Maximum Substrate Research Articles

Silica conversion of polysilazanes by low-temperature plasma jet generated from Ar and water-vapor mixed gas

Perhydropolysilazane (PHPS), which contains no organic catalyst, chemically reacts with H2O in the atmosphere by heating it at 450 °C for more than 1 h to turn it into a SiO2 film. If silica conversion can be achieved at temperatures below 100 °C, which plastics can withstand, it may be applicable to a wide range of applications, such as flexible electronics. Here, we report a technique for forming SiO2 films with leakage current characteristics very close to those of thermally oxidized (THOX) films that works at a very low temperature of 52 °C with high speed. Using a 9-kV, 30-kHz power supply, a low-temperature plasma jet containing a gas mixture of Ar and water vapor irradiated an 8 nm thick PHPS thin film, inducing silica conversion at a maximum substrate temperature of 52 °C. The current density-electric field strength (J-E) characteristics of metal oxide semiconductor capacitors fabricated with this SiO2 film showed characteristics very close to those of THOX films. In addition, the mechanism of silica conversion of PHPS through low-temperature plasma jet irradiation using this gas mixture was clarified in real-time FT-IR measurements.

Ideal performance assessment of non-recirculating anaerobic fluidized bed reactors treating low to high strength organic loads with low retention time

This study investigated the ideal performance of non-recirculating Anaerobic Fluidized Bed Reactors (AnFBRs) for treating organic wastewater of varying strengths under low Hydraulic Retention Time (HRT). Four 4.58 L AnFBRs were used to treat synthetic wastewater with an Organic Loading Rate (OLR) ranging from 4.50 to 40.11 gCOD/L-d, and HRT between 1.1 and 4.4 hours. The AnFBRs achieved high removal efficiencies ranging from 83 % to 96 % at steady state, except during the organic shock load, which reduced removal performance to 12 %. Shortened HRT conditions led to a decreasing trend in reactor pH due to an incomplete anaerobic cycle. The modified Stover-Kincannon model estimated the maximum substrate utilization rate of AnFBR's to be 196.08 gCOD/L-d, with a correlation coefficient of 0.98. Under shortended HRT, microbial diversity analysis identified predominant non-filamentous bacterial families, such as Streptococcaceae and Veillonellaceae, which collaborate during biofilm development in anaerobic environments. It was suggested that the porous media provided secure attachment sites for the biomass growth and biofilm formation under shock load and high shear force conditions. While these results offer valuable insights, further studies are needed to confirm these findings and enhance the understanding of the use porous media in non-recirculating AnFBRs.

High-Speed Stress Field Measurement In A Soft Substrate During Droplet Impact

In this study, we utilized high-speed photoelastic tomography to quantify dynamic stress fields within a soft substrate during droplet impact. This manuscript details the measurement technique, which employs a high-speed polarization camera and the principles of photoelastic tomography. Our method successfully enabled the quantitative measurement of dynamic stress fields in a soft substrate during droplet impact. Additionally, we conducted an analysis of the impact force derived through the spatial integration of the measured stress field. The discussion explored the interplay between the maximum impact force, droplet viscosity, and substrate elasticity. Our findings indicate that the maximum impact force 𝐹max can be expressed as a function with a self-similar variable of 𝑅𝑒 / 𝐶𝑎^2 , where 𝑅𝑒 is Reynolds number representing the droplet inertial force and droplet viscous force and 𝐶𝑎 is Cauchy number representing the ratio of the droplet inertial force and substrate elastic force. This combination, 𝑅𝑒 / 𝐶𝑎^2 , represents the relationship between the relaxation time of droplet and substrate deformation ( 𝜂/ 𝐸), the contact time of the droplet (𝑅 / 𝑉), and the ratio of substrate elastic force to droplet inertial force. Consequently, the maximum impact force 𝑅𝑒 / 𝐶𝑎^2 is determined by the balance between the relaxation and contact times. We believe that our developed method will significantly enhance the understanding of droplet impact phenomena. Furthermore, it holds potential for broader applications in various engineering processes, such as analyzing stress distribution in materials caused by liquid jet impact and studying cavitation bubbles in viscoelastic materials. This method's ability to provide detailed quantitative measurements of dynamic stress fields offers a valuable tool for future research and technological advancements in related fields.

