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Soluble microbial products (SMPs), dissolved organic matter excreted by activated sludge, can interact with antibiotics in wastewater and natural water bodies. Interactions between SMPs and antibiotics can influence antibiotic migration, transformation, and toxicity but the mechanisms involved in such interactions are not fully understood. In this study, integrated spectroscopy approaches were used to investigate the mechanisms involved in interactions between SMPs and a representative antibiotic, trimethoprim (TMP), which has a low biodegradation rate and has been detected in wastewater. The results of liquid chromatography-organic carbon detection-organic nitrogen detection indicated that the SMPs used in the study contained 15% biopolymers and 28% humic-like substances (based on the total dissolved organic carbon concentration) so would have contained sites that could interact with TMP. A linear relationship of fluorescent intensities of tryptophan protein-like substances in SMP was observed (R

Orange peel waste (OPW) and sewage sludge (SS) valorization for volatile fatty acids (VFAs) production from anaerobic co-fermentation are attractive and feasible. The highest VFAs reached 11996.3 mg COD/L within 10 d at the mass ratio (TS/TS) of 1:1, which was approximately 30-fold of that in sole SS fermentation. The OPW provided plenty of organic substrates and facilitated the fermentation processes by disintegrating SS structure and inhibiting methanogenesis due to the abundant limonene. Also, the OPW feeds reshaped the microbial community and enriched fermentative bacteria, especially those saccharolytic ones (i.e. Prevotella-7). The key genes involved in membrane transport (i.e. ptsG), glycolysis (i.e. pgk), pyruvate metabolism (i.e. ace), and fatty acid biosynthesis (i.e. accA), which are associated with VFAs biosynthesis, were up-regulated in OPW/SS reactors. Overall, it was the increase in bioavailable organic matter and functional microorganisms, and the simultaneous enhancement of metabolic activity that improved the efficient VFAs production.

This study mainly investigated the environmental risks of polyhexamethylene guanidine (PHMG) occurred in waste activated sludge (WAS) on the antibiotic resistance genes (ARGs) spread during anaerobic fermentation, and disclosed the critical mechanisms. The total ARGs abundance was increased by 32.2-46.4% at different stressing levels of PHMG. The main resistance mechanism categories of ARGs shifted to the target alternation and efflux pump. PHMG disintegrated WAS structure and increased the cell permeability, which benefitted the mobile genetic elements (MGEs) release and horizontal transfer of ARGs. Besides, PHMG induced the enrichment of potential ARGs hosts (i.e., Burkholderia, Bradyrhizobium and Aeromonas). Moreover, PHMG upregulated the metabolic pathways (i.e., two-component system, quorum sensing, and ATP-binding cassette transporters) and critical genes expression (i.e., metN, metQ, rpfF, rstA and rstB) related with ARGs generation and dissemination. Structural equation model analysis revealed that microbial community structure was the predominant contributor to the ARGs propagation.

The catalytic ozonation treatment of secondary biochemical effluent for papermaking wastewater by Ag-doped nickel ferrite was investigated. Ag-doped catalysts prepared by sol-gel method were characterized, illustrating that Ag entirely entered the crystalline of NiFe2O4 and changed the surface properties. The addition of catalyst enhanced the removal efficiency of chemical oxygen demand and total organic carbon. The results of gas chromatography-mass spectrometer, ultraviolet light absorbance at 254 nm and three-dimensional fluorescence excitation-emission matrix suggested that aromatic compounds were efficiently degraded and toxic substances, such as dibutyl phthalate. In addition, the radical scavenging experiments confirmed the hydroxyl radicals acted as the main reactive oxygen species and the surface properties of catalysts played an important role in the reaction. Overall, this work validated potential applications of Ag-doped NiFe2O4 catalyzed ozonation process of biologically recalcitrant wastewater.

In this study, NiFe2O4 and Ag0.1Ni0.95Fe2O4 were successfully prepared by the sol–gel method and applied to catalyze ozone for dibutyl phthalate (DBP) degrading. The synthesized catalysts were char...

Anaerobic digestion (AD) is an effective approach for waste activated sludge (WAS) disposal with substantial recovery of valuable substrates. Previous studies have extensively explored the correlations of common operational parameters with AD efficiency, but the impacts of intrinsic characteristics of WAS on the AD processes are generally underestimated. This study focused on disclosing the association of intrinsic drawbacks in WAS with AD performance, and found that the cemented WAS structure, low fraction of biomass and various high levels of inhibitory pollutants (e.g., organic pollutants and heavy metals), as the integral parts of WAS all greatly restricted the AD performance. The main potential strategies and underlying mechanisms to mitigate the restrictions for efficient WAS digestion, including the practical pretreatment methods, bioaugmentation and aided substances addition, were critically analyzed. Also, future directions for the improvement of WAS digestion were proposed from the perspectives of technical, management and economic aspects.

Extracellular polymeric substances (EPS) are essential for bacteria to interact with external environments and play a key role in the formation of microbial aggregates. Unveiling the black box of EPS has become an urgent topic in the field of microbiology, medical science and environmental science. Here, we develop an explicit approach to describe the molecular structure and behaviors of EPS using interacting-particle reaction dynamics (iPRD). Three representative states of EPS (i.e., normal EPS layer, metal bridging EPS layer and extracted EPS layer) are qualitatively simulated at molecular scale and validated with previous research results on EPS. Furthermore, an averaged concentration representation method is proposed to quantitatively model the EPS-oriented bioprocesses. Through this method, the contents of protein and polysaccharide in EPS extracted by cation exchange resin are accurately predicted by our model (R2>0.982). This work gives new insights into EPS at the molecular scale and opens up new avenues for further exploring and modeling complex molecular structure and behaviors of EPS.

