Plug-flow Bioreactor Research Articles

A comprehensive study of glucose and oxygen gradients in a scaled-down model of recombinant HuGM-CSF production in thermoinduced Escherichia coli fed-batch cultures

The effect of gradients of elevated glucose and low dissolved oxygen in the addition zone of fed-batch E. coli thermoinduced recombinant high cell density cultures can be evaluated through two-compartment scale-down models. Here, glucose was fed in the inlet of a plug flow bioreactor (PFB) connected to a stirred tank bioreactor (STB). E. coli cells diminished growth from 48.2 ± 2.2 g/L in the stage of RP production if compared to control (STB) with STB-PFB experiments, when residence time inside the PFB was 25 s (34.1 ± 3.5 g/L) and 40 s (25.6 ± 5.1 g/L), respectively. The recombinant granulocyte-macrophage colony-stimulating factor (rHuGM-CSF) production decreased from 34 ± 7% of RP in inclusion bodies (IB) in control cultures to 21 ± 8%, and 7 ± 4% during the thermoinduction production phase when increasing residence time inside the PFB to 25 s and 40 s, respectively. This, along with the accumulation of acetic and formic acid (up to 4 g/L), indicates metabolic redirection of central carbon routes through metabolic flow and mixed acid fermentation. Special care must be taken when producing a recombinant protein in heat-induced E. coli, because the yield and productivity of the protein decreases as the size of the bioreactors increases, especially if they are carried at high cell density.

Spatial monitoring of hydrolysis in a plug-flow bioreactor: a support for flexible operation?

Hydrolysis at changing hydraulic retention time, recirculation, bedding straw content in the feed, bioaugmentation and the impact of those changes on gradient formation in the liquid phase in plug-flow reactors (PFRs) was examined. The pH-value, conductivity and oxidation–reduction potential (ORP) were monitored at three spots along the PFRs to study potential correlations to process performance during a total process time of 123 weeks. The on-line monitoring showed good correlations to acidogenesis: namely, the pH and ORP to the acidification, to butyric (and lactic) acid concentration and to the acid yield. The ORP (measured at the inlet) showed the most stable correlation to acidogenesis under dynamic operation, while the conductivity (at the outlet) correlated to the acid concentration in dependence on the feedstock. Multiple measurement spots as used in this study allow to gain more information about acidogenic fermentation than a single spot, simplifying process control and automation attempts with recalcitrant feedstock.Graphical

Treatment of 2-naphthalene sulfonate by free and immobilized cells of indigenous isolate Comamonas sp. C2 and toxicity evaluation of biotransformed sample

An indigenous bacterial strain Comamonas sp. C2, capable of utilizing 2-naphthalene sulfonate (2-NS) as a sole source of carbon, was isolated after enrichment of microbial diversity present in sample collected from sewage treatment plant (STP) receiving untreated or partially treated effluent from textile industries. The isolate was able to degrade 100 mg/L of 2-NS, when grown in sulfur free minimal salt medium (SFMSM), after an incubation of 8 h. The release of sulfite/sulfate ions during biotransformation, assay of protocatechuate 4, 5-dioxygenase activity and formation of metabolic intermediates like salicylaldehyde, protocatechuate and 2-hydroxy-4-carboxy-muconatesemialdehyde in the biologically treated sample indicated to the meta-cleavage of aromatic ring of 2-NS. An immobilized-cell plug flow bioreactor (PFR) was developed and evaluated for its efficiency to treat simulated feed supplemented with 100 mg/L of 2-NS. The cells of C2 were immobilized on pieces of polyurethane foam (PUF) and refractory brick pieces (RBP). The PFR, when operated at an HRT of 36 h, achieved complete degradation of 100 mg/L of 2-NS corresponding to 89% lowering of COD. The reduction in overall toxicity of 2-NS after biological treatment was evaluated using plant (Triticum aestivum and Vigna radiata) and animal (freshwater fish Channa punctatus) models, exposed to both untreated and PFR treated samples. To the best of our knowledge, there are no similar reports on exploitation of the metabolic potential of Comamonas sp. in 2-NS degradation and validation of the biological transformation by toxicity analysis.

