Semi-continuous Conditions Research Articles

Enhancing biogas production from cheese whey using Zero-Valent Iron: A comparative analysis of batch and semi-continuous operation modes

Cheese whey (CW) is the primary by-product of dairy industries, and its anaerobic treatment presents several challenges. Among these is the production of high levels of volatile fatty acids (VFAs) due to rapid biodegradation, which leads to a drop in pH and adversely impacts methanogenesis. This study aims to evaluate the impact of Zero-Valent Iron (ZVI) on the anaerobic digestion of CW under both semi-continuous and batch conditions. Since ZVI generates H2 and increases pH under soluble CO2 conditions, the study also focuses on the effects of ZVI on solubilization/hydrolysis, acidification, and microbial response. Three anaerobic bioreactors (R25-PZVI with 25 g/L powder ZVI, R50-SZVI with 50 g/L scrap ZVI, and R-Control without ZVI), at semi-continuous mode, treated cheese whey at varying organic loading rates. After 118 days, R25-PZVI showed the highest CH4 yield and best COD removal, followed by R50-SZVI. Despite NaOH additions, it maintained a lower VFA/ALK ratio than the control. Under semi-continuous mode, CH4 composition in R25-PZVI was 59%, rising to over 95% under batch conditions due to the higher pressure and subsequent solubilization of H2 and CO2. The ZVI mainly impacted methanogenesis and acidogenesis and not solubilization/hydrolysis. 25-PZVI's superior performance was due to its increased H2 generation and alkalinity over 50 g/L SZVI, as was found in the abiotic test. Under semi-continuous conditions, Methanobacterium (a hydrogenotrophic methanogen) and Methanosarcina were the dominant genera in the R25-PZVI reactor. Under batch conditions, Methanothrix displayed a higher abundance, which explained the increased acetic acid utilization.

An Innovative Look into Ammonium Nitrogen Removal Using Algae and Zeolites as an Element of a Circular Bioeconomy

This work focused on the potential of simultaneously removing ammonium nitrogen from industrial wastewater using immobilized microalgae and powdered zeolite. Experiments were performed with different species and doses of microalgae embedded in spherical hydrogels in semicontinuous conditions. Ammonium nitrogen uptake by microalgae promoted the slow release of previously adsorbed ammonium nitrogen from zeolite that was then also absorbed by microalgae. Results showed that immobilized microalgae can reach a removal efficiency of up to 60% (C. vulgaris) and 42% (S. armatus). A higher removal efficiency was obtained for zeolites and immobilized C. vulgaris or S. armatus up to 86% and 79%, respectively. Moreover, a higher maximum sorption capacity for C. vulgaris (13.8 mg/g) was achieved than for S. armatus (5.5 mg/g). The recycling of spent hydrogel, zeolite, and wastewater is possible. Such an approach represents a circular bioeconomy loop.

A simple characterization of the existence of upper semicontinuous order-preserving functions

We introduce an upper semicontinuity condition concerning a not necessarily total preorder on a topological space, namely strong upper semicontinuity, and in this way we extend to the nontotal case the famous Rader’s theorem, which guarantees the existence of an upper semicontinuous order-preserving function for an upper semicontinuous total preorder on a second countable topological space. We show that Rader’s theorem is not generalizable if we adopt weaker upper semicontinuity conditions already introduced in the literature. We characterize the existence of an upper semicontinuous order-preserving function for all strongly upper semicontinuous preorders on a metrizable topological space.

The stability of minimal solution sets for set optimization problems via improvement sets

In this paper we investigate the stability of solution sets for set optimization problems via improvement sets. Some sufficient conditions for the upper semicontinuity, lower semicontinuity, and compactness of E-minimal solution mappings are given for parametric set optimization under some suitable conditions. We also give some examples to illustrate our main results.

Valorization of Fourth-Range Wastes: Evaluating Pyrolytic Behavior of Fresh and Digested Wastes

Changes in daily habits and a stressful lifestyle create modifications in consumer preferences and open opportunities to new market products. This is the case of fourth-range products in which the industrial sector generates a waste stream of high quality. Valorization of this type of waste as a single stream is desirable to avoid lowering quality with other low-grade materials. Anaerobic digestion of fourth-range wastes was studied under discontinuous and semi-continuous conditions. A high carbon content characterizes the organic material composed of fruit and vegetable wastes. The fast degradation of the substrate indicated no limitations associated with the hydrolysis stage, as observed from kinetic parameters estimated from batch assays. However, the easiness of degradation did not translate into short hydraulic retention times when operating under semi-continuous conditions. Additionally, the insufficient amount of nutrients prevented the development of a well-balanced digestion process. Specific methane production was 325 mL CH4/g VS added at a hydraulic retention time of 30 days. However, solid accumulation was observed at the end of the experiment, indicating that conditions established did not allow for the complete conversion of the organic material. Digestate evaluation using thermal analysis under inert conditions showed a thermal profile evidencing the presence of complex components and a high tendency to char formation.