This work explored the feasibility of paper waste (PW)/sewage sludge (SS) co-fermentation for volatile fatty acids (VFAs) production, and disclosed its correlation with the key operational parameters (i.e., pH and PW/SS ratio). The results indicated that the maximal VFAs was 251.55 mg COD/g TSS at optimal conditions, which was approximately 10-folds of sole SS fermentation. PW feeding contributed to the bioavailable substrates and C/N balance during co-fermentation process. The pH exhibited evident impacts on organics solubilization/hydrolysis, in which acidic pH was more beneficial for carbohydrates metabolism while alkaline pH was better for proteins. Under optimal operational conditions, the metabolic functions associated with VFAs production (i.e., substrate membrane transport, intracellular metabolism and VFAs biosynthesis) were up-regulated. Moreover, functional microorganisms (i.e., Saccharofermentans and Bacteroides) responsible for VFAs generation were enriched. This work provided an innovative approach to recovery valuable products from biowastes, and in-depth understandings of microbial features in PW/SS co-fermentation systems.

Constructed wetland-microbial fuel cell (CW-MFC) is a novel technology for wastewater treatment with electrical generation. This work proposed a Fe-C micro-electrolysis substrate (Fe-C) with biomass modified ceramsite to enhance pollutants removal and electricity generation. The key influencing factors were revealed, and the COD, NH

Nitrous oxide (N2O), as a powerful greenhouse gas, has drawn increasing attention in recent years and different strategies for N2O reduction were explored. In this study, a novel strategy for valuable polyhydroxyalkanoates (PHA) production coupling with N2O reduction by mixed microbial cultures (MMC) using different substrates was evaluated. Results revealed that N2O was an effective electron acceptor for PHA production. The highest PHA yield (0.35 Cmmol PHA/Cmmol S) and PHA synthesis rate (227.47 mg PHA/L/h) were obtained with acetic acid as substrate. Low temperature (15℃) and pH of 8.0 were beneficial for PHA accumulation. Results of the thermogravimetric analysis showed that PHA produced with N2O as electron acceptor has better thermal stability (melting temperature of 99.4℃ and loss 5% weight temperature of 211.4℃). Our work opens up new avenues for simultaneously N2O reduction and valuable bioplastic production, which is conducive to resource recovery and climate protection.

The N-Acy-L-homoserine lactones (AHLs) mediated quorum sensing (QS) system exhibited important ecological significance in bacterial biofilm formation. However, the previous studies mainly focused on indigenous AHLs while the role of exogenous AHLs has remained unclear. This study evaluated the roles of exogenous AHLs on the biofilm formation of Pseudomonas aeruginosa. Both the C6-HSL and C8-HSL promoted the biofilm formation of P. aeruginosa with an enhancement of 2.47 and 1.88 times, respectively. Further analysis showed that exogenous AHLs contributed greatly to the adhesive ability instead of growth rate. Also, the bacterial motility and metabolic activities were significantly improved by AHLs. Moreover, the microbial functional genes (i.e. lasI, lasR, rhlI and rhlR) involved in regulating the biofilm formation were highly expressed in AHLs reactors. These findings expanded the knowledge of AHLs functions in mediating biofilm formation, and provided insightful guidance on the biofilm regulation in the wastewater treatment via biofilm technology.

An efficient attempt to improve the anaerobic fermentation of food wastes (FW) via the reuse of linear alkylbenzene sulphonates (LAS)-enriched laundry wastewater was reported. The production of short-chain fatty acids (SCFAs) from FW was enhanced by approximate 6-folds with high proportions of butyric and valeric acids at appropriate LAS level. Mechanism investigations demonstrated that the solubilization of macromolecule organics in FW was effectively improved by surface tension reduction. The hydrolysis and acidification processes during FW fermentation were accelerated and enhanced with the stimulation of microbial activities (higher activities of hydrolases and ATP concentrations). Also, the abundances of anaerobic microorganisms responsible for SCFAs production were enriched. Metatranscriptomic analysis indicated that the encoding genes involved in the metabolism of fermentation substrates for SCFAs production were highly expressed in LAS-added reactors. It was the simultaneous increase of bioavailable substrates and metabolic activities that contribute to the efficient SCFAs production in LAS-added reactors.

Metabolic uncouplers are widely used for the in-situ reduction of excess sludge from activated sludge systems. However, the interaction mechanism between the metabolic uncouplers and extracellular polymeric substances (EPS) of activated sludge is unknown yet. In this study, the interactions between a typical metabolic uncoupler, o-chlorophenol (oCP), and the EPS extracted from activated sludge were explored using a suite of spectral methods. The binding constants calculated for the four peaks of three-dimensional excitation-emission matrix fluorescence were in a range of 1.24–1.76 × 103 L/mol, implying that the tyrosine protein-like substances governed the oCP-EPS interactions. Furthermore, the results of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and 1H nuclear magnetic resonance indicated that the carboxyl, carbonyl, amine, and hydroxyl groups of EPS were the main functional groups involved in the formation of the oCP-EPS complex. The results of this study are useful for understanding the interactions between metabolic uncouplers and the EPS of activated sludge as well as their fates in biological wastewater treatment systems.

