon microbial redox reactions to eliminate diverse contaminants and ensure aquatic ecological health. However, refractory organic nitrogen compounds (RONCs, e.g., nitro-, azo-, amide-, and N-heterocyclic compounds) with complex structures and high toxicity inhibit microbial metabolic activity and limit the transformation of organic nitrogen to inorganic nitrogen. This will eventually result in non-compliance with nitrogen discharge standards. Numerous efforts suggested that applying exogenous electron donors or acceptors, such as solid electrodes (electrostimulation) and limited oxygen (micro-aeration), could potentially regulate microbial redox reactions and catabolic pathways, and facilitate the biotransformation of RONCs. This review provides comprehensive insights into the microbial regulation mechanisms and applications of electrostimulation and micro-aeration strategies to accelerate the biotransformation of RONCs to organic amine (amination) and inorganic ammonia (ammonification), respectively. Furthermore, a promising approach involving in-situ hybrid anaerobic biological units, coupled with electrostimulation and micro-aeration, is proposed towards engineering applications. Finally, employing cutting-edge methods including multi-omics analysis, data science driven machine learning, technology-economic analysis, and life-cycle assessment would contribute to optimizing the process design and engineering implementation. This review offers a fundamental understanding and inspiration for novel research in the enhanced biotechnology towards RONCs elimination. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Self-acidification was mainly attributed to sulfur disproportionation. • Supplying alkalinity to bulk was essential to control self-acidification. • S0FB achieved 7–129 times higher of TN removal rate than S0PB. • S0FB achieved 26–65 times higher of TP removal rate than S0PB. The sulfur fluidizing bioreactor (S0FB) has significant superiorities in treating nitrate-rich wastewater. However, substantial self-acidification has been observed in engineering applications, resulting in frequent start-up failures. In this study, self-acidification was reproduced in a lab-scale S0FB. It was demonstrated that self-acidification was mainly induced by sulfur disproportionation process, accounting for 93.4 % of proton generation. Supplying sufficient alkalinity to both the influent (3000 mg/L) and the bulk (2000 mg/L) of S0FB was essential for achieving a successful start-up. Furthermore, the S0FB reached 10.3 kg-N/m3/d of nitrogen removal rate and 0.13 kg-PO 4 3-/m3/d of phosphate removal rate, respectively, surpassing those of the documented sulfur packing bioreactors by 7–129 times and 26–65 times. This study offers a feasible and practical method to avoid self-acidification during restart of S0FB and highlights the considerable potential of S0FB in the treatment of nitrate-rich wastewater. [ABSTRACT FROM AUTHOR]

A bioelectrochemical system (BES) is a technology with potential for accelerating the degradation of recalcitrant compounds, the components and configurations of which are important for treatment performance. In the present work, a membraneless sleeve-type BES (termed BioE) was designed for the treatment of synthetic coal gasification wastewater (CGW, phenol as a model pollutant) and real CGW. Compared with the biological control (termed Bio), the phenol removal rate and COD removal efficiency increased by 2.6 and 2.1 fold in the BioE, respectively. However, the coulombic efficiency of this system was relatively low, ranging from 0.42% to 2.6%. This combination of results indicated that anode respiration was not the main process in the BioE. The increased CH 4 production and higher levels of methanogens obtained from the BioE confirmed that the methanogenic process proceeded, possibly facilitated by the diffusion of H 2 from the cathode to the anode. This study provides new insight into biocathode function for COD oxidation removal in BESs. Moreover, this study indicates that pursuing a high coulombic efficiency may not be necessary for wastewater treatment, as it consumes less energy at the lower value. Unlabelled Image • A membrane-less sleeve type BES (BioE) was designed for treatment of CGW • The removal of phenol/COD was enhanced while the CE was relatively low (0.42% ~2.6%) • Enhanced methanogenic process and higher biomass promoted the phenol/COD removal • H 2 produced from the cathode may accelerate phenol transformation and COD removal [ABSTRACT FROM AUTHOR]