Effects of Nitrate Recycle on the Sludge Densification in Plug-Flow Bioreactors Fed with Real Domestic Wastewater

The impact of adding a modified Ludzack–Ettinger (MLE) configuration with Nitrate Recycle (NRCY) on continuous-flow aerobic granulation has yet to be explored. The potential negative effects of MLE on sludge densification include that: (1) bioflocs brought by NRCY could compete with granules in feast zones; and (2) carbon addition to anoxic zones could increase the system organic loading rates and lead to higher feast-to-famine ratios. Two pilot-scale plug flow reactor (PFR) systems fed with real domestic wastewater were set up onsite to test these hypotheses. The results showed that MLE configuration with NRCY could hinder the sludge granulation, but the hindrance could be alleviated by the NRCY location change which to some extent also compensates for the negative effect of higher feast-to-famine ratios due to carbon addition in MLE. This NRCY location change can be advantageous to drive sludge densification without a radical washout of the sludge inventory, and had no effects on the chemical oxygen demand (COD) and nitrogen removal efficiencies. The PFR pilot design for the MLE process with a modified NRCY location tested in this study could be developed as an alternative to hydrocyclones for full-scale, greenfield, continuous sludge densification applications.

Environmental ammonia analysis based on exclusive nitrification by nitrifying biofilm screened from natural bioresource

Biofilm-based biological nitrification is widely used for ammonia removal, while hasn't been explored for ammonia analysis. The stumbling block is the coexist of nitrifying and heterotrophic microbes in real environment resulting in non-specific sensing. Herein, an exclusive ammonia sensing nitrifying biofilm was screened from natural bioresource, and a bioreaction-detection system for the on-line analysis of environmental ammonia based on biological nitrification was reported. The nitrifying microbes were aggregated into a nitrifying biofilm through a result-oriented bioresource enrichment strategy. The predominant nitrifying population and progressive surface reaction in the plug flow bioreactor led to the exclusive and exhaustive ammonia biodegradation for the establishment of a novel analytical method. The on-line ammonia monitoring prototype achieved complete biodegradation for determining ammonium nitrogen within 5 min and showed exceptional reliability in long-term real sample measurements without frequent calibration. This work offers a low-threshold natural screening paradigm for developing sustainable bioresource-based analytical technologies.

Basic Technological Parameters of the Activation Process for Two Bioreactor Configurations

Abstract Technological parameters of the activation process in wastewater treatment plant activation systems are analyzed for basic bioreactor configurations, for the chemostat and for the plug flow, both with the recirculation of concentrated activated sludge. The first type of bioreactors represents conventional aerated tanks, but also loop bioreactors. The second type of bioreactors includes, for example, oxidation ditches. The paper presents an evaluation of the basic technological parameters of the activation process for the two mentioned configurations of bioreactor systems with recirculation of concentrated activated sludge. In addition, a new relation for sludge age evaluation is proposed for an activation system with a plug flow bioreactor. The article also provides examples of connections between the values of the technological parameters of the activation process for the two analyzed types of bioreactor systems.

Distinct seasonal variations of dissolved organic matter across two large freshwater lakes in China: Lability profiles and predictive modeling

