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Anaerobiosis, Hydrogen-Ion Concentration, Nitrogen, Oxidation-Reduction, Sewage, Bioreactors, and Waste Disposal, Fluid

In order to assess the performance of anaerobic ammonium oxidation (anammox) bioreactors, it is necessary to study the stoichiometry of the anammox reaction and pH. This study focused on the effect of the hydraulic retention time (HRT) on the effluent pH in anammox-upflow anaerobic sludge blanket (UASB) bioreactors. Anammox-UASB bioreactors with and without a recirculation system were used to investigate the effluent pH and bioreactor performance. It was concluded that under varying HRT conditions, the decrease in effluent pH did not indicate the deterioration of nitrogen removal, but did indicate that the nitrogen removal efficiency was reduced owing to a sudden increase in the nitrogen loading rate resulting from the decrease in HRT. Moreover, the results showed that the HRT directly affected the concentration of OH - , which affected the increase/decrease in effluent pH. This study demonstrated that effluent pH is a more powerful tool than previous techniques used to assess bioreactor performance. We suggest that the effluent pH could be used for preliminary assessment.
(Copyright © 2020 Elsevier Ltd. All rights reserved.)

New Zealand, Nitrates analysis, Selection Bias, Bioreactors, and Denitrification

Woodchip bioreactors are a practical, low-cost technology for reducing nitrate (NO 3 ) loads discharged from agriculture. Traditional methods of quantifying their performance in the field mostly rely on low-frequency, time-based (weekly to monthly sampling interval) or flow-weighted sample collection at the inlet and outlet, creating uncertainty in their performance and design by providing incomplete information on flow and water chemistry. To address this uncertainty, two field bioreactors were monitored in the US and New Zealand using high-frequency, multipoint sampling for in situ monitoring of NO 3 -N concentrations. High-frequency monitoring (sub hourly interval) at the inlet and outlet of both bioreactors revealed significant variability in volumetric removal rates and percent reduction, with percent reduction varying by up to 25 percentage points within a single flow event. Time series of inlet and outlet NO 3 showed significant lag in peak concentrations of 1-3 days due to high hydraulic residence time, where calculations from instantaneous measurements produced erroneous estimates of performance and misleading relationships between residence time and removal. Internal porewater sampling wells showed differences in NO 3 concentration between shallow and deep zones, and "hot spot" zones where peak NO 3 removal co-occurred with dissolved oxygen depletion and dissolved organic carbon production. Tracking NO 3 movement through the profile showed preferential flow occurring with slower flow in deeper woodchips, and slower flow further from the most direct flowpath from inlet to outlet. High-frequency, in situ data on inlet and outlet time series and internal porewater solute profiles of this initial work highlight several key areas for future research.
(Published by Elsevier Ltd.)

Cellulose, Fermentation, Aspergillus, Bioreactors, and Lipase

We evaluated the conditions to produce lipase in solid-state cultivation using a recently isolated strain of Aspergillus brasiliensis 157f in bioreactors of different configurations: static flat-bed, plugged-flow bed with forced water-saturated aeration, and pilot-scale rotating drum bioreactor, using malt bagasse as substrate. Lipase production was optimized applying experimental design analysis, which showed optima parameters defined as pH 7.7, addition of 11.3 % of soybean oil to the medium, and culture temperature of 32.7 oC, in static flat-bed. The highest enzyme activity (9.8 U.g-1 substrate) was obtained in the plugged-flow bed with forced water-saturated aeration. The fermented culture medium was lyophilized to create a solid enzymatic preparation (SEP), which was used to test the possibility of using this cheap biocatalyst in bioreactors to mediate esterification and transesterification reactions. SEP presented lipase activities of 7.35 U.g-1 substrate, indicating the possibility of further enhancing aspects of the use of such biocatalyst.

Cell Culture Techniques, Cells, Cultured, Humans, Male, Biobehavioral Sciences, Bioreactors, Endothelial Cells cytology, Endothelial Cells metabolism, Fibroblasts cytology, Fibroblasts metabolism, Printing, Three-Dimensional, and Tissue Engineering

