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Photocatalytic membranes (PMs), coupling of membrane filtration and photocatalysis, have exhibited the potential for application in the wastewater treatment. In this study, we firstly adopted the supramolecular aggregates of melamine (M), cyanuric acid (C), and urea (U) in specific dimethyl sulfoxide (DMSO) as precursors to prepare carbon nitride MCU-C 3 N 4 with high photocatalytic performance, and a kind of novel-designed photocatalytic membrane was prepared via filtrating the mixture of graphene oxide (GO) nanosheets and MCU-C 3 N 4 on PVDF membrane supports, and then crosslinked using glutaraldehyde (GA) to construct a steady coating on the GO/MCU-C 3 N 4 /PVDF membrane. GO/MCU-C 3 N 4 /PVDF composite membrane exhibited higher permeation flux than that of GO/PVDF membrane and exhibited excellent separation performance for oil-in-water emulsion. A visible light-driven self-cleaning four-stage filtration by a self-built dead-end filtration system was carried out to evaluate membrane antifouling property, and GO/MCU-C 3 N 4 /PVDF membrane (M2) possessed higher flux recovery ratio (FRR) (∼92.36%) and lower irreversible fouling resistance (R ir) ratio (∼8%) under 30min visible-light irradiation, maintaining relatively higher FRR (>72%) during 4 cycling of four-stage filtrating experiments. GO/MCU-C 3 N 4 /PVDF PMs are equipped with high permeation flux, separation performance, anti-fouling property and stability, indicating potential application in water treatment. Image 1 • GO/MCU-C 3 N 4 /PVDF photocatalytic membrane can be driven by visible light. • GO/MCU-C 3 N 4 /PVDF is prepared by vacuum-assisted self-assembly and crosslink. • GO/MCU-C 3 N 4 /PVDF has high permeation flux and good separation performance. • GO/MCU-C 3 N 4 /PVDF has high FRR and low Rir/Rt under visible light irradiation. • GO/MCU-C 3 N 4 /PVDF has relatively good recyclability and universality. [ABSTRACT FROM AUTHOR]

Abstract A metal-free modified carbon nitride MCU(DMSO)-C 3 N 4 (3:3:1) with a honeycomb-like morphology was prepared via firstly introducing cyanuric acid and urea into melamine in dimethyl sulfoxide (DMSO) as the precursor for the MCU-C 3 N 4. A variety of characterization methods, including XRD, XPS, FT-IR, SEM, TEM, UV–vis, photoluminescence (PL), and photocurrent generation, were applied to investigate the structure, morphology, optical, and photoelectrochemical properties of the g-C 3 N 4 and MCU-C 3 N 4 (3:3:1). Rhodamine B (RhB), methylene blue (MB), and bisphenol A (BPA) were selected as target pollutants to evaluate photocatalytic activity of the MCU-C 3 N 4 (3:3:1) under visible light irradiation. MCU-C 3 N 4 (3:3:1) exhibits significantly enhanced photocatalytic activity compared with g-C 3 N 4 , where 99.49% RhB is removed within 40min, 97.7% MB is removed within 80 min, and 84.37% BPA is removed within 90 min. The improved photodegradation efficiency was mainly due to the larger surface area, the stronger REDOX ability, and the increased separation efficiency of photogenerated electron-hole pairs. The active radical trapping experiments and electron spin resonance tests indicated that h+ and O 2 − radicals were the dominant active species whereas OH radicals could be a minor factor. A possible photocatalytic mechanism is proposed. This strategy here provides an ideal platform for the design of photocatalysts with large surface area and high porosity for various pollutant controlling applications. Highlights • Honeycomb-like MCU-C 3 N 4 (3:3:1) is well prepared by molecular self-assembly. • High-surface area of MCU-C 3 N 4 improves the photoinduced charges separation. • MCU-C 3 N 4 has greater improvements in degradation of RhB, MB and BPA than g-C 3 N 4. • This preparation strategy for MCU-C 3 N 4 (3:3:1) is facile and environment-friendly. [ABSTRACT FROM AUTHOR]

