Lag Phase Time Research Articles

Improvement of biomethane potential of sewage sludge anaerobic co-digestion by addition of “sherry-wine” distillery wastewater

Abstract Co-digestion of sewage sludge (SS) with other unusually treated residues has been reported as an efficient method to improve biomethane production. In this work, Sherry-wine distillery wastewater (SW-DW) has been proposed as co-substrate in order to increase biomethane production and as a breakthrough solution in the management of both types of waste. In order to achieve this goal, different SS:SW-DW mixtures were employed as substrates in Biomethane Potential (BMP) tests. The biodegradability and biomethane potential of each mixture was determined selecting the optimal co-substrate ratio. Results showed that the addition of SW-DW as a co-substrate improves the anaerobic digestion of SS in a proportionally way in terms of CODs and biomethane production The optimal co-substrates ratio was 50:50 of SS:SW-DW obtaining %VSremoval = 54.5%; YCH4 = 225.1 L CH4/kgsv or 154 L CH4/kgCODt and microbial population of 5.5 times higher than sole SS. In this case, %VSremoval = 48.1%; YCH4 = 183 L CH4/kgsv or 135 L CH4/kgCODt. The modified Gompertz equation was used for the kinetic modelling of biogas production with successful fitting results (r2 = 0.99). In this sense, at optimal conditions, the maximum productivity reached at an infinite digestion time was ( Y CH 4 MAX ) = 229 ± 5.0 NL/kgSV; the specific constant was K = 25.0 ± 2.3 NL/kgSV·d and the lag phase time constant was (λ) = 2.49 ± 0.19.

Combining Ionizing Irradiation and Ultrasound Technologies: Effect on Beans Hydration and Germination.

The present work studied, for the first time, the effect of two technologies on the hydration and germination process of beans: ionizing irradiation and ultrasound. In addition, this work proposed a possible biological effect of ultrasound to describe its effect on grain hydration. Carioca beans were irradiated at doses of 2.3 and 3.8 kGy using γ-rays, establishing different metabolic activities for the beans. Then, they were hydrated with and without the ultrasound technology (91 W/L and 25 kHz) at 25°C. Both the hydration and germination kinetics were evaluated considering the application of both technologies alone and in combination. As results, irradiation did not significantly affect (P>0.05) the hydration rate, the equilibrium moisture, or the lag phase time, but ultrasound affected them, reducing 50% of the processing time. On the other hand, only the equilibrium moisture was slightly reduced by the interactive effect of irradiation and ultrasound technology, which was discussed based on different metabolism levels. Furthermore, the germination process of carioca bean was hindered by both the studied variables, reducing its germination capacity to 0% in some cases. Therefore, by studying the effect of ultrasound on beans with different active metabolism (due to different irradiation doses), it was suggested that both physical and biological mechanisms are involved during hydration process and that both can be affected by ultrasound. Further, irradiation could be used on carioca beans with objectives such as avoid germination, insects, and microorganism's growth, without an important effect on the hydration kinetics. PRACTICAL APPLICATION: Ultrasound technology has demonstrated to accelerate the soaking process of several legume grains. However, sometimes, grains are irradiated for disinfestation purpose to improve their shelf life. Indeed, irradiation can change the grain properties as the cooking time, hydration time, and germination capacity. Therefore, this work verified if irradiation changes the desirable effect of ultrasound on grain processing: soaking and germination. Moreover, this work novelty is also based on describing the phenomena: by proposing a possible biological effect, further approaches to improve the grain processing can be achieved.

Influence of pH controlling on fermentation performance in kitchen waste and cow manure

ABSTRACT In order to make the process more sustainability and more efficient in co-digestion of kitchen waste (KW) and cow manure (CM), the effect of pH controlling at initial fermentation time (I), first gas stagnation time (A), and combination of both times (C) were investigated. Five pH values (6.5, 7.0, 7.5, 8.0 and 8.5) were set in each case to find out the optimal way of pH regulation with the consideration of changes in biogas and methane production, volatile solid (VS) reduction, and lag-phase time. The results show that adjusting pH of the co-digestion system could significantly improve biogas production except when pH was set to 6.5 in groups I and A. Adjusting pH twice (group C) could increase the system stability. When pH value was set to 7.5 twice, highest methane production (16501.10 mL), the highest methane yield of 287.64 mL/g VSadded, and a relatively short lag-phase time (27.3d) were obtained by C7.5.

