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关键词： Woodchip bioreactor   Modeling   Macromolecular rate theory   Selection   Temperature   Longevity  

摘要： Nitrate (NO3-) removal rates in a denitrifying woodchip bioreactor (DWB) removing NO3- from mine water in a subarctic climate was modeled with the purpose of determining the processes controlling variability in NO3- removal rates over time. The Eyring equation was used to define the temperature dependency, while a rate law was used to describe the NO3- concentration dependency of the NO3- removal rates. The results show that the temperature and NO3- concentration dependency of the NO3- removal rates changes over time in the DWB due to the preferential selection of conceptualized NO3- - reducing bacteria favoring low temperatures, with the mean temperature optimum of the NO3- reducing consortium decreasing from 24.2 degrees C to 16.0 degrees C following the first year of DWB operations. It is suggested that the selection of the low temperature NO3- reducers in the DWB represented an increased dependence on cross-feeding between a fermentative community, producing the reactive organic carbon substrate, and a denitrifying community, consuming the organic carbon substrate, with the temporal variability in NO3- removal rates being controlled by the stabilization of the microbial community structure. It is also suggested that the life expectancy of DWBs is more related to the stability of the cross-feeding between the fermenting microbial community and the denitrifying microbial community, than to the total carbon content.

关键词： Aerobic granular sludge   Filamentous bacteria   Membrane bioreactor   Microbial community   Hydraulic conditions  

摘要： The investigation aimed at revealing the influence of an external disturbance on the rapid reformation of larger aerobic granular sludge (AGS) in an internal-circulation membrane bioreactor (IC-MBR) after long-term operation. The used IC-MBR was continuously operated well for more than one year, in which, the biomass was still in the state of AGS with a balanced average size at around 200 mu m and an even size distribution. By providing short-time aeration to the biomass within this bioreactor, the characteristics of biomass were totally changed in a very short time, including the surface hydrophilicity, physic-chemical properties, and the structure of microbial community, which created suitable conditions for the growth of filamentous bacteria (Saccharibacteria). Such a variation was very beneficial to the reformation of larger AGS, which resulted in the average size of AGS increased to nearly 400 mu m with a compact structure and clear edge in no more than one month.

关键词： ammonia-oxidizing bacteria   dewatered alum sludge   neutralized used acid   nitrogen attenuation   nitrite-oxidizing bacteria  

摘要： BACKGROUND Different types of nitrogen-containing wastewater have been treated with dewatered alum sludge (DAS) or neutralized used acid (NUA) or with a combined DAS-NUA biofilter. The connections between the spatiotemporal structures of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) and the nitrogen removal performance of DAS-NUA biofilter have not been fully clarified. To address this issue, AOB and NOB genetic characteristics response to nitrogen conversions in a laboratory-scale DAS-NUA biofilter were investigated. RESULTS The spatiotemporal distribution of the AOB in DAS was heterogeneous in the bioreactor. The trends observed in its structure were a function of depth along the flowpaths and time. However, AOB in NUA and NOB in both substrates were time and space independent. The spatial and temporal behavior of nitrifying bacteria mainly depended on the pH, followed by dissolved oxygen. The Shannon indexes of AOB and NOB and the relative abundances of Nitrosomonas and Nitrobacter had significantly negative relationships with NH4+-N and total nitrogen concentrations in effluents. CONCLUSIONS The Shannon indexes of AOB and NOB and the relative abundances of Nitrosomonas and Nitrobacter were the key indicators of nitrogen removal and have implications for effective nitrogen attenuation strategies. (c) 2018 Society of Chemical Industry

