Preparation of foamed glass using ash of sewage sludge obtained from municipial wastewater treatment

U disertaciji je istražena mogućnost priprave visokokvalitetnog pjenostaklenog materijala iz pepela dobivenog spaljivanjem mulja nastalog pročišćavanjem komunalnih otpadnih voda, koji zbog rastućih količina i nepovoljnog kemijskog sastava predstavlja opasnost za okoliš. Uz pepeo za pripravu pjenostakla korišteni su otpadno ambalažno staklo i otpadni vapnenac kao agens za pjenjenje. Utvrđeno je da se pjenostaklo ujednačene poroznosti i volumne stabilnosti te poboljšane tlačne čvrstoće (≈ 30 MPa) u odnosu na komercijalne pjenostaklene proizvode može pripraviti brzinom zagrijavanja od 5 °C/min do temperature od 850 °C uz zadršku od 15 min na vršnoj temperaturi. U pjenostaklu može se zbrinuti visoki maseni udio pepela (do 28 %) s niskim masenim udjelom vapnenca (1–2 %). Izluživanjem teških metala iz uzoraka pjenostakla utvrđeno je da su koncentracije teških metala u eluatima unutar zakonskih dopuštenih granica za neopasne otpade te da pjenostakla pokazuju antibakterijsku aktivnost prema klinički relevantnoj bakteriji Acinetobacter baumannii. Poboljšana mehanička svojstva dobivenog pjenostakla posljedica su stvaranja novih mineralnih faza tijekom toplinske obrade. Dodatkom pepela dolazi do pojačane kristalizacije natrijevog-kalcijevog silikata, α-kvarca, diopsida i volastonita. Kristalizacija ovih faza osim što doprinosi poboljšanju tlačne čvrstoće materijala istovremeno smanjuje izluživanje teških metala iz pjenostaklene matrice. Antibakterijska aktivnost posljedica je visoke pH-vrijednosti eluata uzrokovane otapanjem nevezanog kalcijevog oksida čije su čestice utvrđene elektronskom mikroskopijom na stijenkama pora.In this PhD thesis thepossibility of high quality foam glass material production from sewage sludge ash prepared by incineration of sewage sludge from waste water treatment plants, that due to its increasing quantities and adverse chemical composition represent an environmental hazard was investigated. Besides ash as starting materials,waste container glass culet and waste limestone as a foaming agent were used. It has been found that foam glass with uniform porosity and volume stability with improved compressive strength (≈ 30 MPa) in relation to commercial foam glass products, can be prepared through heating by 5 °C/min to 850 °C with holding time of 15 min at final temperature. Prepared foam glass can utilize a high content of ash (up to 28 wt.%) with small share of foaming agent (1 – 2 wt.%). Leaching of heavy metals from foam glass samples showed that heavy metal concentrations in eluates are within the legislative limits for non-hazardous wastes and that they show antibacterial activity against a clinically relevant bacterium Acinetobacter baumannii. Improved mechanical properties of prepared foam glass resulted from enhanced crystallization of sodium calcium silicate, α-quartz, diopside and wollastonite. Crystallization of these phases apart from contributing to the improvement of the compressive strength of the material simultaneously reduces the leaching of heavy metals from foam glass matrix. The antibacterial activity was the result of high pH value of eluates, which were the consequence of alkaline reaction of unreacted calcium oxide adhered to walls of pores, particles of which were detected by electron microscopy

Preparation of foamed glass using ash of sewage sludge obtained from municipial wastewater treatment