Extracellular polymeric substances (EPS) are present both outside of the cells and in the interior of microbial aggregates, and account for a main component in microbial aggregates. EPS can influence the properties and functions of microbial aggregates in biological wastewater treatment systems, and specifically EPS are involved in biofilm formation and stability, sludge behaviors as well as sequencing batch reactors (SBRs) granulation whereas they are also responsible for membrane fouling in membrane bioreactors (MBRs). EPS exhibit dual roles in biological wastewater treatments, and hence the control of available EPS can be expected to lead to changes in microbial aggregate properties, thereby improving system performance. In this review, current updated knowledge with regard to EPS basics including their formation mechanisms, important properties, key component functions as well as sub-fraction differentiation is given. EPS roles in biological wastewater treatments are also briefly summarized. Special emphasis is laid on EPS controlling strategies which would have the great potential in promoting microbial aggregates performance and in alleviating membrane fouling, including limitation strategies (inhibition of quorum sensing (QS) systems, regulation of environmental conditions, enzymatic degradation of key components, energy uncoupling etc.) and elevation strategies (enhancement of QS systems, addition of exogenous agents etc.). Those strategies have been confirmed to be feasible and promising to enhance system performance, and they would be a research niche that deserves further study. [ABSTRACT FROM AUTHOR]

pH plays an important role in heavy metal removal during micellar-enhanced ultrafiltration (MEUF). In the present work, the influence of pH on heavy metal speciation and removal from wastewater by MEUF was investigated using an anionic surfactant (sodium dodecyl sulfate, SDS) and a hydrophilic membrane (polyether sulfone). Experiments were performed with pH values in the range of 1–12. Metal ion removal efficiency (R) was used to assess the effects of the MEUF process. Results showed that better removal rate of copper and cadmium was achieved at high pH values (pH > 3) with SDS feed concentration of 8 mM, while the optimal pH range was 3–10 for zinc and lead. The corresponding efficiencies for heavy metal removal decreased with the increasing feed concentration of metal ions under the pH conditions of 1–12. Furthermore, the heavy metal ion removal rate (50 mg/L) followed the order of Pb 2+ > Cd 2+ > Zn 2+ > Cu 2+ . These results showed that pH is a key parameter in metal ion speciation and removal during MEUF. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a communication process between cells, in which bacteria secrete and sense the specific chemicals, and regulate gene expression in response to population density. Quorum quenching (QQ) blocks QS system, and inhibits gene expression mediating bacterial behaviors. Given the extensive research of acyl-homoserine lactone (AHL) signals, existences and effects of AHL-based QS and QQ in biological wastewater treatments are being subject to high concern. This review summarizes AHL structure, synthesis mode, degradation mechanisms, analytical methods, environmental factors, AHL-based QS and QQ mechanisms. The existences and roles of AHL-based QS and QQ in biomembrane processes, activated sludge processes and membrane bioreactors are summarized and discussed, and corresponding exogenous regulation strategy by selective enhancement of AHL-based QS or QQ coexisting in biological wastewater treatments is suggested. Such strategies including the addition of AHL signals, AHL-producing bacteria as well as quorum quenching enzyme or bacteria can effectively improve wastewater treatment performance without killing or limiting bacterial survival and growth. This review will present the theoretical and practical cognition for bacterial AHL-based QS and QQ, suggest the feasibility of exogenous regulation strategies in biological wastewater treatments, and provide useful information to scientists and engineers who work in this field. [ABSTRACT FROM AUTHOR]

A new type of 0D-2D Z-scheme heterojunction photocatalyst (MoO 3 /g-C 3 N 4) was successfully prepared via simple hydrothermal calcination method. The catalytic activities of MoO 3 /g-C 3 N 4 was evaluated by the degradation effect of tetracycline. The results indicated that the 0D-2D MoO 3 /g-C 3 N 4 Z-scheme heterojunction was significantly better than that of original g-C 3 N 4. Especially, the optimal 0.5 wt% MoO 3 /g-C 3 N 4 could reach 85.9% removal efficiency within 100 min under visible light irradiation (λ > 420 nm), and its degradation rate constant was 2.3 times higher than that of g-C 3 N 4 ·In addition, the effects of real water matrix, natural sunlight irradiation on tetracycline removal were examined. Reactive-species-trapping experiments show that both photo-generated •O 2 − and h+ are the main active species in the photocatalytic process. Besides, the results of •O 2 − and •OH detection further indicated that the yield amount of •O 2 − and •OH in MoO 3 /g-C 3 N 4 case showed enhancement when compared with g-C 3 N 4. Moreover, the quite stable crystal structure and excellent recycling ability endowed the MoO 3 /g-C 3 N 4 composite with a great potential for applying in photocatalytic fields. [Display omitted] • 0D /2D MOCN is well prepared by simple calcination synthesis method. • The removal rate of tetracycline by 0D/2D MOCN is higher than that of CNNS. • 0D /2D MOCN possess remarkable stability and reusability. • Constructing 0D/2D Z-scheme MOCN improves the photoinduced charge separation of CNNS. [ABSTRACT FROM AUTHOR]

