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Persulfate oxidation (PS) is widely employed as a promising alternative for waste activated sludge pretreatment due to the capability of generating free radicals. The product differences and microbiological mechanisms by which PS activation triggers WAS digestion through multiple modes need to be further investigated. This study comprehensively investigated the effects of persulfate oxidation activated through multiple modes, i.e., ferrous, zero-valent iron (ZVI), ultraviolet (UV) and heat, on the performance of sludge digestion. Results showed that PS_ZVI significantly accelerated the methane production rate to 12.02 mL/g VSS. By contrast, PS_Heat promoted the sludge acidification and gained the maximum short-chain fatty acids (SCFAs) yield (277.11 ± 7.81 mg COD/g VSS), which was 3.41-fold compared to that in PS_ZVI. Moreover, ferrous and ZVI activated PS achieved the oriented conversion of acetate, the proportions of which took 73% and 78%, respectively. MiSeq sequencing results revealed that PS_Heat and PS_UV evidently enriched anaerobic fermentation bacteria (AFB) (i.e., Macellibacteroides and Clostridium XlVa). However, PS_Ferrous and PS_ZVI facilitated the enrichment of Woesearchaeota and methanogens. Furthermore, molecular ecological network and mantel test revealed the intrinsic interactions among the multiple functional microbes and environmental variables. The homo-acetogens and sulfate-reducing bacterial had potential cooperative and symbiotic relationships with AFB, while the nitrate-reducing bacteria displayed distinguishing ecological niches. Suitable activation modes for PS pretreatments resulted in an upregulation of genes expression responsible for digestion. This study established a scientific foundation for the application of sulfate radical-based oxidation on energy or high value-added chemicals recovery from waste residues. [Display omitted] • Effect of multiple activated persulfate oxidation on sludge digestion was studied. • Heat and UV activated persulfate effectively promoted the accumulation of SCFAs. • ZVI and Ferrous activated persulfate were beneficial for methane production. • Microbial community structures were altered by multiple persulfate activation modes. • Suitable activation modes for persulfate upregulated the critical genes expression. [ABSTRACT FROM AUTHOR]

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

Boosting acetate production from waste activated sludge (WAS) fermentation is often hindered by the inefficient solubilization in the hydrolysis step and the high hydrogen pressure ( p H 2) during the acidogenesis of C3–C5 short-chain fatty acid (SCFAs), i.e., propionate (HPr), butyrate (HBu) and valerate (HVa). Therefore, this study employed persulfate (PS) oxidation and C3–C5 incomplete-oxidative sulfate reducing bacteria (io-SRB) metabolizers to tailor SCFAs conversion from WAS fermentation. The decomposition efficiency, performance of SCFAs production was investigated. Results showed that the PS significantly promoted WAS decomposition, with a dissolution rate of 39.4%, which is 26.0% higher than the un-treated test. Furthermore, SCFAs yields were increased to 462.7 ± 42 mg COD/g VSS in PS-HBu-SRB, which was 7.4 and 2.2 times higher than that of un-treated and sole PS tests, respectively. In particular, the sum of acetate and HPr reached the peak value of 85%, indicating that HBu-SRB mediation promoted the biotransformation of HBu and macromolecular organics by reducing the p H 2 restriction. Meanwhile, sulfate radical (SO 4 ∙-)-based oxidation (SR-AOPs) was effective in the decomposition of WAS, the oxidative product, i.e., sulfate served the necessary electron acceptor for the metabolism of io-SRB. Further analysis of Mantel test revealed the cluster of the functional genus and their interaction with environmental variables. Additionally, molecular ecological network analysis explored the potential synergistic and competitive relationships between critical genera. Additionally, the potential synergistic and competitive relationships between critical genera was explored by molecular ecological network analysis. This study provides new insights into the integration of SR-AOPs with microbial mediation in accelerating SCFAs production from WAS fermentation. [Display omitted] • Integration of SR-AOPs and io-SRB mediation tailored SCFAs conversion from WAS. • SR-AOPs efficiently promoted WAS decomposition with hydrolysis rate increased by 26%. • HBu-SRB promoted C2–C3 SCFAs conversion by reducing the p H 2 restriction. • Synergetic relationship among io-SRB and fermentative genera was revealed. • Thermodynamic mechanism of acetate-oriented conversion by io-SRB was explored. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

Microbial electrolysis cell (MECs) were investigated as a promising technology to manage waste activated sludge (WAS) reduction and bio-methane generation. The effect of WAS concentration on the MECs performance was discussed. At the optimal concentration of 15 g COD/L, maximum methane yield of MECs fed with alkaline pretreated WAS (A-WAS) were achieved with the value of 77.13 ± 2.52 L CH 4 /kg-COD on Day 3, which had been improved by 1.5-fold compared with MECs fed with raw WAS (R-WAS), while that was negligible in open circuit controls. Efficient sludge reduction was also obtained in terms of TCOD, total protein, TSS and VSS removal. Pyrosequencing revealed the dominance of exoelectrogen Geobacter and hydrogen-producing bacteria Petrimonas in MECs fed with WAS . Methanocorpusculum with the capacity of methane generation using CO 2 and H 2 also showed overwhelming dominance (96.01%). The large proportions of Petrimonas and Methanocorpusculum indicated the occurrence of hydrogenotrophic methanogenesis in our methane-producing MECs. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel strategy for improving VFAs bioproduction from waste activated sludge (WAS) was developed. [•] WAS hydrolysis, VFAs production and protein degradation were improved. [•] A synergistic effect occurred with co-digesting WAS and ABS. [•] FTIR and 3D-EEM were successfully employed to explore the mechanism. [ABSTRACT FROM AUTHOR]

Highlights: [•] SCFAs yield was enhanced by co-digesting waste activated sludge and corn stover. [•] Corn stover proportion in feedstock determined the acidification product spectrum. [•] Corn stover addition improved the hydrolysis and acidification of particulate organics. [•] Optimal feedstock proportion was 65%WAS:35%CS from carbon balance and cost estimation. [Copyright &y& Elsevier]

