Evaluation of pathogens inactivation during thermophilic anaerobic digestion of faecal sludge

There is an urgent need to develop comprehensive and sustainable sanitation systems in developing countries, including faecal sludge (FS) treatment technologies that help reduce environmental and human health risks. Anaerobic digestion (AD) is widely used for the treatment of biowastes but its potential for FS sanitization still needs to be assessed. The goal of this work was to evaluate pathogens inactivation during thermophilic AD of a synthetic surrogate for FS through biomethane potential (BMP) tests. Salmonella, Ascaris suum eggs and phages T4 and MS2 were selected as models for bacterial, parasitic and viral pathogens, respectively. Salmonella were not detected anymore after 110 minutes of thermophilic AD. In anaerobic conditions at 55°C, concentrations of phages T4 and MS2 were below detection levels after 3 and 4 days, and no potentially viable Ascaris eggs were found after 15 days. Methods need to be optimized in order to improve the reliability of viability checks on Ascaris eggs. Future experiments could focus on this model, which will a priori be the limiting factor for the dimensioning of anaerobic digesters that yield safe-to-use end products.