U disertaciji je istražena mogućnost priprave visokokvalitetnog pjenostaklenog materijala iz pepela dobivenog spaljivanjem mulja nastalog pročišćavanjem komunalnih otpadnih voda, koji zbog rastućih količina i nepovoljnog kemijskog sastava predstavlja opasnost za okoliš. Uz pepeo za pripravu pjenostakla korišteni su otpadno ambalažno staklo i otpadni vapnenac kao agens za pjenjenje. Utvrđeno je da se pjenostaklo ujednačene poroznosti i volumne stabilnosti te poboljšane tlačne čvrstoće (≈ 30 MPa) u odnosu na komercijalne pjenostaklene proizvode može pripraviti brzinom zagrijavanja od 5 °C/min do temperature od 850 °C uz zadršku od 15 min na vršnoj temperaturi. U pjenostaklu može se zbrinuti visoki maseni udio pepela (do 28 %) s niskim masenim udjelom vapnenca (1–2 %). Izluživanjem teških metala iz uzoraka pjenostakla utvrđeno je da su koncentracije teških metala u eluatima unutar zakonskih dopuštenih granica za neopasne otpade te da pjenostakla pokazuju antibakterijsku aktivnost prema klinički relevantnoj bakteriji Acinetobacter baumannii. Poboljšana mehanička svojstva dobivenog pjenostakla posljedica su stvaranja novih mineralnih faza tijekom toplinske obrade. Dodatkom pepela dolazi do pojačane kristalizacije natrijevog-kalcijevog silikata, α-kvarca, diopsida i volastonita. Kristalizacija ovih faza osim što doprinosi poboljšanju tlačne čvrstoće materijala istovremeno smanjuje izluživanje teških metala iz pjenostaklene matrice. Antibakterijska aktivnost posljedica je visoke pH-vrijednosti eluata uzrokovane otapanjem nevezanog kalcijevog oksida čije su čestice utvrđene elektronskom mikroskopijom na stijenkama pora.In this PhD thesis thepossibility of high quality foam glass material production from sewage sludge ash prepared by incineration of sewage sludge from waste water treatment plants, that due to its increasing quantities and adverse chemical composition represent an environmental hazard was investigated. Besides ash as starting materials,waste container glass culet and waste limestone as a foaming agent were used. It has been found that foam glass with uniform porosity and volume stability with improved compressive strength (≈ 30 MPa) in relation to commercial foam glass products, can be prepared through heating by 5 °C/min to 850 °C with holding time of 15 min at final temperature. Prepared foam glass can utilize a high content of ash (up to 28 wt.%) with small share of foaming agent (1 – 2 wt.%). Leaching of heavy metals from foam glass samples showed that heavy metal concentrations in eluates are within the legislative limits for non-hazardous wastes and that they show antibacterial activity against a clinically relevant bacterium Acinetobacter baumannii. Improved mechanical properties of prepared foam glass resulted from enhanced crystallization of sodium calcium silicate, α-quartz, diopside and wollastonite. Crystallization of these phases apart from contributing to the improvement of the compressive strength of the material simultaneously reduces the leaching of heavy metals from foam glass matrix. The antibacterial activity was the result of high pH value of eluates, which were the consequence of alkaline reaction of unreacted calcium oxide adhered to walls of pores, particles of which were detected by electron microscopy

Preparation of foamed glass using ash of sewage sludge obtained from municipial wastewater treatment

U disertaciji je istražena mogućnost priprave visokokvalitetnog pjenostaklenog materijala iz pepela dobivenog spaljivanjem mulja nastalog pročišćavanjem komunalnih otpadnih voda, koji zbog rastućih količina i nepovoljnog kemijskog sastava predstavlja opasnost za okoliš. Uz pepeo za pripravu pjenostakla korišteni su otpadno ambalažno staklo i otpadni vapnenac kao agens za pjenjenje. Utvrđeno je da se pjenostaklo ujednačene poroznosti i volumne stabilnosti te poboljšane tlačne čvrstoće (≈ 30 MPa) u odnosu na komercijalne pjenostaklene proizvode može pripraviti brzinom zagrijavanja od 5 °C/min do temperature od 850 °C uz zadršku od 15 min na vršnoj temperaturi. U pjenostaklu može se zbrinuti visoki maseni udio pepela (do 28 %) s niskim masenim udjelom vapnenca (1–2 %). Izluživanjem teških metala iz uzoraka pjenostakla utvrđeno je da su koncentracije teških metala u eluatima unutar zakonskih dopuštenih granica za neopasne otpade te da pjenostakla pokazuju antibakterijsku aktivnost prema klinički relevantnoj bakteriji Acinetobacter baumannii. Poboljšana mehanička svojstva dobivenog pjenostakla posljedica su stvaranja novih mineralnih faza tijekom toplinske obrade. Dodatkom pepela dolazi do pojačane kristalizacije natrijevog-kalcijevog silikata, α-kvarca, diopsida i volastonita. Kristalizacija ovih faza osim što doprinosi poboljšanju tlačne čvrstoće materijala istovremeno smanjuje izluživanje teških metala iz pjenostaklene matrice. Antibakterijska aktivnost posljedica je visoke pH-vrijednosti eluata uzrokovane otapanjem nevezanog kalcijevog oksida čije su čestice utvrđene elektronskom mikroskopijom na stijenkama pora.In this PhD thesis thepossibility of high quality foam glass material production from sewage sludge ash prepared by incineration of sewage sludge from waste water treatment plants, that due to its increasing quantities and adverse chemical composition represent an environmental hazard was investigated. Besides ash as starting materials,waste container glass culet and waste limestone as a foaming agent were used. It has been found that foam glass with uniform porosity and volume stability with improved compressive strength (≈ 30 MPa) in relation to commercial foam glass products, can be prepared through heating by 5 °C/min to 850 °C with holding time of 15 min at final temperature. Prepared foam glass can utilize a high content of ash (up to 28 wt.%) with small share of foaming agent (1 – 2 wt.%). Leaching of heavy metals from foam glass samples showed that heavy metal concentrations in eluates are within the legislative limits for non-hazardous wastes and that they show antibacterial activity against a clinically relevant bacterium Acinetobacter baumannii. Improved mechanical properties of prepared foam glass resulted from enhanced crystallization of sodium calcium silicate, α-quartz, diopside and wollastonite. Crystallization of these phases apart from contributing to the improvement of the compressive strength of the material simultaneously reduces the leaching of heavy metals from foam glass matrix. The antibacterial activity was the result of high pH value of eluates, which were the consequence of alkaline reaction of unreacted calcium oxide adhered to walls of pores, particles of which were detected by electron microscopy

