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关键词： HRT   hydraulic retention time   Lv   volumetric load   Q   flow   V   m   mixed liquor discharge volume   V   s   supernatant discharge volume   SOC   soluble organic carbon   SRT   solids retention time   TAN   total ammoniacal nitrogen   TIC   total inorganic carbon   TIN   total inorganic nitrogen   TN   total nitrogen   TIP   total inorganic phosphorus   TOC   total organic carbon   TON   total organic nitrogen   TOP   total organic phosphorus   TSS   total suspended solids   TSS   m   mixed liquor total suspended solids   TSS   x   supernatant total suspended solids   TP   total phosphorus   VSS   volatile suspended solids  

摘要： In thiswork, a strategy based on photo-sequencing batch operationwas used to select cyanobacteria over unsettled green algae in awastewater treatment system, evaluating for the first time the effect of hydraulic regimes on nutritional dynamics and microorganisms' competition. During 30 days of operation, an initial microalgae mixed consortia dominated by the green microalgae Scenedesmus sp. was cultivated in two different photo-sequencing batch reactors operated at hydraulic retention time (HRT) of 6 days (PSBR6) and 4 days (PSBR4) at a theoretical solids retention time (SRT) of 10 d. Both reactorswere compared with a semi-continuous reactor (SC10) operated at 10 d of HRT and 10 days of SRT (used as a control). The results indicated that PSBR6 and PSBR4 decreased Scenedesmus sp. population by 88% and 48%, respectively. However, only PSBR6 provided suitable conditions to select cyanobacteria from an initial green algae dominated culture. These conditions included volumetric loads of 11.72 mg TN L-1 d(-1), 2.04mg TP L-1 d(-1) and 53.31 mg TOC L-1 d(-1). The remaining nutrients in the culture led also to a phosphorus limiting N: P ratio (34: 1) that improved the increase of cyanobacteria from an initial 2% until 70% of the total population. In addition, PSBR6 reached a biomass production of 0.12 g L-1 d(-1), while removing TN, TP and TOC by 58%, 83% and 85%, respectively. Conversely, the application of higher nutrients loads caused by lowerHRT (PSBR4) led to an increase of only 13% of cyanobacteriawhile SC10 remained with the same biomass composition during all the experimental time. Thus, this study showed that the dominance of cyanobacteria in microalgal-based wastewater treatment systems can be controlled by the operational and nutritional conditions. This knowledge could contribute to control microalgae contamination from up-scaling cyanobacterial biomass production in wastewater treatment systems. (c) 2018 Elsevier B.V. All rights reserved.

关键词： Microfiltration   Mixed matrix membrane   Ag3PO4/g-C3N4 nanoparticles   Anti-biofouling  

摘要： Herein we represent the effects of the presence of Ag3PO4/g-C3N4 nanoparticles in the PES membranes matrix on the permeation properties and anti-biofouling performance by using two different solvents including DMAc and DMSO. The Ag3PO4/g-C3N4 nanocomposites were synthesized via co-precipitation and thermal pyrolysis methods A new polyethersulfone (PES) microfiltration membrane containing g-C3N4 nanosheets/Ag3PO4 nanoparticles was prepared via the nonsolvent induced phase inversion process. High hydrophilicity and the antibacterial properties of Ag3PO4-NH2 nanoparticles made them a superior choice to be combined with g-C3N4 nanosheets to modify the membrane characteristics as a nanofiller additive. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), mean pore size measurement, water contact angle, and energy dispersive X-ray (EDS) were applied for the membrane characterization. Also, the permeation performance and antibacterial properties of the membranes were studied. All the membranes incorporated with nanoparticles presented better membrane properties in comparison with the pristine PES membrane. The water permeation was improved from 262.3 L m(2-) h to 360.0 L m(2-) h for membrane containing 0.5 wt% of the functionalized Ag3PO4/g-C3N4 nanocomposite in the PES/DMSO matrix. To some extent, the excellent antimicrobial ability of these nanohybrid membranes could turn them in to a desirable candidate to overcome biofouling issues in applications such as the membrane bioreactor (MBR) systems. The MBR results also revealed that the pure water flux and the critical flux were enhanced. (C) 2018 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