Numerical Study on Simulating the Deposition Process of Cold Spray Multi-Particle Al-6061 based on CEL Method

Cold spray is a solid-state deposition technique that improves the performance of part surfaces. Most scholars use the CEL framework to simulate the deposition of single particles on the substrate; Single particle depositions cannot fully characterize coating conditions. This article proposes to use the CEL method to simulate the deposition process of cold spray multi-particles on the Al6061 substrate. A multi-particle wrapped model is nested in a deposition model created by CEL to simulate the cold spray multi-particle deposition process. The Euler-Lagrangian method has the characteristics of high accuracy and robustness, and was selected as the method for multi-particle deposition model simulation; The CEL framework is a feasible method to simulate the actual cold spray multi-particle deposition process. The results show that the CEL framework can simulate the deposition of cold sprayed Al6061 multi-particles on the Al6061 substrate, observe the EVF Void value of the coating, and monitor the porosity of the coating after deposition. It is observed that the maximum substrate surface temperature after deposition is 528.2K and is located at the junction of particle and particle impact; By analyzing the temperature change curve of five points collected on the substrate over time, the curve appears multiple inflection points, indicating that heat transfer occurs between the particles and the substrate during the deposition process; the substrate first heats up and then cools down. During the multi-deposition process, the particles undergo plastic deformation and continuously squeeze the coating, thereby achieving interconnection between the particles and the substrate; Mechanical interlocking between particles forms a coating.

Efficient sulfide and methane removal in anaerobic secondary effluent using a pilot-scale membrane-aerated biofilm reactor

Anaerobic secondary treatment can enable energy-efficient removal of organic matter but may produce effluent containing dissolved methane and sulfide that must be managed before discharge or reuse. In this study, we operated a Membrane-aerated Biofilm Reactor (MABR) to achieve reliable removal of dissolved sulfide and methane from anaerobic secondary effluent at pilot-scale. The pilot-scale MABR was equipped with gas permeable polymethyl pentene (PMP) membranes, promoting surface growth of aerobic biofilm via diffusion-based aeration (lumen-to-surface diffusion). The system treated anaerobic secondary effluent from a demonstration-scale anaerobic membrane bioreactor (AnMBR) processing 90 m3/d primary effluent. MABR influent flow rate was increased from 8.2 to 32.7 m3/d to elevate substrate loading rates to the biofilm. The MABR consistently achieved >99 % removal of sulfide and dissolved methane, even at the maximum substrate loading rate: 2.3 g-S/m2/d for sulfide and 2.5 g-CH4/m2/d for dissolved methane. Despite effective sulfide and methane removal, incomplete nitrification (<25 % ammonia removal) occurred, with a portion of ammonia converted into nitrous oxide (N2O), a greenhouse gas 298 times more potent than CO2. Operating the MABR incurred low energy costs: 0.01 to 0.05 kWh/m3 for the compressor supplying air to the membrane lumen and 0.01 kWh/m3 for the influent pump. An in-depth mass balance of N2O emissions from the MABR revealed that N2O was subject to counter-diffusion (surface-to-lumen diffusion) in which >99 % of the N2O produced within the biofilm was recovered in off-gas from the gas permeable membranes (hollow fibers).

