m abbasalizadeh

Microplastics in sewage sludge represent a formidable obstacle to the use of biosolids in agricultural lands. Ultrasonic pretreatment is extensively utilized in sludge management to enhance biodegradability, reduce organic contaminants, and improve process efficiency through cavitation-induced physical and chemical effects. This research evaluates the effects of conventional ultrasonic sludge pretreatment—operating at a frequency of 20 kHz, a power level of 400 W, a temperature of 25°C, and 15 minutes—on sludge containing biodegradable polyethylene (PE) and non-biodegradable polyvinyl chloride (PVC) microplastics. Structural, morphological, and chemical analyses were conducted using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The SEM results, obtained at magnifications of 60× (PE) and 100× (PVC) with scales of 500 µm and 300 µm, revealed no major physical modifications, such as cracks, fractures, or surface erosion, in either PE or PVC microplastics. Similarly, surface morphology remained largely unchanged across all examined resolutions, including 500 nm and 300 nm, suggesting their structural stability following treatment. Likewise, FTIR spectra demonstrated the chemical resilience of both polymers, as not major alterations were observed in their characteristic absorption peaks (e.g., 2920 and 2850 cm⁻¹ for PE, 1430 and 1250 cm⁻¹ for PVC). Overall, the findings indicate that conventional ultrasonic sludge pretreatment exerts negligible influence on the physical and chemical integrity of the studied microplastics, highlighting their resistance to ultrasonic cavitation and potential persistence in sewage sludge used for agricultural applications.

In this study, the thermodynamic and thermoeconomic analysis of a multigeneration system which produces power, cooling, domestic heating, hydrogen and freshwater has been carried out. The main source of energy for this system is a solar parabolic trough collector (PTC). The working fluid applied for this solar collector is Al2O3-Therminol VP1 nanofluid. The subsystems of this multigeneration system are a steam Rankine cycle for power production, an organic Rankine cycle for power production, a double-effect absorption refrigeration system for cooling production, a domestic water heater for hot water production, a PEM electrolyzer for hydrogen production and a RO desalination unit for freshwater production. In the ORC cycle a TEG unit is applied instead of the condenser for extra power production. The system is analyzed by using the EES software. The effects of different parameters as well as the effects of nanoparticles on the performance of the proposed system were investigated. According to the results, the energy and exergy efficiency of the system are 33.81 % and 23.59 %, respectively. Among the studied working fluids in the ORC cycle, n-pentane shows the best performance. The energy and exergy efficiency of the system increases by the nanoparticle volume concentration and the solar radiation increase. Moreover, the collector inlet temperature has a negative effect on the hydrogen and freshwater production rates. Finally, it is proved that the PTC collector has the highest amount of exergy destruction rate in the studied system.

In this study, renewable energy sources including a high-temperature solar parabolic trough collector and geothermal water integrated with a modified Kalina cycle, a combined ORC-EJR cycle, an electrolyzer, an RO desalination unit, and a domestic water heater. SiO2 and TiO2 nanoparticles dissolved in Therminol VP1 are applied as the working fluid of the solar collector. A comparative analysis of introduced working fluids is performed from energy, exergy as well as cost analysis point of view to evaluate their efficiencies. Solar irradiation, ambient temperature, and collector inlet temperature were the parameters investigated to discover their effects on energy and exergy efficiency, solar collector outlet temperature, hydrogen production rate, and freshwater production rate. The highest generated outlet temperature of the solar collector outlet was 693.8 K obtained by Therminol VP1/SiO2 nanofluid. The maximum energy and exergy efficiencies of the proposed system were 36.69 % and 17.76 %, respectively. Moreover, it is found that by increasing the solar collector inlet temperature, the hydrogen production rate decreases while the water production rate increases.