Acta Scientiarum-technology 

About: Acta Scientiarum-technology is an academic journal published by Editora da Universidade Estadual de Maringá (Eduem). The journal publishes majorly in the area(s): Engineering & Computer science. It has an ISSN identifier of 1806-2563. It is also open access. Over the lifetime, 1187 publications have been published receiving 6354 citations.

Controle ótimo em reator batelada alimentada para a hidrólise enzimática da celobiose - DOI: 10.4025/actascitechnol.v25i1.2236

Abstract: Glucose can be obtained from cellulose through enzymatic hydrolysis by the enzymes of the celullase complex. Cellobiose hydrolysis by cellobiase exhibits substrate and product inhibition, which reduces the reaction's performance. The researches available in the literature on this subject were made in batch reactors; a study concerning the possibility on the use of another type of reactor has not yet been made. The aim of this work is to analyze the use of a fed-batch reactor to this enzymatic reaction. Feed policy was determined using the optimal control theory, where substrate conversion and final product concentration were maximized. Simulated results were compared with experimental data obtained by Calsavara et al . (1999) in a batch reactor and indicated that substrate inhibition overcomes product inhibition. The fed-batch operation was advantageous in some situations.

Shear strength of steel fiber-reinforced concrete beams

Abstract: This study analyzed the mechanical behavior of shear strength of steel fiber-reinforced concrete beams. Six beams subjected to shear loading were tested until failure. Additionally, prisms were tested to evaluate fiber contribution to the concrete shear strength. Steel fibers were straight, hook-ended, 35 mm long and aspect ratio equal to 65. Volumetric fractions used were 1.0 and 2.0%. The results demonstrated a great contribution from steel fibers to shear strength of reinforced concrete beams and to reduce crack width, which can reduce the amount of stirrups in reinforced concrete structures. Beam capacity was also evaluated by empirical equations, and it was found that these equations provided a high variability, while some of them have not properly predicted the ultimate shear strength of the steel fiber-reinforced concrete beams.

Temperature distributions in pavement and bridge slabs heated by using vertical ground-source heat pump systems

Abstract: Temperature distribution which occurs in pavement and bridge slabs heated for de-icing and snow melting during cold periods is determined by using vertical ground-source heat pump (GSHP) systems with U-tube ground heat exchanger (GHE). The bridge and pavement models (slabs) for de-icing and snow melting were constructed. A three-dimensional finite element model (FEM) was developed to simulate temperature distribution of bridge slab (BS) and pavement slab (PS). The temperature distribution simulations of PS and BS were conducted numerically by computational fluid dynamics (CFD) program named ‘Fluent’. Congruence between the simulations and experimental data was determined.

Evaluation of extracts of Moringa oleifera Lam seeds obtained with NaCl and their effects on water treatment - doi: 10.4025/actascitechnol.v34i3.9605

Abstract: Several natural coagulants have been studied for use in water treatment. The seed of Moringa oleifera Lam, for example, is a natural coagulant whose extract has been mentioned as effective not only for removing color, turbidity, and compounds with absorption at UV-254 nm, but also for significantly reducing the amount of sludge and bacteria in wastewaters. Therefore, the present study (1) evaluated the molecular weight of the extract of Moringa oleifera seed utilizing electrophoresis, and (2) compared the efficiency of different extracts obtained, using solutions of NaCl (0.01 M, 0.1 M and 1 M), distilled water, and Moringa oleifera Lam seed, acting as a natural coagulant in order to obtain drinking water. The tests were performed in Jar Test, and the effectiveness of the process was assessed regarding the removal of color, turbidity and UV-254 nm. It was observed that the molecular weight found in this study is consistent with literature data. Moreover, the highest removal efficiency of color, turbidity, and UV-254 nm occurred with 1M NaCl solution, with coagulant concentration between 100 and 300 mg L -1 . The results obtained evidenced that the seed of Moringa oleifera Lam is a great alternative for use as a coagulant in drinking water treatment systems.

Fenton and Photo-Fenton oxidation of tannery wastewater

Abstract: Fenton and Photo-Fenton processes are attractive alternatives in effluent treatment, especially when applied to recalcitrant compounds. The aim of this work was to evaluate the efficiency of Fenton and Photo-Fenton processes for the treatment of wastewater from leather industry, investigating the reduction of COD, ammoniac nitrogen concentration and toxicity in treated wastewaters. The results showed that the kinetic of degradation by Fenton and Photo-Fenton reactions can be divided in two stages: an initial fast process, where approximately 70% of the COD reduction takes place, followed, by a slow process, where a reaction takes up to 4 hours, resulting in about 90% of COD reduction. Different mass ratios of Fe 2+ /H 2 O 2 were tested and the results showed that the efficiency of the Fenton and photo-Fenton reactions increases from 65 to 90% as the concentration of hydroxyl radicals (•OH) increases. No significant difference in the ammoniac nitrogen amount reduction for the Fenton and Photo-Fenton processes was observed, either before or after coagulation. The ammonia removal was ascribed to the oxidation of nitrogen organic compounds, possibly forming N2 and nitrate ions. The toxicity biossays using Artemia salina decreased as the wastewater was degraded and increased if the hydrogen peroxide residue at the end of the reaction was high.