3D printing is a rapidly evolving field for biological (bioprinting) and non-biological applications. Due to a high degree of freedom for geometrical parameters in 3D printing, prototype printing of bioreactors is a promising approach in the field of Tissue Engineering. The variety of printers, materials, printing parameters and device settings is difficult to overview both for beginners as well as for most professionals. In order to address this problem, we designed a guidance including test bodies to elucidate the real printing performance for a given printer system. Therefore, performance parameters such as accuracy or mechanical stability of the test bodies are systematically analysed. Moreover, post processing steps such as sterilisation or cleaning are considered in the test procedure. The guidance presented here is also applicable to optimise the printer settings for a given printer device. As proof of concept, we compared fused filament fabrication, stereolithography and selective laser sintering as the three most used printing methods. We determined fused filament fabrication printing as the most economical solution, while stereolithography is most accurate and features the highest surface quality. Finally, we tested the applicability of our guidance by identifying a printer solution to manufacture a complex bioreactor for a perfused tissue construct. Due to its design, the manufacture via subtractive mechanical methods would be 21-fold more expensive than additive manufacturing and therefore, would result in three times the number of parts to be assembled subsequently. Using this bioreactor we showed a successful 14-day-culture of a biofabricated collagen-based tissue construct containing human dermal fibroblasts as the stromal part and a perfusable central channel with human microvascular endothelial cells. Our study indicates how the full potential of biofabrication can be exploited, as most printed tissues exhibit individual shapes and require storage under physiological conditions, after the bioprinting process.

Ammonia, Biofilms, Nitrification, Saline Waters, Bioreactors, and Salinity

Nitrifying biofilms developed in brackish water are reported to be more robust to salinity changes than freshwater biofilms. This makes them a promising strategy for water treatment systems with variable salinity, such as recirculating aquaculture systems for Atlantic salmon. However, little is known about the time required for nitrification start-up in brackish water or the microbial community dynamics. To investigate the development of nitrifying biofilms at intermediate salinity, we compared the startup of moving bed biofilm reactors with virgin carriers in brackish- (12‰ salinity) and freshwater. After 60 days, the brackish water biofilm had half the nitrification capacity of the freshwater biofilm, with a less diverse microbial community, lower proportion of nitrifiers, and a significantly different nitrifying community composition. Nitrosomonas and Nitrosospira-like bacteria were the main ammonia oxidizers in the brackish water biofilms, whereas Nitrosomonas was dominant in freshwater biofilms. Nitrotoga was the dominant nitrite oxidizer in both treatments. Despite the lower nitrification capacity in the brackish water treatment, the low ammonia and nitrite concentration with rapidly increasing nitrate concentration indicated that complete nitrification was established in both reactors within 60 days. The results suggest that biofilms develop nitrification in brackish water in comparable time as in freshwater, and brackish start-up can be a strategy for bioreactors with varying salinity.
(Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Electricity, Electrodes, Sewage, Waste Disposal, Fluid, Waste Water, Bioreactors, and Membranes, Artificial

Integration of an electrochemical process with membrane bioreactor (MBR) has attracted considerable attention in the last decade for simultaneous improvement in pollutant removal and hydraulic performance of MBR. Electrochemical MBR (eMBR) with sacrificial anodes has been observed to achieve enhanced phosphorus (up to 40%) and micropollutant removal (5-60%). This is because direct anodic oxidation, indirect oxidation by reactive oxygen species and electrocoagulation can supplement the biological process. The application of an electric field can substantially reduce membrane fouling by 10% to 95% in the eMBR as compared to the conventional MBR. Sacrificial electrodes (e.g., iron or aluminium) have been reported to be more suitable for fouling mitigation than non-sacrificial electrodes (e.g., titanium). However, during prolonged operation, metal ions released from sacrificial electrodes can adversely affect microbial activity and could accumulate in activated sludge. Depending on the current density and electrode material (sacrificial or non- sacrificial), anodic oxidation, electrocoagulation, electrophoresis and/or electroosmosis mechanisms are responsible for suppressing membrane fouling propensity. This paper critically reviews the current status of the electrochemical MBR technology and presents a concise summary of eMBR configurations and electrode materials. Comparative removal of bulk organics, nutrients and micropollutants in the eMBR and conventional MBR is discussed, and performance governing factors are elucidated. Impacts of operating conditions such as current density on mixed liquor properties (e.g., floc size and zeta potential) and microbial activity are elucidated. The extent of membrane fouling mitigation along with associated mechanisms as well as energy consumption is explained and critically analysed. Future research directions are suggested to fast track the scalability of eMBR, which include but are not limited to electrode lifetime, development of self-cleaning conductive membranes, optimisation of operating parameters, removal of emerging micropollutants, accumulation of toxic metals in activated sludge, and degradation by-products and ecotoxicity.
(Copyright © 2020 Elsevier B.V. All rights reserved.)