Large quantities of antibiotics are manufactured, used, and eventually discharged into alga-containing water environment as prototypes, by-products, or transformation products. Different activities of Chlamydomonas reinhardtii toward cefradine (CFD) were studied, and the results indicated that CFD is resistant (removal rate of 5.45–14.72%) in simulated natural water environment. Cefradine was mainly removed by hydrolysis, adsorption, desorption, photodecarboxylation, and photoisomerization. The effects of C. reinhardtii density, initial solution pH, and different light sources on CFD removal efficiency were investigated. The optimum conditions occurred at a density of algae 10 × 104 cells/mL, a solution pH of 9.0, and the ultraviolet (UV) light. Additionally, the removal kinetics under 16 different conditions was explored. The results showed that the removal of CFD fits well with a pseudo-first-order kinetic, and the half-life times are from 0.8 to 261.6 days. This study summarizes the CFD removal mechanisms in alga-containing water environment, highlights the important role played by light irradiation in eliminating CFD, and obtains the important kinetic data on CFD removal.

As a frequently used product with antimicrobial activity, consumed allicin might be discharged and concentrated in waste-activated sludge (WAS). However, the influence of allicin (as an exogenous pollutant) on WAS fermentation has not been clearly revealed. This study aimed to disclose the impacts of allicin on volatile fatty acid (VFA) generation during WAS fermentation. The results showed that the appropriate presence of allicin (10 mg/g TSS) significantly enhanced the VFA yield (1894 versus 575 mg COD/L in the control) with increased acetate proportion (24.3%). Further exploration found that allicin promoted WAS solubilization, hydrolysis and acidification simultaneously. Metagenomic analysis revealed that the key genes involved in extracellular hydrolysis metabolism (i.e., CAZymes), membrane transport (i.e., gtsA and ytfT), substrate metabolism (i.e., yhdR and pfkC) and fatty acid synthesis (i.e., accA and accD) were all highly expressed. Allicin also induced the bacteria to produce more signalling molecules and regulate cellular functions, thereby enhancing the microbial adaptive and regulatory capacity to the unfavourable environment. Moreover, the variations in fermentative microbes and their contributions to the upregulation of functional genes (i.e., ytfR, gltL, INV, iolD and pflD) for VFA generation were disclosed. Overall, the simultaneous stimulation of functional microbial abundances and metabolic activities contributed to VFA production in allicin-conditioned reactors.

The enrichment of polyhydroxyalkanoates (PHA) accumulating bacteria (PAB) in mixed microbial cultures (MMC) is extremely difficult to be predicted and optimized. Here we demonstrate that mechanistic and deep learning models can be integrated innovatively to accurately predict the dynamic enrichment of PAB. Well-calibrated activated sludge models (ASM) of the PAB enrichment process provide time-dependent data under different operating conditions. Recurrent neural network (RNN) models are trained and tested based on the time-dependent dataset generated by ASM. The accurate prediction performance is achieved (R2>0.991) for three different PAB enrichment datasets by the optimized RNN model. The optimized RNN model can also predict the equilibrium concentration of PAB (R2=0.944) and corresponding time, which represents the end of the PAB enrichment process. This study demonstrates the strength of integrating mechanistic and deep learning models to predict long-term variations of specific microbes, helping to optimize their selection process for PHA production.

The effects of food wastes (FW) composition and zero-valent iron (ZVI) on the volatile fatty acids (VFAs) generation, bacterial community succession and related metabolic functions during long-term FW and waste activated sludge (WAS) co-fermentation were investigated. The VFAs production in the carbohydrate-enriched reactor was approximately 3.0-folds of that in FW reactor. The ZVI contributed to the VFAs promotion by 3.6- and 6.7-folds in carbohydrate-enriched and FW reactors, respectively. Firmicutes (20.1-74.7%), Actinobacteria (0.9-26.3%), Bacteroidetes (3.4-65.7%), and Proteobacteria (9.1-28.5%) were the main bacteria in different fermentation reactors, and they were closely associated with the fermentation substrates and ZVI. Further analysis demonstrated that the key metabolic capacity (i.e. amino acid, carbohydrate and energy metabolism) and the genetic expressions of enzymes (i.e. fabA, fabZ, accA and accB) involved in VFAs generation were also related to FW composition, and were improved by the ZVI, which accounted for the significant VFAs promotion.

This research proposed an innovative approach to synchronously enhance the recovery of phosphorus (P) as vivianite and volatile fatty acids (VFAs) during waste activated sludge (WAS) and food waste (FW) co-fermentation. A high performance was achieved under 30% FW addition and pH uncontrolled, which gained 83.09% of TP recovery as high-purity vivianite (93.90%), together with efficient VFAs production (7671 mg COD/L). The FW supplement could enhance VFAs production and subsequently lower pH to contribute to the release of Fe2+ and PO43−. Also, it could dampen disrupting effects of strong acidic pH on microbial cells (lowering LDH release). Moreover, the flexible pH variation caused by biological acidification could maintain relatively higher microbial activities (increasing enzymes’ activities), which was advantageous to the biological effects involved in Fe2+ and PO43 release and VFAs generation. Therefore, this research provide a promising and economic alternative to dispose of WAS and FW simultaneously for valuable resource recovery.

l-Threonine and three kinds of conductive polymers were applied for anode modification in microbial fuel cells (MFCs) for decolorization of Congo red with simultaneous electricity generation. The description of modified anodes with FTIR, surface contact angle, and CV analysis showed that the anode surface was successfully grafted with functional groups, with improving wettability, as well as the increasing specific surface area and electrochemical activity. For l-threonine modification, the highest decolorization rate of 97% of the MFC, and meanwhile, the maximum current density of 155.8 mA/m2, was obtained at the modified concentration of 400 mg/L. For conductive polymer modifications, the poly (aniline-1,8-diaminonaphthalene) (short for PANDAN) owned the highest performance, with the current density 185 mA/m2, and the decolorization rate was 97%. Compared with l-threonine, the modifications by conductive polymers were more suitable for MFC decolorization due to their functional groups and unique conductivity. In addition, high-throughput sequencing analysis was conducted for the conductive polymers modified anodes to reveal their bioelectrochemical mechanisms.

