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Influence of Temperature and Reaction Time on the Efficiency of Alkaline Pretreatment of Hay Biomass

Zdeb Magdalena, Skóra Aneta, Pawłowska Małgorzata

Journal of Ecological Engineering

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2021

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Vol. 22, nr 2

120--127

EN

Low biodegradability caused by polymeric structure is the main barrier in the use of lignocellulosic materials in biofuels production by using biological methods. Pretreatment of the biomass is the way to improve the suitability of hardly biodegradable biomass for biogas or bioethanol production. Evaluation of the influence of thermal and thermochemical alkaline pretreatment on the efficiency of hydrolysis of hay (mixture of various grass species) was the aim of the study. The batch scale experiment was carried out with the use of NaOH and distilled water as solvents, and the changes in pretreatment time (2, 4 and 8 hours) and temperature (22 and 80°C) were also considered. The efficiency of biomass solubilisation was assessed based on the results obtained from the measurements of chemical oxygen demand (COD) and volatile fatty acids (VFA) concentration in the hydrolysates. The solubility of the biomass, expressed as a percentage of soluble COD in total COD, was calculated. The experiment showed that the highest solubilisation of hay biomass was observed at 80°C under alkaline conditions. In this case, the solubility of the COD was 3-times higher, and the VFA concentration in hydrolysates was 4-times higher in comparison to the distilled water-based test at 22°C. It was noted that time of the process significantly influenced the efficiency of biomass solubilisation only during the experiment carried out at 22°C. Extension of hydrolysis time from 2 to 8 hours increased the value of soluble COD of 70% and 55% for water and alkaline solvent, respectively. The process conducted at 80°C was not time-dependent over the considered period.

2

Anaerobic Digestion of Wheat Straw Pretreated with Soaking in Water and Alkali Medium

Zdeb Magdalena

Journal of Ecological Engineering

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2021

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Vol. 22, nr 9

246--254

EN

The influence of the alkaline pretreatment of wheat straw with use 0.05M solution of NaOH by 22 hours at 25 °C temperature on the effectiveness of anaerobic digestion under mesophilic condition was the subject of this study. The water soaked straw was used as a control. The results showed that alkaline pretreatment improved the solubility of the straw biomass, increasing dissolved COD and concentration of VFA in the feedstock of 10% and 21%, respectively, compared to the water soaked samples. Consequently, the cumulative biogas yield was enhanced by 21.5%, reaching 412.1 mL gVS-1 for the pretreated biomass. The digestates were similar in terms of TS and VS, but it significantly differed in terms of phenols concentration, the content of which was considerably higher both in the feedstock as also as in digestate containing alkaline pretreated straw. Initial concentration of phenols in the feedstock of 27 mg L-1 did not block the anaerobic digestion, although its inhibiting effect is forecasted. It was concluded that soaking the straw at low loading of NaOH (4% of raw mass (w/w)) under ambient conditions can efficiently improve its usability for biogas production.

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Efekty oddziaływania dezintegrującego alkalizacji i sonifikacji na zawiesiny osadu czynnego

Krzemińska D., Kamizela T., Kowalczyk M.

Inżynieria i Ochrona Środowiska

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2014

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T. 17, nr 4

547--557

PL

W artykule przedstawiono efekty dezintegracji chemicznej, sonifikacji oraz metody łączącej reagenty chemiczne z propagacją fali ultradźwiękowej. Zastosowanie tych metod do dezintegracji zawiesin osadu czynnego miało na celu określenie możliwości aplikacyjnych w układzie biologicznego oczyszczania ścieków. Zyski wynikające z dezintegracji osadu czynnego i zawracania otrzymanego produktu do komory osadu czynnego dotyczą generowania łatwo przyswajalnego źródła węgla dla mikroorganizmów prowadzących proces denitryfikacji i defosfatacji. Dezintegrację można też stosować w przypadku problemów eksploatacyjnych z flotującym i pęczniejącym osadem, jak również jako metodę ograniczania przyrostu osadu czynnego. Przedstawiona praca stanowi wstępny etap badań, który zasadniczo obejmował określenie siły dezintegrującej badanych czynników. Wyniki przeprowadzonych doświadczeń mogą także posłużyć do optymalizacji dezintegracji innych rodzajów osadów. Wyniki badań pozwoliły na stwierdzenie, że kombinacja metod dezintegracji chemicznej wodorotlenkiem sodu wraz z sonifikacją osadów była najefektywniejszym sposobem dezintegracji. Metoda wstępnej alkalizacji i kolejno sonifikacji osadów wymaga jednak dalszej optymalizacji z uwagi na występujące wysokie temperatury osadów po dezintegracji, a zwłaszcza nadal nieakceptowalny odczyn.

EN

The article presents the results of chemical disintegration, sonication and hybrid method. Application of these methods to disintegration of activated sludge suspensions was aimed at determining their applicability in wastewater treatment system. Disintegration of activated sludge and recycling the product to the bioreactor is used for the generation of easily assimilated carbon source for the microorganisms involved in the process of denitrification and phosphorus removal. Disintegration can also be used in the case of operational problems with floating swelling sludge, as well as a method for limiting the amount of excess sludge. This paper is a preliminary stage of research, which essentially consisted of identifying the disintegration effects of hybrid method. The results of the experiments can also be used to optimize the disintegration of other types of sewage sludge. The results revealed that a combination of chemical disintegration with sodium hydroxide and sonication was the most effective way of activated sludge disintegration. The method of initial alkalization and subsequent sonication requires further optimization in view of the high temperatures and particularly unacceptable reaction of sludge after the disintegration.