Biological lability of dissolved organic matter (DOM) is a crucial indicator of carbon cycle and contaminant attenuation in freshwater lakes. In this study, we employed a multi-stage plug-flow bioreactor and spectrofluorometric indices to characterize the seasonal variations in DOM composition and lability across Poyang Lake (PY) and Lake Taihu (TH), two large freshwater lakes in China with distinct hydrological seasonality. Our findings showed that the export of floodplain-derived organics and river-lake interaction led to a remarkable increase in terrestrial aromatic and humic-like DOM with high molecular weights and long turnover times in PY. Consequently, the labile fraction was extremely low (average LDOC% of 3%) during the rising-to-flood season (spring and summer). Conversely, autochthonous production in TH considerably enriched semi-labile (average SDOC% of 26%) and biodegradable DOM (average BDOC% of 34%) during the phytoplankton bloom to post-bloom season (summer and autumn). This was reflected by the accumulation of low-light-absorbing and protein-like components with high biological and fluorescence indices. In the dry and non-bloom season (winter), the better preservation of humic substances maintained the high molecular weight and humic degree of DOM in PY, while the decay of aquatic plants strengthened autochthonous production, resulting in a similar BDOC% of PY samples (23%–34%) to TH samples (18%–33%). We further applied partial least squares regression using DOM optical indices as predictive proxies, which generated a greater prediction strength for BDOC% (R2 = 0.80) compared to SDOC% (R2 = 0.57) and LDOC% (R2 = 0.28). The regression model identified aromaticity (SUVA254) as the most effective and negative predictor and low molecular weight (A250/A365) as the highly and positively influential factor. Our study provides new evidence that the seasonality of DOM lability profiles is regulated by the trade-off between flow-related variation and phytoplankton production, and presents an approach to describe and predict DOM lability across freshwater lakes.

Effect of bioaugmentation with Paenibacillus spp. and thin slurry recirculation on microbial hydrolysis of maize silage and bedding straw in a plug-flow reactor

In this work, the effect of bioaugmentation on the hydrolysis and acidogenesis efficiency of bedding straw mixed with maize silage is examined. A plug-flow bioreactor was operated for 70 weeks with maize silage as a reference feedstock and subsequently with an increasing straw content of 30% and 66% (w/w). Bioaugmentation with two Paenibacillus species was conducted at each process condition to investigate the impact on hydrolysis of the recalcitrant lignocellulosic feedstock. A stable acidogenic digestion of the substrates was achieved, during which acetic and butyric acid were accumulated as main byproducts. Specific hydrolysis rates between 258 and 264 gO2 kg−1VS were determined for pure maize silage and maize silage mixed with 30% of straw, while the specific hydrolysis rate decreased to 195 gO2 kg−1VS when a mixture with 66% of straw was applied. Bioaugmentation with Paenibacillus spp. increased the specific hydrolysis rate by up to 41–63% for pure maize silage and the mixture with 30% of straw, while no increase was observed with a mixture of 66% of straw. Acid production, however, was enhanced by 21 to 42% following bioaugmentation for all substrate mixtures. A positive effect on the physiological state of cultures, as recorded with frequency-dispersed polarizability, was seen after bioaugmentation, which remained for two retention times during the continuous fermentation mode. Recirculation of the thin sludge further prolonged the positive effects of bioaugmentation. The results of this work provide a basis to optimize the amount of the bioaugmented microorganisms and hydrolysis of biogenic material with respect to sustainable effects on process performance and costs.

Development and operation of immobilized cell plug flow bioreactor (PFR) for treatment of textile industry effluent and evaluation of its working efficiency.

The release of untreated/partially treated effluent and solid waste from textile dyeing industries, having un-reacted dyes, their hydrolysed products and high total dissolved solids (TDS) over the period of time had led to the deterioration of ecological niches. In an endeavour to develop a sustainable and effective alternative to conventional approaches, a plug flow reactor (PFR) having immobilized cells of consortium of three indigenous bacterial isolates was developed. The reactor was fed with effluent collected from the equalization tank of a textile processing unit located near city of Amritsar, Punjab (India). The PFR over a period of 3 months achieved 97.98 %, 82.22 %, 87.36%, 77.71% and 68.75% lowering of colour, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS) and total suspended solids (TSS) respectively. The comparison of the phytotoxicity and genotoxicity of untreated and PFR-treated output samples using plant and animal models indicated significant lowering of respective toxicity potential. This is a first report, as per best of our knowledge, regarding direct treatment of textile industry effluent without any pre-treatment and with minimal nutritional inputs, which can be easily integrated into already existing treatment plant. The successful implementation of this system will lower the cost of coagulants/flocculants and also lowering the sludge generation.