The occurrence of antibiotic resistance genes (ARGs) in waste activated sludge (WAS) fermentation was investigated with persulfate (PS)-based treatment. ARGs affiliated with multidrug (mexP), macrolide (blaOXA-129), tetracycline (tetB), sulfonamide (sul1), and vancomycin (vanRG) types were significantly decreased by PS/Fe treatment. Mechanistic investigations revealed that PS/Fe possessed oxidating potential and exhibited devastating effects on WAS fermentation. First, PS/Fe promoted cell structure damage, which facilitated ARGs release from potential hosts. A co-occurrence network analysis indicated that Fe/PS suppressed the proliferation of potential host bacteria. In addition, the PS/Fe treatment induced the decreased abundance of certain functional genes involved in pathways associated with ARGs dissemination. Finally, variation partitioning analysis demonstrated that the microbial community structure exhibited more vital effects on ARGs fates than physicochemical factors (i.e., pH and ORP) and gene expression (i.e., two-component system). This work provided a deeper understanding of the critical factors used to determine ARGs fates during WAS fermentation.

An efficient approach of bioconverting the organic wastes in liquor wastewater (LW) and waste activated sludge (WAS) to valuable short-chain fatty acids (SCFAs) via anaerobic fermentation was explored. The maximal SCFAs concentration was 5400 mg COD/L with approximate 80.0% acetic and propionic acids under optimized conditions (LW/WAS ratio 1:1, pH 8 and fermentation 4 d). Mechanisms investigation found that the fermentation of LW/WAS made up the drawbacks of sole WAS fermentation by improving the bioavailable substrates and low C/N ratio to stimulate the microbial activities. The bioconversion efficiency of substrates for SCFAs generation was therefore enhanced. The humic acids present in LW could also play positive roles in SCFAs promotion. Moreover, the performance of LW/WAS fermentation was highly correlated with appropriate fermentation pH. The fermentative bacteria responsible for SCFAs production were highly enriched and the activities of key hydrolases, acid-forming enzymes and ATP concentration were greatly improved at pH 8.

This study reported a novel and efficient approach to improve the anaerobic fermentation performance of waste activated sludge (WAS) by the indigenous iron activated persulfate (PS/Fe) treatment. Firstly, the production of short-chain fatty acids (SCFAs), especially acetic acid, was remarkably enhanced within shorter fermentation time. Mechanism investigations demonstrated that the PS/Fe treatment could simultaneously accelerate and enhance the hydrolysis and acidification process while inhibit the methanogenesis during WAS fermentation. The activities of key enzymes and the abundances of anaerobic microorganisms responsible for SCFAs production were stimulated in the presence of PS/Fe which would promote the biological processes. Secondly, the PS/Fe treatment improved the quality of fermentation residue by reducing the toxic organic compounds in the residue and enhancing the dewaterability of fermented sludge, which was beneficial to the final disposal of WAS with added economical and environmental values.

This work revealed the impacts of exogeneous allicins on the antibiotic resistance genes (ARGs) variations during waste activated sludge (WAS) fermentation process. The overall abundance of ARGs was respectively reduced by 4.84 and 9.42% in presence of 0.01 and 0.05 g allicin/g TSS. Allicins disrupted the EPS structure and increased the permeability of cell membranes, which resulted in the release of ARGs for subsequent removal. Allicins also reduced intracellular ATP levels, which was disadvantageous to ARGs dissemination. Besides, allicins affected the microbial community and decreased the abundance of potential hosts based on bacterial taxa-ARGs network analysis. Moreover, the metabolic pathways and genetic expressions (i.e., two-component system, quorum sensing, and SOS response) involved in ARGs propagation were down-regulated, which caused the ARGs alleviation in allicins-stressed reactors. Overall, the simultaneous responses of cellular status, bacterial host, and genetic regulation accounted for the effective ARGs reduction induced by allicins during WAS fermentation.

This study mainly investigated the feasibility of utilizing cellulase to enhance waste activated sludge (WAS) and paper waste (PW) co-fermentation for the generation of volatile fatty acids (VFAs). The introduction of cellulase effectively enhanced the co-fermentation efficiency, and the maximum VFAs generation reached 3014 mg COD/L with 60 mg cellulase/g TSS while it was 1512 mg COD/L in the control reactor. The presence of cellulase evidently improved the concentration of soluble bioavailable substrates (e.g., carbohydrates and proteins) via inducing the EPS disintegration and PW disruption. More importantly, the functional anaerobes (i.e., Macellibacteroides and Bacteroides) and the microbial activities (i.e., ATP, key acid-forming enzymes, and genetic expressions) that related with the VFAs biosynthesis were enriched and enhanced due to the stimulation of cellulase, contributing to the ultimate VFAs promotion. This study provided a novel strategy to recover valuable products from waste biomass with constructive mechanistic exploration.