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

Highlights: [•] VFAs yield was enhanced from digesting rhamnolipid-pretreated waste activated sludge. [•] RL was generated in situ during WAS fermentation. [•] Particulate organics solubilization was improved. [•] The activity of methanogen was inhibited in the presence of RL. [•] Hydrolytic enzymes activity was improved. [Copyright &y& Elsevier]

[Display omitted] In the work, Bi 2 WO 6 /C-TiO 2 photocatalyst was successfully synthesized for the first time by loading narrow bandgap semiconductor Bi 2 WO 6 on MOF-derived carboxyl modified TiO 2. The phase structure, morphology, photoelectric properties, surface chemical states and photocatalytic performance of the prepared photocatalysts were systematically investigated using various characterization tools. The degradation efficiency of oxytetracycline by 6BT Z-scheme heterojunction photocatalyst under visible light could reach 93.6 % within 100 min, which was related to the high light harvesting and effective separation and transfer of photo-generated carriers. Furthermore, the effects of various environmental factors in actual wastewater were further investigated, and the results showed that 6BT exhibited good adaptability, durability and resistance to interference. Unlike most works, the degradation system with a different single active species were designed and constructed based on their formation mechanism. In addition, for the first time, a positive study was conducted on the priority attack sites, intermediate products, and degradation pathways for the photocatalytic degradation of oxytetracycline by a single active species through HPLC-MS and Fukui index calculations. The toxicity changes of intermediate products produced in three different single active species oxidation systems were evaluated using toxicity assessment software tools (T.E.S.T.), Escherichia coli growth experiments, and wheat growth experiments. Among them, the intermediate products formed through O 2 – oxidation had the lowest toxicity and the main active sites it attacked were the 20C, 38O, 18C, 41O, and 55O atoms with high f+ values in the oxytetracycline molecular structure. This work provided the insight into the role of each active species in the degradation of antibiotics and offered new ideas for the design and synthesis of efficient and eco-friendly photocatalysts. [ABSTRACT FROM AUTHOR]

In this study, the feasibility of free nitrous acid (FNA) pretreatment coupled with quorum sensing (QS) was investigated to enhance hydrogen recovery from waste activated sludge (WAS) via electro-fermentation (EF). 3-oxo-hexanoyl-homoserine lactone (3OC6-HSL), as the signal molecule, was only added in the first three cycles of sludge inoculation at the phase of microbial electrolysis cells (MECs) startup. Results showed that QS combined FNA (AHL-FMEC) enabled highest hydrogen yield and current (4.3 mg/g VSS and 4.5 mA), while that generated from sole FNA/QS treated WAS (FMEC/AHL-RMEC) were only 3.5/3.0 mg/g VSS and 1.5/1.5 mA, respectively. Fourier transform infrared (FT-IR) spectra illustrated the effective conversion of organics in AHL-FMEC, the utilization efficiencies of proteins and carbohydrates achieved to 75.0% and 79.7%, respectively. Besides, the internal resistance decreased from 34.5 Ω (FMEC) to 22.9 Ω (AHL-RMEC), further to 18.0 Ω, indicating the promoted bioelectrochemical activity of electroactive bacteria (EAB) in AHL-FMEC. Correspondingly, both EAB (21.7%), e.g., Geobacter (9.3%) and Pseudomonas (3.2%) and anaerobic fermentation bacteria (AFB, 28.6%), e.g., Proteiniclasticum (14.2%) and Petrimonas (3.6%) enriched to peaks in AHL-FMEC. Moreover, molecular ecological network (MEN) analysis revealed the underling relationships among AFB, EAB and homo-acetogen in EF system, suggesting the possible cooperative QS has been constructed. The results obtained in this study may provide a new insight for efficient hydrogen recovery from electro-fermentation of WAS. Unlabelled Image • Enhanced hydrogen yield was gained by coupling free nitrous acid and quorum sensing. • FNA and QS promoted higher VFAs yield and organics utilization than sole FNA. • Electrochemical activity of microbial electrolysis cell was boosted by QS regulation. • 21.7% EAB and 28.6% AFB were enriched during bioelectrolysis. • Synergetic relationships of microbes were explored by molecular ecological network. [ABSTRACT FROM AUTHOR]

• Coupling SO 4 ∙‾ oxidation with io-SRB mediation enhanced acetogenesis from WAS. • SO 4 ∙‾ and ∙OH were the key radicals responsible for coupled Fe(VI)/S(IV) oxidation. • io-SRB mediation promoted the organics transformation on the basis of SO 4 ∙‾ oxidation. • SO 4 ∙‾/io-SRB altered the structure of WAS fermentative acidogenic microbiome. • Synergistic relationships among io-SRB, hydrolyzing bacteria and acidogens were revealed. Acetate (HAc) production via acetogenesis is a promising biorefinery approach for waste activated sludge (WAS); however, it is hampered by the thermodynamic constraints of the bioconversion of 3–5 carbon atom short-chain fatty acids (SCFAs). Sulfate radical (SO 4 ∙‾)-based advanced oxidation is regarded as an appropriate candidate for accelerating WAS fermentation. In this study, we enriched an incomplete-oxidative sulfate reducing bacteria (io-SRB), combined with SO 4 ∙‾ oxidation (generated by potassium ferrate (PF) and sodium sulfite (Na 2 SO 3)), to boost WAS acetogenesis. Generated sulfate during SO 4 ∙‾ oxidation served as the necessary substrates for io-SRB metabolism. A proof-of-concept based on experimental data for the whole process is presented. Results confirmed that the PF + Na 2 SO 3 + SRB test achieved the maximum SCFAs generation (4261 ± 210 mg COD/L with 60.9 ± 0.5% HAc) over the PF + Na 2 SO 3 test without io-SRB mediation (2521 ± 109 mg COD/L with 50.6 ± 0.3% HAc). Particle size analysis and fluorescence spectroscopy indicated that PF + Na 2 SO 3 oxidation had positive effects on accelerating soluble organics release. SO 4 ∙‾ was the key radical, playing the most important role, as indicated by electron paramagnetic resonance and radical scavenging analysis. X-ray photoelectron spectroscopy revealed that io-SRB mediation further promoted the transformation of polysaccharides and proteins into carboxylic acids, based on SO 4 ∙‾ oxidation. Moreover, 79% Fe(VI) was reduced to Fe(III), and most S(IV) was converted to SO 4 2−, approximately 40% of which was metabolized by io-SRB consortium. Clearly, SO 4 ∙‾ oxidation and io-SRB stimulation significantly altered the composition of the key microbiome, with fermentative acidogenic bacteria predominating. The possible synergistic relationships among io-SRB, hydrolyzing bacteria and acidogens were revealed by molecular ecological network analysis. This study provides new insights into the improvement of value-added bio-metabolite recovery from SO 4 ∙−-based WAS fermentation. [ABSTRACT FROM AUTHOR]

