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关键词： Optical tomography  

摘要： Activated Sludge Membrane Bioreactors (AS-MBR) are recognized as a commercially competitive alternative to conventional wastewater treatments. However, membrane fouling remains one of the main challenges and disadvantages of the process. This study evaluates the suitability of Optical Coherence Tomography (OCT) in monitoring the cake layer development in-situ in AS-MBR under continuous operation. Real-time direct imaging of the cake layer was feasible when limiting the continuous movement of the AS flocs in the reactor by turning aeration off for few minutes prior to scanning a given membrane area. The cake layer morphology was evaluated using both 2D and 3D image analysis. The 3D analysis respect to 2D analysis provided a more representative characterization of the fouling formed in the system. The non-invasive nature of OCT imaging enabled monitoring fouling development over time, where an increase in thickness and a decrease in roughness was observed in the first 200 h of operation. The 3D OCT image analyses were also compared with the 3D confocal laser scanning microscopy (CLSM) image analyses performed at the end of the study. Results demonstrate that OCT imaging can be applied for online, real-time monitoring and analysis of fouling behavior in AS-MBR systems.

关键词： Membrane bioreactor   Electrochemical processes   Electrically-enhanced membrane bioreactor   Membrane fouling   Energy consumption  

摘要： Research and development activities on standalone systems of membrane bioreactors and electrochemical reactors for wastewater treatment have been intensified recently. However, several challenges are still being faced during the operation of these reactors. The current challenges associated with the operation of standalone MBR and electrochemical reactors include: membrane fouling in MBR, set-backs from operational errors and conditions, energy consumption in electrochemical systems, high cost requirement, and the need for simplified models. The advantage of this review is to present the most critical challenges and opportunities. These challenges have necessitated the design of MBR derivatives such as anaerobic MBR (AnMBR), osmotic MBR (OMBR), biofilm MBR (BF-MBR), membrane aerated biofilm reactor (MABR), and magnetically-enhanced systems. Likewise, electrochemical reactors with different configurations such as parallel, cylindrical, rotating impeller electrode, packed bed, and moving particle configurations have emerged. One of the most effective approaches towards reducing energy consumption and membrane fouling rate is the integration of MBR with low-voltage electrochemical processes in an electrically-enhanced membrane bioreactor (eMBR). Meanwhile, research on eMBR modeling and sludge reuse is limited. Future trends should focus on novel/fresh concepts such as electrically-enhanced AnMBRs, electrically-enhanced OMBRs, and coupled systems with microbial fuel cells to further improve energy efficiency and effluent quality.

关键词： Anaerobic membrane bioreactor   Effluent characterization   Salinity   Soluble microbial products   Microbial community  

摘要： The performance of anaerobic membrane bioreactor (AnMBR) was evaluated treating synthetic wastewater with various concentrations of NaCl (0-40 g/L), as well as the recovery phase. The effluent COD removal efficiency decreased from 96.4% to 95.0%, 91.4%, 86.7% and 77.7% with stepwise increasing of salt concentration from 0 to 5, 10, 20 and 40 g NaCl/L, respectively, then gradually increased to 94.1% during the recovery phase. Additionally, the significant changes in the content and composition of soluble microbial products (SMP) and extracellular polymer substance (EPS) were obtained under higher salt stress. GC-MS analyses were carried out for the effluent, and some new types of compounds, such as Dodecane, Undecane, and Ethyl Acetate, were found during salt exposure phases. The characterization of the microbial community was also investigated based on the analysis of genomic 16S rDNA, revealing the increasing salinity (5-40 g NaCl/L) could reduce the diversity of sludge microbial community in AnMBR. Meanwhile, the significant effects on the composition of dominate phyla (Proteobacteria, Bacteroidetes, Firmicutes and Chlorofiexi) were found during the salt exposure phase.