The impacts of the influent type in wastewater treatment plants (WWTPs) on the distribution patterns of the microbial community and functional characteristics were investigated. The obtained results indicated that the influent types exhibited evident influences on the microbial distribution patterns. The diversity and richness of functional microbes in HI-WWTP (with a ratio of >30% industrial wastewater in influents) were evidently decreased compared with those in HM- (with 70–90% municipal wastewater in influents) and M-WWTPs (with >90% municipal wastewater in influents). The core functional bacteria included denitrifiers, anaerobic fermentation bacteria (AFB), organic degrading bacteria (ODB), phosphorus accumulating organisms (PAO) and nitrite oxidizing bacteria (NOB), but they exhibited distinct abundances in WWTPs receiving different categories of wastewater. The denitrifiers in HI-WWTPs was 15.6–32.5% higher than that in other WWTPs, while PAOs had higher abundances in M − and HI-WWTPs (28.9% and 39.3%, respectively) compared with HM-WWTPs. Clear co-occurrence relationships were found among the main functional microbes with similar metabolic characteristics. Moreover, information on functional genes related to carbon, nitrogen and phosphorus metabolism, which is closely associated with pollutant removal efficiency, was obtained. M-WWTPs had higher abundances of genetic expressions for organic matters degradation (i.e. amino acid (10.42%) and carbohydrate (9.86%) metabolisms). Nar, Nir and Nor showed lowest abundances in HM-WWTPs, causing the low nitrogen removal (63.04–65.79%). However, influent type had little effect on genetic expression related with phosphorus removal. This work provided new insights into the interrelationship among bacterial co-occurrence, microbial activity and pollutant removal in WWTPs with different influent types.

The denitrification process is crucial for biological nitrogen removal in wastewater treatment plants (WWTPs). In this study, the nitrogen removal efficiency in full-scale WWTPs with different treatment processes and influent characteristics was investigated. The results indicated that the average total nitrogen removal rate (NRR) and denitrification rate in the A/O or A2/O systems were 67.5% and 2.08 mg N h−1 gMLVSS−1, respectively. However, cyclic activated sludge systems (CASSs) showed more efficient nitrogen removal with an average NRR and denitrification rate of 79.6% and 9.89 mg N h−1 gMLVSS−1, respectively. The microbial communities in WWTPs with similar influent compositions were similar and mainly shaped by BOD5. Candidatus Competibacter, Caldilineaceae and Anaerolineaceae were the functional genera closely associated with nitrogen removal based on high-throughput sequencing and correlation analysis. This study provides new insights into the regulation and amelioration of full-scale WWTPs to meet the increasingly stringent nitrogen discharge standard.

In this study, the effect of Chlamydomonas reinhardtii on the fate of CuO nanoparticles (CuO-NPs) in aquatic environment were investigated in terms of the colloidal stability, the free Cu2+ releasing, extracellular adsorption Cu (Cuex) and intracellular assimilation Cu (Cuin). The results showed that, with the increasing microalgal density, the absolute value of zeta potential of CuO-NPs decreased and the mean hydrodynamic diameter (MHD) became larger, leading to a better aggregation and settling behavior of CuO-NPs. The microalgae also promoted the free Cu2+ releasing, however, inhibited adsorption and assimilation of metal nanoparticles (MNPs) into microalgal cells, resulting in the reduction of the Cuex and Cuin per microalgal cell. The phenomenon was probably due to the reduced chance of contact between microalgae and MNPs. The internalization of CuO-NPs was also observed in microalgal cells by high resolution transmission electron microscope (HRTEM). Furthermore, the results of fast fourier transform (FFT)/inversed FFT (IFFT) analysis indicated that the CuO-NPs was reduced to Cu2O-NPs in the microalgae cells. The above results suggested that the microalgae can significantly affect the fate of MNPs, and subsequently, influencing the bioavailability and toxicity of MNPs in the aquatic environment.

This study presented an innovative method for phosphorus (P) recovery as vivianite from waste activated sludge (WAS) via optimizing iron dosing and pH value during anaerobic fermentation (AF). The optimal conditions for vivianite formation were in the pH range of 6.0–9.0 with initial PO43− >5 mg/L and Fe/P molar ratio of 1.5. Notably, FeCl3 showed advantages over ZVI for the simultaneous release of Fe2+ and PO43− during WAS fermentation, especially in acidic conditions. The FeCl3 dosing at pH 3.0 could contribute to 78.81% Fe2+ release and 85.69% of total PO43− release from WAS. They were ultimately recovered in the form of high-purity vivianite (93.67%). Clostridiaceae (40.25%) was the predominant bacteria in FeCl3-pH3 reactors, which played key roles in inducing dissimilatory iron reduction for Fe2+ formation. Therefore, P recovery as vivianite from WAS fermentation might be a promising and highly valuable approach to relieve the P crisis.

Partial denitrification (PD), which could provide sufficient nitrite for subsequent anaerobic ammonium oxidation, is a novel strategy for mainstream nitrogen removal. In this study, the performance of using glycerol as electron donor for nitrite accumulation in PD process was evaluated. Results showed that a C/N of 4.5 was effective for nitrite production (average nitrite accumulation rate: 34.32 mg N h−1 gMLVSS-1; average nitrate-to-nitrite transformation ratio (NTR): 91.1%) with pH ranging from 6.0 to 9.0. Also, a stable nitrite accumulation was achieved in long-term operation with the average NTR of 80.1%. Mechanism investigation found that the denitrifying bacteria Saccharibacteria (77.9%) was enriched in glycerol-driven reactors. Moreover, the enzymatic activity as well as the encoding genes (i.e. narG, narH and napA) involved in nitrate reduction were much higher than that for nitrite reduction (i.e. nirK), and this disparity was responsible for the efficient nitrite accumulation in glycerol-driven PD system.