Bioprocess Evaluation of Petroleum Wastewater Treatment with Zinc Oxide Nanoparticle for the Production of Methane Gas: Process Assessment and Modelling.

The process evaluation of zinc oxide nanoparticle (ZnO NP) was added to enhance the degradation of petroleum wastewater (PWW) fermentation system with different mixing ratios for enhancing methane production. The results showed that the highest methane yield and total solids (TS) removal ratio reached 485mL/g-VS L PWW added and 81.9% at the ZnO NPg-VS L PWW ratio of 4.5:15, respectively. The proposed model CO2 sequester 545mL CO2/L PWW, production rate 750mL CH4 g-VS L PWW/h, and CH4 yield was 4.85L CH4 g-VS L PWW at 4.5:15 of ZnO NPg-VS L PWW. The kinetic analysis indicated that the modified Gompertz model best fitted the actual evolution of methane yields, as evidenced by the low root mean square prediction error (RMSPE) as well as high correlation difference between (Diff.%) the predicted and actual values. The parameters analyses were highlighted that the PWW digestion with ZnO NP substantially enhanced the hydrolysis rate (khyd), methanogenesis potential (fd), lag phase time h (λ), and methane production rate (Rm) of PWW. The evolution of soluble metabolites, utilization of ZnO NP and carbohydrates were also improved by co-fermentation.

Dark fermentative hydrogen production from food waste: Effect of biomass ash supplementation

This work aimed to investigate the effects of supplementing two distinct types of ash, namely fly ash (FA) and bottom ash (BA) on the dark fermentation (DF) process of food waste (FW) for H2 production. Both types of biomass combustion ash (BCA) were collected in an industrial bubbling fluidized bed combustor, using residual forest biomass as fuel. Results indicated that adding BCA at different doses of 1, 2 and 4 g/L could effectively enhance H2 generation when compared to the control test without BCA addition. This stimulatory effect was attributed to the crucial role of metal elements released from BCA such as sodium, potassium, calcium, magnesium, and iron in the provision of buffering capacity and inorganic nutrients for the functioning of hydrogen-forming bacteria. The highest H2 yield of 169 mL per g of volatile solids (VS) were obtained by adding only a small amount of BA (1 g/L) to the reactive system, representing a significant increment of 1070% compared to the control reactor. Furthermore, a significant decrease in the bacterial lag phase time from 26 h to 2.7 h, as well as about a 12-fold increase in the energy recovery as H2 gas was observed at BA dosage of 1 g/L in comparison with the control reactor. Overall, this study suggested that a proper addition of BCA could promote the DF process of FW and enhance biohydrogen production.

NONLINEAR BEHAVIOR AND THERMAL DAMAGE OF THERMAL LAGGING IN CONCENTRIC LIVING TISSUES SUBJECTED TO GAUSSIAN DISTRIBUTION SOURCE

The effects of thermal lagging with high-order became essential to describe non-equilibrium heating in tissues. This paper studies the temperature rise behavior in living tissues theoretically during the treatment by magnetic tumor hyperthermia based on the non-linear form of the dual-phase-lag model. Experimentally, it was found that the concentration of magnetic particles is in Gaussian distribution through the radial direction when magnetic fluid is injected into the living tissue space. Hence, the governing partial differential equation in concentric spherical space is solved in the Laplace transform domain. Some comparisons between the non-linear and linear effects of phase-lag time’s parameters on bio-heat transfer have been studied and discussed. The thermal damage quantity for the tumor has been calculated with different values of the phase-lag times. The results show that the nonlinear and linear effects of phase-lag times on bio-heat transfer have significant effects on the tumor, the tissue, and the thermal damage quantity.

