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关键词： Outer-selective hollow fiber   Thin-film composite   Osmotic membrane bioreactor   Municipal wastewater treatment   Membrane fouling control  

摘要： This paper investigates the efficiency of fouling mitigation methods using a novel outer selective hollow fiber thin-film composite forward osmosis (OSHF TFC FO) membrane for osmosis membrane bioreactor (OMBR) system treating municipal wastewater. Two home-made membrane modules having similar transport properties were used. Two operation regimes with three different fouling mitigation strategies were utilized to test the easiness of membrane for fouling cleaning. These two membrane modules demonstrated high performance with high initial water flux of 14.4 LMH and 14.1 LMH and slow increase rate of mixed liquor's salinity in the bioreactor using 30 g/L NaCl as draw solution. OMBR system showed high removals of total organic carbon and NH4 + -N (> 98%). High fouling cleaning efficiency was achieved using OSHF TFC FO membrane with different fouling control methods. These results showed that this membrane is suitable for OMBR applications due to its high performance and its simplicity for fouling mitigation.

关键词： Optimal control   Maximum principle of Pontryagin   Fructo-oligosaccharides   Fed-batch bioreactor  

摘要： The production of high-content fructo-oligosaccharides by fermentation in a fed-batch bioreactor is considered. Fed-batch scenario allows to reduce inhibition mechanisms caused by the presence of by-products, such as glucose, while maximizing biomass production. The determination of the feed flow rate profile that maximizes the concentration of fructo-oligosaccharides is performed by resorting to the maximum principle of Pontryagin. The optimization procedure takes into account inequality constraints on the state and control variables and allows the determination of the unspecified final fermentation time corresponding to maximal fructo-oligosaccharides content. The performance of the approach is demonstrated by simulations in the case of fructo-oligosaccharide production by Aspergillus sp. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Airlift bioreactor   Average shear rate   Liquid velocity profile   Computational fluid dynamics  

摘要： The shear rate is an important bioreactor parameter that needs to be evaluated due to its impact on microorganism morphology and viability, and consequently on bioproduct formation. Airlift bioreactors, classified as low-shear devices, are used as an alternative to conventional stirred-tank reactors. Considerable efforts have been made to characterize the shear environments in airlift bioreactors, using the average shear rate as a key parameter. However, there is no agreement among the values obtained in different studies, which can differ even in orders of magnitude. The methodologies used to obtain av in the different studies could be the reason for the lack of agreement among them. In this work, av in a concentric tube airlift bioreactor was evaluated using computational fluid dynamics (CFD), as well as based on universal velocity profiles for liquid flows in smooth pipes and annuli. Good agreement was obtained between the CFD-based average shear rates and the values obtained from universal velocity profiles, indicating that CFD simulation is a valuable tool for av prediction.

关键词： Chain elongation   Selective pressure   Open-culture fermentation   Mixed-culture fermentation   Biobased chemicals   Methanol   Butyrate   n-Valerate  

摘要： BackgroundChain elongation forms a new platform technology for the circular production of biobased chemicals from renewable carbon and energy sources. This study aimed to develop a continuous methanol-based chain elongation process for the open-culture production of a new-generation biofuel precursor and potential platform chemical: n-valerate. Propionate was used as a substrate for chain elongation to n-valerate in an anaerobic open-culture bioreactor. In addition, the co-production of n- and iso-butyrate in addition to n-valerate via, respectively, acetate and propionate elongation was ***-Valerate was produced during batch and continuous experiments with a pH in the range 5.5-5.8 and a hydraulic retention time of 95h. Decreasing the pH from 5.8 to 5.5 caused an increase of the selectivity for n-valerate formation (from 58 up to 70 wt%) during methanol-based propionate elongation. n-Valerate and both n- and iso-butyrate were produced during simultaneous methanol-based elongation of propionate and acetate. Propionate was within the open-culture preferred over acetate as a substrate with 10-30% more consumption. Increasing the methanol concentration in the influent (from 250 to 400mM) resulted in a higher productivity (from 45 to 58mmolC/L/day), but a lower relative product selectivity (from 49 to 43 wt%) of n-valerate. The addition of acetate as a substrate did not change the average n-valerate productivities. Within the continuous bioreactor experiments, 6 to 17wt% of formed products was methane. The microbial community during all steady-states in both methanol-based elongation bioreactors was dominated by species related to Clostridium luticellarii and Candidatus Methanogranum. C. luticellarii is the main candidate for n-valerate formation from methanol and ***-Valerate was for the first time proven to be produced from propionate and methanol by an open-culture bioreactor. Methanogenic activity can be inhibited by decreasing