Maximizing the internal carbon sources in raw wastewater was found to be an alternative option to alleviate the financial burden in external carbon sources (ECS) addition to the biological nutrient removal (BNR) process. Based on previous studies on particulate recovery via fine-sieving technologies, alkali pretreatment was used to improve the short-chain fatty acid (SCFA) production from the fine-sieving fractions (FSF). Hydrolysis performance and methane production were monitored to evaluate the reasons for the SCFA boost. Besides, the microbial community structure was evaluated by high-throughput sequencing. Furthermore, mass balance and financial benefits were preliminarily estimated. The results showed that alkali pretreatment effectively promoted the generation of SCFAs with 234 mg/g volatile suspended solids (VSS), almost double that of the control test. This was partially attributed to the efficient hydrolysis, with soluble polysaccharides and protein increased by 2.1 and 1.2 times compared to that of the control, respectively. Inhibition of methanogens was also devoted to the accumulation of SCFAs, with no methane production until 150 h at high pH value. Finally, a preliminary evaluation revealed that 44.51 kg/d SCFAs could be supplied as the electron donor for denitrification, significantly reducing the cost in ECS addition for most wastewater treatment plants (WWTPs) with carbon insufficiency. [ABSTRACT FROM AUTHOR]

Extraction of short-chain fatty acids (SCFAs) from fermentation liquid of waste activated sludge (WAS) is the key bottleneck hindering its application as electron donor in denitrification. This study explores the feasibility of polyether-type polyurethane (PU)-modified layered double hydroxides (LDHs, prepared using eggshell waste as calcium source) in SCFAs adsorbing from WAS fermentation liquid (SFL). The adsorption parameters were first optimized by adsorption tests using artificial fermentation liquid (AFL). Then, adsorption kinetics, thermodynamic and isotherms were explored to further understand the adsorption mechanism. It revealed that SCFAs absorption by PU-LDHs from SFL was an endothermic and spontaneous process with positive enthalphy (ΔH◦) values and negative Gibbs free energy (ΔG◦) values. In addition, the maximum adsorption capacity of 208.0 mg SCFAs/g PU-LDHs was obtained from the Langmuir isotherm. Noting that both soluble carbohydrates and soluble proteins were simultaneously extracted, with efficiencies of 30.9%, 6.2%, respectively, compared with 62.9% SCFAs. The reuse tests confirmed that the prepared PU-LDHs can be used at least three times with high adsorptive capacity. With PU-LDHs-loaded SFL as external carbon source in the biodenitrification process, a denitrification rate of 0.014 mg NO 3 −-N/mg mixed liquid suspended solids (MLSS)·d was recorded. This study provided a sound basis for the preparation of cost-effective biodenitrification carbon source from SFL by a novel adsorbent. Image 1 • A waste-to-resource concept was established for eggshell waste and WAS treatment. • PU-LDHs can be repeatedly used as the carrier of SCFAs with high adsorption capacity. • PU-LDHs retained SFL showed good performance as electron donor in denitrification. • Recycle test confirmed PU-LDHs can be reused multiple times for biodenitrification. [ABSTRACT FROM AUTHOR]

Free nitrous acid (FNA) has been recently reported to be an effective and eco-friendly inactivator for waste activated sludge (WAS), while the limited decomposition of the extracellular polymeric substance (EPS) matrix hampers resource recovery from WAS. This work employed peracetic acid (PAA) to assist FNA and explored the contribution of co-pretreatment to hydrogen recovery in a prefermentation-bioelectrolysis cascading system. The results showed that co-pretreatment led to approximately 8.8% and 20.4% increases in the exfoliation of particulate proteins and carbohydrates, respectively, from tightly bound EPS (TB-EPS) over that of sole FNA pretreatment. Electron paramagnetic resonance analysis verified that the synergistic effect of FNA, PAA and various generated free radicals was the essential process. This effect further promoted the accumulation of volatile fatty acids (VFAs) after 96 h of prefermentation, and the peak concentration in co-pretreated WAS (AD-FPWAS) was approximately 2.5-fold that in sole FNA-pretreated WAS (AD-FWAS). Subsequently, the cascading utilization of organics in the bioelectrolysis step contributed to efficient hydrogen generation. A total of 10.8 ± 0.3 mg H 2 /g VSS was harvested in microbial electrolysis cells (MECs) fed with AD-FPWAS, while 6.2 ± 0.1 mg H 2 /g VSS was obtained from AD-FWAS. X-ray photoelectron spectroscopy (XPS) revealed the effective decomposition of the phospholipid bilayer in the cytomembrane and the transformation of macromolecular organics into VFAs and hydrogen in the cascading system. Further microbial community analysis demonstrated that co-pretreatment enhanced the accumulation of functional consortia, including anaerobic fermentative bacteria (AFB, 28.1%), e.g., Macellibacteroides (6.3%) and Sedimentibacter (6.9%), and electrochemically active bacteria (EAB, 57.0%), e.g., Geobacter (39.0%) and Pseudomonas (13.6%), in the prefermentation and MEC steps, respectively. The possible synergetic and competitive relationships among AFB, EAB, homo-acetogens, nitrate-reducing bacteria and methanogens were explored by molecular ecological network analysis. From an environmental and economic perspective, this promising FNA and PAA co-pretreatment approach provides new insight for energy recovery from WAS biorefineries. Image 1 • PAA, FNA and their intermediates led to effective EPS decomposition. • PAA + FNA pretreatment boosted 2.5-fold VFAs and 1.7-fold H 2 recovery versus sole FNA. • XPS confirmed the destruction of phospholipid bilayer and organics transformation. • 28% AFB in prefermentation and 57% EAB in bioelectrolysis were enriched. • Synergetic relationships of AFB, EAB, homoacetogen, NRB and methanogen were explored. [ABSTRACT FROM AUTHOR]