Coincidence Points of Parameterized Generalized Equations with Applications to Optimal Value Functions

The paper studies coincidence points of parameterized set-valued mappings (multifunctions), which provide an extended framework to cover several important topics in variational analysis and optimization that include the existence of solutions of parameterized generalized equations, implicit function and fixed-point theorems, optimal value functions in parametric optimization, etc. Using the advanced machinery of variational analysis and generalized differentiation that furnishes complete characterizations of well-posedness properties of multifunctions, we establish a general theorem ensuring the existence of parameter-dependent coincidence point mappings with explicit error bounds for parameterized multifunctions between infinite-dimensional spaces. The obtained major result yields a new implicit function theorem and allows us to derive efficient conditions for semicontinuity and continuity of optimal value functions associated with parametric minimization problems subject to constraints governed by parameterized generalized equations.

Physicochemical Parameters and Microbial Community in Anaerobic Digestion of Organic Wastes

The demand for an alternative source of energy and challenge of increase in wastes pollution initiates the need for renewable energy and management of waste using anaerobic digestion (AD). Anaerobic digestion is an effective and efficient method of waste treatment and energy generation. The study focused on investigating the physicochemical parameters and microbial community in anaerobic digestion of organic wastes and was conducted using chicken wastes and food wastes as organic substrate under semi-continuous conditions at hydraulic retention time (HRT) of forty-two (42) days in fifteen liter (15L) fabricated digesters labeled D1, D2 and D3 at 37OC. The pH, volatile fatty acid (VFA), moisture content (MC), total ammonia, total solid, volatile solid, alkalinity was assessed before and after digestion while the microbial community diversity was analyzed using 16S rRNA amplicon-based nextgeneration sequencing (NGS). The results indicated a pH value of 6.65 ± 0.12, 7.27 ± 0.13, 6.43 ± 0.27, volatile fatty acid of 72.17 ± 1.42, 58.35 ± 2.58, 40.56 ± 0.38 and moisture content of 98.9 ± 2.65, 92.3 ± 1.81, 96.4 ± 3.60 at day 42 for D1 (Chicken waste and food wastes), D2 (Chicken wastes+), D3 (control) respectively. A collective biogas yield of 686±17.00 kpa for D1, 700±11.00kpa for D2 and 521±21.00 kpa for D3 were recorded. The characterization of biogas analyzed with nondispersive infrared (NDIR) gas analyzer (gas board 3100p) revealed a percentage methane content of 46.11±1.11, 52.4±1.05, 50.31±1.33 for D1, D2 and D3 respectively. The microbial community identified phylum Bacteroidetes, Firmicutes, proteobacteria, Tenericutes, Verrucomicrobia, Actinobacteria, Euryarchaeota among others. The study shows that physicochemical properties and microbial community diversity are useful tools to indicate digester performance and also to enhance anaerobic digestion process.

Effects of organic loading rates on high-solids anaerobic digestion of food waste in horizontal flow reactor: Methane production, stability and mechanism

To maximize the methane production efficiency of high-solids anaerobic digestion (HSAD) of food waste (FW), a horizontal flow reactor was operated under mesophilic, semi-continuous condition at organic loading rates (OLRs) ranging from 1.00 to 13.80 kg-VS/(m3 d). The gas production, substrate transformation, and microbial community characteristics of the horizontal flow HSAD reactor were evaluated. The results indicated that the methane yield (0.173–0.516 L/(g d)) fluctuated with the increasing OLR, volumetric methane production rate (0.25–5.69 L/(L d)) increased with increasing OLR, and the volatile solids (VS) reduction rate ranged between 83.30% and 93.05%. The relationship of biogas or methane production with OLR and HRT in the horizontal flow HSAD reactor were characterized with an empirical equation. The concentrations of soluble COD and volatile fatty acid exhibited significant fluctuations, and free ammonia-nitrogen peaked at the OLR of 13.80 kg-VS/(m3 d). Microbial community analysis revealed that the methanogenic metabolic pathway changes along the propelling direction of the horizontal flow HSAD reactor from CH3COOH and H2/CO2 pathways to CH3COOH, H2/CO2, and H2/methyl co-dominant pathways. These results provide theoretical support for stable methane production from FW and deeper insight into horizontal flow HSAD for FW treatment.