关键词： Membrane bioreactor   Ozonation   Membrane fouling   Wastewater treatment   Microbial community  

摘要： The comparison of long-term ceramic membrane bioreactors (MBRs) without and with in-situ ozonation was investigated in this study in terms of membrane fouling, activated sludge, effluent quality and microbial community in wastewater treatment. The optimal dosage of in-situ ozonation for long-term MBR operation was firstly determined as 5 mg/L (0.66 mg-ozone/g-mixed liquor suspended solid (MLSS)) with the optimal filterability of mixed liquor. During the long-term filtration experiment, MBR-ozone with in-situ ozonation demonstrated its significantly alleviated ceramic membrane fouling performance compared with MBR-control without in-situ ozonation as a result of the enhanced filterability of mixed liquor and organic foulants removal from membrane surface by in-situ ozonation oxidation. Furthermore, ozonation was beneficial to phosphorus removal and the total phosphorus (TP) concentration in effluent of MBR-control (0.82 +/- 0.63 mg/L) was >2-fold higher than that of MBR-ozone (0.29 +/- 0.41 mg/L). The improved phosphorus removal performance by ozonation was due to the increased abundance of phosphate accumulating bacteria of Candidatus Accumulibacter in activated sludge. However, ozonation was detrimental to nitrogen removal mainly as a result of the inhibition of denitrification with the decreased relative abundance of denitrification genus of Dechloromonas in activated sludge. Overall, ceramic MBR with in-situ ozonation had not only significantly alleviated membrane fouling but also remarkably improved phosphorus removal performance. (C) 2018 Elsevier B.V. All rights reserved.

关键词： wastewater treatment   antibiotic resistance genes   membrane bioreactor   indicator organisms   metagenomics  

摘要： Reclaimed water provides a water supply alternative to address problems of scarcity in urbanized cities with high living densities and limited natural water resources. In this study, wastewater metagenomes from 6 stages of a wastewater treatment plant (WWTP) integrating conventional and membrane bioreactor (MBR) treatment were evaluated for diversity of antibiotic resistance genes (ARGs) and bacteria, and relative abundance of class 1 integron integrases ARGs confering resistance to 12 classes of antibiotics (ARG types) persisted through the treatment stages, which included genes that confer resistance to aminoglycoside [aadA, aph(6)-I, aph(3')-I, aac(6')-I, aac(69-II, ant(2")-I], beta-lactams [class A, class C, class D beta-lactamases (bIaova chloramphenicol (acetyltransferase, exporters, floR, cmIA), fosmidomycin (rosAB), macrolide-lincosamide-streptogramin (macAB, ereA, ermFB), multidrug resistance (subunits of transporters), polymyxin (arnA), quinolone (qnrS), rifamycin (arr), sulfonamide (sul1, sul2), and tetracycline (tetM, tetG, tetE, tet36, tet39, tetR, tet43, tetQ, tetX). Although the ARG subtypes in sludge and MBR effluents reduced in diversity relative to the influent, clinically relevant beta lactamases (i.e., b/aKpc, biaoxA) were detected, casting light on other potential point sources of ARG dissemination within the wastewater treatment process. To gain a deeper insight into the types of bacteria that may survive the MBR removal process, genome bins were recovered from metagenomic data of MBR effluents. A total of 101 close to complete draft genomes were assembled and annotated to reveal a variety of bacteria bearing metal resistance genes and ARGs in the MBR effluent. Three bins in particular were affiliated to Mycobacterium smegmatis, Acinetobacter Iwoffii, and Ravobacterium psychrophila, and carried aquired ARGs aac(2')-lb, bla(OXA-278), and tet36 respectively. In terms of indicator organisms, cumulative log removal values (LRV) of Escherichia coli,

关键词： Biofilm modeling   Photo-bioreactor   Mixed liquor recirculation   Purple non-sulfur bacteria   Organic waste recovery  

摘要： A mathematical model was proposed to evaluate organic utilisation and biofilm thickness in a recently developed photo-bioreactor with pipe-overflow recirculation. The model was applied to describe organic uptake by biofilms under light starvation conditions and to determine biofilm growth during simultaneous occurrence of biofilm detachment in response to the development of shear force on the biofilm surface while mixed liquor trickled down the pipe. The proposed model, consisting of a one-dimensional bulk liquid model and a two-dimensional biofilm model, was used to describe purple non-sulfur bacteria (PNSB) activities in biofilms that developed on the pipes. The model was simulated at high recirculation to predict simultaneous substrate removal and biofilm growth. A good correlation was observed between the model prediction and experimental results for substrate removal and biofilm thickness for thin and fully active biofilms.