• Effect of biogenic healing agents on crack-healing crystal polymorph was studied. • MC-Ao based bioconcrete exhibited better healing potential. • 82% of aragonite-form CaCO 3 was introduced in the MC-Ao based bioconcrete. • Mixed cultures resulted in a 61% decrease of production cost versus pure cultures. Microbially induced CaCO 3 precipitation (MICP), mainly in the form of calcite, has been reported to be an efficient approach for self-healing cracks in concrete. However, little is known about the implementation of aragonite, the other common crystalline form of CaCO 3 , in bioconcrete. Therefore, a systematic investigation of the crystal polymorphs and the healing efficiency of different cultures, i.e., two microbial consortia under anaerobic (MC-Aa) and anoxic (MC-Ao) conditions and nonureolytic pure-culture bacteria (Bacillus cohnii), was conducted in this study. The results showed that the MC-Ao agent exhibited the maximum values of completely healed crack widths (1.22 mm) after 28 d of healing, which is larger than the values of 0.79 and 0.73 mm for B. cohnii and MC-Aa, respectively. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analyses confirmed that the biominerals induced by MC-Aa and B. cohnii are calcite, while those of MC-Ao were 82% aragonite and 18% calcite. It is noteworthy that this proportion of aragonite is the highest reported level for the MICP system to date. In addition, economic evaluation verified that the microbial consortia resulted in a 61% decrease in production costs compared to pure cultures. The intriguing findings obtained in this study may provide a scientific basis for the potential implementation of microbial consortia under anoxic conditions, such as a new self-healing agent, in bioconcrete. [ABSTRACT FROM AUTHOR]

Most studies on the production of volatile fatty acids (VFAs) from waste activated sludge (WAS) digestion have focused on operating conditions, pretreatments and characteristic adjustments. Conditioning by extra carbon sources (ECS), normally added in a solid form, has been reported to be an efficient approach. However, this has caused considerable waste of monomeric sugars in the hydrolysate. In this study, the effects of two added forms (pretreated straw (S) and hydrolyzed liquid (L)) of cornstover (CS) on WAS acidification were investigated. To obtain different cellulosic compositions of CS, low-thermal or autoclaved assisted alkaline (TA or AA) pretreatments were conducted. The results showed that AA-L test achieved the highest VFAs value (653 mg COD/g VSS), followed by AA-S (613 mg COD/g VSS). These values were 12% and 28% higher, respectively, than that obtained in the TA-L and TA-S tests. Meanwhile, higher percentages of acetic acid were observed after AA pretreatment (~62% versus ~53% in TA). The added forms of CS played an important role in structuring the innate microbial community in the WAS, as shown by high-throughput sequencing and canonical correspondence analysis. The findings obtained in this work may provide a scientific basis for the potential implementation of co-digesting WAS with ECS simultaneously obtaining energy and high value-added products. [ABSTRACT FROM AUTHOR]

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

Membrane separation for wastewater remediation has been perplexed by membrane fouling, and the design of highly antifouling membranes for high-flux operation remains challenging. Herein, Sm 0.5 Sr 0.5 CoO 3-δ (SSC700) membrane was coupled with peroxymonosulfate (PMS) catalysis. SSC700 demonstrated superb efficacy in batch and fixed-bed reactions, generating sulfate radicals (SO 4 −•) and hydroxyl radicals (HO•) for pollutants oxidation. Additionally, in robust SSC700 membrane/PMS systems, Rhodamine B (RhB) realized > 91% removal for 50 h from laboratory wastewater under fluxes above 368 L/(m2·h), and strikingly, ciprofloxacin, RhB and sulfamerazine in the secondary effluent attained 60–80% (50 h), almost 100% (100 h) and 50–60% (50 h) removal under fluxes around 1000, 600 and 900 L/(m2·h), respectively. The highly reactive Co2+/Co3+/Co4+ redox couples accounted for the prominent activity, stability and antifouling capability of SSC700 membranes. Apart from Co species, Sm/Sr played significant roles in organics degradation. Also, bio-toxicity evolution during ciprofloxacin mineralization was monitored. This study dedicates to the design of functional membranes/PMS integrated systems for synergistic wastewater decontamination and membrane defouling. [Display omitted] • SSC700 membrane/PMS coupling system was constructed for organics oxidation. • SSC700 membrane demonstrated long-lasting stability under high-flux operation. • SSC700 membrane exhibited prominent fouling resistance. • Co2+/Co3+/Co4+ redox couple and O ads jointly facilitated reactive species generation. • In situ generated HO•/SO 4 −• attained ultra-high utilization efficiency. [ABSTRACT FROM AUTHOR]