Kinetics of microbial cell growth, utilization of organic substrates and methane production in upflow anaerobic filters in two and three separated stages treating sanitary landfill leachates

AbstractThis paper deals with the kinetics of microbial cell growth, utilization of organic substrates and methane production in upflow anaerobic filters in two and three separated stages (UAF‐2SS and UAF‐3SS) treating sanitary landfill leachates, under three temperatures (20, 27, and 34°C), fed with volumetric organic loads (VOLs) for UAF‐2SS (1.8, 2.25, 2.76, 3.45, 3.71, 4.64 kgCOD (chemical oxygen demand)/m3/d) and UAF‐3SS (1.7, 2.25, 2.44, 2.6, 3.15, 3.45, 3.5, 4.57, 4.64, 6.31, 11.61, 14.18, 17.48 kgCOD/m3/d). Kinetic parameters were obtained at temperature (20–34°C), pH (8.8–9.1), each one of three stages within the UAF‐2SS and UAF‐3SS reactors containing methanogenic bacteria (Methanococcus sp., and Methanobacterium sp.) and Clostridium sp.: Maximum substrate utilization rate (rm,s) resulted in 102 mg COD/L/h, maximum microbial cell growth rate (μm) varied 102–103 CFU (colony forming units)/mL/h, methane (CH4) production rate (rm,CH4) tended to vary 100–101 mg CH4/d and the maximum production coefficient (Y) varied 0–102 CFU/mL/h/mgCOD/L/h.

Methane yield response to pretreatment is dependent on substrate chemical composition: a meta-analysis on anaerobic digestion systems

Proper pretreatment of organic residues prior to anaerobic digestion (AD) can maximize global biogas production from varying sources without increasing the amount of digestate, contributing to global decarbonization goals. However, the efficiency of pretreatments applied on varying organic streams is poorly assessed. Thus, we performed a meta-analysis on AD studies to evaluate the efficiencies of pretreatments with respect to biogas production measured as methane yield. Based on 1374 observations our analysis shows that pretreatment efficiency is dependent on substrate chemical dominance. Grouping substrates by chemical composition e.g., lignocellulosic-, protein- and lipid-rich dominance helps to highlight the appropriate choice of pretreatment that supports maximum substrate degradation and more efficient conversion to biogas. Methane yield can undergo an impactful increase compared to untreated controls if proper pretreatment of substrates of a given chemical dominance is applied. Non-significant or even adverse effects on AD are, however, observed when the substrate chemical dominance is disregarded.

Assessment of microbial population in integrated CW-MFC system and investigation of organics and fecal coliform removal pathway

The current study is focused on understanding the operational mechanism of an integrated constructed wetland-microbial fuel cell (CW-MFC) reactor emphasizing fecal coliform (FC) removal. Few studies are available in the literature investigating the inherent mechanisms of pathogen inactivation in a CW-MFC system. Raw domestic wastewater was treated in three vertical reactors, one planted constructed wetland (R1), one planted CW-MFC (R2), and one unplanted CW-MFC (R3). Spatial analysis of treated effluents showed a considerable amount of organics and fecal coliform removal at the vicinity of the anode in R2. Assessment of the microbial population inside all the reactors revealed that EABs (Firmicutes, Bacteroidetes, and Actinobacteria) were more abundant in R2 compared to R1 and R3. During the activity study, biomass obtained from R2 showed a maximum substrate utilization rate of 1.27 mg COD mgVSS−1 d−1. Kinetic batch studies were carried out for FC removal in all the reactors, and the maximum first order FC removal rate was obtained at the anode of R2 as 2.13 d−1 when operated in closed circuit mode. This value was much higher than the natural die-off rate of FCs in raw wastewater which was 1.16 d−1. Simultaneous bioelectricity monitoring inferred that voltage generation can be correlated to faster FC inactivation, which was probably due to EABs outcompeting other exogenous microbes in a preferable anaerobic environment with the presence of an anode. Reactor R2 was found to be functioning as a symbiotic bio-electrochemical mesocosm.

Does pre-enrichment of anodes with acetate to select for Geobacter spp. enhance performance of microbial fuel cells when switched to more complex substrates?

