1. Improving lignocellulosic and non-lignocellulosic biomass characteristics through torrefaction processMaja Ivanovski, Danijela Urbancl, Aleksandra Petrovič, Janja Stergar, Darko Goričanec, Marjana Simonič, 2022, izvirni znanstveni članek Opis: In this study, three locally available biomasses, namely miscanthus, hops, sewage sludge,
and additionally, their mixtures, were subjected to the torrefaction process to improve their fuel
properties. The torrefaction process was conducted at 250–350 ◦C and 10–60 min in a nitrogen
(N2) environment. The torrefaction temperature and time were studied to evaluate the selected
biomass materials; furthermore, heating values, mass and energy yields, enhancement factors,
torrefaction severity indexes (TSI), and energy-mass co-benefit indexes (EMCI) were calculated. In
addition, thermogravimetric (TGA) and Fourier transform infrared analyses (FTIR) were performed
to characterize raw and torrefied biomass under the most stringent conditions (350 ◦C and 60 min).
The results showed that with increasing torrefaction temperature and duration, mass and energy
yields decreased, and heating values (HHVs) increased for all studied biomasses. The results of the
TSI and EMCI indexes showed that the optimum torrefaction conditions were as follows: 260 ◦C
and 10 min for pure miscanthus and hops, whilst this could not be confirmed for the sewage sludge.
Furthermore, the combination of sewage sludge and the above-mentioned types of lignocellulosic
biomass exhibited better fuel properties than sewage sludge alone.
Ključne besede: lignocellulosic biomass, sewage sludge, torrefication, thermogravimetry, TSI
Objavljeno v DKUM: 10.04.2025; Ogledov: 0; Prenosov: 14
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2. Experimental and mathematical investigation of anaerobic granulate density via settling velocityAljaž Klasinc, Gregor Drago Zupančič, Matjaž Hriberšek, Aleš Hribernik, Aleksandra Lobnik, Matej Zadravec, 2022, izvirni znanstveni članek Opis: The objective of this study was to determine the density of anaerobic granules on different
heights of a full-scale Upflow Anaerobic Sludge Bed reactor. The density was defined through the
settling velocities of anaerobic granules, measured in a full-scale Upflow Anaerobic Sludge Bed
reactor. In this study, granular density was calculated with the measured settling velocities and
developed mathematical model. The developed mathematical model is based on the Stokes model.
In the experiment, granules were taken from different heights of an Upflow Anaerobic Sludge Bed
reactor, from 0.6 to 7.6 m. The granules’ diameters varied between 1 and 5 mm. The granules were
taken from six different heights through the reactor. The settling velocity of the active granules
(with gas in the granule pore and on the surface of the granule) was measured first. After the active
granules’ settling velocity measurement, the granules were placed in a vortex to obtain degassed
granules (granules without any gas in the pores or on the surface), for which the settling velocities
were also measured later. It is shown that granules’ densities at different heights are independent of
the reactor height.
Ključne besede: Upflow Anaerobic Sludge Bed reactor, microstructure, anaerobic granular sludge, settling velocity, density
Objavljeno v DKUM: 26.03.2025; Ogledov: 0; Prenosov: 5
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3. Hydrothermal co-carbonization of sewage sludge and whey : enhancement of product properties and potential application in agricultureAleksandra Petrovič, Tjaša Cenčič, Lidija Škodič, Sabina Vohl, Lidija Čuček, 2023, izvirni znanstveni članek Ključne besede: hydrothermal co-carbonization, sewage sludge, cheese whey, product characterisation, potential application
Objavljeno v DKUM: 24.02.2025; Ogledov: 0; Prenosov: 6
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4. Sustainable hydrothermal co-carbonization of residues from the vegetable oil industry and sewage sludge : hydrochar production and liquid fraction valorisationAleksandra Petrovič, Tjaša Cenčič, Jelena Parlov Vuković, Tomislav Jednačak, Silvo Hribernik, Sabina Vohl, Danijela Urbancl, Marina Tišma, Lidija Čuček, 2024, izvirni znanstveni članek Opis: In this study, the hydrothermal co-carbonization (co-HTC) of residues from the vegetable oil industry (pumpkin oil cake– PC, hemp oil cake– HC) and sewage sludge (SS) was investigated for the first time. The co-HTC was performed at 250 C and atreatment time of 5 h. The effects of the mass ratio of the feedstocks (1:1, 1:3 and 3:1) on the properties of the HTC products were investigated using various analytical methods (NMR, XRD, 3D-EEM, FTIR, etc.). The co-HTC of SS with oil cakes resulted in improved fuel properties of the hydrochar and an increase in C content from 36.9 to 53.7 wt%, and an increase in the higher heating value (HHV) from 14.8 to 23.6 MJ/kg. The combination with HC gave hydrochars with a higher HHV and higher C content than the combination with PC. The hydrochar yield varied in the range of 39.4–55.3 wt%. NMR analysis revealed a higher proportion of aliphatic (~60 %) than aromatic compounds (~35 %) in the hydrochars, as well as a high content of orthophosphate and unsaturated fatty acids. The liquid fractions were rich in nutrients and organic compounds, but toxic to aquatic organisms. The hydrochars and liquid fractions performed well in the germination test with plant species.