Coupling energy-production processes: The use of residues from bioethanol production to improve the anaerobic digestion of corn stover

Currently, industry is migrating towards sustainable practises, where the wastes produced in one process are used as feedstock for other productive purposes. In the present study, we show that a by-product from the fabrication of second-generation bioethanol can be used to improve the production of biogas from corn stover. The washing water generated during the pretreatment stage of bioethanol production was recovered and reused as a co-substrate for the anaerobic digestion of corn stover. This water contained high concentrations of lignocellulolytic enzymes that once added to the digester improved the methane production kinetics. In comparison with digestion in the absence of these extra enzymes, the ultimate methane yield (P) increased 42%, with a reduction in the lag-phase time (λ) of 67% and an increase in the methane production rate (Rm) of almost 30%. These results were compared with those obtained during the co-digestion of corn stover and cattle manure, which is a well-known strategy to improve methane yields from lignocellulosic residues. However, despite the fact that the use of cattle manure improved methane yields, the results obtained using the enzyme-rich washing water were significantly better. The present study describes a simple strategy for the revalorisation of a by-product from the production of second-generation bioethanol.

Investigation of the effects of different conductive materials on the anaerobic digestion

In recent years, the efforts of enhancement of the transformation of organic matter into methane have intensified and direct interspecies electron transfer (DIET) mechanisms have great importance in this regard. In this study, magnetite, graphite powder, activated carbon and iron (II) sulfate were used to investigate DIET mechanisms during the conversion of glucose into methane. Obtained methane gas measurements at the end of the 30-day incubation period (37 ± 1 °C) were evaluated with the modified Gompertz model, first-order kinetic model and two-stage first-order kinetic model. Maximum total and soluble COD removal efficiencies were observed in the magnetite-added R2 reactor (73.75% and 90.68%, respectively). While there was no significant difference in terms of cumulative methane gas measurements, a significant decrease was observed in the lag phase time for the magnetite-added R2 reactor (reduced by half) with regard to the modified Gompertz model. According to the first-order kinetic model, the maximum conversion rate of glucose into methane and the peak methane production rate were observed in the graphite powder-added R3 reactor (k = 0.1744 day−1 and 93 mL/day). According to the two-stage kinetic model, the maximum methanation rate was observed in the magnetite-added R2 reactor (k2 = 0.7223 day−1). The sludge in the magnetite-added R2 reactor has best settleability (SVI = 53.4 mL/g).

MODELAMIENTO DE CRECIMIENTO MICELIAL DE CEPAS PARENTALES, HÍBRIDAS Y RECONSTITUIDAS DE Pleurotus Y Lentinula

The kinetics of mycelial growth of parental strains, hybrid and reconstituted of Pleurotus and Lentinula was calculated using the mycelial growth diameter for (malt extract agar) MEA and for wheat grain was determinate using the mycelial growth volume, the parameters were adjusted to 3 nonlinear models (Baranyi, Exponential, Logistic) and one Linear Model to determine the specific growth speed (μmax) and lag phase time (λ). The hybrid and reconstituted strains of Pleurotus spp. and Lentinula showed similar mycelial morphology with exception of the hybrid PD4xLC3. The mycelial kinetics of the dikaryotic strains on MEA using 4 mathematical models showed a μmax between 6.30 and 23.49 mm day-1 and the lag phase ranged from 0.22 to 4.47 h; while on wheat grain presented μmax since 0.08 to 11.41 cm3 day-1 and lag duration between 0.06 and 8.04 h. The hybrid strain PO5xLC2 and the reconstituted strain of Pleurotus djamor PD1xPD4 showed the highest μmax and lowest lag phase on MEA and wheat grain respectively in comparison to the other strains include their parental strains. The results evidenced that the use of hybrid and reconstitued strains of Pleurotus and Lentinula improves the production of edible fungi production.

An Experimental Study on Recovery of Energy from Biodegradable Waste with Eichhornia Crassipes in TKRCET, Hyderabad, Telangana

Objectives: The work is to recover the energy from food and vegetable waste with water hyacinth and cowdung. Methods: The present study focuses the lights to recover energy from organic waste and to adopt safe disposal and conserving natural resources. Laboratory scale batch digesters were set up to find the biogas production potential of Food waste and Vegetable waste with water hyacinth and cow dung. Food waste was collected from our TKR college mess similarly Vegetable waste was collected from the Hyderabad market and prepared for further analysis. Similarly water hyacinth was collected from a Meerpet lake in Hyderabad. Six digesters with varying Vegetable wastes and Food wastes were combined individually by increasing concentrations with fixed amount of water hyacinth and Cow dung by water displacement method. The effect of food waste and vegetable waste concentration on the biogas yield was investigated and the experiments were characterised before and after digestion. Findings: Modified Gompertz Equation (MGE) model was fitted to the experimental values and kinetic parameters such as maximum cumulative biogas potential Bmax (L/gVS), specific biogas production rate, Rb (L gVS-1d-1) and lag phase time, λ(d), were estimated. Experimental values were compared with MGE using MAT LAB. Applications/Improvements: From the experimental study observed that an aerobic degradation took place and the biogas produced was measured daily. Kinetic analysis of the biogas production was done and compared & conclusions were drawn. Keywords: Anaerobic Digestion, Food Waste, Modified Gompertz Equation (MGE), Vegetable Waste Kinetic Modelling, Water Hyacinth