关键词： Denitrifying bioreactor   Biochar   Nitrogen   Phosphorus   Column experiment  

摘要： Denitrifying bioreactors are edge-of-field structures that remove excess nitrogen (N) from intercepted agricultural drainage by supporting the activity of denitrifying microorganisms with a saturated organic carbon substrate. Although these bioreactors successfully mitigate N export, the typical woodchip systems have little effect on phosphorus (P), which is also often present in environmentally harmful quantities in drainage waters. Currently, the evidence that amending woodchip bioreactors with biochar enhances both N and P removal rates is mixed, but more work is required to test this hypothesis under controlled conditions. To determine the effect of biochar amendment on nitrate (NO3-N) and phosphate (PO4-P) removal in woodchip bioreactors, three media types-aged woodchips (W), 10% (B-10) and 30% (B-30) biochar by volume-were tested under different operational conditions during five-day laboratory trials with horizontal, flow-through columns. Nutrient removal was observed under different flow rates yielding hydraulic residence times of 3, 6, and 12 hours with four formulations of simulated agricultural drainage, all combination of 16.1 or 4.5 mg L-1 NO3-N and 1.9 or 0.6 mg L-1 PO4-P. Each unique treatment with respect to media type, HRT, and influent formulation was tested in triplicate using independent columns. All treatments successfully removed NO3-N, but PO4-P removal was inconsistent. Cumulative NO3-N removal efficiencies ranged 15-98% with an average removal rate of 11.0 g m(-3) d(-1);biochar amendment enhanced removal only in response to sufficiently high loading rates. Cumulative PO4-P removal efficiencies ranged from 66% removal to 170% export of the influent load;biochar addition was associated with increased export. These results indicate that pine-feedstock biochar poses a substantial increase to PO4-P leaching risk and only modestly enhances NO3-N removal given sufficiently high loading.

关键词： Solid digestate   Aged refuse   Organic fraction of municipal solid waste   Landfill leachate   Nitrogen removal   Circular economy  

摘要： Digestate from biogas plants managing municipal solid waste needs to be stabilized prior to final utilization or disposal. Based on the concept of urban mining, aged refuse from a closed landfill was used to treat landfill leachate, but nitrogen removal by biological denitrification was limited. The aim of this study was to use a digestate layer in bioreactors containing aged refuse to enhance the biological denitrification capacity of the aged refuse, stabilize digestate, and mitigate the ammonia emissions from digestate leaching with leachate recirculation. Six identical landfill columns filled with 0% (RO), 5% (R5), and 15% (R15) of solid digestate above aged refuse (ratios based on Total Solids) were setup and nitrified leachate was periodically fed and recirculated to the columns. The nitrate removal rate in R5 and R15 was 3.4 and 10 times higher relative to the control (no digestate added). A 31.5-35.9% increase of solid digestate biostability was confirmed by tests performed under both aerobic and anaerobic conditions. The results showed that instead of land use, the solid fraction of digestate could be utilized as an inexpensive functional layer embedded in an old landfill site to enhance the denitrification capacity and achieve digestate stabilization with minimal ammonia leaching from digestate.

