Magdalena Lebiocka

This paper analyzes the effect of inlet pressure on the index of biodegradability of cavitated herbal waste (HW) following its suspension in mechanically treated wastewater (MTW) for further biological processes. Hydrodynamic cavitation (HC) was carried out at inlet pressures of 3.5, 5.0, and 7.0 bar. The BOD5/COD ratio increased by 30% between the 5th and 10th minutes of the process, with the inlet pressure amounting to 3.5 bar, which indicated increased biodegradability of HW. For the higher inlet pressures used, the value of the biodegradability index (BI) increased by 23% and 13% for 5.0 and 7.0 bar, respectively, after 60 min of the process. The value of COD as well as the VS, TS, TC and TOC concentrations dropped for each analyzed inlet pressure, which indicated that complex organic compounds were effectively destroyed. The highest disintegration degree (DDCOD) was achieved with an inlet pressure of 3.5 bar. SEM analysis was performed to analyze the changing morphological structure of the HW. It was proven that the structural morphology of the herbal waste was significantly influenced by hydrodynamic cavitation, which could affect subsequent biological processing.

The main aim of this study was to evaluate the effect of the addition of selected industrial food wastes on the fate of micro- and macro-elements within an anaerobic digestion process (AD), as well as define the relationship between their content and AD efficiency. Orange peels, (OP), orange pulp (PL) and brewery spent grain (BSG) were used as co-substrates, while municipal sewage sludge (SS) was applied as the main component. The introduction of co-substrates resulted in improvements in feedstock composition in terms of macro-elements, with a simultaneous decrease in the content of HMs (heavy metals). Such beneficial effects led to enhanced methane production, and improved process performance at the highest doses of PL and BSG. In turn, reduced biogas and methane production was found in the three-component digestion mixtures in the presence of OP and BSG; therein, the highest accumulation of most HMs within the process was also revealed. Considering the agricultural application of all digestates, exceedances for Cu, Zn and Hg were recorded, thereby excluding their further use for that purpose.