关键词： Ion exchange column   UASB bioreactor   selenate removal   adsorption   integrated treatment system  

摘要： The application of an integrated process configuration comprising of an ion exchange (IX) column and an upflow anaerobic sludge blanket (UASB) bioreactor for the simultaneous removal of SO42- and total Se from synthetic mine wastewater was evaluated. Use of an IX column as a pre-treatment (not as post-treatment) to the UASB bioreactor gave the best overall removal performance. The combined treatment reduced the total Se and SO42- concentration from 8.0 and 1441 mg/L to 0.2 and 28.0 mg/L, respectively. This study demonstrated for the first time that an IX process as a pre-treatment to a biological process can significantly improve the oxyanion removal efficiency and the overall treatment of Se-laden wastewaters.

关键词： Anaerobic ceramic membrane bioreactor   Silicon carbide membrane   Domestic wastewater   Food waste recycling wastewater   rDNA sequencing   rRNA sequencing  

摘要： This study evaluated the feasibility of using a silicon carbide (SiC) anaerobic ceramic membrane bioreactor (AnCMBR) to co-manage domestic wastewater (DWW) and food waste recycling wastewater (FRW). A pilot-scale SiC-AnCMBR was put into operation for 140 days under two different organic loading rates (OLRs): 5 kg COD m(-3) d(-1) (OLR 5) and 3 kg COD m(-3) d(-1) (OLR 3). The organic removal efficiency was 93.5 +/- 3.7% over the operational period. Methane production increased significantly after sludge re-seeding at OLR 3. rDNA and rRNA microbial results showed that the active archaeal community was affected by sludge re-seeding, whereas the active bacterial community was not, indicating that a shift in the active archaeal community was responsible for the increased methane production. Our results thus suggest that SiC-AnCMBRs are a promising option for co-managing DWW and FRW. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Succinic acid   bioreactor   fermentation   batch and continuous process   biorefinery  

摘要： Succinic acid (SA) has been recognized as one of the most important bio-based building block chemicals due to its numerous potential applications. Fermentation SA production from renewable carbohydrate feedstocks can have the economic and sustainability potential to replace petroleum-based production in the future, not only for existing markets, but also for new larger volume markets. Design and operation of bio-reactors play a key role. During the last 20 years, many different fermentation strategies for SA production have been described in literature, including utilization of immobilized biocatalysts, integrated fermentation and separation systems and batch, fed-batch, and continuous operation modes. This review is an overview of different fermentation process design developed over the past decade and provides a perspective on remaining challenges for an economically feasible succinate production processes. The analysis stresses the idea of improving the efficiency of the fermentation stage by improving bioreactor design and by increasing bioreactor performance.

关键词： fouling mechanism   MBR   model   transmembrane pressure  

摘要： Identifying the fouling degree of a membrane bioreactor (MBR) provides guidance on the determination of suitable membrane cleaning methods. There is still a lack of knowledge on the effects of powdered activated carbon (PAC) refresh ratio on the MBR fouling mechanism. Major fouling mechanisms of an MBR with constant flow rate at different PAC replenishment ratios were investigated by individual and combined mechanistic fouling models. The root mean square errors were employed to assess the prediction accuracy of the used fouling models. The combined models showed better prediction. The cake-complete model provided far better fits of the transmembrane pressure data, and provided good fits of other individual model predictions regardless of the PAC refreshment ratio. Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed that the cake layer clogging was the main fouling mechanism followed by complete blockage and standard plugging. The cake-complete model may be used to predict the fouling mechanisms in PAC/MBR systems.