关键词： Electrically bound biofilm reactor   E-waste   Biofilm enhancement   Nematic Liquid Crystal Display Electrode (NLCE)   Electric potential   Electrostatic force  

摘要： Existing conventional attached growth wastewater systems are greatly hampered by long start-up times, frequent biofilm sloughing and/or erosion which lead to poor or inconsistent performance. In this study, a novel electrically bound biofilm process has been developed, and its efficacy in achieving an improved bacterial adhesion for the removal of organic waste has been demonstrated. An electrically bound biofilm reactor (EBBR) was developed, consisting of a conductive nematic liquid crystal electrode (NLCE) as the anode, obtained from an inutile desktop monitor. Three metal electrodes, namely, Al, Cu and Pt were evaluated as candidate cathodes. Electric potential and choice of the cathode were chosen as the two optimization parameters for enhancing biofilm attachment. At the optimized condition (corresponding to 1 V and Pt-NLCE electrode combination), enhanced biofilm attachment was observed, with reduction in suspended solids up to 79.3% and a bio degradation rate of 71.2%, within a reaction time of 28 h. The presence of active functional groups and chromophores (containing C (math)N, NH2 and C=O functional groups) were confirmed using Cyclic Voltammetry (CV), Fluorescence spectroscopy, Raman and Fourier transform infrared (FTIR) spectroscopy. High biofilm stability (over 120 h) and rapid start-up times (of the order of few hours) were observed, which can be attributed to (a) the presence of these functional groups on NLCE, and (b) electrostatic attractive forces in the EBBR, unlike in conventional attached growth systems. Enhanced biofilm attachment combined with rapid start-up times paves way for a sustainable approach towards future wastewater treatment efforts.

关键词： Lactate   Acetate   Butyrate   Clostridium butyricum   Microbial communities   Fermentation   Etf complexes   Phylogenetic analysis   Metabolic pathways  

摘要： Background: Interactions between microorganisms during specific steps of anaerobic digestion determine metabolic pathways in bioreactors and consequently the efficiency of fermentation processes. This study focuses on conversion of lactate and acetate to butyrate by bacteria of dark fermentation. The recently recognized flavin-based electron bifurcation as a mode of energy coupling by anaerobes increases our knowledge of anaerobic lactate oxidation and butyrate formation. Results: Microbial communities from dark fermentation bioreactors or pure culture of Clostridium butyricum are able to convert lactate and acetate to butyrate in batch experiments. The ability of C. butyricum to transform lactate and acetate to butyrate was shown for the first time, with ethanol identified as an additional end product of this process. A search for genes encoding EtfAB complexes and their gene neighbourhood in C. butyricum and other bacteria capable of lactate and acetate conversion to butyrate as well as butyrate-producers only and the lactate oxidiser Acetobacterium woodii, revealed that the Etf complexes involved in (i) lactate oxidation and (ii) butyrate synthesis, form separate clusters. There is a more extent similarity between Etf subunits that are involved in lactate oxidation in various species (e.g. A. woodii and C. butyricum) than between the different etf gene products within the same species of butyrate producers. A scheme for the metabolic pathway of lactate and acetate transformation to butyrate in C. butyricum was constructed. Conclusions: Studies on the conversion of lactate and acetate to butyrate by microbial communities from dark fermentation bioreactors or Clostridium butyricum suggest that a phenomenon analogous to cross-feeding of lactate in gastrointestinal tract also occurs in hydrogen-yielding reactors. A scheme of lactate and acetate transformation pathway is proposed, based on the example of C. butyricum, which employs flavin-based electron bifurcation. T

关键词： Unknown   Process control   Bioreactors   operation mode   Saccharomyces cerevisiae   State estimation   INITIAL CONDITIONS  

摘要： The measurement or estimation of bioprocess states is critical for process control and optimization applications. However, certain disturbances or unknown inputs can generate significant model-plant mismatch if not considered by the process models. To better estimate the process states in the presence of these disturbances or unknown inputs, a nonlinear unknown input observer is applied. Experimental studies of batch and fed-batch operations of a bioreactor were performed using a recombinant Saccharomyces cerevisiae to produce beta-carotene. Previously developed kinetic models produce model-plant mismatch with changes to the initial conditions or operating mode of the bioreactor. The observer is applied to the bioreactor system to estimate the batch and fed -batch state variables. State estimates from the designed observer are compared to model predictions and experimental measurements. Results show improved state estimation over first-principles model predictions when applying the unknown input observer to the nonlinear dynamic process with unknown disturbances.