A practical approach of synchronously recovering vivianite and volatile fatty acids (VFAs) by food waste (FW) and waste activated sludge (WAS) co-fermentation in continuous operation was investigated. Approximately 82.88% P as high-purity vivianite (95.23%) and 7894 mg COD/L VFAs were finally recovered. The simultaneous addition of FW and FeCl3 contributed to the fermentation conditions by adjusting pH biologically and increasing the concentration of organic substrates, which enhanced the Fe3+ reduction efficiency and microbial activities (e.g., hydrolases and acidogenic enzymes). Microbial analysis found the functional bacteria related to Fe3+ reduction and VFAs generation were further enhanced and enriched. Besides, results indicated that the efficiencies of Fe2+ and P release and VFAs recovery were highly linked to SRT, the satisfactory fermentation performance was obtained at SRT of 6 d. This research would provide a practical waste recycling technology to treat FW and WAS simultaneously for recovering vivianite and VFAs synchronously.

In this study, the distribution, removal efficiency, and potential risks of 9 typical endocrine active compounds (EACs) in two full-scale wastewater treatment plants (WWTPs) were investigated. The EAC concentrations ranged from 0.2 to 7394.2 ng/L in influents. The source of influents was a critical factor in determining the EAC levels. EACs were primarily removed in the secondary biological processing units, with removal efficiencies fluctuating from 13.7% to 98%. The biological treatment processes and operating parameters (i.e., HRT and SRT) influenced the EAC removal efficiency. Bisphenol A (BPA) and estriol were mainly removed by biodegradation, while antidepressants were primarily eliminated by sludge adsorption according to the distribution patterns and mass flow of EACs in WWTPs. Novosphingobium, Saprospiraceae, etc. were the core functional bacteria for EAC biodegradation. In addition, sertraline in effluents and dewatered sludge may pose medium environmental risks, while the other EACs pose low environmental risks.

The effects of different hypochlorite types (namely Ca(OCl)2 and NaOCl) on the waste activated sludge (WAS) anaerobic fermentation, and microbial community and activity were investigated. The results indicated that both Ca(OCl)2 and NaOCl contributed to volatile fatty acids (VFAs) production by simultaneously enhancing the solubilization, hydrolysis and acidification processes. The maximal VFAs was respectively 1379.5 (at 10 d) and 1621.5 (at 8 d) mg COD/L at the optimal dose of NaOCl and Ca(OCl)2 while it was merely 157.4 (at 6 d) mg COD/L in the control. However, the Ca(OCl)2 might affect the anaerobic process in a continuous mode while the NaOCl was relatively transient, which caused distinctive influences on the microbial structure and activity, and subsequently VFAs production in WAS fermentation systems. Moreover, Ca(OCl)2 treatments showed advantages over NaOCl on WAS dewatering and VSS reduction, implying the superiority of utilizing Ca(OCl)2 as additives for WAS disposal.

This study explored the influences of peroxydisulfate (PDS) and peroxymonosulfate (PMS) activated with different catalysts on the anaerobic fermentation of waste activated sludge (WAS). All the treatments were effective in promoting short-chain fatty acids (SCFAs) production, particularly acetic acid, in the order of PMS/MnO2 > PMS/Zn > PDS/Zn > PMS/Fe > PDS/Fe > PDS/MnO2. Mechanistic investigations demonstrated that WAS disintegration was intensely induced by the free radicals (i.e., SO4 − and OH) generated in PDS and PMS treating reactors. It significantly promoted the solubilization and hydrolysis processes and thereby provided sufficient bioavailable substrates for further acidogenic metabolisms. Additionally, it enlarged the abundance of functional bacteria responsible for SCFAs production. The simultaneous promotion of bioavailable substrates and fermentative microorganisms markedly contributed to the SCFAs enhancement. Moreover, the dewaterability and stabilization of fermented sludge were both improved with the PDS and PMS treatments, which were beneficial to the final disposal of WAS.

Due to the shortage of phosphorus resources and the limitations of existing phosphorus recovery methods, phosphorus recovery in the form of vivianite has attracted considerable attention with its natural ubiquity, easy accessibility and foreseeable economic value. This review systematically summarizes the chemistry of vivianite, including the characteristics, formation process and influencing factors of the material. Additionally, the potential of phosphorus recovery as vivianite from wastewater has also been comprehensively examined from the prospects of economic value and engineering feasibility. In general, this method is theoretically and practically feasible, and brings some extra benefits in WWTPs. However, the insufficient understanding on vivianite recovery in wastewater/sludge decelerate the development and exploration of such advanced approach. Further researches and cross-field supports would facilitate the improvement of this technique in the future.

The accurate determination of widespread artificial sweeteners (ASs) and the information of their distributions in environments are of significance to investigate the environmental behaviors. This paper firstly reviews the typical analytic methodologies for ASs and the main influencing factors during the analytic processes. Solid-phase extraction (SPE) with LC-ESI-MS is currently the leading-edge method. However, the efficiency and accuracy for ASs analysis in environmental samples are also dependent on the SPE cartridges, buffers and pH, matrix effects, and sample stability. A basic procedure for ASs determination in different environmental samples is proposed. The current occurrences of ASs in environments are then evaluated. The ASs, especially the acesulfame and sucralose, are widely detected in various environmental medium. The concentrations of investigated ASs are generally in the order of wastewater treatment plants (WWTPs) influent > WWTPs effluent > surface water > groundwater > drinking water; and atmosphere > soil. The ASs levels in the environment exhibit significant differences among different regions. Further analysis indicates that the phenomenon is highly correlated with the consumption patterns and the removal efficiency of WWTPs in a specific country.