Many factors affect the performance of microbial fuel cells (MFCs). Considerable attention has been given to the impact of cell configuration and materials on MFC performance. Much less work has been done on the impact of the anode microbiota, particularly in the context of using complex substrates as fuel. One strategy to improve MFC performance on complex substrates such as wastewater, is to pre-enrich the anode with known, efficient electrogens, such as Geobacter spp. The implication of this strategy is that the electrogens are the limiting factor in MFCs fed complex substrates and the organisms feeding the electrogens through hydrolysis and fermentation are not limiting. We conducted a systematic test of this strategy and the assumptions associated with it. Microbial fuel cells were enriched using three different substrates (acetate, synthetic wastewater and real domestic wastewater) and three different inocula (Activated Sludge, Tyne River sediment, effluent from an MFC). Reactors were either enriched on complex substrates from the start or were initially fed acetate to enrich for Geobacter spp. before switching to synthetic or real wastewater. Pre-enrichment on acetate increased the relative abundance of Geobacter spp. in MFCs that were switched to complex substrates compared to MFCs that had been fed the complex substrates from the beginning of the experiment (wastewater-fed MFCs - 21.9 ± 1.7% Geobacter spp.; acetate-enriched MFCs, fed wastewater - 34.9 ± 6.7% Geobacter spp.; Synthetic wastewater fed MFCs – 42.5 ± 3.7% Geobacter spp.; acetate-enriched synthetic wastewater-fed MFCs - 47.3 ± 3.9% Geobacter spp.). However, acetate pre-enrichment did not translate into significant improvements in cell voltage, maximum current density, maximum power density or substrate removal efficiency. Nevertheless, coulombic efficiency (CE) was higher in MFCs pre-enriched on acetate when complex substrates were fed following acetate enrichment (wastewater-fed MFCs – CE = 22.0 ± 6.2%; acetate-enriched MFCs, fed wastewater – CE =58.5 ± 3.5%; Synthetic wastewater fed MFCs – CE = 22.0 ± 3.2%; acetate-enriched synthetic wastewater-fed MFCs – 28.7 ± 4.2%.) The relative abundance of Geobacter ssp. and CE represents the average of the nine replicate reactors inoculated with three different inocula for each substrate. Efforts to improve the performance of anodic microbial communities in MFCs utilizing complex organic substrates should therefore focus on enhancing the activity of organisms driving hydrolysis and fermentation rather the terminal-oxidizing electrogens.

Numerical study of combined phase change material and water cooling in hybrid wavy microchannels for HCPV cell

HCPV cells are known for their high efficiency in converting sunlight into electricity. However, this increased efficiency also generates higher levels of heat, posing a risk of cell damage. Therefore, the study proposes the combination of a phase change material (CPCM) and liquid flow in hybrid wavy microchannels to ensure stable temperature within the high-concentration photovoltaic (HCPV) cells. A three-dimensional numerical model has been developed to capture the thermal behavior of PCM integrated with water cooling in a microchannel heat sink. The comparison and analysis involved contrasting cases with phase change material (PCM) and cases without PCM. The PCM cases were studied at Reynolds number (Re) 100, while the cases without PCM were investigated at Reynolds numbers of 100 and 200. Three distinct types of PCM were employed, specifically OM 32, Rt 35, and PA - SA/EG. The various microchannel geometries under consideration included Raccoon, wavy, and hybrid wavy microchannels. The results showed that using both PCM and water cooling in a microchannel is preferable over using only water cooling. The outcomes reveal that employing PCM 3 (CPCM) in conjunction with the raccoon wavy microchannel design, there is an 11.61% reduction in the maximum pressure drop, along with a decrease of 6.58% in the maximum solid substrate temperature. Moreover, this configuration attains the highest electrical efficiency, reaching 39.32%.