Simultaneous biodegradation of BTX by isolated degrading bacterial strains in a newly designed modulated bio-scrubber assisted to airlift parallel bioreactors.

A new approach in this present study, isolated bacteria from refinery sludge were used in a laboratory-scale bio-scrubber, connecting with two parallel airlift bioreactors to eliminate harmful and toxic fumes of BTX. One of the main features of this bio-scrubber is using porous mineral pumice fillers (Lava Rock) inside poly-urethane foam (PUF)module tower, connecting with agitator bio-phasic continuously stirred tank bio-reactor (CSTbR) to increase retention time and contact surface. The bio-scrubber and airlift plug flow bio-reactor(PFbR) were used in parallel with cooling flow to be more efficient in preservation of the corresponding heater and endothermic from removal reactions. Performance of bio-scrubber in removing BTX vapors with 10 % silicone oil and grade 350 poise as organic phase in the inlet concentration range of 180 ± 0.3 to 1950.5 ± 0.1mg /m3 (ppmv) for up to 6 months in two air flow rate's 2.5 and 3.5 (lit/min) that each treatment lasted about 2 months. The rate of biodegradation in this study was carried out by mixing 3 isolated bacteria, obtaining from refinery sludge, named DBIS-03, DTIS-12, and DXIS-09, which they had highest biodegradability than all the isolated strains. The results of BTX biodegradation at each EBRT (Empty Bed Retention Time) showed that the removal efficiency of BTX with isolated bacterial samples was able to grow and multiply on porous fillers and regenerate the growth medium of autotrophic bacterial strain with O2 gas and micronutrients from contaminated air flow with minimum concentration. Benzene, toluene and xylene inputs maximum concentration over a period of 20 days loading, respectively: B :99.2 % (at 2.5 lit/min and 183.2 ± 0.2mg /m3 (ppmv)), T: 98 % (at 2.5 lit/min and 327.1 ± 0.1mg /m3 ( ppmv)) and X: 85.9 % (at 2.5 lit/min and 296.8 ± 0.8mg /m3 (ppmv)) compared to 3.5 lit/min and so show the best performance in removing BTX from polluted air in period of 30 days.

Simulation on non-ideal behaviour of plug flow bioreactor based on the growth study of Lactobacillus species

ABSTRACT The physical properties of a biological system vary with time due to the growth of biomass, and thus the flowability of such a medium inside any bioreactor also changes with time. The present study aims to study the non-ideal behaviour of a plug flow bioreactor (PFBR) under non-reactive conditions for a biological system. Different physical parameters of this study have been incorporated from the batch growth study of Lactobacillus sp. The growth of bacteria culture was simulated using a PVA solution to conduct residence time distribution (RTD) experiments in pulse and step mode. Different parameters of the dispersion model were measured, and the non-zero variance indicated that dispersion always occurred along the path of reaction which led to turbulence and diffusion. The Peclet No was non-infinite; thus, PFBR always deviates from the ideal behaviour of the plug flow reactor. During the velocity distribution study, it had also been established that the Peclet number was decreased with the increase of Reynolds Number at a certain medium viscosity. Moreover, the non-ideality of PFBR further increased due to the change of physical properties of the medium. Here, a polynomial relation had been established between the Peclet number and medium viscosity. Therefore, the current study might be a value addition towards the designing of the plug flow bioreactor.