Most studies have employed aeration-biofiltration process for the simultaneous removal of iron, manganese and ammonia in groundwater. However, what's inside the 'black box', i.e., the potential contribution of functional microorganisms behavior and interactions have seldom been investigated. Moreover, little attention has been paid to the correlations between environmental variables and functional microorganisms. In this study, the performance of industrial-scale biofilters for the contaminated groundwater treatment was studied. The effluent were all far below the permitted concentration level in the current drinking water standard. Pyrosequencing illustrated that shifts in microbial community structure were observed in the microbial samples from different depths of filter. Microbial networks showed that the microbial community structure in the middle- and deep-layer samples was similar, in which a wide range of manganese-oxidizing bacteria was identified. By contrast, canonical correlation analysis showed that the bacteria capable of ammonia-oxidizing and nitrification was enriched in the upper-layer, i.e., Propionibacterium, Nitrosomonas, Nitrosomonas and Candidatus Nitrotoga. The stable biofilm on the biofilter media, created by certain microorganisms from the groundwater microflora, played a crucial role in the simultaneous removal of the three pollutants. [ABSTRACT FROM AUTHOR]

Aiming to strengthen the performance of waste activated sludge digestion, pretreatment is a prerequisite for keeping operations within an industrially acceptable time- frame. In this study, the performance of microaeration coupled with thermophilic (MT) pretreatment on waste activated sludge solubilization and acidification was investigated. The results showed that the maximum soluble organics concentrations, including soluble proteins and carbohydrates, reached 2290 mg COD/L in 24 h when the ventilation rate and temperature were 0.05 vvm and 70 °C. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) test on pure-culture ( E.coli ) and scanning electron microscopy analysis indicated that MT pretreatment effectively destroyed microbial cell wall and resulted in an increase in soluble proteins. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed that MT pretreatment reduced the diversity of the bacterial community during pretreatment. Along with the dissolution of a large quantity of organic matter, microbial species such as Lactococcus and Methyloversatilis bloomed at the end of acidification period, which contributed to SCFAs production. This study revealed that MT pretreatment facilitated the WAS hydrolysis efficiency and enhanced SCFAs (3149 mg COD/L with fermentation for 96 h) production, especially for acetic acid (50%) accumulation, which provides a new perspective for the application and recovery of sludge resources. [ABSTRACT FROM AUTHOR]

An up-flow membrane-less bioelectrochemical system integrated with bio-contact oxidation (BES-BCO) was developed for degradation and/or mineralization of the Acid Orange 7 (AO7) in wastewater. The performance of BES-BCO was evaluated based on decolorization removal efficiency, chemical oxygen demand (COD) removal efficiency and the concentration of decolorized byproducts in effluent. The study found that the BES-BCO system can degrade AO7 and COD effectively. Further, the toxic decolorized byproducts of azo dye, which are not generally degrade in the traditional BES system, can be further mineralized by the BES-BCO system. In addition, the COD removal efficiency increased with the increase of aeration at BCO. However, higher DO concentration at anode can hinder the electrons transfer between anode and exoelectrogen, resulting in a significant decrease of decolorization removal efficiency. This study provided a novel compact technology for advanced treatment of azo dyes wastewater for engineering applications, and concluded that the integrated BES-BCO system is effective for advanced treatment of azo dye-containing wastewater. [ABSTRACT FROM AUTHOR]

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

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

Electro-fermentation (EF) has been extensively studied for recovering hydrogen and phosphorus from waste activated sludge (WAS), while was limited for the further application due to the low hydrogen yield and phosphorus recovery efficiency. This study proposed an efficient strategy for hydrogen and vivianite recovery from the simulated sludge fermentation liquid by sacrificial iron anode in EF. The optimum hydrogen productivity and the utilization efficiency of short chain fatty acids (SCFAs) reached 45.2 mmol/g COD and 77.6% at 5 d in pH 8. Phosphate removal efficiency achieved at 90.8% at 2 d and the high crystallinity and weight percentage of vivianite (84.8%) was obtained. The functional microbes, i.e., anaerobic fermentative bacteria, electrochemical active bacteria, homo-acetogens and iron-reducing bacteria were highly enriched and the inherent interaction between the microbial consortia and environmental variables was thoroughly explored. This work may provide a theoretical basis for energy/resource recovery from WAS in the further implementation. [Display omitted] • Enhanced hydrogen and vivianite recovery were realized in pH 8 via Fe mediated EF. • Appropriate iron release led to the higher crystallinity of vivianite in pH 8 group. • EAB, AFB and homo-acetogens preferred to enrich in pH 8 than other pH conditions. • The mutual symbiosis of microbes and environmental factors was the main mechanism in EF. [ABSTRACT FROM AUTHOR]

The electron utilization efficiency in photocatalytic hydrogen evolution (PHE) is crucial for solar energy conversion and storage. Prolonged lifetime and effective use of accumulated electrons based on the storage-release behavior is a potential strategy to regulate the electronic utilization efficiency. Herein, this study utilized Mo 2 TiC 2 -Ru as the "electron-parking" to construct a ZnIn 2 S 4 /Mo 2 TiC 2 -Ru photocatalyst. The ZnIn 2 S 4 /Mo 2 TiC 2 -Ru exhibits a visible light-driven PHE rate of 5.72 mmol·g−1·h−1, and maintains a PHE rate of ∼1.67 mmol·g−1·h−1 under dark conditions. The photogenerated electrons could be directionally stored in Mo 2 TiC 2 -Ru to create an electron-rich environment, this can inhibit backflow and recombination of electrons, and could regulate the water dissociation and hydrogen adsorption kinetics. Importantly, the stored electrons could release in the dark, increasing the quantity of electrons and overcoming intermittent sunlight and regional environmental influences. This work provides insights and references for the development of capacitive cocatalysts with an "electron-parking" engineering for efficient and sustained PHE reactions. [Display omitted] • ZnIn 2 S 4 /Mo 2 TiC 2 -Ru with "electron-parking" engineering were successfully fabricated. • Electrons can be stored in Mo 2 TiC 2 -Ru to form an electron-rich environment. • The Mo 2 TiC 2 -Ru "electron-parking" inhibits the backflow of photogenerated electrons. • Mo 2 TiC 2 -Ru provides suitable water dissociation and hydrogen adsorption sites. • The stored electrons could be released in the dark and continue to generate H 2. [ABSTRACT FROM AUTHOR]