Growth kinetics of lead resistant Bacillus infantis isolated from battery industry waste

The current investigation presents an innovative approach to address the challenge of removing heavy metal lead from industrial waste through advanced biological remediation techniques. By amalgamating theoretical insights with empirically acquired data, this research endeavours to develop efficient bioreactor strategies suitable for large-scale applications. Initially, bacteria naturally endowed with lead resistance has been isolated from a native source. Extensive microbiological assessments, including a 16S rDNA study, verified the identity of the lead-resistant bacterial cells as Bacillus infantis 4352-1T. In order to evaluate the efficacy of Bacillus infantis 4352-1T for lead removal an attempt has been made to study the growth dynamics of Bacillus infantis 4352-1T cells in batch mode, using lead amended selective media. It has been observed that Monod's equation effectively defined the cell growth behaviour within the lead concentration range of 0.05–0.25 kg lead/m3. Notably, the experiment was also facilitated the derivation of essential intrinsic kinetic parameters, such as the maximum specific cell growth rate (0.0237 h−1) and substrate saturation constant (0.018 kg/m3). Beyond lead concentrations of 0.25 kg lead/m3, up to 0.43 kg lead/m3, it has also been observed the pronounced influence of substrate inhibition which is quantitatively elucidated by the Haldane equation.

A Hybrid Ultrasonic Membrane Anaerobic System (UMAS) Development for Palm Oil Mill Effluent (POME) Treatment

The high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) levels in palm oil mill effluent (POME) wastewater make it an environmental contaminant. Moreover, conventional POME wastewater treatment approaches pose economic and environmental risks. The present study employed an ultrasonic membrane anaerobic system (UMAS) to treat POME. Resultantly, six steady states were procured when a kinetic assessment involving 11,800–21,700 mg·L−1 of mixed liquor suspended solids (MLSS) and 9800–16,800 mg·L−1 of mixed liquor volatile suspended solids (MLVSS) was conducted. The POME treatment kinetics were explained with kinetic equations derived by Monod, Contois and Chen and Hashimoto for organic at loading rates within the 1–11 kg·COD·m−3·d−1 range. The UMAS proposed successfully removed 96.6–98.4% COD with a 7.5 day hydraulic retention time. The Y value was 0.67 g·VSS/g·COD, while the specific micro-organism decay rate, b was 0.24 day−1. Methane (CH4) gas production ranged from 0.24 to 0.59 litres per gram of COD daily. Once the initial steady state was achieved, the incoming COD concentrations increased to 88,100 mg·L−1. The three kinetic models recorded a minimum calculated solids retention time of 12.1 days with maximum substrate utilization rate, K values ranging from 0.340 to 0.527 COD·g−1·VSS·d−1 and maximum specific growth rate, µmax from 0.248 to 0.474 d−1. Furthermore, the solids retention time (SRT) was reduced from 500 to 12.1 days, resulting in a 98.4% COD level reduction to 1400 mg·L−1.

Pseudomonas aeruginosa based concurrent degradation of beta-cypermethrin and metabolite 3-phenoxybenzaldehyde, and its bioremediation efficacy in contaminated soils