关键词： Ciprofloxacin   Dosage   Sponge membrane bioreactor   Hospital wastewater  

摘要： This study aimed to evaluate treatment performance and membrane fouling of a lab-scale Sponge-MBR under the added ciprofloxacin (CIP) dosages (20;50;100 and 200 mu g L-1) treating hospital wastewater. The results showed that Sponge-MBR exhibited effective removal of COD (94-98%) during the operation period despite increment of CIP concentrations from 20 to 200 mu g L-1. The applied CIP dosage of 200 mu g L-1 caused an inhibition of microorganisms in sponges, i.e. significant reduction of the attached biomass and a decrease in the size of suspended flocs. Moreover, this led to deteriorating the denitrification rate to 3-12% compared to 35% at the other lower CIP dosages. Importantly, Sponge-MBR reinforced the stability of CIP removal at various added CIP dosages (permeate of below 13 mu g L-1). Additionally, the fouling rate at CIP dosage of 200 mu g L-1 was 30.6 times lower compared to the control condition (no added CIP dosage).

关键词： Volatile fatty acids   In situ recovery   Immersed membrane bioreactor   Fouling control   Food waste  

摘要： Volatile fatty acids (VFAs) are the key intermediates from anaerobic digestion (AD) process that can be a platform to synthesize products of higher value than biogas. However, some obstacles still exist that prevent large-scale production and application of VFAs, key among them being the difficulty in recovering the acids from the fermentation medium and low product yields. In this study, a novel anaerobic immersed membrane bioreactor (iMBR) with robust cleaning capabilities, which incorporated frequent backwashing to withstand the complex AD medium, was designed and applied for production and in situ recovery of VFAs. The iMBR was fed with food waste and operated without pH control, achieving a high yield of 0.54 g VFA/g VSadded. The continuous VFA recovery process in the iMBR was investigated for 40 days at OLRs of 2 gVS/L/d and 4 gVS/L/d without significant change in the permeate flux at a maximum suspended solids concentration of 31 g/L.

关键词： UASFF   POME   Temperature   Anaerobic digestion  

摘要： This study investigates the performance of anaerobic digestion of palm oil mill effluent (POME) in an up-flow anaerobic sludge fixed film (UASFF) bioreactor at four different temperatures (24, 38, 50 and 60 degrees C) under optimized operating conditions (feed flow rate (Q(F)) of 1.5Lday and up-flow velocity (V-up) of 0.75m/h). Influent COD concentration was 14150mg/L. Six quality parameters viz. COD removal, methane yield, TSS removal, oil and grease removal, effluent volatile fatty acids (VFA) and pH were monitored as the process response. COD removal and methane yield of 92% and 0.325 CH4/g COD(removed)day were achieved respectively in mesophilic temperature (38 degrees C) at HRT of 1.5day. Higher values (94% COD removal and 0.331 CH4/g COD(removed)day) were obtained under thermophilic condition (50 degrees C). A 94% oil and grease removal was achieved at a temperature of 50 degrees C while it was 85 and 65% at 38 and 24 degrees C, respectively. The granules structure and activity did not undergo any changes at temperature of 50 degrees C. An increase in temperature from 50 to 60 degrees C caused a detrimental effect on treatment efficiency as the methanogenic activity was relatively terminated within <6days.

关键词： PBBR   Pseudomonas pseudoalcaligenes   GC-MS   Fluorene   External mass transfer  

摘要： The main objective of this study was to analyze the effects of the external mass transfer on fluorene (polycyclic aromatic hydrocarbon) degradation with immobilized LDPE (low-density polyethylene) in a packed bed bioreactor (PBBR). A most effective bacterial species Pseudomonas pseudoalcaligenes NRSS3 (MF9921912) was isolated from petroleum contaminated soil and immobilized on LDPE. The effect of different flow rates (10, 20, 30, 40, and 50 mL/h) on the degradation of fluorene was studied in a continuous PBBR. The overall removal efficiency of fluorene was found to be 88.49% in PBBR. The rate constants were estimated at different flow rates. The effect of flow rates on external mass transfer was also studied and correlated with the obtained experimental data. A correlation between Reynolds number (NRe) and Colburn factor (J(D)) (J(D) = KNRe(n-1)) was used to study the mass transfer aspects. The model was tested with various values of K, and n and based on experimental data, a new correlation J(D) = 5.71N(Re)(-0.2) was obtained to predict the removal of fluorene in PBBR. The intermediate metabolites of the degraded sample were also analyzed by GC-MS and found that 1,2-benzenedicarboxylic acid and catechol were formed during the biodegradation process.