Existence and essential stability of Nash equilibria for biform games with Shapley allocation functions

<abstract> <p>We define the Shapley allocation function (SAF) based on the characteristic function on a set of strategy profiles composed of infinite strategies to establish an <italic>n</italic>-person biform game model. It is the extension of biform games with finite strategies and scalar strategies. We prove the existence of Nash equilibria for this biform game with SAF, provided that the characteristic function satisfies the linear and semicontinuous conditions. We investigate the essential stability of Nash equilibria for biform games when characteristic functions are perturbed. We identify a residual dense subclass of the biform games whose Nash equilibria are all essential and deduce the existence of essential components of the Nash equilibrium set by proving the connectivity of its minimal essential set.</p> </abstract>

Anaerobic Co-Digestion of Sheep Manure and Waste from a Potato Processing Factory: Techno-Economic Analysis

Anaerobic co-digestion of sheep manure and potato waste was studied under batch and semi-continuous conditions. Biochemical methane potential tests were carried out for the different substrates before evaluating co-digestion at high-solid content. The reactors presented stable performance under mesophilic conditions, at an organic loading rate (OLR) of 3.5–4.0 kg VS/m3 and a hydraulic retention time (HRT) of approximately 20 days. Increasing the OLR of semi-continuous reactors decreased the methane yield and degradation efficiency of the digestion. Methane-specific production was in the range of 196 and 467 mL CH4/g vs. (sheep manure system and co-digestion, respectively). Based on the experimental data obtained, a techno-economic study was performed for wet and solid-state fermentation systems, with the first configuration presenting better results. The economic feasibility of the hypothetical plant was analyzed considering the variability in electricity and compost selling prices. The economic feasibility of the plant was determined with an electricity selling price of EUR 0.25/kWh, and assuming a centralized plant serving several farmers. Still, this price was considered excessive, given the current electricity market values.

Activity and sulfur resistance of co-impregnated bimetallic PdNi/γ-Al2O3 catalysts during hydrogenation of styrene

Pyrolysis gasoline (PyGas) is an unstable byproduct of the pyrolysis of naphtha and other hydrocarbons for the production of olefins. PyGas is stabilized by hydrogenation at mild conditions. The hydrogenation of styrene to ethylbenzene is considered a model test reaction for studying the selectivity of the catalysts because it has the slowest rate of conversion. The catalytic activity and selectivity of two bimetallic co-impregnated Pd–Ni catalysts supported on γ-alumina were assessed and compared to those of a commercial monometallic Pd catalyst (AXENS LD265). The laboratory-prepared catalysts had different metal content and Pd:Ni atomic ratios (1:1 and 1:7). Catalytic tests of selective hydrogenation of styrene to ethylbenzene were made in a batch stirred tank reactor and in a continuous fixed bed trickle bed reactor. The sulfur resistance of the bimetallic catalysts in semicontinuous condition, was assessed by means of the same operational conditions using thiophene as a model poison compound. The support, Pd–Ni co-impregnated catalysts and LD265 commercial catalysts were further characterized by N2 chemisorption, EPMA, OM, ICP elemental analysis, temperature programmed reduction, XPS and X-Ray diffraction. The results indicated the presence of different metal species: Pd0, Pdδ+, Ni0 and NiO. The lab-prepared bimetallic catalysts were found to be active for the selective hydrogenation of styrene (both in the batch and continuous system). During the continuous evaluations, the commercial LD265 catalyst had an intermediate activity level that lied between the values corresponding to the Pd–Ni bimetallic catalysts: PdNi(1:1) $$ \gg $$ LD265 > PdNi(1:7). During the poison free semicontinuous evaluations, the pattern of conversion as a function of contact time of co-impregnated Pd–Ni catalysts are quite similar to that of commercial LD265 catalyst, though the catalytic activity is slightly better for PdNi(1:1). After 90 min of contact time the order of conversion was: PdNi(1:1) > LD265 > PdNi(1:7). On the other hand, during the poison semicontinuous tests (with 300 pp of thiophene), the initial reaction rates of the co-impregnated catalysts decreased, pointing a poisoning of the active sites by thiophene. PdNi(1:1) had higher initial reaction rate than PdNi(1:7) during poison free or poisoned in both conditions. PdNi(1:7) was more sulfur resistant than PdNi(1:1). The higher activity of the PdNi(1:1) catalyst was attributed to the presence of Pd0 and Pdn+/Nim+ species that favored respectively, the homolytic cleavage of the H–H bond and the adsorption of styrene. The higher sulfur resistance of the PdNi(1:7) catalyst would be associated with the higher Cl/Al surface atomic ratio in this catalyst (electronic effect) and the presence of electrodeficient species of Pd (Pdxδ+OyClz) that prevented the adsorption of thiophene by steric hindrance (geometrical effect of the large species) or by electronic effects.