Beta-cypermethrin is one of the widely used pyrethroid insecticides, and problems associated with the accumulation of its residues have aroused public attention. Thus, there is an urgent need to effectively remove the beta-cypermethrin that is present in the environment. Biodegradation is considered a cost-effective and environmentally friendly method for removing pesticide residues. However, the beta-cypermethrin-degrading microbes that are currently available are not optimal. In this study, Pseudomonas aeruginosa PAO1 was capable of efficiently degrading beta-cypermethrin and its major metabolite 3-phenoxybenzaldehyde in water/soil environments. Strain PAO1 could remove 91.4% of beta-cypermethrin (50 mg/L) in mineral salt medium within 120 h. At the same time, it also possesses a significant ability to metabolize 3-phenoxybenzaldehyde—a toxic intermediate of beta-cypermethrin. The Andrews equation showed that the maximum substrate utilization concentrations of beta-cypermethrin and 3-phenoxybenzaldehyde by PAO1 were 65.3558 and 49.6808 mg/L, respectively. Box–Behnken design-based response surface methodology revealed optimum conditions for the PAO1 strain-based degradation of beta-cypermethrin as temperature 30.6 °C, pH 7.7, and 0.2 g/L inoculum size. The results of soil remediation experiments showed that indigenous micro-organisms helped to promote the biodegradation of beta-cypermethrin in soil, and beta-cypermethrin half-life in non-sterilized soil was 6.84 days. The bacterium transformed beta-cypermethrin to produce five possible metabolites, including 3-phenoxybenzyl alcohol, methyl 2-(4-hydroxyphenoxy)benzoate, diisobutyl phthalate, 3,5-dimethoxyphenol, and 2,2-dimethyl-1-(4-phenoxyphenyl)propanone. Among them, methyl 2-(4-hydroxyphenoxy)benzoate and 3,5-dimethoxyphenol were first identified as the intermediate products during the beta-cypermethrin degradation. In addition, we propose a degradation pathway for beta-cypermethrin that is metabolized by strain PAO1. Beta-cypermethrin could be biotransformed firstly by hydrolysis of its carboxylester linkage, followed by cleavage of the diaryl bond and subsequent metabolism. Based on the above results, P. aeruginosa PAO1 could be a potent candidate for the beta-cypermethrin-contaminated environmental bioremediation.

Microbial Reductive Dechlorination by a Commercially Available Dechlorinating Consortium Is Not Inhibited by Perfluoroalkyl Acids (PFAAs) at Field-Relevant Concentrations.

Perfluoroalkyl acids (PFAAs) have been shown to inhibit biodegradation (i.e., organohalide respiration) of chlorinated ethenes. The potential negative impacts of PFAAs on microbial species performing organohalide respiration, particularly Dehalococcoides mccartyi (Dhc), and the efficacy of in situ bioremediation are a critical concern for comingled PFAA-chlorinated ethene plumes. Batch reactor (no soil) and microcosm (with soil) experiments, containing a PFAA mixture and bioaugmented with KB-1, were completed to assess the impact of PFAAs on chlorinated ethene organohalide respiration. In batch reactors, PFAAs delayed complete biodegradation of cis-1,2-dichloroethene (cis-DCE) to ethene. Maximum substrate utilization rates (a metric for quantifying biodegradation rates) were fit to batch reactor experiments using a numerical model that accounted for chlorinated ethene losses to septa. Fitted values for cis-DCE and vinyl chloride biodegradation were significantly lower (p < 0.05) in batch reactors containing ≥50 mg/L PFAAs. Examination of reductive dehalogenase genes implicated in ethene formation revealed a PFAA-associated change in the Dhc community from cells harboring the vcrA gene to those harboring the bvcA gene. Organohalide respiration of chlorinated ethenes was not impaired in microcosm experiments with PFAA concentrations of 38.7 mg/L and less, suggesting that a microbial community containing multiple strains of Dhc is unlikely to be inhibited by PFAAs at lower, environmentally relevant concentrations.

Particle-based approach for modeling phase change and drop/wall impact at thermal spray conditions