Solid-state fermentation of stale bread by an edible fungus in a semi-continuous plug-flow bioreactor

Stale bread, one of the major food wastes, holds great potential to produce new food products by solid-state fermentation using the edible filamentous fungus Neurospora intermedia. Yet, this process is limited to small-scale batch production. In this study, a plug-flow bioreactor was developed and successfully operated semi-continuously without addition of external inoculum. Two critical process parameters namely residence time and inoculum-to-substrate ratio (ISR) were studied in two experimental set-ups, 48 h and ISR 10:65 or 24 h and 20:55. The fermentation performance was assessed by the CO2 evolution rate and starch degradation in the substrate. Both experiments resulted in a relatively stable CO2 evolution rate up to 10 days and the starch content was reduced from 65 % in bread to 40.6 % and 43.2 %, respectively, in the product. Performance of the plug-flow bioreactor was compared to batch fermentation in tray bioreactors using the same ratio of inoculum. No significant differences of the final starch content were observed between the bioreactors, which indicate improved productivity by the semi-continuous process compared to the batch. The fungal biomass yield was calculated to range from 0.12 to 0.5 mol Cbiomass/mole Csubstrate. A material balance of the process revealed that 220 g dry bread and 200 ml water were required to produce 400 g fermented product with a fungal biomass content of 15 % in 24 h.

Continuous influenza virus production in a tubular bioreactor system provides stable titers and avoids the "von Magnus effect".

Continuous cell culture-based influenza vaccine production could significantly reduce footprint and manufacturing costs compared to current batch processing. However, yields of influenza virus in continuous mode can be affected by oscillations in virus titers caused by periodic accumulation of defective interfering particles. The generation of such particles has also been observed previously in cascades of continuous stirred tank reactors (CSTRs) and is known as the “von Magnus effect”. To improve virus yields and to avoid these oscillations, we have developed a novel continuous tubular bioreactor system for influenza A virus production. It was built using a 500 mL CSTR for cell growth linked to a 105 m long tubular plug-flow bioreactor (PFBR). Virus propagation took place only in the PFBR with a nominal residence time of 20 h and a production capacity of 0.2 mL/min. The bioreactor was first tested with suspension MDCK cells at different multiplicities of infection (MOI), and then with suspension avian AGE1.CR.pIX cells at a fixed nominal MOI of 0.02. Maximum hemagglutinin (HA) titers of 2.4 and 1.6 log10(HA units/100 μL) for suspension MDCK cells and AGE1.CR.pIX cells, respectively, were obtained. Flow cytometric analysis demonstrated that 100% infected cells with batch-like HA titers can be obtained at a MOI of at least 0.1. Stable HA and TCID50 titers over 18 days of production were confirmed using the AGE1.CR.pIX cell line, and PCR analysis demonstrated stable production of full-length genome. The contamination level of segments with deletions (potentially defective interfering particles), already present in the virus seed, was low and did not increase. Control experiments using batch and semi-continuous cultures confirmed these findings. A comparison showed that influenza virus production can be achieved with the tubular bioreactor system in about half the time with a space-time-yield up to two times higher than for typical batch cultures. In summary, a novel continuous tubular bioreactor system for cell culture-based influenza virus production was developed. One main advantage, an essentially single-passage amplification of viruses, should enable efficient production of vaccines as well as vectors for gene and cancer therapy.

Continuous-flow aerobic granulation in plug-flow bioreactors fed with real domestic wastewater

This pilot study was designed to explore the feasibility of achieving successful aerobic granulation in continuous flow infrastructure like that existing in modern wastewater treatment plants (WWTPs). Results demonstrated that aerobic granulation of activated sludge can be achieved in plug-flow reactors (PFRs) fed with primary effluent from a domestic WWTP with seasonal temperature variation between 10 and 22.5 °C. It took about 90 days during the reactor startup to reach a state of sustained aerobic granulation. The characteristics of aerobic granules formed were comparable to those measured in sequential batch reactors (SBRs). The feast-to-famine concentration profiles measured in the plug-flow pilot reactors were found to be in line with those present in the full-scale treatment trains, lending support to the feasibility of converting existing infrastructure to continuous flow aerobic granulation systems. A selection pressure based on settling velocity (Vs) was applied in a Vs selector to retain bioparticles with Vs greater than ~9–9.75 m h−1. It was theorized that an external Vs selection pressure would be necessary but would not be the sole condition sufficient to drive aerobic granulation. The alternating feast-to-famine internal selection provided by the PFRs is also believed to be a required condition to transform biomass from flocs toward dense and compact aerobic granules. While the pilot-scale Plug-flow Aerobic Granulation (PAG) reactor achieved similar COD and NH3 removal efficiencies as the full-scale WWTP treatment train, its effluent from Vs selector contained an average of 138 mg L−1 total suspended solids (TSS) as a result of the biomass ‘wash-out” by the Vs selection pressure. Pilot results suggest a second clarifier for polishing, in addition to the Vs selector, may be needed in a full-scale application of the technique unless other downstream processes (flocculation, sedimentation, filtration) are provided to reach final water quality goals.

