Factors affecting decay of Salmonella Birkenhead and coliphage MS2 during mesophilic anaerobic digestion and air drying of sewage sludge

• Published in: Journal of water and health Vol. 13; no. 2; pp. 459 - 472
• Main Authors: Mondal, Tania, Rouch, Duncan A, Thurbon, Nerida, Smith, Stephen R, Deighton, Margaret A
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01.06.2015
• Subjects: Air; Air drying; Air temperature; Ambient temperature; Anaerobic digestion; Anaerobic treatment; Anaerobiosis; Anatomical structures; Autoclaving; Bacteria; Bioreactors; Competition; Deactivation; Decay; Digestion; Drying; Enzymes; Hydrogen-Ion Concentration; Incubation period; Inoculation; Levivirus - physiology; Microorganisms; Mineral nutrients; Moisture content; Pathogens; Peptide Hydrolases - metabolism; Protease; Proteinase; Salmonella; Salmonella - physiology; Sewage; Sewage - microbiology; Sewage - virology; Sewage disposal; Sewage sludge; Sludge; Sludge treatment; Studies; Temperature; Temperature effects; Viability; Viruses; Waste Disposal, Fluid - methods; Australia; United States > US; Melbourne Victoria Australia
• DOI: 10.2166/wh.2014.313
• ISSN: 1477-8920

Factors affecting the decay of Salmonella Birkenhead and coliphage, as representatives of bacterial and viral pathogens, respectively, during mesophilic anaerobic digestion (MAD) and air drying treatment of anaerobically digested sewage sludge were investigated. Controlled concentrations of S. Birkenhead were inoculated into non-sterile, autoclaved, γ-irradiated and nutrient-supplemented sludge and cultures were incubated at 37 °C (MAD sludge treatment temperature) or 20 °C (summer air drying sludge treatment temperature). Nutrient limitation caused by microbial competition was the principal mechanism responsible for the decay of S. Birkenhead by MAD and during air drying of digested sludge. The effects of protease activity in sludge on MS2 coliphage decay in digested and air dried sludge were also investigated. MS2 coliphage showed a 3.0-3.5 log10 reduction during incubation with sludge-protease extracts at 37 °C for 25 h. Proteases produced by indigenous microbes in sludge potentially increase coliphage inactivation and may therefore have a significant role in the decay of enteric viruses in sewage sludge. The results help to explain the loss of viability of enteric bacteria and viral pathogens with treatment process time and contribute to fundamental understanding of the various biotic inactivation mechanisms operating in sludge treatment processes at mesophilic and ambient temperatures.