Optimization of semi-continuous cultivation conditions for the improvement of lipid productivity from thermo-tolerant Chlorella vulgaris XJW

ABSTRACT Chlorella vulgaris XJW (C. vulgaris XJW), one temperature tolerable microalgae with biodiesel production potential, was selected from Ulungur Lake in Xinjiang. In this research, optimal semi-continuous cultivation conditions were obtained by employing uniform design method. The total biomass and lipid productivity of C. vulgaris XJW cultured with semi-continuous mode in Column photobioreactor were affected by renewal rate, renewal period, nitrogen concentration and phosphorus concentration. According to the regression equation, the optimal semi-continuous cultivation conditions for the total biomass of C. vulgaris XJW was renewal rate of 33%, renewal period of 4 days, NaNO3 concentration of 0.69 g·L−1 and K2HPO4 concentration of 0.02 g·L−1. In the optimal conditions, the maximum total biomass of C. vulgaris XJW was 3.682 g·L−1, which was 20.1% higher than the highest value in unoptimized semi-continuous cultivation conditions, and 2.6 times higher than that in batch cultivation. Meanwhile, the optimal semi-continuous cultivation conditions for lipid productivity of C. vulgaris XJW was renewal rate of 27%, renewal period of 3 days, NaNO3 concentration of 1.03 g·L−1 and K2HPO4 concentration of 0.02 g·L−1. In the optimal conditions, the maximum lipid productivity of C. vulgaris XJW was 110.43 mg·L−1d−1, which was 16.8% higher than the highest value in unoptimized semi-continuous cultivation conditions, and 2.7 times higher than that in batch cultivation. Results were consistent with the predicted values obtained by model equations, which confirmed the reliability of model equations. The models achieved in this work could accurately predict the semi-continuous cultivation conditions of C. vulgaris XJW with total biomass and lipid productivity as indicators. Good cultivation model would make the large-scale cultivation of this kind of microalgae possible, providing enough materials for the biodiesel production.

Integration of Subcritical Water and Enzymatic Hydrolysis to Obtain Fermentable Sugars and Second-Generation Ethanol from Sugarcane Straw

Converting the chemical and biologically resistant structure of cellulosic biomass into useful products is a technological and economic challenge. The use of sustainable and efficient conversion technology sustainably has been gaining prominence. This work aimed to evaluate the integration of subcritical water hydrolysis (SWH) and enzymatic hydrolysis of sugarcane straw to obtain fermentable products and second-generation ethanol. SWH was conducted under semi-continuous conditions at 200 °C, 5 mL/min, and a 19-min retention time. Enzymatic hydrolysis using an enzyme blend produced simple sugars that were evaluated for fermentation using two strategies: (i) Saccharomyces cerevisiae SA-1; and (ii) co-culture of S. cerevisiae SA-1 and Scheffersomyces stipitis NRRLY-7124. Integrating subcritical water and enzymatic hydrolysis resulted in greater fermentable sugar yield (2.40 ± 0.01 g/L of xylose and 8.9 ± 0.6 g/L of glucose) than subcritical pre-treatment on its own. The co-culture fermentation strategy was more efficient than fermentation by S. cerevisiae on its own, resulting in 2.8 ± 0.3 g/L of ethanol. Subcritical water hydrolysis pre-treatment disrupted the lignocellulosic matrix, leading to increased enzymatic accessibility of cellulose, with minimal formation of degradation compounds, and with minimal waste formation. Future work can optimize the hydrolysis process to increase the yield of simple sugars, increase fermentation efficiency by controlling oxygen concentration and removing acetic acid, and consequently increase the yields of second-generation ethanol.