Solid state fermentation pilot-scaled plug flow bioreactor, using partial least square regression to predict the residence time in a semicontinuous process

Plug flow bioreactor (PFB) used in solid state fermentation gives the possibility to have semicontinuous culture. However, it is complicated to follow a single particle during its residence inside the bioreactor and to therefore study precisely the culture process all along the device. In this study, semicontinuous production of fungal compounds was successfully obtained by cultivating Aspergillus niger with a PFB prototype. Kinetic productions of the same metabolites along the bioreactor were obtained at laboratory scale to predict the residence time of the particles inside the PFB from Partial Least Square (PLS). This original methodology allowed (1) the comparison between the production kinetics at the two production scales (pilot and laboratory) and (2) the observation of eventual changes following the scale-up of the process offering a good overall insight of the PFB performance.

Experimentation and CFD modeling of continuous degradation of formaldehyde by immobilized Ralstonia eutropha in a semi-pilot-scale plug flow bioreactor.

This study focuses on continuous formaldehyde (FA) biodegradation by Ralstonia eutropha immobilized on polyurethane foam in a semi-pilot-scale plug flow packed-bed bioreactor. The stepwise increasing of the influent FA concentration from 43.9 to 1325.1mgL-1 was studied in the bioreactor during 70days of operation. A complete removal of FA was achieved for inlet concentration up to 425.5mgL-1 and the initial specific biodegradation rate reached to its maximum value about 44.3mggcell-1h-1 at 425.5mgL-1. However, further increase of inlet concentration resulted in decrease of the biodegradation performance of the immobilized cells due to the inhibitory effect of FA on the enzymatic system involved in the biodegradation process. Based on kinetic modeling results, the Luong equation with the following constants could best describe the behavior of the bio-system: maximum specific FA biodegradation rate (qmax) of 124mggcell-1h-1, half-saturation constant (KS) of 337.2mgL-1, maximum degradable FA concentration (Smax) of 1582mgL-1, and shape factor (n) of 1.49. Also, three-dimensional simulation of the bioreactor was performed using an integrated computational fluid dynamics (CFD) approach that takes into account both the biokinetic constants of the immobilized system as well as the fluid properties under steady-state condition. Eulerian computations successfully anticipated the concentration gradients through the reactor for different inlet FA concentrations, and uniform vertical velocity pathlines and non-dispersed plug flow inside the reactor were verified by the presented velocity distribution and flow streamlines.

Nitrous oxide and methane emissions from a plug-flow full-scale bioreactor and assessment of its carbon footprint

