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关键词： Biodegradability   Electro-oxidation   Membrane bioreactor   Polycyclic aromatic hydrocarbons  

摘要： Naphthalene (NAPH) and phenanthrene (PHEN) are two of the most abundant polycyclic aromatic hydrocarbons (PAHs) found in nature, and they are considered in the list of US EPA priority pollutants. The contribution of this research lies in the comprehensive analysis of a strategy for the coupling of electro-oxidation (EO) and biodegradation in a submerged membrane bioreactor (SMBR) with the objective to remove PAHs, using NAPH and PHEN as model compounds. The electrochemical degradation of NAPH and PHEN in aqueous synthetic solution has been carried out using two different anodes: Ti/IrO2 and Ti/SnO2. The effects of EO operating parameters (current density, reaction time, and pH) on the NAPH and PHEN removals were investigated applying 2(3) factorial design with both electrodes. Additionally, the EO effluents were analyzed for COD, NH4-N, and biodegradability (respirometry tests). The highest removals of both compounds were reached with Ti/IrO2 anode, at acidic conditions (pH of 2), current density of 50 mA cm(-2), and electrolysis time of 60 min. However, the Ti/SnO2 anode allowed greater reduction of the biomass inhibition, which means that the enhancement of the EO effluent biodegradability was reached;therefore, this electrode was selected for the coupled EO-SMBR system, applying the operating conditions that improved the biodegradability of the effluent. The EO process allowed NAPH and PHEN removal efficiencies of 96 +/- 5% and 94 +/- 3%, respectively. The membrane bioreactor was operated with organic load of 0.6 +/- 0.1 gCOD gVSS(-1) d(-1), hydraulic retention time of 6 h, and solid retention time of 30 d, obtaining average COD, NH4-N, NAPH, and PHEN removals of 98 +/- 0.5%, 91 +/- 6.4%, 99.1 +/- 0.96%, and 99.7 +/- 0.4% respectively. The sorption of phenanthrene onto the biomass had a low contribution, 0.9 +/- 0.2%, concluding that biodegradation was the main removal mechanism in the bioreactor. The coupled system EO-SMBR allowed high NAPH and PHEN removal effi

关键词： Solid-state cultivation   Aspergillus   Trichoderma   Citric acid   Sugarcane bagasse   Bench packed-bed bioreactor  

摘要： Solid-state cultivation (SSC) is microbial growth on solid supports under limited water conditions. Citric acid is a microbial aerobic metabolic product with several industrial applications, with production potential that can be obtained by SSF. Several wastes from agro-industries are used in SSF, such as sugarcane bagasse and vinasse. Cultures of mixed fungi or co-cultures are used in this SSF in order to complement the inoculum's xylanolytic enzymes for action on the lignocellulosic material (bagasse). Thus, this study aims to evaluate the effect of inoculum (Aspergillus niger and Trichoderma reesei consortium) in the production of citric acid from sugarcane bagasse impregnated with vinasse using bench packed-bed reactors (PBR). The results show the importance of T. reesei and A. niger in inoculum at a ratio of 50:50 and 25:75, suggesting the use of solid support due to the complementation of the hydrolytic enzymes. The highest concentration of citric acid, approximately 1000 mg L-1, was obtained for 100 mm of bed height in 48 and 72 h, with maximum glucose yield in citric acid (2.2 mg (citric acid) mg (-1)(glucose)). k(L)a indicates that maintaining solid moisture and liquid film thickness is important to keep the oxygen transfer in SSC.

关键词： Anaerobic membrane bioreactor   Biofouling   Membrane fouling   Fouling control  

摘要： The performance of the different configurations of AnMBRs is affected by operating parameters including solid retention time (SRT), hydraulic retention time (HRT), organic loading rate (OLR), sludge recycle rate, temperature and wastewater characteristics. Generally, the optimum operating condition is characterized by a longer SRT and HRT, higher OLR at a mesophilic temperature range. These parameters also affect the propensity of membrane fouling which is considered as the major challenge limiting its sustainable use. Hence, these parameters need to be understood and optimized. The common fouling control strategies include sub-critical flux operation, membrane relaxation, backwashing, biogas sparging, sludge recycle and use of coagulants and turbulence promoters are inadequate in fully controlling the fouling process. Hence, new and emerging technologies like enzymatic or bacterial degradation through quorum quenching technology are being explored. Moreover, integration of rotary disks/membrane, attached growth system, dynamic membrane, electrochemical membrane and baffled reactor configurations are introduced as modifications to the conventional AnMBR. Review of these strategies reveal that these novel configurations of AnMBR and the use of quorum quenching technology offer a potential sustainable approach to fouling control, and hence should be explored further.