Fixed Point Theorems of A Set-Valued Integral Type Mapping in Complete Partial IMetric Spaces

In our paper we prove that the set valued mappings of integral type with lower semi continuous non-negative lebesgue integrable mapping have a fixed point in complete partial metric spaces. The same result was proved without needed to the lower semi continuous condition. We give two examples to illustrating the necessity for non-negative and lower semi continuous conditions.

Generalizing algebraically defined norms

We extend the algebraic construction of finite dimensional varying exponent L^{p(cdot )} space norms, defined in terms of Cauchy polynomials to a more general setting, including varying exponent L^{p(cdot )} spaces. This boils down to reformulating the Musielak–Orlicz or Nakano space norm in an algebraic fashion where the infimum appearing in the definition of the norm should become a (uniquely attained) minimum. The latter may easily fail, as turns out, and in this connection we examine the Fatou type semicontinuity conditions on the modulars. Norms defined by ODEs are applied in studying such semicontinuity properties of L^{p(cdot )} space norms with p(cdot ) unbounded.

Semicontinuity of the solution maps to vector equilibrium problems with equilibrium constraints

ABSTRACT In this paper, we are concerned with parametric vector equilibrium problems with equilibrium constraints. We first introduce concepts of generalized semicontinuity and convexity of vector-valued maps in ordered spaces and discuss their properties, as well as their relationships with well-known concepts. Next, employing mentioned concepts of generalized semicontinuity of vector-valued maps, we study sufficient conditions of upper semicontinuity for solution maps to such problems. Then, combining these generalized semicontinuity along with generalized convexity assumptions, sufficient conditions for lower semicontinuity of solution maps to the reference problems are established. Several examples are provided to illustrate the relaxation and essentialness of assumptions. Our results are new, even for special cases of the underlying problems.

On the stability of solutions for the generalized vector quasi-equilibrium problems via free-disposal set

<p style='text-indent:20px;'>In this paper, we mainly discuss the stability of generalized vector quasi-equilibrium problems (GVQEPs) where the ordering relations are defined by free-disposal set. Firstly, by virtue of the oriented distance function <inline-formula><tex-math id="M1">\begin{document}$ (\triangle) $\end{document}</tex-math></inline-formula>, gap functions for (GVQEPs) are given and some properties of them are studied. Then, under some types of continuity assumption, the sufficient conditions of the upper semicontinuity and the upper Painlevé-Kuratowski convergence of solutions for (GVQEPs) are talked about. Moreover, sufficient and necessary conditions of the lower semicontinuity and the lower Painlevé-Kuratowski convergence of solutions for (GVQEPs) are obtained in normed linear spaces. Some examples are given to illustrate the results, and our results are new and extend some known results in the literature.

Zinc-iron silicate for heterogeneous catalytic ozonation of acrylic acid: efficiency and mechanism.

This research aimed at researching the degradation of acrylic acid (AA) in aqueous solution, by catalytic and non-catalytic ozonation processes performed in a semi-continuous reactor. Zinc–iron silicate was synthesized and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, Fourier transformation infrared (FT-IR) and energy dispersive spectrometry (EDS). The characterization studies showed that Fe–Si binary oxide, Zn–Si binary oxide, ZnO and Fe2O3 deposits were formed on the surface of poor crystallinity zinc–iron silicate which contained abundant functional groups. Catalytic ozonation test results revealed that zinc–iron silicate exhibited high catalytic activity and stability in catalytic ozonation of AA in aqueous solution. The inclusion of zinc–iron silicate in the ozonation process enhanced AA decomposition by 28.7% and TOC removal by 20%, compared to the ozonation alone. The main AA removal mechanisms involved direct oxidation by ozone and indirect oxidation by hydroxyl radicals generated by the ozone chain reaction accelerated by zinc–iron silicate. The surface characteristics and chemical composition are significant factors determining the catalytic activity of zinc–iron silicate.

Tính nửa liên tục trên của ánh xạ nghiệm bài toán cân bằng với ràng buộc cân bằng

The paper is to investigate vector equilibrium problems with equilibrium constraints in Hausdorff topological vector spaces ordered by cones. By using relaxation of semicontinuity and generalized convexity properties of vector-valued maps, sufficient conditions for upper semicontinuity of solution maps to the reference problems are established, and many counterexamples are also provided to illustrate the essentialness of these conditions. The approaches and results obtained in this paper are new even for the scalar problems

Multiple solutions for a Choquard system with periodic potential

In this paper we prove the existence of infinitely many geometrically distinct solutions of a Choquard system with periodic potential. For this purpose, we prove a new global critical point theorem without the τ-upper semi-continuity condition on the variational functional.