关键词： Sludge reduction   Anaerobic side-stream reactor   Carrier   Ultrasonication   Microbial community  

摘要： The sludge in situ reduction process by inserting an anaerobic side-stream reactor (ASSR) in a sludge return line provides a cost-effective approach to reduce sludge production in activated sludge systems. In this study, four pilot-scale membrane bioreactors (MBRs), including an AO-MBR for control, ASSR coupled MBR (ASSR-MBR), a MBR with ASSR packed with carriers (AP-MBR) and an AP-MBR with part of sludge ultrasonicated before fed into ASSR (AUP-MBR) were operated in parallel to investigate enhancing effects of ultrasonication and packing carriers on sludge reduction and pollutants removal performance under both normal and low temperature. Low temperature showed negligible impact on COD removal, deteriorated NH4+-N and TN removal from 98.3% to 69.7% at 21.6 degrees C to 92.5% and 48.8% at 2.6 degrees C, and decreased sludge reduction efficiency (SRE) in ASSR-MBR Packing carriers and ultrasonication both enhanced sludge reduction, especially under low temperature with SRE values increased from 8.2% of ASSR-MBR to 17.1% of AP-MBR and 32.6% of AUP-MBR at 4.5 +/- 2.5 degrees C. Packing carriers and ultrasonication increased cell rupture by 11.1% and 14.5% in aerobic MBR, enhanced protease activity in ASSR by 60.0% and 116.3%, and reduced ATP content for heterotrophic metabolism by 31.4% and 7.3%, respectively. MiSeq sequencing results showed that packing carriers enriched hydrolytic bacteria (Terrimonas, Dechloromonas and Woodsholea), slow growers (Sulfuritalea, Thauera and Azospira) and predatory bacteria (Bdellovibrio and norank_Saprospiraceae), while ultrasonication further enriched hydrolytic bacteria (norank_Saccharibacteria and Ferruginibacter). Packing carriers is more cost-effective than ultrasonication to enhance sludge reduction by partial damage to bacterial cells and promoting better interaction between bacteria, enzymes and substrates to favor particles hydrolysis. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： baffled anaerobic bioreactor   degradation mechanism   degradation pathway   dominant PVA-degrading bacterial   polyvinyl alcohol  

摘要： Polyvinyl alcohol (PVA) is the main pollutant in printing and dyeing wastewaters. This pollutant exhibits great demand, poor biodegradability and refractory degradation. In this study, PVA wastewater treatment experiments were conducted in a stably operating baffled anaerobic bioreactor (ABR) by using simulated PVA wastewater. The PVA degradation pathway and mechanism of the mixed dominant PVA-degrading bacterial strains were identified through the analysis of their degradation products. From the results, we inferred that PVA was degraded in a stepwise process under the synergistic action of different extracellular and intracellular enzymes produced by the mixed dominant PVA-degrading bacterial strains. In this process, PVA was first degraded into ketones, fatty acids and alcohols. It was then regenerated into acetic acid, hydrogen and carbon dioxide. Finally, these substances could be further utilized by methanogens. PVA was thus degraded completely. This study may serve as a reference for future works on the degradation of PVA in the ecological environment. It may also guide the sustainable development of PVA.

关键词： PhACs   Photocatalytic degradation   Ag2O/P-25 photocatalysts   Matrix effect   Transformation products  