[Display omitted] • The SAD efficiency under high salinity could reach 70 %–80 % of salt-free condition. • Salt-tolerant SAD microbes were key to efficient SAD under high-salinity stress. • The salinity-tolerance abilities of difference SOBs were ranked. • High-salinity inhibited biomass yield rather than individual microbial function. This study investigated the performance of sulfur-dominated autotrophic denitrification (SAD) process under four different salinities of 0 %, 0.5 %, 3 %, and 6 %, simulating groundwater, sewage, seawater, and industrial wastewater scenarios, respectively. In terms of removal efficiency, the nitrate removal rates at 0.5 % and 3 % salinities decreased by 5.8 % and 16.8 %, respectively, compared to 0 % salinity. At 6 % salinity, the efficiency fluctuated during long-term operation, ranging from 56.0 % to 89.9 % of the value at 0 % salinity. According to the succession of microbial communities across time and salinity gradients, the dominant denitrification functional microorganisms were ranked by their salinity-tolerance ability as low-tolerant bacteria (0 %–0.5 %: Simplicispira , Herpetosipin , and Thermomonas), medium-tolerant bacteria (0 %–3 %: Thiobacillus and Sulfurimonas), high-tolerant bacteria (3 %–6 %: Thiogranum , Xanthomarina , and Vicingus), and halophilic bacteria (6 %: Aequorivita). Additionally, Aequorivita and Thiogranum , as the top 2 genera under 6 % salinity, presented positive and negative correlations with nitrate removal efficiency. The molecular ecological network revealed that increased positive interactions of 58.7 % among dominant genera occurred at 6 % salinity, confirming an effective cooperation coping with the high-salinity stress. In addition, the microbial responses to high-salinity primarily exhibited 22 %–45 % decrease in protein content, a 15 % decrease in live cells proportion, and a comparable level of individual functional gene expression. The results indicate that the efficiency of SAD by high salinity is determined by biomass amount and individual microbial capacity. This study offered new sights for understanding microbial succession and relationships in response to saltwater with diverse origins and varying water qualities in SAD systems. [ABSTRACT FROM AUTHOR]

An important way to promote the environmental industry's goal of carbon reduction is to promote the recycling of resources. Membrane separation technology has unique advantages in resource recovery and advanced treatment of industrial wastewater. However, the great promise of traditional organic membrane is hampered by challenges associated with organic solvent tolerance, lack of oxidation resistance, and serious membrane fouling control. Moreover, the high concentrations of organic matter and inorganic salts in the membrane filtration concentrate also hinder the wider application of the membrane separation technology. The emerging cost-effective graphene oxide (GO)-based membrane with excellent resistance to organic solvents and oxidants, more hydrophilicity, lower membrane fouling, better separation performance has been expected to contribute more in industrial wastewater treatment. Herein, we provide comprehensive insights into the preparation and characteristic of GO membranes, as well as current research status and problems related to its future application in industrial wastewater treatment. Finally, concluding remarks and future perspectives have been deduced and recommended for the GO membrane separation technology application for industrial wastewater treatment, which leads to realizing sustainable wastewater recycling and a nearly "zero discharge" water treatment process. [Display omitted] • Detailed description of the demand for industrial wastewater advanced treatment. • The characteristics and performance of GO membrane in advanced treatment of industrial wastewater were described. • The innovative application of GO membrane in advanced treatment of industrial wastewater was summarized. • How to deal with membrane fouling of GO membrane in industrial wastewater treatment was discussed in detail. • The application potential of GO membrane in industrial wastewater treatment was prospected in detail. [ABSTRACT FROM AUTHOR]

• Simultaneous and efficient removal of nitrogen and phosphorus was achieved in SCW. • Sulfate was formed mainly through SAD and sulfur disproportionation process in SCW. • Key functional genes of nitrogen metabolism were significantly enriched in SCW. • Thiobacillus and Sulfurimonas was selectively enriched in SCW. • Better TAN removal performance was obtained in CW-SCW combined operation mode. Constructed wetlands (CWs) integrated with sulfur autotrophic denitrification to stimulate high-rate nitrogen removal from carbon-limited wastewater holds particular application prospect due to no excessive carbon source addition, high efficiency, and good stability. In this study, we conducted elemental sulfur-based constructed wetland (SCW) and traditional constructed wetland (CW) under different C/N (2, 1, and 0.5) to explore the feasibility and mechanisms for nitrogen removal from low C/N wastewater. Compared with CW, SCW was demonstrated more robust in nitrogen removal in the case of low C/N influent. When the influent C/N control was at 0.5, SCW observed total nitrogen (TN) and nitrate removal efficiency of 69.36 ± 3.96% and 81.71 ± 3.96%, with the corresponding removal rate of 1.18 ± 0.66 and 1.70 ± 0.92 g-N·m–2·d–1, which were 2.11 and 10.03 times of CW, respectively. The nitrate removal rate constant k in the SCW was 1.05, 3.83, and 10.33 times higher than the CW with C/N of 2, 1 and 0.5. Furthermore, 14.40, 54.51, and 79.82% of nitrogen were removed by the sulfur autotrophic denitrification (SAD) in SCW, which also contributed 43.89, 73.68, and 71.70% of sulfate production. Moreover, the combined system of CW-SCW is proved be an efficient operation mode for simultaneously removing total ammonia nitrogen (TAN) and nitrate. In the SCW, the richness of the microbial community was improved and sulfur-oxidizing genera (e.g. Thiobacillus, Sulfurimonas) was selectively enriched, which affect the performance the elemental sulfur-based denitrification process. The nitrate reduction pathway was overwhelmed by denitrification and the dissimilatory nitrate reduction process. These findings offer elemental sulfur-based autotrophic denitrification constructed wetland has excellent potential to enhance nitrogen removal from carbon-limited wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