关键词： Biogas   Dissolved methane   AnMBR   Membrane contactor   Degassing membrane   Hollow fiber  

摘要： The need for a more sustainable wastewater treatment is more relevant now due to climate change. Production and reuse of methane from anaerobic treatment is one pathway. However, this is defeated by the presence of dissolved methane in the effluent and would be released to the environment, adding to the greenhouse gas emissions. This review paper provided summary and analysis of studies involved in the production of dissolved methane from AnMBR, focusing with actual methane measurement (gas and dissolved) from AnMBR with different types of wastewater. Then more focused discussion and analysis on the use of membrane-based technology or membrane contactors in the recovery of dissolved methane from AnMBR effluent are included, with its development and energy analysis. The dissolved methane removal and recovery rate of membrane contactors can be as high as 96% and 0.05 mol methane/m(2)/h, respectively, with very low additional energy requirement of 0.01 kWh/m(3) for the recovery. Future perspectives presented focus on the long-term evaluation and modelling of membrane contactors and on the membrane modifications to improve the selectivity of membranes to methane and to limit their fouling and wetting, thus making the technology more economical for resource recovery. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Nutrient recovery   Anaerobic membrane bioreactor   Phosphorus removal   Chemical precipitation   Plant availability  

摘要： Anaerobic membrane bioreactors (AnMBRs) represent an emerging environmental biotechnology platform with the potential to simultaneously recover water, energy, and nutrients from concentrated wastewaters. The removal and beneficial capture of nutrients from AnMBR permeate has yet to be fully explored, therefore this study sought to foster iron phosphate recovery through a tertiary coagulation process, as well as characterize the recovered nutrient product (RNP) and assess its net phosphorus release, diffusion, and availability for plant uptake. One of the primary goals of this study was to optimize the dose of the coagulant, ferric chloride, and coagulant aid, aluminum chlorohydrate (ACH), for continuous application to the coagulation -flocculation -sedimentation (CFS) unit of an AnMBR pilot plant treating municipal wastewater, through controlled bench-scale jar tests. Anaerobic systems present unique challenges for nutrient capture, including high, dissolved hydrogen sulfide concentrations, along with settleability issues. The addition of the coagulant aid increases settleability, while enhancing phosphorus removal by up to 20%, decreasing iron demand. Water quality analysis indicated that a variety of factors affect nutrient capture, including the COD (chemical oxygen demand) concentration of the permeate and the limiting coagulant dose. COD >200 mg/L was shown to decrease the phosphorus removal efficiency by up to 15%. A combination of inductively coupled plasma optical emission spectrometer (ICP-OES) elemental analysis, inductively coupled plasma mass spectrometer (ICP-MS) elemental analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) spectroscopy analysis was used to characterize the P-rich RNP which revealed a 2.58% w/w phosphorus content and the lack of a well-defined crystalline structure. Detailed studies on resin extractable phosphorus to assess the plant uptake potential also demonstrated t

关键词： Immobilized laccase   Continuous mode   Silica-chitosan support  

摘要： A silica-chitosan support was employed for laccase immobilization. The hybrid support was obtained using calcium ion as linking agent that coordinates silanol and hydroxyl groups of chitosan. The insoluble biocatalyst was then packed in a column and used in a flow system for phenol removal. The immobilized enzyme reactor (IMER) showed a good storage stability (70 % of activity in 70 days) and good reusability (90-50 % of catalytic activity at the 4th reuse in function of chitosan type). The best performance for the phenol removal was obtained with a low molecular weight chitosan from crab shells at pH 5 and with a flow rate of 0.7 mL/min. The apparent Michaelis-Menten (Vmax app , Kmapp) and the inherent (Vmax inh , Kminh) constants were also determined to evaluate the influence of the phenol structure on the performance of the system. The enzymatic oxidation of a phenol mixture (4-methylcatechol, catechol, caffeic acid, syringic acid, vanillic acid, p-coumaric acid, and tyrosol) was followed for 21 h in a continuous mode by HPLC. The phenol mixture removal of 90 % was also confirmed by FolinCiocalteu assay.

关键词： LRV   MBR   pathogen  

摘要： In this study, a critical review, gathering all available log removal values (LRV) data reported for membrane bioreactors (MBRs) in recent literature was conducted. One of the key outcomes of this work is that the correlation of MBR operating parameters and LRV was not possible with available literature data, as a full set of operational data was rarely reported. Nevertheless, in excess of 500 virus, 600 bacteria, and 20 protozoa LRV data points were extracted from multiple sources, grouped according to microorganism type, and the LRV performance and variability summarized in the form of normal probability density functions (PDFs). As presented, these LRV PDFs are suitable to permit further probabilistic quantitative microbiological risk assessment activities. In this work, the LRV PDFs were used to propose target pathogens and microbial surrogates by selecting the microorganisms that were most conservatively removed by MBRs. In terms of protozoa,Cryptosporidiumwas the most conservatively removed pathogen andClostridium perfringenswas the most often reported microbial surrogate. Enterovirus displayed the most conservative overall removal in MBR and was selected as the target pathogen. From the data reported,Escherichia coliwas selected as an appropriate microbial surrogate for demonstration of LRV of bacteria.

