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  • Author: Helena Čížková x
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Adéla Čížková, Dagmar Juchelková and Helena Raclavská

The influence of hygienisation of sewage sludge on the process of pyrolysis

The aim of this work was to determine the influence of liming on the process of pyrolysis. Three samples of sludge from two wastewater treatment plants were selected for this study on pyrolysis: sludge without liming and limed sludge from the Central Wastewater Treatment Plant in Ostrava and sludge from the Wastewater Treatment Plant in Sviadnov. The samples had different content of calcite (CaCO3). The limed sludge contained 7% of CaCO3, sludge without liming 3.8% and sludge without liming from WWTP Sviadnov contained 0.5% of calcite. The results of laboratory pyrolysis proved that limed sludge released the maximum amount of carbon - 55.46 %, while sludge without liming from WWTP Sviadnov released only 48.92%. Calcite produces during its decomposition CaO and the product influences the pyrolysis process because it supports cracking of volatile organic compounds

Open access

Vojtěch Kružík, Adéla Grégrová, Aleš Rajchl and Helena Čížková

Abstract

Fast evaluation of honey quality is a topical and significant problem of the food industry, bee keepers and consumers. In this work, 22 samples of commercially available honey aromas (with methyl and ethyl esters of phenylacetic acid predominated), 13 samples of authentic honey collected directly from bee keepers (characterised by high content of benzaldehyde, 2-phenylethanol, hotrienol and 2-phenylacetaldehyde) and 63 honeys purchased from an outdoor market were evaluated based on volatiles profiles determined through solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC/MS) and then suspicious samples were identified. The results were statistically processed and compared with results of a sensory analysis. Six honeys, which differed significantly in volatiles profiles (outliers detected by Factor Analysis), selected volatile substance representation (furan-2-carbaldehyde, 1,4-dimethylpyrazole, benzaldehyde, 2-phenylacetaldehyde) and honey aroma intensity and pleasantness were subjected to targeted analyses (i.e. determination of 5-(hydroxymethyl)-2-furaldehyde, diastase activity, unauthorized additive presence). Four of these suspicious samples were found to have high content of 5-(hydroxymethyl)-2-furaldehyde (more than 40 mg/kg), three honeys had low values for diastase activity (less than 8) and three samples positive for triacetin addition. The fact that all these samples revealed a breach of least one of the selected quality parameters defined by the Codex Alimentarius standard proved the proposed methodology to be a useful tool for fast quality evaluation of honey.