Industrial wastewater treatment plant enriches antibiotic resistance genes and alters the structure of microbial communities

Antibiotic resistance is an emerging global health crisis, driven largely by overuse and misuse of antibiotics. However, there are examples in which the production of these antimicrobial agents has polluted the environment with active antibiotic residues, selecting for antibiotic resistant bacteria and the genes they carry. In this work, we have used shotgun metagenomics to investigate the taxonomic structure and resistance gene composition of sludge communities in a treatment plant in Croatia receiving wastewater from production of the macrolide antibiotic azithromycin. We found that the total abundance of antibiotic resistance genes was three times higher in sludge from the treatment plant receiving wastewater from pharmaceutical production than in municipal sludge from a sewage treatment plant in Zagreb. Surprisingly, macrolide resistance genes did not have higher abundances in the industrial sludge, but genes associated with mobile genetic elements such as integrons had. We conclude that at high concentrations of antibiotics, selection may favor taxonomic shifts towards intrinsically resistant species or strains harboring chromosomal resistance mutations rather than acquisition of mobile resistance determinants. Our results underscore the need for regulatory action also within Europe to avoid release of antibiotics into the environment

Removal of emerging pathogenic bacteria using metal-exchanged natural zeolite bead filter

Hospital wastewaters can become a route for dissemination of antibiotic-resistant bacteria to the environment if not properly treated. Some of these bacteria are able to survive conventional disinfection treatments (e.g. chlorination, UV irradiation), which evokes the need for novel disinfection methods. The metal-exchanged zeolites were tested as novel antibacterial agents for wastewater treatment. The natural zeolite clinoptilolite enriched with silver (AgNZ) showed far better antibacterial activity towards hospital pathogenic bacterium Acinetobacter baumannii when compared with copper-exchanged zeolite (CuNZ), with minimal bactericidal concentration of 0.25-2 (AgNZ) compared with 32-64 mg L-1 (CuNZ) in a batch system and respective log 5.6 reduction compared with log 0.5 reduction in a flow system with pure bacterial culture. In the flow system with real effluent wastewater from the treatment plant, the removal of carbapenem-resistant bacteria using AgNZ was 90-100% during the 4 days of the experimental run. These results indicate that the AgNZ efficiently removes pathogenic bacteria from the wastewater, including A. baumannii, and is promising as a disinfectant material in a bead filter system

Emerging Trends in the Epidemiology of COVID-19: The Croatian ‘One Health’ Perspective

During the four pandemic waves, a total of 560,504 cases and 10,178 deaths due to COVID-19 were reported in Croatia. The Alpha variant, dominant from March 2021 (>50% of positive samples), was rapidly replaced by Delta variants (>90%) by August 2021. Several seroprevalence studies were conducted in different populations (general population, children/adolescents, professional athletes, healthcare workers, veterinarians) and in immunocompromised patients (hemodialysis patients, liver/kidney transplant recipients). After the first pandemic wave, seroprevalence rates of neutralizing (NT) antibodies were reported to be 0.2–5.5%. Significantly higher seropositivity was detected during/after the second wave, 2.6–18.7%. Two studies conducted in pet animals (February-June 2020/July–December 2020) reported SARS-CoV-2 NT antibodies in 0.76% of cats and 0.31–14.69% of dogs, respectively. SARS-CoV-2 NT antibodies were not detected in wildlife. Environmental samples taken in the households of COVID-19 patients showed high-touch personal objects as most frequently contaminated (17.3%), followed by surfaces in patients’ rooms (14.6%), kitchens (13.3%) and bathrooms (8.3%). SARS-CoV-2 RNA was also detected in 96.8% affluent water samples, while all effluent water samples tested negative. Detection of SARS-CoV-2 in humans, animals and the environment suggests that the ‘One Health’ approach is critical to controlling COVID-19 and future pandemics

Ružička days : International conference 18th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: chemical analysis and synthesis, chemical and biochemical engineering, food technology and biotechnology, medical chemistry and pharmacy, environmental protection and meeting of young chemists