• pCNB inhibited the ammonia oxidation, plant and microbial growth in CW. • BES improved the tolerance of CW to pCNB by highly efficient degradation of pCNB. • ECW could significantly enhance TN and nitrate removal compared with CW. • Low voltage enhanced electroactive pCNB degradation bacteria growth in ECW. Constructed wetlands (CWs) integrated with the bioelectrochemical system (BES-CW) to stimulate bio-refractory compounds removal holds particular promise, owing to its inherent greater scale and well-recognized environmentally benign wastewater advanced purification technology. However, the knowledge regarding the feasibility and removal mechanisms, particularly the potential negative effects of biorefractory compounds on nitrogen removal performance for the CWs is far insufficient. This study performed a critical assessment by using BES-CW (ECW) and conventional CW (CW) to investigate the effects of p-Chloronitrobenzene (pCNB) on nitrogen transformations in CWs. The results showed that low concentration (1 mg·L−1) of pCNB would inhibit the ammonia oxidation in CWs, while ECW could improve its tolerance to pCNB to a certain level (8 mg·L−1) due to the high pCNB degradation efficiencies (2.5 times higher than CWs), accordingly, much higher TN and nitrate removal efficiencies were observed in ECWs, 81.71% - 96.82% (TN) higher than CWs, further leading to a lower N 2 O emission from ECWs than CWs. The main intermediate of pCNB degradation was p-Chloroaniline (pCAN) and the genera Geobacter and Propionimicrobium were consider to be the responsible pCNB degradation bacteria in the present study. However, too high concentration (20 mg·L−1) of pCNB would have a huge impact on ECW and CW, especially microbial biomass. Nevertheless, ECW could improve the 1.87 times higher microbial biomass than CW on the substrate. Accordingly, considerably higher functional gene abundance was observed in ECW. Therefore, the introduction of BES has great potential to ensure CW stability when treating industrial wastewater containing bio-refractory compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

Tetrabromobisphenol A (TBBPA) has aroused widespread pollution in industrial wastewater. Microbial fuel cell (MFC) was proved powerful in organics degradation and simultaneous resource recovery during wastewater treatment. However, the TBBPA biotransformation potential, pathway and the related molecular mechanism remain poorly understood. In this study, the enhanced degradation and detoxification performance of TBBPA in MFC anode was confirmed, evidenced by the shorter degradation period (2.3 times shorter) and less generation of bisphenol A. UPLC-QTOF-MS analysis verified TBBPA metabolism went through reductive debromination, hydrolytic debromination, oxidative ring cleavage and o -methylation. Accompanied with those biochemical processes, the metabolites underwent dynamic changes. The distinctly decreased abundance and fewer interactions with other functional genera for the potential reductive dehalogenators (Pseudomonas , etc.) possibly led to the suppressed reductive debromination (5.1%) in the closed bioanode. Otherwise, the more abundant potential function bacteria with more collaborated interrelations, including hydrolytic dehalogenators (Acinetobacter, etc.), aromatics degrading bacteria (Geobacter , Holophaga , etc.) and electroactive bacteria (Geobacter , Desulfovibrio , etc.) made great sense to the enhanced hydrolytic debromination and detoxification of TBBPA. This study revealed that MFC anode was beneficial to TBBPA degradation and provided theoretical support for the decomposition and transformation of micro-pollutants in the municipal sewage treatment coupled with MFC process. [Display omitted] • Microbial fuel cells greatly favored TBBPA bio-degradation and detoxification. • Dynamic route via reductive/hydrolytic debromination, ring cleavage and methylation. • Electroactive, debromination and aromatics degrading related genera dominated. • More tightened interactions and collaboration of dominated genera were found. [ABSTRACT FROM AUTHOR]

• HAR and ABFR combined process was developed for treating azo dye wastewater. • Separating HAR and ABFR into two individual reactors was preferable than stacking them together. • Bioelectrochemical reactions obviously enhanced the decolorization process. • The effect of reflux ratio on azo dye wastewater treatment was investigated. A combined process that consisted of a hybrid anaerobic reactor (HAR) with an integral bioelectrochemical system and aerobic biofilm reactor (ABFR) was established for simulated azo dye wastewater treatment (domestic wastewater containing dye acid orange 7). The split combination form that separated HAR and ABFR into two individual reactors recorded a decolorization efficiency of 81.23 ± 0.12%, which was about 8% higher than that HAR and ABFR were stacked together into a single up-flow reactor. Implementation of reflux improved the decolorization and chemical oxygen demand (COD) removal in both the processes. Decolorization efficiency achieved 97.52 ± 0.66% in split process at a reflux ratio of 1 and the COD was 89 ± 2 mg/L in the final effluent. Further increasing the reflux ratio to 3 did not have any significance in treatment performance of the reactors. This study comprehensively revealed the influence of combination forms and reflux ratio on the performance of combined process. [ABSTRACT FROM AUTHOR]