Abstract
Anaerobic digestion (AD) is a commonly used method of processing waste. Regardless of the type of the used digestate (fertilizer, feedstock in case of solid-state fermentation, raw-material in case of thermal treatment) effective pathogen risk elimination, even in the case of high pathogen concentration is essential. An investigation of the survival time and inactivation rate of the Salmonella Senftenberg W775, Enterococcus spp., and Ascaris suum eggs during thermophilic anaerobic digestion performed on laboratory scale and confirmation of hygienization in full-scale operation were performed in this study. Except for sanitization efficiency, the AD process performance and stability were also verified based on determination of pH value, dry matter content, acidity, alkalinity, and content of fatty acids. The elimination of pathogen was met within 6.06 h, 5.5 h, and about 10 h for the Salmonella Senftenberg W775, Enterococcus spp., and Ascaris suum, respectively in the laboratory trials. The obtained results were confirmed in full-scale tests, using 1500 m3 Kompogas® reactors, operating in MBT Plant located in Poland. Sanitization of the digestate was achieved. Furthermore, the process was stable. The pH value, suspended solids, and ammonium content remained stable at 8.5, 35%, and 3.8 g/kg, respectively. The acetic acid content was noted between almost 0.8 and over 1.1 g/kg, while the concentration of propionic acid was noted at maximum level of about 100 mg/kg. The AD conditions could positively affect the pathogen elimination. Based on these results it can be found that anaerobic digestion under thermophilic conditions results in high sanitation efficiency.
Highlights
According to the EU regulation [1] food and kitchen waste belong to category 3 and require proper management to eliminate the potential health risks
The anaerobic digestion under thermophilic conditions has been determined to be a suitable process for eliminating pathogenic microorganism, instead of pasteurization [17]
The laboratory and full-scale experiments confirm the elimination of Salmonella Senftenberg W 775 and Enterococcus spp. bacteria along with inactivation of the Ascaris suum eggs, during co-digestion of OFMWSW with addition of restaurant waste
Summary
According to the EU regulation [1] food and kitchen waste belong to category 3 and require proper management to eliminate the potential health risks. Regarding to a biogas plant, at the initial stage, kitchen waste has to be pasteurized within a minimum of 60 min in a minimum temperature at 70 ◦ C. Salmonella is one of the most likely pathogens to be spread in the environment via animal slurry and sewage sludge [2]. All serotype of Salmonella are potentially pathogenic to both animals and people. Foodborne enteritis (food poisoning) is the most common infection caused by Salmonella, which is a significant public health concern. Salmonellosis is the second most commonly reported gastrointestinal infection and an important cause of foodborne outbreaks in the European Union [3]
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