Microaerobic sludge bed systems could align with low-energy, reasonable carbon-nitrogen (C/N) ratio, and synchronous removal objectives during wastewater treatment. However, its ability to treat municipal wastewater (MW) with varying low C/N ratio, low NH 4 + concentration, along with managing sludge bulking and loss are still unclear. Against this backdrop, this study investigated the performance of an Upflow Microaerobic Sludge Bed Reactor (UMSR) treating MW characterized by varying low C/N ratios and low NH 4 + concentrations. The study also thoroughly examined associated sludge bulking and loss, pollutant removal efficiencies, sludge settleability, microbial community structures, functional gene variations, and metabolic pathways. Findings revealed that the effluent NH 4 +-N concentration gradually decreased to 0 mg/L with a decrease in the C/N ratio, whereas the effluent COD was unaffected by the influent, maintaining a concentration below 50 mg/L. Notably, TN removal efficiency reached 90% when C/N ratio was 3. The decrease in the C/N ratio (C/N ratio was 1) increased microbial community diversity, with abundances of AOB, AnAOB, aerobic denitrifying bacteria, and anaerobic digestion bacteria reaching 8.34%, 0.96%, 5.07%, and 9.01%, respectively. Microorganisms' metabolic pathways significantly shifted, showing increased carbohydrate and cofactor/vitamin metabolism and decreased amino acid metabolism and xenobiotic biodegradation. This study not only provides a solution for the effluent of different pre-capture carbon processes but also demonstrates the UMSR's capability in managing low C/N ratio municipal wastewater and emphasizes the critical role of microbial community adjustments and functional gene variations in enhancing nitrogen removal efficiency. [Display omitted] • Microaerobic bed suited variable and low C/N ratio wastewater. • TN removal reached 90% when influent C/N ratio was 3. • Reduced C/N ratio in influent increased microbial diversity. • Microaerobic sludge bed followed carbon capture processes. [ABSTRACT FROM AUTHOR]

Constructed wetlands have been widely employed as a cost-effective and environmentally friendly alternative for treating primary and secondary sewage effluents. In this study, biochar and pyrite were utilized as electron donor substrates in intermittent-aerated vertical flow constructed wetlands to strengthen the nutrient and heavy metals removal simultaneously, and the response of nutrient reduction and microbial community to heavy metals stress was also explored. The results indicated that biochar addition exhibited a better nitrogen removal, while pyrite addition greatly promoted the phosphorus removal. Moreover, the high removal efficiencies of Cu2+, Pb2+ and Cd2+ (above 90%) except for Zn2+ were obtained in each system. However, the exposure of heavy metals decreased phosphorus removal while had little effect on nitrogen removal. The influent load and intermittent aeration implementation led to a significant shift in microbial community structures, but microbial biodiversity and abundance decreased under the exposure of heavy metals. Particularly, Thiobacillus and Ferritrophicum , associated with sulfur autotrophic denitrification and iron autotrophic denitrification, were more abundant in pyrite-based wetland systems. • Biochar and pyrite addition was beneficial to nitrogen and phosphorus removal. • Biochar-mediated heterotrophic denitrification played significant role in enhancing total nitrogen removal. • Exposure to heavy metals had little impact on denitrification but hindered phosphorus removal. [ABSTRACT FROM AUTHOR]

Photocatalysis has been proven to be an excellent technology for treating antibiotic wastewater, but the impact of each active species involved in the process on antibiotic degradation is still unclear. Therefore, the S-scheme heterojunction photocatalyst Ti 3 C 2 /g-C 3 N 4 /TiO 2 was successfully synthesized using melamine and Ti 3 C 2 as precursors by a one-step calcination method using mechanical stirring and ultrasound assistance. Its formation mechanism was studied in detail through multiple characterizations and work function calculations. The heterojunction photocatalyst not only enabled it to retain active species with strong oxidation and reduction abilities, but also significantly promoted the separation and transfer of photo-generated carriers, exhibiting an excellent degradation efficiency of 94.19 % for tetracycline (TC) within 120 min. Importantly, the priority attack sites, degradation pathways, degradation intermediates and their ecological toxicity of TC under the action of each single active species (·O 2 −, h+, ·OH) were first positively explored and evaluated through design experiments, Fukui function theory calculations, HPLC-MS, Escherichia coli toxicity experiments, and ECOSAR program. The results indicated that the preferred attack sites of ·O 2 − on TC were O20, C7, C11, O21, and N25 atoms with high f+ value. The toxicity of intermediates produced by ·O 2 − was also lower than those produced by h+ and ·OH. • S-scheme heterojunction Ti 3 C 2 /g-C 3 N 4 /TiO 2 (TCNTO 580) was synthesized using melamine and Ti 3 C 2 as precursors. • The formation mechanism of TCNTO 580 was studied through multiple characterizations and theoretical calculations. • Priority attack sites and degradation pathways of TC by single active species were explored through HPLC-MS and Fukui index. • Toxicity changes of intermediates by single active species were evaluated using micro toxicity experiment and ECOSAR. • The preferred attack sites of ·O 2 − on TC were O20, C7, C11, O21, and N25, and the toxicity of intermediates was the lowest. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • Specific colonization pattern of key symbionts in MES was firstly investigated. • Co-colonization of EAB and CSB promoted caproate biosynthesis in MES. • CSB and EAB mutually interacted in metabolic activity and enhanced electron transfer. • Ecological mechanism was revealed in terms of MEN analysis and Mantel test. • Economic benefit and carbon emission were preferable via co-colonization. As promising and value-added platform chemicals, the biosynthesis of medium-chain fatty acids (MCFAs, C6-C12) via chain elongation (CE) in microbial electrosynthesis systems (MES) has recently garnered significant attentions due to the unique bioelectrocatalytic behaviors and the reduction of exogenous electron donors (EDs). Caproate-synthesizing bacteria (CSB) played a crucial role in the generation of acetyl-CoA, which subsequently underwent reverse β oxidation to synthesize MCFAs. However, the presence of electrochemically active bacteria (EAB) was also pivotal for MES as they generated hydrogen in the cathodic electron transfer pathways, the specific colonization patterns of key symbionts remained unknown. The aim of this study was to investigate the selective colonization of EAB and CSB on the performance of caproate production in MES. The reactors colonized EAB and CSB achieved the maximum caproate concentration of 5332.5 mg COD/L, which was 7.9 and 1.3 times higher compared to that inoculated with either sole EAB or CSB, respectively. Moreover, the reactors colonized with mixed culture exhibited a clear redox peak and preferable electron transfer efficiency. CSB and EAB mutually interacted in metabolic activities, thereby resulting in increased substrate utilization and caproate production. The findings of this study provide a new strategy and insights for value-added chemicals recovery in microbial electrosynthesis platform. [ABSTRACT FROM AUTHOR]