Treatment of feces from beef cattle fed the enteric methane inhibitor 3-nitrooxypropanol.

The study evaluated the residual effect of the known enteric methane inhibitor 3-nitrooxypropanol (3NOP) on anaerobic digestion of cattle feces (feces) in a CH4 potential batch test and two consecutive runs of an anaerobic leach bed reactor at a solids retention time of 40 days. The feces used in this study were collected from beef cattle fed forage- (backgrounding) or grain- (finishing) based diets supplemented with 3NOP in feedlot and metabolism studies. The results showed that CH4 yields were not significantly different from treatments using control feces and feces collected from cattle fed a diet supplemented with 3NOP in both CH4 potential and leach bed studies. Spiking feces with 200 mg 3NOP kg-1 dry matter decreased CH4 production rate by 8.0-18.1% estimated from the Gompertz equation, increased the lag phase time (0.4-3.4 d) in all the treatments, while there was no significant difference in the overall CH4 yield. Results from this study showed that 3NOP can be used as an effective enteric CH4 inhibitor with no residual effect on anaerobic digestion.

Flash Flood Forecasting Using Support Vector Regression Model in a Small Mountainous Catchment

Flash floods in mountainous catchments are often caused by the rainstorm, which may result in more severe consequences than plain area floods due to less timescale and a fast-flowing front of water and debris. Flash flood forecasting is a huge challenge for hydrologists and managers due to its instantaneity, nonlinearity, and dependency. Among different methods of flood forecasting, data-driven models have become increasingly popular in recent years due to their strong ability to simulate nonlinear hydrological processes. This study proposed a Support Vector Regression (SVR) model, which is a powerful artificial intelligence-based model originated from statistical learning theory, to forecast flash floods at different lead times in a small mountainous catchment. The lagged average rainfall and runoff are identified as model input variables, and the time lags associated with the model input variables are determined by the hydrological concept of the time of response. There are 69 flash flood events collected from 1984 to 2012 in a mountainous catchment in China and then used for the model training and testing. The contribution of the runoff variables to the predictions and the phase lag of model outputs are analyzed. The results show that: (i) the SVR model has satisfactory predictive performances for one to three-hours ahead forecasting; (ii) the lagged runoff variables have a more significant effect on the predictions than the rainfall variables; and (iii) the phase lag (time difference) of prediction results significantly exists in both two- and three-hours-ahead forecasting models, however, the input rainfall information can assist in mitigating the phase lag of peak flow.

Carbohydrate to Itaconic Acid Conversion by Aspergillus terreus and the Evaluation of Process Monitoring Based on the Measurement of CO2

In this work, itaconic acid (IA) was produced biotechnologically by Aspergillus terreus fungal strain from glucose. The performance of the batch fermentation was kinetically assessed and the maximal IA production potential, maximal production rate and lag-phase time were determined as 28.1 g/L, 3.83 g/L day and 1.52 days, respectively. In addition, the bioprocess was evaluated based on the most frequently used parameters, in particular IA titer (26.3 g/L), yield (0.22 g/g substrate) and productivity (0.1 g/L h), which were comparable to the already published literature. Furthermore, an on-line monitoring system was installed to the fermenter in order to measure the CO2 content of the bioreactor off-gas. Actually, it was indicated by the results that the CO2 production could have a linear-like relationship with the quantity of fungal biomass. Hence, the data collected in such a way may have the potential to establish an alternative methodology for the monitoring of biomass growth in the course of the biological transformation taking place.Graphic

Efecto del pretratamiento térmico de residuos de alimentos sobre la producción de metano

