Variability of Micro- and Macro-Elements in Anaerobic Co-Digestion of Municipal Sewage Sludge and Food Industrial By-Products

Abstract

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.

Waste Activated Sludge-High Rate (WASHR) Treatment Process: A Novel, Economically Viable, and Environmentally Sustainable Method to Co-Treat High-Strength Wastewaters at Municipal Wastewater Treatment Plants

“…Full-scale anaerobic co-digestion with municipal wastewater sludges was shown to be effective for the treatment of a wide variety of wastewaters from the food industry, including fats, oils, and greases (FOG); dairy manufacturing wastewater; slaughterhouse wastewater; and winery wastewater (WWW), among others [ 3 , 4 , 5 , 6 , 7 , 8 ]. Wastewaters generated by the food industry are often also biodegradable by aerobic biomass, and co-treatment with domestic wastewater in the aerobic bioreactors at municipal WWTPs was also successfully used for co-treatment [ 9 , 10 ].…”