Our research investigated the hormesis effect of cefradine on the specific growth rates (μ) of single-celled algae (Chlamydomonas reinhardtii) from aqueous solutions. We found the specific growth rate of C. reinhardtii slightly increased with cefradine concentrations within the range 0.5–10 mg/L. Effects of algae density, initial solution pH, and temperature on the adsorption batch assays were investigated. The optimum conditions for cefradine adsorption occurred at a density of 5 × 106 algae cells/mL, a solution pH of 7.0, and a temperature of 25.0 °C. A Box–Behnken design was employed to evaluate correlations between influential factors and cefradine adsorption. The results showed a significant interaction between algae density and temperature. The maximum removal rate could reach 50.13% under the optimal conditions. Additionally, the adsorption mechanisms were explored through Langmuir and Freundlich isotherm equations, adsorption kinetics, and thermodynamics. The results suggested that the adsorption process was monolayer, spontaneous, and endothermic with an increase in randomness at the algae–solution interface, which followed a pseudo-second-order model. All the data indicated that the alga performed a better removal capacity in the antibiotic-containing wastewater treatment process. This study lays the groundwork for a better understanding of the interaction mechanism between cefradine and Chlamydomonas reinhardtii in water solutions under dark condition.

1,4-Dioxane is an emerging pollutant, which widely exists in natural environments and poses potential risks to the living organisms. However, its effect on the denitrification process is still unknown. In this study, the effects of 1,4-dioxane on the denitrification process were therefore investigated by using Paracoccus denitrificans as the model denitrifier. The obtained results showed that the exposure of 1,4-dioxane exhibited remarkable lag or inhibition on the denitrification process, especially with high dose. In the control without 1,4-dioxane exposure, Paracoccus denitrificans showed high denitrification efficiency (98.5%). However, the efficiency decreased to 78.5, 63.9, and 9.3% with 0.50, 0.75, and 1.0% (v/v) 1,4-dioxane dose, respectively. The dose-induced inhibition of denitrification by 1,4-dioxane could be partially attributed to the negative effects on proliferation and viability of functional microorganisms by conjugating and disrupting the cell membranes. Furthermore, 1,4-dioxane caused biotoxicity to the intracellular activities of denitrifiers via disturbing carbon source utilization and interfering the key enzymes responsible for glycolysis. The decrease of microbial viability and activity inevitably resulted in the decline of key enzymes (NAR, NIR, NOR, and N2OR) closely related with denitrification process, which could be the direct reason for the decrease of denitrification performance.

Aiming to efficiently dispose printing and dyeing wastewater with “high organic nitrogen and aromatic compounds, but low carbon source quality”, the reinforced anaerobic hydrolysis-denitrification coupling process, based on improved UASB reactors and segregated collection-disposition strategy, was designed and applied at the pilot scale. Results showed that the coupling process displayed efficient removal for these two kinds of pollutants (nitrogen and aromatics), since the concentration of NH3-N (shortened as ρ (NH3-N)) < 8 mg/L, ρ (TN) < 15 mg/L with long-term stability for the effluent, and both species and abundances of aromatics reduced greatly by UASBs according to GC-MS. Microbial community analysis by PCR-DGGE showed that Bacteroidetes and Alphaproteobacteria were the dominant communities in the bioreactors and some kinds of VFAs-producing, denitrifying and aromatic ring opening microorganisms were discovered. Further, the nirK and bcrA genes quantification also indicated the coupling process owned outstanding denitrification and aromatic compound-degrading potential, which demonstrates that the coupling process owns admirable applicability for this kind of wastewater treatment.

The combined biological processes of branched water-adjustment, chemical precipitation, hydrolysis acidification, secondary sedimentation, Anoxic/Oxic and activated carbon treatment were used for chemical industrial wastewater treatment in the Taihu Lake Basin. Full-scale treatment resulted in effluent chemical oxygen demand, total nitrogen, NH3–N and total phosphorus of 35.1, 5.20, 3.10 and 0.15 mg/L, respectively, with a total removal efficiency of 91.1%, 67.1%, 70.5% and 89.3%, respectively. In this process, short-circuited organic carbon from brewery wastewater was beneficial for denitrification and second-sulfate reduction. The concentration of effluent fluoride was 6.22 mg/L, which also met the primary standard. Gas Chromatography-Mass Spectrometry analysis revealed that many types of refractory compounds were present in the inflow. Microbial community analysis performed in the summer by PCR-denaturing gradient gel electrophoresis and MiSeq demonstrated that certain special functional bacteria, such as denitrificans, phosphorus-accumulating bacteria, sulfate- and perhafnate-reducing bacteria, aromatic compound-degrading bacteria and organic fluoride-degrading bacteria, present in the bio-tanks were responsible for the acceptable specific biological pollutant reduction achieved.

Palygorskite (PAL) is a good heavy metal adsorbent due to its high surface area, low cost, and environmentally compatibility. But the natural PAL has limited its adsorption capacity and selectivity. In this study, a cost-effective and readily-generated absorbent, l-threonine-modified palygorskite (L-PAL), was used and its performance for Cu(II) removal in simulated aquaculture wastewater was evaluated. After preparation, L-PAL was characterized by using Fourier transform infrared spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffractometer, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis. The impacts of pH, adsorbent dosage, contact time, and initial Cu(II) concentration on the adsorption capacity of L-PAL were examined. The Cu(II) adsorption capacity on L-PAL was enhanced almost 10 times than that of raw PAL. The adsorption isotherms of Cu(II) fit the Langmuir isotherms, and the adsorption kinetics was dominated by the pseudo-second-order model. The thermodynamic parameters at four temperatures were calculated, which indicated that the adsorption was spontaneous and endothermic. The adsorption mechanism involves complexation, chelation, electrostatic attraction, and micro-precipitation. Furthermore, L-PAL is shown to have a high regeneration capacity. These results indicate that L-PAL is a cheap and promising absorbent for Cu(II) removal and hold potential to be used for aquaculture wastewater treatment.