摘要： Pharmaceutically active compounds (PhACs) are emerging pollutants causing serious challenges to wastewater treatment plants due to poor biodegradability. In this study, the enhanced removal of highly recalcitrant and commonly monitored PhACs, carbamazepine (CBZ) and diclofenac (DCF) by heterogeneous photocatalysis was investigated using 5% Ag2O/P-25 photocatalyst. The photocatalyst was characterized by scanning electron microscope (SEM-EDX), Brunauer-Emmett-Teller (BET), Fourier transfer infrared spectroscopy (FTIR) and UV-vis diffuse reflectance spectra (UV-DRS). The effects of catalyst dose, initial pollutants concentration, and mineralization during the photocatalytic degradation of PhACs were investigated. The matrix effect was assessed in deionized water (DW) and real membrane bioreactor effluent (RME). Optimal CBZ and DCF removals of 89.10% and 93.5%, respectively for 180 min of UV irradiation were achieved at catalyst dosage of 0.4 g L-1 in DW matrix. However, the optimal catalyst dosages for CBZ and DCF in RME matrix were increased by factor 2 and 1.5, respectively, to achieve the same degree of removal. Declining trends of removal rate were observed when initial concentrations of both the PhACs were increased under optimal catalyst dosages, and kinetics seem to fit the Langmuir-Hinshelwood model. Photo-induced holes and (OH)-O-center dot were the dominant oxidation species involved in the photocatalytic degradation of the PhACs. A plausible reusability of 5% Ag2O/P-25 photocatalyst was observed for both the PhACs. Moreover, various aromatic/aliphatic intermediates generated during the photodegradation CBZ were identified using fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry, and a possible multi-step degradation pathway was proposed. Overall, the removal of PhACs using 5% Ag2O/P-25 photocatalyst showed promising results in real wastewater.

关键词： Membrane aerated bioreactor   Surfactin production   Aeration   Dimensional analysis   Experimental design   Process relationship  

摘要： Aeration by a membrane contactor is a convenient method to produce surfactin, a bacterial surfactant compound, while avoiding foam to overflow as it is the case with most of aerated bioreactors equipped with gas sparger. This work helps improving knowledge on oxygen transfer in membrane-aerated bioreactors and optimizing the adjustment of culture aeration performances. In this work, oxygenation of a surfactin solution was studied in a bioreactor aerated by a microporous hollow fiber membrane contactor. First, a dimensional analysis was coupled in an innovative way with a fractional design of experiments, thus reducing greatly the number of experiments. Then, the analysis of the model helped to understand thoroughly the influence of the four main parameters, namely the liquid flow rate inside the fibers, the gas pressure outside the fibers, the liquid volume in the tank and the amount of surfactant in the bulk. Empirical process relationships were proposed to predict either the volumetric oxygen transfer coefficient (k(L)a) or the liquid-side oxygen transfer coefficient (k(L)) (with an average standard deviation < 11%). The liquid flow rate, the liquid volume and the gas pressure were found to be significantly influencing unlike the surface tension. The validity of the relationships with surfactin fermentations obtained at a larger scale was demonstrated.

关键词： Membrane bioreactor   Ceramic membrane   Ferrous   Phosphorus removal   Membrane fouling  

摘要： Ferrous dosing is used to reduce phosphorus concentration and alleviate polymeric membrane fouling in membrane bioreactor (MBR). However, limited studies have been conducted to investigate the impacts of ferrous dosing on ceramic membrane fouling, nutrient removal efficiency and microbial community. Accordingly, the aim of this study was to investigate the effect of intermittent ferrous dosing with Fe/P molar ratios of 2 and 1 (with a dosing frequency of every two days) on the overall nutrient removal, functional microbial changes and membrane fouling in ceramic membrane bioreactors (CMBR) in treatment of wastewater. TP concentration of 10 mg/L in influent decreased to 1.94 +/- 0.62 mg/L (control), 0.38 +/- 0.22 mg/L (Fe/P = 1) and 0.31 +/- 0.18 mg/L (Fe/P = 2) in the effluent, respectively. Meanwhile, the effluent total nitrogen (TN) concentrations with Fe/P = 1 treatment (6.80 +/- 2.02 mg/L) and Fe/P = 2 treatment (5.12 +/- 2.28 mg/L) were lower than that of the control (7.72 +/- 2.36 mg/L). Compared to Fe/P = 1, the TN removal performance was better tot Fe/P = 2 mainly due to the increased abundance of denitrthting bacteria (Zoogloea and Acinetobacter). In addition, excess iron dose might have toxic effects on bacterial physiology, however the Fe concentrations that cause cell damage vary for different bacteria. The relative abundance of Zoogloea (aerobic denitrifying bacteria) continuously increased with ferrous addition (Fe/P = 2), while other bacteria including Dechtoromonas, tlyphomicrobiwn and nauera (anoxic denitrifying bacteria), Nitrospira (nitrifying bacteria) and Candidalus Accumulibacter (phosphorus accumulating organism) decreased sharply. Furthermore, membrane fouling was effectively moderated by ferrous dosing and Fe/P = 1 treatment showed improved membrane fouling mitigation than Fe/P = 2. Overall, intermittent ferrous addition in CMBR with Fe/P molar ratio of 1 was beneficial to the removal of nutrients (TP, TN and organics), enhanced succession o