关键词： Heterotrophic nitrification-aerobic denitrification   IF-MBR   Simultaneous removal of organic matter and nitrogen   Oxygen limited   Rhodobacter  

摘要： An internal-loop fluidized membrane bioreactor (MBR) was operated to treat low-strength municipal wastewater by simultaneous removal of organic matter and nitrogen under oxygen-limited condition. Novel porous polymer carriers were used to immobilize microbes as well as alleviate membrane fouling. The dissolved oxygen (DO) concentration was varied from 0.07 to 0.5 mg/L at the top of the reactor throughout the experiment. The running conditions for the MBR were loading ammonia 50 mg/L, chemical oxygen demand (COD) 320 mg/L, hydraulic retention time (HRT) 8 h, pH 7.8-8.2, and C/N ratio 2.6. High removal percentages of COD, total nitrogen, and NH4+-N were achieved as high as 88%, 76%, and 96%, respectively, with only nitrite accumulated (10-13 mg/L) in effluent at optimal DO concentration of 0.12 +/- 0.06 mg/L. With a membrane flux of 8 L/m(2)/h corresponding to 8 h HRT, transmembrane pressure remained below 20 KPa during 60 days of continuous operation without need for membrane chemical cleaning or backwashing. High-throughput sequencing analysis indicates that heterotrophic bacteria plays a significant role in nitrogen removal;Rhodobacter is the known heterotrophic nitrification aerobic denitrification bacteria in the present system. In addition, the proliferation of filamentous bacteria in this system enhanced nitrogen and COD removal.

关键词： Ethanol   Product inhibition   Product removal   Vacuum   Phenomenological modeling  

摘要： Vacuum ethanol removal effect on the fermentative performance of Kluyveromyces marxianus was assessed. Yeast was cultured in bench bioreactor at initial glucose concentration of 90 g L-1 in two sequential batches of 36 h, with a vacuum ethanol removal step and glucose feed before the second batch. Ethanol concentration after the first batch was 34.13 g L-1 (Y-P/S 038 g g(-1);Q(P) 0.94 g L-1.h(-1)), and 40.90 g L-1 (Y-P/S 0.18 g g(-1);Q(P) 0.43 g L-1.h(-1)) after the second batch. Ethanol production in a control assay without vacuum extraction only happened in the first batch (36.37 g L-1;Y-P/S 0.4 g g(-1);Q(P) 1.01 g L(-1)h(-1)). The phenomenological modeling showed product inhibition and the importance of product removal to process improvement, although the yeast had needed an adaptation period to recover its fermentative metabolism after the stress caused by vacuum. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Sequential Batch Reactor   Biofilm Carriers   Activated Carbon   Ozonation   Permeate Flux   Activated Sludge Process  

摘要： The present study focuses on overcoming the drawback as fouling in a membrane bioreactor (MBR), which can be alleviated by integrating advanced oxidation process, adsorption, and biofilm carriers in the activated sludge process. The optimal sludge retention time, carbon and ozone dosage was 150 minutes, 15 g and 1.5 Lmin(-1), respectively. The percentage removal was observed to be above 90% for chemical oxygen demand and total organic carbon whereas for total dissolved solids was only 40% under transmembrane pressure of 20 kPa. The increase in permeate flux was 30% as compared to MBR. Sequential batch membrane bioreactor (SBMBR) showed 12% reduction in energy consumption for three hour operation at the flow rate of 0.72 L/h (transmembrane pressure 20 kPa), and it was confirmed in the SEM of carbon, membrane, UV, CV and HPLC also. The energy consumption required also confirms the less internal fouling via the extended backwash of four hours.