The amount of waste activated sludge (WAS) has grown dramatically in China. WAS is considered as a problematic and hazardous waste, which should be disposed in a safe and sustainable manner. In order to recycle WAS to an anaerobic granular sludge (AnGS) process for anaerobic digestion, Fe powder and steel slags (rusty and clean slags) were used to enhance the granulation process. The results demonstrated that both rusty and clean slags encouraged the development of granular sludge. Adding 10 g/L clean slags could increase AnGS granulation rate by 37%. In the presence of clean slags, extracellular polymeric substances (EPS) concentration in granules increased noticeably to 715 mg/g mixed liquor suspended solids (MLSS). High throughput sequencing analysis exhibited more diversity and higher abundance of functional microbial communities in the batch bottle with 10 g/L clean slags. This study suggested that adding clean slags at 10 g/L dosage was a sustainable and effective method for the sludge granulation. Image 1 • By reusing WAS and steel slags, AnGS was successfully developed within 23 d. • Adding 10 g/L clean slags for AnGS formation increased granulation rate by 37%. • Steel slags could replace high-concentration iron for accelerating granulation. • Adding steel slags obtained a more diversity and a better community structure. [ABSTRACT FROM AUTHOR]

Concentration polarization is an important issue in micellar enhanced ultrafiltration (MEUF) of wastewater containing heavy metal ions at low surfactant concentrations. In this paper, we studied removal of Cd(Ⅱ) by cross flow MEUF at low sodium dodecyl sulfate (SDS) concentration levels, and the role of concentration polarization in flux decline and Cd(Ⅱ) rejection was emphasized. Concentration polarization resistance and SDS concentration near membrane were calculated to characterize concentration polarization. The results showed that SDS concentration near membrane was 13 mM when feed concentration was merely 0.8 mM. By combining phase diagram of SDS, structures of SDS micelles in concentration polarization layer were deduced and thin layer structure transformed to porous structure formed by accumulated globular micelles when SDS concentration increased. Although micelles formed in concentration polarization layer was responsible for flux decline, they also provided adsorption sites for Cd(Ⅱ). Image 103725 • Effect of operate conditions on Cd rejection and permeate flux was evaluated. • Concentration polarization resistance was calculated by resistance in series model. • Accumulation amount of SDS near membrane was calculated by a mass balance equation. • Relationship between flux decline, Cd rejection and concentration polarization was revealed. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a process widely exist in bacteria, which refers to the cell-cell communication through secretion and sensing the specific chemical signal molecules named autoinducers. This review demonstrated recent research progresses on the specific impacts of signal molecules in the granular sludge reactors, such corresponding exogenous strategies contained the addition of QS signal molecules, QS-related enzymes and bacteria associated with QS process. Accordingly, the correlation between QS signaling molecule content and sludge granulation (including the formation and stability) was assumed, the comprehensive conclusion elucidated that some QS signals (acyl-homoserine lactone and Autoinducer 2) can accelerate the growth of particle diameter, the production of extracellular polymeric substance (EPS), microbial adhesion and change the microbiome structure. But diffusable signal factor (DSF) acted as a significant disincentive to the formation and stability of GS. As a result, it deserved serious attention on the value and role of QS signals in the GS. This review attempts to illuminate the potential method for addressing the main bottleneck: to accelerate the formation of granules and keep the high stability of GS for a long-term reactor. Therefore, review discussed the possible trends of GS: QS and intercellular/intracellular signaling which can lay a theoretical foundation for mechanism of GS formation and stability, would be of practical significance for further application in the future. Image 10514 • Particle diameter in the granules were relative to the variety of signal molecules. • The production of EPS was enhanced by AHLs and AI-2 and reduced by DSF. • Augmentation of signal molecules changed the microbial community in the granules. • Mechanism of signal molecules functioned in granules could be effectively applied. [ABSTRACT FROM AUTHOR]