关键词： Microfluidics   Cell culture  

摘要： Various microfluidic devices have overcome many disadvantages common to conventional bioreactor systems by enabling active manipulation of cell-culture conditions, monitoring of cellular responses in high-throughput mode, and extraction of target cells in a relatively rapid and low-cost manner. However, existing microfluidic devices still have limitations, including the complexity of their operation and a lack of availability of dynamic control of the chemical environment. Here, we present a novel microfluidic bioreactor array device capable of not only the stable and dynamic programing of cell-culture environments but also the selective extraction of target cells. This device comprises 64 microchambers in a 16 X 4 array format, and each microchamber is integrated with a robust and nanoporous membrane on one side and an H-shaped entrance on the other. The membrane made of self-assembled particles allowed continuous and sequential delivery of various nutrients containing gene inducers to compartmentalized microbial cells, thereby enabling dynamic cell culturing. Additionally, the H-shaped entrance was used for local and selective blocking of the microchamber by employing LTV-curable material, thereby enabling the retrieval of target cells from the device while sequestering nontarget cells in the microchambers. Our results demonstrated that the targeted rare cells could be isolated and separated from a mixture of cells by repeating the extraction procedure. Therefore, we anticipate that this microfluidic bioreactor array device will be widely used for not only screening/extraction but also off-chip postanalyses of various microorganisms.

摘要： The anaerobic membrane bioreactor (AnMBR) is an emerging technology, which has the potential for anaerobic digestion of wastewaters (WW) at high efficiency while generating biogas as a by-product (Harb et al., 2017). One of the main challenges associated with AnMBRs is reduced efficiency at low temperatures due to decreases in both bioreactor and membrane performance which makes using AnMBRs in North America impractical as WW is temperature is typically in the range of 10 – 20°C (Environment Canada, 2017). The addition of powdered activated carbon (PAC) could be a solution to the increased fouling and low chemical...(COD) removals that occur at low temperatures as it has abrasive and adsorptive properties. There are some studies that have observed the effect of PAC on AnMBRs resulting in increased quality of permeate but none tested varying concentrations of PAC at psychrotrophic temperatures using raw WW. Hence, this was investigated in this study. Three-lab scale AnMBRS were set up in parallel and monitored for both bioreactor and membrane parameters over a two-phase experiment. Initially the membranes were operated at 10°C and 24°C to establish the performance under mesophilic and psychrophilic conditions without the presence of PAC. Then all three reactors were converted to psychrophilic conditions and three different concentrations of PAC were added to the reactors, 0.5, 1.0, and 2.0 g/L. To determine the effect of PAC on membrane performance, transmembrane pressure (TMP) and concentrations of organic sub-fractions were monitored. Bioreactor performance was evaluated by monitoring chemical oxygen demand (COD) and suspended solids (SS) in the waste activated sludge (WAS) feed and permeate. Stage 1 of the research showed that membrane fouling increased at psychrotrophic temperatures as the cycle lengths decreased from 9 days at 24°C to 3 days at 10°C. Similarly, the bioreactor performance also decreased significantly with the temperature drop, resulting in lower