• MIT caused initial lag but final promoting effect on the VFAs in WAS fermentation. • MIT disintegrated WAS and disturbed ecological interaction & microbial metabolism. • Functional microorganisms for VFA production and MIT-tolerance were domesticated. • The adaptive mechanisms of microbiome to MIT stress were unveiled. • Syntrophic interaction of acetogen and methanogen was disrupted with total methanogenic activity suppression. In the post-COVID-19 pandemic era, various antimicrobials have emerged and concentrated in waste-activated sludge (WAS), affecting the biological treatment of WAS. However, there is still a knowledge gap in the dynamic response and adaptive mechanism of anaerobic microbiome under exogenous antimicrobial stress. This study found that methylisothiazolinone (MIT, as a typic antimicrobial) caused an interesting lag effect on the volatile fatty acids (VFAs) promotion in the WAS anaerobic fermentation process. MIT was effective to disintegrate the extracellular polymeric substances (EPS), and those functional anaerobic microorganisms were easily exposed and negatively impacted by the MIT interference after the loss of protective barriers. Correspondingly, the ecological interactions and microbial metabolic functions related to VFA biosynthesis (e.g., pyruvate metabolism) were downregulated at the initial stage. The syntrophic consortia gradually adapted to the interference and attenuated the MIT stress by activating chemotaxis and resistance genes (e.g., excreting, binding, and inactivating). Due to the increased bioavailable substrates in the fermentation systems, the dominant microorganisms (i.e., Clostridium and Caloramator) with both VFAs production and MIT-tolerance functions have been domesticated. Moreover, MIT disrupted the syntrophic interaction between acetogens and methanogens and totally suppressed methanogens' metabolic activities. The VFA production derived from WAS anaerobic fermentation was therefore enhanced due to the interference of antimicrobial MIT stress. This work deciphered dynamic changes and adaptive evolution of anaerobic syntrophic consortia in response to antimicrobial stress and provided guidance on the evaluation and control of the ecological risks of exogenous pollutants in WAS treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The short-chain fatty acids (SCFAs) accumulated in waste activated sludge (WAS) fermentation was adopted as an alternative extra carbon source for biohydrogen production in microbial electrolysis cells (MECs). WAS was pretreated by bi-frequency ultrasonic and the highest SCFAs were accumulated at 3rd day. Three groups of tests were conducted in single chamber MECs for H2 production under different SCOD concentrations. SCOD removals were up to 60% at diluted influent, but reduced to 50% at original concentration. Highest H2 yield was 1.2 mL H2/mg COD at 2-fold dilution with 155% energy efficiency. Results showed that >90% of acetate and ∼90% of propionate were effectively converted to hydrogen, and next were n-butyrate and n-valerate (at dilutions), but <20% of iso-butyrate and iso-valerate were converted. The overall biohydrogen recovery in this study was 120 ml H2/g VSS/d. This work shows a possibility of cascade utilization of WAS fermentation liquid and H2 generation in MEC. [Copyright &y& Elsevier]

Sulfadiazine (SDZ) is widely used in clinical treatment, livestock husbandry and aquaculture as an antibacterial agent, resulting in environmental risks. In this work, batch experiments were conducted to investigate the characteristics of SDZ biodegradation and reaction mechanisms in a nitrate anaerobic denitrifying system for the first time. The results showed that 98.52% of the SDZ, which had an initial concentration of 50 mg L−1, was degraded after 70 h, indicating that the removal efficiency of SDZ in anaerobic denitrifying system was 55.27% higher than that in anaerobic system. Furthermore, LC-MS-MS analysis confirmed that SDZ could be degraded into 16 byproducts via 3 main degradation pathways that contained 6 different reactions. After analyzing the microbial communities of the reactor, the denitrifying bacteria and desulfurizing bacteria Desulforhabdus , Ignavibacterium , SBR1031_norank , Nocardioides , etc. were highly associated with the removal of SDZ in the system. The biological toxicity test of the effluent indicated that the remaining organic matter and inorganic matter of the effluent could provide nutrients for E. coli and promote its growth. In other words, anaerobic denitrifying systems are highly efficient, simple and environmentally friendly, and have an impressive prospect in the biodegradation of sulfonamide antibiotics. Image 1 • Mixed microbes were first cultivated to remove SDZ in anaerobic denitrifying system. • Nitrate system could promote SDZ degradation and eliminate the biotoxicity of SDZ. • 3 metabolic pathways of SDZ that based on 6 chemical reactions were speculated. • Denitrification and desulfurization bacteria could promote SDZ degradation together. [ABSTRACT FROM AUTHOR]