Ključne besede: hydrothermal co-carbonization, sewage sludge, vegetable oil industry residues, hydrochar, liquid fraction, valorisation
Objavljeno v DKUM: 17.01.2025; Ogledov: 0; Prenosov: 11
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5. Ozonation of amoxicillin and ciprofloxacin in model hospital wastewater to increase biotreatabilitySeverina Aleksić, Andreja Žgajnar Gotvajn, Katarina Premzl, Mitja Kolar, Sonja Šostar-Turk, 2021, izvirni znanstveni članek Opis: Amoxicillin (AMX) and Ciprofloxacin (CIP) are antibiotics commonly used in human medicine with high environmental toxicity and poor biodegradability. They have been found in various hospital effluents and groundwater, and their environmental impact is still not fully understood. In this work, we investigated the possibility of treating model wastewaters containing the antibiotics AMX and CIP using ozonation, with the addition of H$_2$O$_2$ under various conditions, including different pH values, H$_2$O$_2$, and ozone dosages. The quantification of and treatment efficacy for antibiotic removal were determined via solid phase extraction followed by chromatographic separation by liquid chromatography coupled with tandem triple quadrupole mass spectrometry (LC/MS/MS). This analytical system is quite efficient for the detection of all major antibiotic classes, even if they are present at very low concentrations. The efficiency of ozonation was determined by measuring the TOC (Total Organic Carbon) changes after ozonation of the model wastewater and by measuring the concentration of the two antibiotics. In a sequential activated sludge process of ozone-treated model wastewater, almost complete TOC removal and an overwhelming decrease in antibiotic concentrations (up to 99%) were observed. Ozonation resulted in complete removal of AMX and CIP in less than 30 and 120 min, respectively. The results of this work indicate that ozonation could be a suitable pretreatment method to reduce the toxicity of contaminants (AMX and CIP) and improve the biodegradability of hospital wastewater.
Ključne besede: antibiotics, amoxicillin, AMX, ciprofloxacin, CIP, hospital wastewater, hydrogen peroxide, ozone, sludge, water treatment
Objavljeno v DKUM: 06.08.2024; Ogledov: 75; Prenosov: 14
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6. Thermo-kinetic analysis of pyrolysis of thermally pre-treated sewage sludge from the food industryAleksandra Petrovič, Janja Stergar, Lidija Škodič, Neža Rašl, Tjaša Cenčič, Lidija Čuček, Darko Goričanec, Danijela Urbancl, 2023, izvirni znanstveni članek Ključne besede: thermal pre-treatment, pyrolysis, industrial sewage sludge, thermogravimetric analysis, kinetic analysis, thermodynamic analysis
Objavljeno v DKUM: 10.05.2024; Ogledov: 258; Prenosov: 15
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7. Reduction of sludge volume in waste waters at the end of the drinking water treatment processRebeka Fakin, 2018, magistrsko delo Opis: Water treatment at Seierstad drinking water treatment plant is done by chemical coagulation using aluminum-based coagulant. The quality of the drinking water source – Lake Farris, has decreased throughout the years, that is why more and more particles, organic matter and dissolved minerals must be removed. That contributes to the volume of sludge being produced at the end of the process. The main objective of the assignment is to reduce sludge volume by coagulation and flocculation in the sedimentation basins using a coagulant/flocculent. In order to choose the right coagulant tests have been performed in the laboratory and on the actual process. The laboratory analyses showed great potential and one of the coagulants has been chosen and tested on the actual process. The testing was followed up for the entire summer of 2016 and then compared to the year before. We have been following the pH and Al3+ content in the water being released back to the environment and visibility in the top water layer in the sedimentation basin. Cost analysis, including the cost of chemicals and electricity usage, has been done. The sludge reduction was successful, and it was approximately 49% less than the year before.
Ključne besede: Water treatment, lake Farris, sludge treatment using coagulation and flocculation, effects of aluminum on the environment.
Objavljeno v DKUM: 09.03.2018; Ogledov: 1569; Prenosov: 146
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