Food waste are the main component of the municipal solid waste and given their high content of organic matter, have high potential for methane production through the anaerobic digestion. However, the predominance of lignocellulosic material hinders its hydrolysis. In this study, by means of assays of biochemical methane potential, the effect of different thermal pre-treatment conditions of the substrate was evaluated by applying temperatures between 72 - 128°C and exposure times of 15 - 33 minutes on the conditions on the performance of CH4. To evaluate the effect of pretreatment, we used the Response Surface Methodology accompanied by the application of first order kinetic and modified Gompertz models. The identified kinetic parameters were validated using confidence levels using the fisher information matrix. It was found that the optimal region, to reach a higher yield in the anaerobic digestion with regard to the production of CH4 higher than 150mLCH4gVS-1 and lag-phase times less than 1 day, was around 100°C with exposure times close to 15 minutes, condition in which a greater solubility was reached and positively improving the hydrolytic stage of the anaerobic process.

Revealing the correlation of biomethane generation, DOM fluorescence, and microbial community in the mesophilic co-digestion of chicken manure and sheep manure at different mixture ratio.

Batch co-digestion tests of chicken manure (CM) and sheep manure (SM) at different ratio (Rs/c) were conducted under mesophilic condition (35 °C). Batch kinetic analysis of bioCH4 production, excitation-emission matrix (EEM) fluorescence of dissolved organic matter (DOM), and microbial community were investigated. The well-fitted modified Gompertz model (R2, 0.98-0.99) resulted that the co-digestion markedly improved the methane production rate and shortened the lag phase time. The highest bioCH4 yield of 219.67 mL/gVSadd and maximum production rate of 0.378 mL/gVSadd/h were obtained at an optimum Rs/c of 0.4. Additionally, a significant variation of DOM was detected at the Rs/c of 0.4 with a consistent degradation of soluble microbial byproduct-like and protein-like organics. The positive synergy effects of co-digestion conspicuously enhanced the bioCH4 production efficiency. FI370 and NADH were significantly correlated to Rs/c (p < 0.05). Moreover, the correlations among process indicator, EEM-peaks and different environmental parameters were evaluated by Pearson correlation analysis. The high diversity of acetoclastic methanogens and hydrogenotrophic methanogens in the co-digestion improved the stability of process. Graphical Abstract.

Numerical solution of generalized DPL model using wavelet method during thermal therapy applications

In this paper, generalized dual-phase-lag (DPL) model has been studied for the numerical analysis of spatial variation of temperature within living biological tissues during thermal therapy applications. A new hybrid numerical scheme based on finite difference scheme and Chebyshev wavelet Galerkin method are used to solve the generalized DPL model with constant heat flux boundary condition. Multi-resolution and multi-scale computational property of Chebyshev wavelet in the present case localizes small scale variations of solution and fast switching of functional bases. Our study demonstrates that due to presence of coupling factor (convection–perfusion), generalized DPL model predicts lower temperature than classical DPL and Pennes model at the tumor position. Higher values of phase lag times results in lower temperature at the tumor position. But, in case of variation of phase lag time due to temperature gradient, the nature of temperature profile also depends on the spatial coordinate. The effect of the blood temperature, porosity and interfacial convective heat transfer on temperature distribution has been investigated. It is found that larger values of porosity and interfacial convective heat transfer results in lower temperature at the tumor position. Also, both porosity and interfacial convective heat transfer are pronounced more at higher values. The whole analysis is presented in dimensionless form.

Effects of pre-treatment and biological acidification on fermentative hydrogen and methane co-production

A sequential two-stage process comprising biological acidification followed by anaerobic digestion was proposed to enhance gaseous biofuel production from the mixture of rice residue and micro-algae after thermo-chemicial hydrolysis. The maximum specific hydrogen yield of 223.1 ± 8.8 mL/g volatile solids (VS) and production rate of 10.4 ± 0.4 mL/g VS/h were achieved from hydrothermal acid pre-treated biomass during biological acidification. Increase in hydraulic retention time of biological acidification from 12 to 144 h significantly affected the distribution of solubilised metabolic products and led to improved biological acidification rates (BARs) from 15.5% to 78.5%. Compared with single stage anaerobic digestion, the first stage acidification phase led to reductions in the lag-phase time and peak time of anaerobic digestion in such a two-stage process. The maximum specific methane production rate of 2.2 ± 0.03 mL/g VS/h was achieved with a deep acidification of 144 h yielding a BAR of 78.5%. Increasing the length of time in biological acidification from 12 to 144 h contributed to improved energy conversion efficiency of 25.4%–64% after 120 h of anaerobic digestion. These results demonstrate that biological acidification is feasible to improve bioenergy recovery in two-stage fermentation.

