Search results for "Bioreactor"
showing 10 items of 397 documents
Impact of crop species on bacterial community structure during anaerobic co-digestion of crops and cow manure
2008
The bacterial communities in three continuously stirred tank reactors co-digesting cow manure with grass silage, oat straw, and sugar beet tops, respectively, were investigated by 16S rRNA gene-based fingerprints and clone libraries. The analyses revealed both clearly distinct and similar phylotypes in the bacterial communities between the reactors. The major groups represented in the three reactors were Clostridia, unclassified Bacteria, and Bacteroidetes. Phylotypes affiliated with Bacilli or Deltaproteobacteria were unique to the sugar beet and straw reactor, respectively. Unclassified Bacteria dominated in sugar beet reactor while in the straw and grass reactor Clostridia was the domina…
Two-Stage Anaerobic Digestion of Energy Crops: Methane Production, Nitrogen Mineralisation and Heavy Metal Mobilisation
2006
Energy crops (willow, sugar beet and grass silage) were digested in pilot scale two-stage anaerobic digesters. The specific methane yields obtained were 0.16, 0.38 and 0.39 m3 kg(-1) added volatile solids (VSadded) for willow, sugar beet and grass, respectively, corresponding to yearly gross energy yields of 15, 53 and 26 megawatt-hours (MWh) per hectare. With grass and sugar beets as substrate, 84-85% of the harvestable methane was obtained within 30 days. In pilot scale two-stage digestion of willow and sugar beet, 56 and 85% of the laboratory scale methane yields were obtained, but digestion of grass in two-stage reactors yielded 5% more methane than digestion in laboratory scale complet…
A comparative study of mechanical properties of fresh and frozen-thawed porcine intervertebral discs in a bioreactor environment
2016
Abstract Limited availability of fresh intervertebral discs (IVDs) necessitates the use of frozen-thawed samples in biomechanical investigations. Several authors have reported the mechanical properties of frozen-thawed IVDs, but few studies have investigated the effects of storage temperature and cooling rate. The validity and reliability of the applied freezing-thawing procedures are still relatively unknown. The study aims to compare the mechanical responses of fresh porcine IVDs and porcine IVDs, which were frozen at different freezing temperatures with a controlled-rate cooling process and then thawed. The specimens were obtained from pigs aged 6 months. A total of 18 functional spine u…
Investigating bacterial populations in styrene-degrading biofilters by 16S rDNA tag pyrosequencing
2014
Microbial biofilms are essential components in the elimination of pollutants within biofilters, yet still little is known regarding the complex relationships between microbial community structure and biodegradation function within these engineered ecosystems. To further explore this relationship, 16S rDNA tag pyrosequencing was applied to samples taken at four time points from a styrene-degrading biofilter undergoing variable operating conditions. Changes in microbial structure were observed between different stages of biofilter operation, and the level of styrene concentration was revealed to be a critical factor affecting these changes. Bacterial genera Azoarcus and Pseudomonas were among…
Nitrous oxide emission in a University of Cape Town membrane bioreactor: The effect of carbon to nitrogen ratio
2017
Abstract The effect of the carbon-to-nitrogen (C/N) ratio in the influent on the nitrous oxide (N 2 O) emission from a University of Cape Town Membrane BioReactor pilot plant was investigated. The membrane was located in a separate tank to single out the production of N 2 O due to the biological processes from N 2 O stripping as a result of the extra aeration needed for the mitigation of membrane fouling. The experimental campaign was divided into two phases, each characterized by a different C/N ratio (namely, 10 and 5 mgCOD/mgTN, Phase I and Phase II, respectively). The decrease of the C/N ratio promoted the increase of N 2 O emissions in both gaseous and dissolved phases, mainly due to a…
Shortcut nitrification-denitrification by means of autochthonous halophilic biomass in an SBR treating fish-canning wastewater
2017
Abstract Autochthonous halophilic biomass was cultivated in a sequencing batch reactor (SBR) aimed at analyzing the potential use of autochthonous halophilic activated sludge in treating saline industrial wastewater. Despite the high salt concentration (30 g NaCl L −1 ), biological oxygen demand (BOD) and total suspended solids (TSS), removal efficiencies were higher than 90%. More than 95% of the nitrogen was removed via a shortcut nitrification-denitrification process. Both the autotrophic and heterotrophic biomass samples exhibited high biological activity. The use of autochthonous halophilic biomass led to high-quality effluent and helped to manage the issues related to nitrogen removal…
Mathematical modelling of greenhouse gas emissions from membrane bioreactors: A comprehensive comparison of two mathematical models.
2018
Abstract This paper compares two mathematical models (Model I and Model II) to predict greenhouse gases emission from a University Cape Town (UCT) – membrane bioreactor (MBR) plant. Model I considers N 2 O production only during denitrification. Model II takes into account the ammonia-oxidizing bacteria (AOB) formation pathways for N 2 O. Both models were calibrated adopting real data. Model comparison was performed in terms of (i) sensitivity analysis (ii) best fit and (iii) model prediction uncertainty. On average 6% of factors of Model I and 9% of Model II resulted to be important. In terms of best fit, Model II had a better capability of reproducing the measured data. The average effici…
The effect of the solids and hydraulic retention time on moving bed membrane bioreactor performance
2018
Abstract The aim of the present paper was to investigate the effect of solids (SRT) and hydraulic (HRT) retention time on Integrated Fixed Film Activated Sludge (IFAS) University of Cape Town (UCT) membrane Bioreactor (MBR). In particular, three different pairs of SRT and HRT values were analysed, namely, Phase I 56 d/30 h, Phase II 31 d/15 h and Phase III 7 d/13 h. The short-term effect of these three SRT/HRT conditions was assessed by analysing several system performance indicators: organic carbon and biological nutrient (nitrogen and phosphorus) removal, biomass respiratory activity, activated sludge filtration properties and membrane fouling. The results showed that the decrease of SRT/…
Enhanced nitrogen removal of low carbon wastewater in denitrification bioreactors by utilizing industrial waste toward circular economy
2020
Abstract Aquaculture needs practical solutions for nutrient removal to achieve sustainable fish production. Passive denitrifying bioreactors may provide an ecological, low-cost and low-maintenance approach for wastewater nitrogen removal. However, innovative organic materials are needed to enhance nitrate removal from the low carbon effluents in intensive recirculating aquaculture systems (RAS). In this study, we tested three additional carbon sources, including biochar, dried Sphagnum sp. moss and industrial potato residues, to enhance the performance of woodchip bioreactors treating the low carbon RAS wastewater. We assessed nitrate (NO3−) removal and microbial community composition durin…
Comparison of Two Mathematical Models for Greenhouse Gas Emission from Membrane Bioreactors
2017
In this study two mathematical models (Model I and Model II), able to predict the nitrous oxide (N2O) and carbon dioxide (CO2) emission from an University Cape Town (UCT) – membrane bioreactor (MBR) plant, have been compared. Model I considers the N2O production only during the denitrification. Model II takes into account the two ammonia-oxidizing bacteria (AOB) formation pathways for N2O. Both models were calibrated adopting real data. Results highlight that Model II had a better capability of reproducing the measured data especially in terms of N2O model outputs. Indeed, the average efficiency related to the N2O model outputs was equal to 0.3 and 0.38 for Model I and Model II respectively.