The development of visible light-responsive photocatalytic membranes (vis-PMs) has opened a promising direction in water purification field. Herein, supramolecular aggregates from cyanuric acid (C), melamine (M), and urea (U) in dimethyl sulfoxide (DMSO) were used to prepare the porous carbon nitride nanosheet (MCU-C 3 N 4) with excellent photocatalytic performance. A sort of 3D heterostructure PMs consisting of MCU-C 3 N 4 and carbon nanotube (CNTs) interposed into graphene oxide (GO) on the PVDF membrane was firstly fabricated by the layer-by-layer (LbL) assembly method, in which CNTs/MCU-C 3 N 4 /GO material was immobilized on the polyelectrolytes (PE) modified PVDF based on their electrostatic attractions. Such PMs with abundant nano-channels had excellent mechanical strength, satisfactory water permeability (14.35 L m−2 h−1 bar−1) and synergetic removal efficiency of rhodamine B (RhB, 98.31%) in long -term operation, relative to the pristine GO membrane and MCU-C 3 N 4 /GO membrane fabricated by the same method. In addition, such PMs also exhibited the satisfactory tetracycline hydrochloride (TC) removal rate (84.81%) under visible light irradiation. Construction and performance of such carbon-based PMs might provide guidance for development of vis-PMs in terms of bonding strength, multidimensional morphology and water purification application. • LbL self-assembly strategy for carbon-based PMs with 3D heterostructure is proposed. • Such PMs are equipped with satisfactory water permeability (14.35 L m−2 h−1 bar−1). • Such PMs exhibit high performance for RhB removal (98.31%) in the integrated system. • RhB removal mechanism on such PMs under photocatalytic filtration process is given. [ABSTRACT FROM AUTHOR]

Paralytic shellfish toxins (PSTs) producing algae are widely distributed in the global coastal aquatic environment, posing a threat to coastal ecosystem health and mariculture safety. However, the levels and potential environmental risks of PSTs frequently detected in shellfish remain largely unexplored in seawater of mariculture zones. In this study, a new method for trace detection of 13 common PSTs (<1.0 ng/L) in seawater was established based on off-line solid phase extraction (SPE) and on-line SPE-liquid chromatography-tandem mass spectrometry (on-line SPE-LC-MS/MS), and a systematic investigation of PSTs in seawater of the Laizhou Bay, a typical aquaculture bay in China, was conducted to understand their pollution status, environmental impact factors and ecological risks for the first time. Eleven PSTs were detected in the seawater of Laizhou Bay with total concentrations ranging from 0.75 to 349.47 ng/L (mean, 176.27 ng/L), which indicates the rich diversity of PSTs in the mariculture bay and demonstrates the reliability of the proposed analytical method. C1, C2, GTX2, GTX3, dc GTX2, and dc GTX3 were found to be the predominant PSTs, which refreshed the knowledge of PST contamination in the coastal aquatic environment. PST levels in seawater exhibited the highest levels in the southeastern mouth of Laizhou Bay and decreased toward the inner bay. Correlation analyses showed that climatic factors, nutrient status and hydrological conditions had significant effects on the distribution of PST in mariculture bay. Preliminary environmental risk assessments revealed that aquatic organisms throughout the waters of Laizhou Bay are at risk of chronic PST toxicity. These findings imply that the risk of PST in seawater of mariculture bay has previously been grossly underestimated, and that the coastal aquatic environment in North China and even the world may be at more serious risk of PST pollution, which should be taken seriously. [Display omitted] • A new analytical method was developed for 13 trace PSTs in seawater (<1.0 ng/L). • Various PSTs widely distributed in nearshore water was reported for the fist time. • GTXs, dc GTXs, and C-toxins are the predominant PSTs in mariculture seawater. • Aquatic organisms in the Laizhou Bay are generally at risk of chronic PST toxicity. • Nutrient and hydrological conditions affect the distribution of PST in Laizhou Bay. [ABSTRACT FROM AUTHOR]