The ability to model the impact of small, high-velocity molten droplets on a cold substrate is a key to designing the thermal spray process. Such drop-wall interactions involve complex phenomena such as droplet splash, phase change, solidification, substrate melting, and re-solidification. In this study, a particle-based approach, Smoothed Particle Hydrodynamics (SPH), is used to simulate the impact of molten droplets on a cold substrate at the thermal spray conditions, i.e., small droplets with high temperature and velocities. A solidification model is developed to simulate the phase change of the droplet and substrate. The present SPH method is validated against the experimental results using tin droplets on stainless-steel and aluminum substrate, and copper droplet on copper substrate. The histories of the spread factor, the substrate temperature, and the splat height at the impingement point are validated. A parametric study on the impact of the high melting point molybdenum droplets on different substrate materials (including tin, stainless steel, zinc, yttrium stabilized zirconia, and aluminum) is performed. The temporal evolution of the solidification interface and the height/thickness of the solidified splat are reported. Temperature distributions across the splat, substrate, and the corresponding melting/re-solidification are investigated. It was found that the cooling rates for the same impingement velocity were nearly the same for the same substrate regardless of the initial substrate temperatures but were higher for higher impingement velocities. A modified Biot number and thermal diffusivity were used to describe the heat transfer characteristics of the splat substrate combination. Results show that a higher modified Biot number for the splat-substrate combination indicates a faster cooling of the splat and a higher maximum substrate temperature. Furthermore, a substrate with high thermal diffusivity also causes heat at the impingement location to be dissipated quickly, resulting in a fast-cooling rate and accelerated solidification.

Screening and evaluation of phenol utilization and growth in Acinetobacter baumannii W29 of wastewater

Phenols are ubiquitous pollutants, mainly from industrial effluent, causing pollution of natural water resources. The research focused on screening efficient phenol-degrading bacteria and kinetic modelling of phenol biodegradation and growth. Membrane filtration was used for the isolation of bacteria from the wastewater sample. The screening of phenol-degrading bacteria was based on the efficiency of phenol utilization. The strain with efficient phenol degradation capacity was characterized by 16S rDNA sequencing and designated Acinetobacter baumannii W29. Biomass growth and phenol utilization rate of the strain were evaluated at different initial phenol concentrations (100-800 mgL-1). Specific growth rate data were fitted to five models, i.e. Monod, Haldane, Aiba, Teisser, and Webb model. The yield coefficient at different initial phenol concentrations was calculated from the slope of the specific growth rate (μ) versus the specific phenol utilization rate (q). The strain showed complete phenol degradation potential up to 1000 mgL-1. The maximal growth rate was achieved at 400 mgL-1 , which coincided with the maximum substrate utilization rate at the same concentration. The specific growth rate showed the best fit with the Haldane model. The strain had a yield coefficient of 0.70 (mg cell mg-1 phenol). The value of µ and Ks revealed the affinity of the strain for high-concentration phenol and the its ability to withstand high phenol concentrations. The kinetic growth behaviour of the strain fitted well with the Haldane model. The findings of the study could be applied to wastewater treatment with a high phenol load.

Simultaneous real-time estimation of maximum substrate uptake capacity and yield coefficient in induced microbial cultures

In this work we present a soft sensor to accurately estimate the yield coefficient YX/S and the substrate uptake capacity qSmax in a cultivation process using offgas measurements and a nonlinear state observer with an underlying mechanistic model. The structural observability analysis of the mechanistic model showed that both parameters are observable given the available measurement information. In different simulation scenarios we analyzed under which conditions an accurate estimation is possible when measurements are uncertain. Testing the proposed soft sensor in-silico showed that qSmax and YX/S can be estimated with reasonable accuracy depending on the parameter sensitivity. Verification of the developed state and parameter estimation was carried out in induced Escherichia coli cultivations. Besides accurate prediction of living biomass, and substrate accumulation, decreasing YX/S and qSmax could be detected. Therefore, the developed soft sensor can be used to control induced cultures and to prevent overfeeding situations.