• The quinoline wastewater treatment was first investigated in the MEC-AD system. • The performance of quinoline degradation was strengthened at a voltage of 1.0 V. • CH 4 production was increased to 1.5-fold in MEC-AD compared to the AD. • Simultaneous quinoline-C and quinoline-N removal were achieved in MEC-AD. • Exoelectrogens, methanogens, anammox and degradation bacteria have coexisted. In this study, the feasibility of quinoline-wastewater treatment was investigated in a coupled microbial electrolysis cell and anaerobic digestion system (MEC-AD). Improved degradation and enhanced mineralization of quinoline were obtained, and the optimal voltage was determined to be 1.0 V. Effective removal of quinoline at relative high concentration, and a 1.5-fold increase in methane production were achieved. The results indicated that the MEC-AD could simultaneously remove carbon and nitrogen from quinoline. Gas chromatography-mass spectrometry analysis identified 2-hydroxyquinoline and 8-hydroxycoumarin as the intermediates of quinoline. The formation and degradation of metabolites were rapid, and they did not accumulate in the MEC-AD. The results of microbial community structure analysis demonstrated that the functional species were enriched and coexisted, and that the dominant bacterial genera were SM1A02 , Comamonas , Desulfovibrio , Geobacter, and Actinomarinales_norank ; the dominant archaeal genera were Methanocorpusculum and Nitrosoarchaeum. Furthermore, the applied current played a selective role in the enrichment of microorganisms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe anode achieved 101–743% higher of hydrogen productivity than other iron sources. • Fe anode led complete removal of phosphate within 2 d (vs. 0–39.4% in other groups). • More crystalline vivianite particles were observed in EF system assisted by Fe anode. • Homo-acetogens (78.0%), EAB (8.0%) and DIRB (2.3%) were enriched in Fe anode group. • Correlation and syntrophy between functional microbes and metabolites were explored. Electro-fermentation (EF) is a promising technology for extracting valuable metabolites from waste biomass, while its effectiveness for phosphorus recovery has received little attention. In this study, we investigated the impact of different iron sources, i.e., FeCl 3 , FeOOH, Fe 2 O 3 , zero-valent iron (ZVI), a built-in Fe anode, and stainless-steel mesh (SSM), on concurrent biohydrogen and vivianite (Fe 3 (PO 4) 2 ·8H 2 O) recovery from sludge fermentation liquid (SFL) in an EF system. Results indicated that the Fe anode group achieved the highest hydrogen productivity of 17.7 mmol/g COD at 5 d, which was 101–743% higher than that of other iron sources. The utilization efficiency of short-chain fatty acids (SCFAs) peaked at 79.1% within 5 d, which was 1.2 folds higher than that of Control (without iron addition). Moreover, the phosphate removal efficiency reached 100% within 2 d and 5 d in Fe anode and SSM group, respectively, while the other groups achieved only 0–39.4% removal. SEM and XRD analyses demonstrated the existence of vivianite particles in the recovered products in the groups of FeCl 3 , FeOOH and Fe anode. Electrochemically active bacteria (EAB), e.g., Geobacter , Comamonas , and Desulfovibrio , accounted for 3.6–60.2% of all groups. Geobacter , Azospira , Comamonas , and Desulfovibrio , which are also considered dissimilatory iron reducing bacteria (DIRB), were enriched to 0.1–40.7% in all groups. Acetoanbacterium and Acetoaerobium , typical homo-acetogens, were enriched to 78.0% in the Fe anode group, while was only 9.0–29.3% in other groups. Correlation and molecular ecological network (MEN) analyses of the functional microbial consortia further indicated the intertrophic interaction. This study provides a theoretical basis for synchronous hydrogen and phosphorus recovery from WAS in the further industrial implementation. [ABSTRACT FROM AUTHOR]

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

• Bi 3 O 4 Br/Ti 3 C 2 Schottky junction with efficient charge transfer was prepared. • The effect of charge transfer on active species generation was discussed. • The Bi 3 O 4 Br/Ti 3 C 2 exhibited excellent photocatalytic degradation activity of bisphenol A. Enhanced photocatalytic active species generation is an important strategy for tuning its visible-light photocatalytic activity, which is highly related to the separation and transfer of photogenerated charge carriers. In this study, we successfully prepared a novel Bi 3 O 4 Br/Ti 3 C 2 two-dimensional/two-dimensional (2D/2D) Schottky junction with special interfacial charge transfer channel via in-situ growth of Bi 3 O 4 Br on the surface of ultrathin Ti 3 C 2. The relevant characterization results indicated that Bi 3 O 4 Br/Ti 3 C 2 had a stable structure and tight interface binding, which shortened the distance of charge transfer, promoted the separation of photogenerated electron-hole pairs, and then enhanced the generation of active species. Therefore, the optimized photodegradation activity and TOC removal efficiency of Bi 3 O 4 Br/Ti 3 C 2 on Bisphenol A (BPA) could reach 91.26% and 70.97% within 60 min visible-light irradiation, respectively. Furthermore, intermediate products and BPA degradation pathways were determined. This work provides a new protocol for the construction of 2D/2D heterojunction photocatalytic systems and regulating photocatalytic active species generation by electronic effective transporting. [ABSTRACT FROM AUTHOR]

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

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

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

Immobilization has been reported to be an efficient approach for bacteria-based self-healing concrete to maintain the high-efficiency mineral-forming capacity of incorporated bacteria over a period of time. However, the relatively high-cost, local unavailability, and low adsorption capacity of the current bacteria carriers make them impractical for potential implementation in large-scale concrete structures. In this study, the feasibility of expanded perlite (EP) as a novel bacteria carrier on quantifying cracks-healing in concrete via immobilization of Bacillus cohnii was demonstrated. The effects of two other self-healing techniques, i.e., direct introduction of bacteria and expanded clay (EC) immobilized bacteria, on the efficiency of crack-healing were also investigated. Experimental results showed that specimens incorporated with EP-immobilized bacteria exhibited the most efficient crack-healing after each healing time. The values of completely healed crack widths were up to 0.79 mm after 28 days of healing, which is larger than the value of 0.45 mm for specimens incorporated with EC-immobilized bacteria. Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) analysis confirmed that mineral precipitations on their crack surfaces are calcite crystals. The findings obtained in this study may provide a scientific basis for the potential implementation of expanded perlite, as a new microorganism carrier, in bacteria-based self-healing concrete. [ABSTRACT FROM AUTHOR]