Two types of cathodic biofilm in microbial fuel cells (MFC) were established for comparison on their performance and microbial communities. Complete autotrophic simultaneous nitrification and denitrification (SND) without organics addition was achieved in nitrifying-MFC (N-MFC) with a total nitrogen (TN) removal rate of 0.35 mg/(L·h), which was even higher than that in denitrifying-MFC (D-MFC) at same TN level. Integrated denaturing gradient gel electrophoresis analysis based on both 16S rRNA and nirK genes showed that Alpha-, Gammaproteobacteria were the main denitrifier communities. Some potential autotrophic denitrifying bacteria which can use electrons and reducing power from cathodes, such as Shewanella oneidensis, Shewanella loihica, Pseudomonas aeruginosa, Starkeya novella and Rhodopseudomonas palustris were identified and selectively enriched on cathode biofilms. Further, relative abundance of denitrifying bacteria characterized by nirK/16S ratios was much higher in biofilm than suspended sludge according to real-time polymerase chain reaction. The highest enrichment efficiency for denitrifiers was obtained in N-MFC cathode biofilms, which confirmed autotrophic denitrifying bacteria enrichment is the key factor for a D-MFC system.

The present study investigated the influences of three metabolic uncouplers (pCP, oCP and oNP) on excess activated sludge reduction and microbial products of extracellular polymeric substances (EPS) and intracellular storage product (polyhydroxybutyrate, PHB) in short-term tests. Results showed sludge was reduced 58.2%, 59.8% and 80.8%, respectively, at pCP, oCP and oNP concentrations of 20mg/L. The dosage of three uncouplers had no obviously influences on COD removal and sludge settleability, but had significant inhibition effect on ammonia removal, especially for oNP. Low concentration of pCP and oNP (5mg/L) dosing resulted in protein and polysaccharide content increased in EPS, however, they were decreased at high pCP and oNP concentrations (>5mg/L). To oCP, the protein content in EPS was increased linearly with oCP concentration. Furthermore, metabolic uncouplers addition stimulated the production of PHB. Among three uncouplers, oCP could be an alternative uncoupler for sludge reduction in activated sludge process.

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are emerging contaminants of environmental concern. Heterotrophic bacteria in activated sludge have an important role in wastewater treatment plants (WWTPs). However, the fate of cultivable heterotrophic ARB and ARGs in WWPTs process remains unclear. In the present study, we investigated the antibiotic-resistant phenotypes of cultivable heterotrophic bacteria from influent and effluent water of three WWTPs and analysed thirteen ARGs in ARB and in activated sludge from anoxic, anaerobic and aerobic compartments. From each influent or effluent sample of the three plants, 200 isolates were randomly tested for susceptibility to 12 antibiotics. In these samples, between 5% and 64% isolates showed resistance to >9 antibiotics and the proportion of >9-drug-resistant bacteria was lower in isolates from effluent than from influent. Eighteen genera were identified in 188 isolates from influent (n=94) and effluent (n=94) of one WWTP. Six genera (Aeromonas, Bacillus, Lysinibacillus, Microbacterium, Providencia, and Staphylococcus) were detected in both influent and effluent samples. Gram-negative and -positive isolates dominated in influent and effluent, respectively. The 13 tetracycline-, sulphonamide-, streptomycin- and β-lactam-resistance genes were detected at a higher frequency in ARB from influent than from effluent, except for sulA and CTX-M, while in general, the abundances of ARGs in activated sludge from two of the three plants were higher in aerobic compartments than in anoxic ones, indicating abundant ARGs exit in the excess sledges and/or in uncultivable bacteria. These findings may be useful for elucidating the effect of WWTP on ARB and ARGs.

Denitrifying MFC was successfully coupled with anaerobic ammonium oxidation process in this study. With the help of cathode electrons, the stoichiometry relationship Δ − NH 3 -N:Δ − NO 2 − -N:Δ + NO 3 − -N was approximate 1:1.37:0.03 during the stable operation, which demonstrated its further nitrite and nitrate reduction. According to microbial community analysis, Candidatus Brocadia sinica was the main anammox community, and Rhodopseudomonas palustris with electrochemical driven denitrifying ability, especially enriched in biofilm. Higher abundance of nirK genes in biofilm (compare to the control) and invariable amx genes in suspended sludge were responsible for its better nitrogen removal. The sludge and biofilm performed their own duties on anammox and denitrification, respectively, according to genes quantification. Under the totally autotrophic system, electron donors were “concentrated supplied” and easy to control, which avoided the suppression of anammox growth, making this autotrophic coupling process appears to be more promising.

A novel, low cost and easy regeneration biosorbent, chem-modified walnut shell (MWNS), was studied to investigate its potential for removal of an anionic dye, reactive brilliant red K-2BP. The MWNS was synthesized with epichlorohydrin and diethylenetriamine as etherifying agent and crosslinking agent, respectively, and its characteristics were performed with Fourier transform infrared spectroscopy, scanning electron microscope, electron dispersive spectroscopy and thermogravimetric analysis. The influences of pH (0.5–11) and adsorbent dosage (0.1–6 g/L) on adsorption capacity of MWNS were evaluated. The maximum K-2BP adsorption capacities (Qm) calculated by best fitting model (Langmuir) were 568.18 mg/g at 313 K, which was almost 10 times than that of raw material. The adsorption kinetic was well confirmed with pseudo-second-order equation. Thermodynamic studies demonstrated adsorption process by MWNS was spontaneous and endothermic. Furthermore, the regeneration capability of MWNS implied MWNS was a cheap, excellent and promising biosorbent for K-2BP removal in azo dye wastewater treatment.