Response of dissimilatory perchlorate reducing granular sludge (DPR-GS) system to high-strength perchlorate and starvation stress in UASB reactor: Performance, kinetics and recovery mechanism

Under high-strength perchlorate concentration ranging from 300 to 1300 mg/L, the dissimilatory perchlorate reducing granular sludge (DPR-GS) was successfully cultivated in an up-flow anaerobic sludge blanket (UASB) reactor to investigate performance and starvation recovery for treating perchlorate wastewater. The mature DPR-GS had excellent perchlorate removal efficiency (98.47%) at 1200 mg/L. Microbial community analysis suggested that the dominant genera in mature DPR-GS were Sulfurospirillum and Acinetobacter. The DPR-GS system conformed well to the modified Stover-Kincannon model with the maximum substrate utilization (Umax) of 90.01 kg/(m3·d) and the saturation value constant (KB) of 83.93 kg/(m3·d). Additionally, the starvation recovery of DPR-GS system was first investigated. The perchlorate removal efficiency recovered to 91.39% after 8 days under the 30-day starvation stress, and the microbial activity also recovered to normal condition. The three-dimensional excitation-emission matrix (3D-EEM) proved that the tryptophan-like component in extracellular polymeric substance (EPS) increased during the starvation period, which was associated with immune functions and played an important role in maintaining the microbial activity. Meanwhile, the secretion of humic acid-like component in EPS promoted electron transfer efficiency, thus improving microbial metabolic activity during the recovery period. Further analysis by the parallel factor (PARAFAC) of 3D-EEM confirmed that the decrease of immune substances and the increase of metabolic products in EPS during the starvation recovery period, which enhanced the recovery of microbial activity and the improvement of perchlorate removal performance. This study revealed the response of the DPR-GS system to high-strength perchlorate and starvation stress, thus provided a further basis of perchlorate tolerance and starvation recovery for the application of DPR-GS system to remove high-strength concentrated perchlorate from contaminated water.

Determination of biokinetic coefficients of an aerobic system for potato starch removal

This study presents an aerobic laboratory scale-reactor completely mixed performance for starch wastewater treatment. The reactor was operated for 119 days divided into 5 operational phases which included the start-up and the variation of cell-residence time. In order to determine the biokinetic coefficients for starch removal, the cell-residence time was varied between 20 to 4 days, and the system operation was set hydraulic retention time of 24 hours with a completely mixed reactor setup. The chemical oxygen demand concentration was 1000mg/L in the inflow of the reactor and dissolved oxygen remained above 2mg/L. In this experimentation time, the parameters such as pH, chemical oxygen demand (in the influent and effluent), dissolved oxygen and Mixed liquor suspended solids were monitored. The calculation of biokinetic constants was done by an approximate method, using the graphical Lineweaver-Burk method. The biokinetic coefficients determined were for Maximum substrate removal rate , Half saturation rate constant or affinity constant ( sludge yield coefficient (Y), and Microbial decay or indigenous respiration rate . The results showed that Y, , and ( were in the range of 0,3- 0,7 mgSSV/mgBOD5, 2- 8 Day1 and 40-120 mg/L (COD- BOD5), respectively. Values of the coefficients were within the range of those reported for conventional activated sludge processes.

Nonius approach for Si1-xGex/Si(0 0 1) epitaxy characterization

In Si(001)\\(Si1-xGex 6–8 nm + Si 100–120 nm) × 2 (0.07 ≤ x ≤ 0.21) structures, grown by MBE on dislocation-free substrates and considered as nonius systems, X-ray reflectometry and diffraction on the reflection (004) revealed second period thickness decreasing compared to the first one due to misfit energy increasing. Electron microscopy of the same samples confirms the smaller thickness of the second period. Three-waves diffraction on the forbidden reflection (002) was applied to compare the structural perfection in two azimuthal directions 〈110〉: along the maximum substrate misorientation from the plane (001) and in the perpendicular direction. In the same sample with reduced photoluminescence quantum yield, it was found that the average period value determined by reflectometry (109.5 nm) was larger than that determined by diffraction on the reflection (004) (97.5 nm), and the angular distance between satellites on curves (002) corresponded to two different period values: 109.5 nm and 102 nm. Misfit dislocations are absent in the studied samples. This suggests both possible appearance of noncrystallographic defects in strained epitaxial layers and only effective thickness values corresponding to perfect structure fragments which are determined by X-ray diffraction.