1,721,039 research outputs found
Caratterizzazione fisico-meccanica di rifiuti inertizzati ai fini dello smaltimento/riutilizzo: risultati preliminari
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A swirling jet-induced cavitation to increase activated sludge solubilisation and aerobic sludge biodegradability
No full textIn this work, a modified swirling jet induced hydrodynamic cavitation (HC) has been used for the pre-treatment of excess sludge. In order to both improve the HC treatment efficiencies and reduce the energy consumption, the effectiveness of the HC reactor on sludge disintegration and on aerobic biodegradability has been investigated at different operating conditions and parameters, such as temperature, inlet pressure, sludge total solid (TS) content and reactor geometry. The inlet pressure was related to the flow velocity and pressure drop. The best results in terms of sludge solubilisation were achieved after 2 h of HC treatment, treating a 50.0 gTS L−1 and using the three heads Ecowirl system, at 35.0 °C and 4.0 bar. Chemical and respirometric tests proved that sludge solubilisation and aerobic biodegradability can be efficiently enhanced through HC pre-treatment technique. At the optimum operating conditions, the specific supplied energy has been varied from 3276 to 12,780 kJ kg TS−1 in the HC treatment, by increasing the treatment time from 2 to 8 h, respectively. Low endogenous decay rates (bH) were measured on the excess sludge at low specific supplied energy, revealing that only an alteration in floc structure was responsible for the sludge solubilisation. On the contrary, higher bH values were measured at higher specific supplied energy, indicating that the sludge solubilisation was related to a decreasing biomass viability, as consequence of dead cells and/or disrupted cells (cell lysis)
Metodo per la stabilizzazione dei suoli inquinati
No full textLa presente invenzione si riferisce a un metodo per la decontaminazione dei suoli inquinati, in particolare per la decontaminazione da metalli pesanti.
Più in particolare, la presente invenzione riguarda un metodo di tipo elettrocinetico per la stabilizzazione delle specie contaminanti nel suolo
Sludge reduction by an anaerobic side-stream reactor process: A full-scale application
No full textIn the present paper, a new process, whose acronym is UTN (University of Trento) system, is proposed and tested at full scale for reducing the amount of sludge of the wastewater treatment plant. The UTN system allows sludge reduction in conventional activated sludge (CAS) due to the cell lysis, the sludge decay and, above all, to the selection of slow growing microorganism. In this study, the first full-scale UTN system was tested by retrofitting an existing wastewater treatment plant located in Marmirolo (Lombardia, Italy) having a treatment capacity of 6,000 population equivalent (PE). Performances of the UTN system were evaluated in terms of sludge reduction, together with organic carbon and nutrients removal efficiencies. Results obtained over 10 month of monitoring period, divided in period I (7 months) and period II (3 months), characterized by different operative conditions, have reported a specific sludge production of 0.37 and 0.23 kg TSS per kg of COD removed, respectively; which is 50% and 69% lower than that observed in the reference period when the plant worked under conventional activated sludge process. Furthermore, results revealed that the UTN system allows a high removal of wastewater typical pollutants, without causing negative effects on the effluent quality, always ensuring compliance with the regulatory discharge limits
Indagine sperimentale sui test di caratterizzazione dei residui di combustione ai fini del loro smaltimento/riutilizzo
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The role of particulate matter in offices for urban air quality management
Full text linkThe particulate matter (PM) in the air of office environments plays an important role in the daily human exposure in urban areas. The present paper reports a few measurements in order to integrate the knowledge of the sector concerning pollution in offices. The parameter analysed is PM, referred to in three fractions of interest, depending on their dimensions. Some considerations are reported in order to set or confirm specific criteria for the correct management of office air quality
Effects of hydrodynamic cavitation, low-level thermal and low-level alkaline pre-treatments on sludge solubilisation
No full textWAS is a polluting and hazardous waste generated in WWTPs that must be treated to prevent pollution and human health risks. Anaerobic digestion is the most used process for sludge stabilization. However, it must be improved in terms of both speed and extend of degradation. With the purpose of reducing the energy and chemical consumption linked to sludge treatment, in this study, different anaerobic digestion pre-treatments such as low-level mechanical (hydrodynamic cavitation, 2 bar), low-level thermal (50 °C) and low-level alkaline (NaOH, KOH and Ca(OH)2, pH 10) methods, and a combination thereof, were tested as strategies to improve sludge solubilisation. When the pre-treatments were used alone, the alkaline pre-treatment showed the highest sludge solubilisation. Among the alkaline reagents tested, NaOH and KOH led to higher DDPCOD (41.6 and 39.4%), while only 8.4% was achieved by using Ca(OH)2. However, the low-level hydrodynamic cavitation assisted thermo-alkaline pre-treatment was the most efficient in terms of both sludge solubilisation (DDPCOD = 53.0%) and energy efficiency (EE = 64.5 mgΔSCOD kJ−1). The synergetic effects of the combined pre-treatment were also confirmed by the highest release of EPS. Furthermore, cytometric analyses showed that the main mechanism involved in sludge solubilisation for the investigated pre-treatments was flocs disintegration rather than cell lysis
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