关键词： Anaerobic membrane reactor   Electric field   Membrane fouling   Electrophoresis   Mixed liquor filterability   Bioelectrochemical oxidation  

摘要： Anaerobic membrane bioreactor (AnMBR) is a promising technology for wastewater treatment. However, membrane fouling as an inevitable challenge restricts its application. Recently novel membrane fouling control technology by applying electric field in AnMBR showed its economics and effectiveness. Nevertheless, the mechanism of fouling suppression is still unclear, limiting the development of this technology. In this study, electro-AnMBR was constructed. Long-term running showed that applying electric field of 0.5 V suppressed the membrane fouling evolution rate by nearly 23% and reduced the organic foulants on membrane by nearly 10%. To clarify the mechanism of fouling suppression, the contribution of electrophoresis to membrane fouling suppression was quantified by theoretical calculation for the first time. Results showed that electrophoresis was approximately equivalent to backwash with a flux of 0.56 L/(m2.h). Besides, impact of electric field on mixed liquor filterability of AnMBR was first investigated by dead-end filtration. Results presented that electric field reduced the filtration resistance of mixed liquor by nearly 77%. Then mixed liquor properties analysis, electrochemical oxidation simulation tests and metagenomic analysis revealed that electric field might improve mixed liquor filterability by bioelectrochemical oxidation. Finally, novel mechanism of electric field suppressed membrane fouling was elucidated, including electrophoresis to drive off the foulants and mixed liquor filterability improvement. This study might contribute to better understanding for membrane fouling control by applying electric field in AnMBR, and was meaningful for technical development.

关键词： Desulfovibrionaceae   Sulfate reducing bacteria   Microbial communities   Reactor performance   Metal precipitation  

摘要： This study demonstrated the adaption of a sulfidic microbial community to mixed metal mine wastes, i.e., tailings leachate solutions, while maintaining bioreactor performance. This overall process occurred using a sulfate reducing bioreactor operated in continuous mode for 172 days with ethanol as electron donor and, at first, a synthetic mine solution and then, tailings leachate solutions. Remarkably, the addition of a succession of leachates increased the sulfate removal efficiency, which reached values around 84.7 +/- 6.9% after the sulfate adaptation period. This increase was also in line with an increase in the soluble chemical oxygen demand removal efficiency and with a slight increase in the pH of the reactor. This high activity supported metal removal efficiencies close to 100% for most metals, except Mn, Ca and Mg whose precipitation was lower (80, 50 and 38%, respectively). The bacterial community in the bioreactor was initially diverse but evolved to be dominated by SRB, in particular Desulfovibrionaceae. Interestingly, the addition of the tailings leachates enriched for the presence of methanogens in the bioreactor, consistent with the consumption of the accumulated acetate.

关键词： Antibiotic resistance genes   Applied voltage   Biogas production   Microbial communities analysis   Anaerobic electrochemical membrane bioreactor  

摘要： Anaerobic biological treatment technologies are one of the major hotspots of antibiotic resistance genes (ARGs). Previous studies have applied the electrochemical process to improve biogas production, however, it was challenged that high voltages might promote membrane permeability and reactive oxygen species overproduction to promote ARGs proliferation. Herein, the biogas production and ARGs proliferation in an anaerobic electrochemical membrane bioreactor (AnEMBR) were investigated at the gradient voltages of 0-0.9 V. Results show the reactor performances (average CH4 production and current generation) were distinctly improved with the increase of applied voltage, and reached the optimum at 0.9 V. However, long-term application (>30 day) of 0.9 V deteriorated the reactor performances. Meanwhile, the relative abundances of most target ARGs in the supernatant and effluent of AnEMBR at 0.9 V increased by 0.68-1.55 and 0.42-1.26 logs compared to those before applying voltage, respectively. After disconnecting the circuit, these ARGs abundances all decreased to the original level. Significant correlations between intlI and ARGs (e.g., tetA, tetQ, sulI, and sulII) were observed, indicating horizontal gene transfer may contribute to the increased ARGs. Moreover, the shift of microbial communities caused by the applied voltage enriched potential ARGs-hosts (e.g., Tolumonas), contributing to the proliferation of ARGs.