Toxicity of hydrogen sulfide toward sulfate-reducing bacteria Desulfovibrio piger Vib-7.

Sulfate-reducing bacteria (SRB) belonging to the intestinal microbiota are the main producers of hydrogen sulfide and their increasing amount due to the accumulation of this compound in the bowel are involved in the initiation and maintenance of inflammatory bowel disease. The purpose of this experiment is to study the relative toxicity of hydrogen sulfide and survival of Desulfovibrio piger Vib-7 through monitoring: sulfate reduction parameters (sulfate consumption, hydrogen sulfide production, lactate consumption and acetate production) and kinetic parameters of these processes. The research is highlighting the survival of intestinal SRB, D. piger Vib-7 under the influence of different hydrogen sulfide concentrations (1-7mM). The highest toxicity of H2S was measured in the presence of concentrations higher than 6mM, where growing was stopped, though metabolic activities were not 100% inhibited. These findings are confirmed by cross correlation and principal component analysis that clearly supported the above mentioned results. The kinetic parameters of bacterial growth and sulfate reduction were inhibited proportionally with increasing H2S concentration. The presence of 5mM H2S resulted in two times longer lag phase and generation time was eight times longer. Maximum rate of growth and hydrogen production was stopped under 4mM, emphasizing the H2S toxicity concentrations to be < 4mM, even for sulfide producing bacteria such as Desulfovibrio. The results are confirming H2S concentrations toxicity toward Desulfovibrio, especially the study novelty should be emphasized where it was found that the exact H2S limits (> 4mM) toward this bacterial strain inhabiting humans and animals intestine.

Quantifying proliferative and surface marker heterogeneity in colony-founding connective tissue progenitors and their progeny using time-lapse microscopy.

Connective tissue progenitors (CTPs) are defined as the heterogeneous population of tissue-resident stem and progenitor cells that are capable of proliferating and differentiating into connective tissue phenotypes. The prevalence and variation in clonal progeny of CTPs can be characterized using a colony formation assay. However, colony assays do not directly assess the characteristics of the colony-founding CTP. We performed large, field-of-view, time-lapse microscopy to manually track colonies back to the founding cells. Image processing and analysis was used to characterize the colonies and their founding cells. We found that the traditional colony-forming unit (CFU) assay underestimates the number of founding cells as colonies can be formed by more than one founding cell. After 6days in culture, colonies do not completely express CD73, CD90, and CD105. Heterogeneity in colony cells was characterized by two cell populations, proliferative and spread cells. Regression modelling of duration of lag phase and doubling time by cell marker suggests the presence of CD90 and CD105 in CTP subpopulations with different proliferative capabilities. From mathematical modelling of clonal colonies, we quantitatively characterized proliferation, migration, and cell marker expression rates to identify desirable clones for selection. Direct assessment of colony formation parameters led to more accurate assessment of CFU heterogeneity. Furthermore, these parameters can be used to quantify the diversity and hierarchy of stem and progenitor cells from a cell source or tissue for tissue engineering applications.

Synergistic effect in anaerobic co-digestion of rice straw and dairy manure - a batch kinetic study

ABSTRACTMethane yield of seven co-digestion mixture proportions (1:0, 5:1, 3:1, 1:1, 1:3, 1:5, and 0:1) of rice straw and dairy manure was investigated at a total solids (TS) loading of 8%. Methane yield was improved by 50–57% and 9–10% with co-digestion at mixture proportions of 1:1,1:3 and 1:5 compared to mono digestion of rice straw and dairy manure, respectively. The modified Gompertz model accounted well for the kinetic behavior of methane yield with an R2 of 0.99 and Root Mean Square Error of 0.06–1.70. It was observed that the co-digestion caused a reduction in lag phase time and improvement in the maximum methane production rate. The positive synergistic effects are a result of nutrient balance with the co-digestion of dairy manure and rice straw.