Fugitive greenhouse gas (GHG) emissions in the form of nitrous oxide (N2O) and methane (CH4) have been reported from many different wastewater treatment plants. However, the majority of the current literature only reports emissions during short periods of time and only focuses on one of the two GHGs. In this study, N2O and CH4 emissions from the aerated parts of a plug-flow full-scale bioreactor treating municipal wastewater were studied over five months from November through March. A multiple gas hood collection system was used to simultaneously monitor the first three aerated compartments of the plug-flow bioreactor. Results show temporal variations in N2O emissions with N2O detected during November, no emissions during December and January, and a recovery of emissions from February onwards. In addition, different spatial emissions were found across the three aerated zones, with the highest N2O emissions detected in the second aerated zone. A daily N2O emission pattern was characterised by an N2O peak correlated with the ammonium that arrived in the monitored zone. However, CH4 emissions occurred during the whole monitored period and showed a spatial variability inside the plug-flow bioreactor, presenting the highest emissions in the first aerated zone and then decreasing in the two subsequent zones. In addition, the dynamic carbon footprint (C-footprint) of the bioreactor is presented in which the contribution of the direct and indirect emissions (related to electricity consumption) is assessed. Results show that CH4 emissions account for the majority of the direct emissions. Moreover, CH4 and N2O emissions represent approximately 60% of the total emissions (direct and indirect) originating from the bioreactors.

Simulation of Substrate, Microbial Interaction with Recycle using Matlab Computational Approach

This research outlines the microbial and substrate interaction in a plug flow bioreactor system for effective utilization of the substrate by the microorganism. To achieve this mathematical models were developed to monitor, predict and simulate the interaction characteristics of the bioreactor using the functional parameters for interaction of microbial and substrate concentration in a plug flow reactor system. The MATLAB computer program language was used to determine the interaction relationship between the substrate and microbial concentration upon the influence of bioreactor volume, space time and discharge time. The characteristics of the behavior in terms of decrease in substrate concentration with increase in microbial concentrate revealed the interaction in the bioreactor with recycle.

Improvement of sewage sludge dewaterability by bioleaching in a continuous plug flow bioreactor: optimization of process parameters.

A novel process for sewage sludge bioleaching by mixed Thiobacilli (Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans) using a 12-stage, 180 L working volume continuous plug-flow bioreactor, is presented. The objective of the present study was to assess the impact of some parameters on the sludge dewaterability and to improve the sludge dewaterability by optimization of these parameters. The parameters examined were sludge moisture content, nutrients dosage, aeration rate, and the number of reactors. The order of the influence of these factors on sludge dewaterability was found to be sludge moisture content > nutrients dosage > aeration rate > number of reactors. The optimized conditions were: sludge moisture content, 98.0%, nutrients dosage, 9 g/L, aeration rate, 8 m3/h, and 10 reactors. Confirmation experiments conducted under optimum conditions demonstrate the sludge dewaterability to be remarkably improved. After 2 days of bioleaching, the moisture of bioleached sludge cake was reduced to below 60%.

Toward Quantitative Understanding of the Bioavailability of Dissolved Organic Matter in Freshwater Lake during Cyanobacteria Blooming

Occurrence of cyanobacterial harmful algal blooms (CyanoHAB) can induce considerable patchiness in the concentration and bioavailability of dissolved organic matter (DOM), which could influence biogeochemical processes and fuel microbial metabolism. In the present study, a laboratory 4-stage plug-flow bioreactor was used to successfully separate the CyanoHAB-derived DOM isolated from the eutrophic Lake Taihu (China) into continuum classes of bioavailable compounds. A combination of new state-of-the-art tools borrowed from analytical chemistry and microbial ecology were used to characterize quantitatively the temporary evolution of DOM and to get deeper insights into its bioavailability. The results showed a total 79% dissolved organic carbon loss over time accompanied by depletion of protein-like fluorescent components, especially the relatively hydrophilic ones. However, hydrophilic humic-like fluorescent components exhibited bioresistant behavior. Consistently, ultrahigh resolution mass spectrometry (FTICR-MS) revealed that smaller, less aromatic, more oxygenated, and nitrogen-rich molecules were preferentially consumed by microorganisms with the production of lipid-like species, whereas recalcitrant molecules were primarily composed of carboxylic-rich alicyclic compounds. Moreover, the bioavailability of DOM was negatively correlated with microbial community diversity in the bioreactor. Results from this study provide deeper insights into the fate of DOM and relevant biogeochemical processes in eutrophic lakes.