Innovative thermo-chemical pretreatment for sludge reduction and energy recovery

Chemical pretreatments has proven to be effective to optimize anaerobic digestion by increasing methane production from sewage sludge and by reducing sludge production. Since May 2015, the ZeroSludge® technology is successfully applied as chemical sludge stabilization at the full scale Italian WWTPs of Siena (100,000 P.E., aerobic stabilization of sludge) attaining more than 70% of sludge reduction. In order to improve this technology towards sludge reduction combined to energy recovery, lab scale experimentation was carried out to assess the potentialities of this innovative pretreatment to enhance anaerobic digestion process. Lab scale results suggested to adopt some measures intended to ensure better anaerobic performances and risks prevention. The modified process allowed to achieve similar results regarding sludge reduction efficiency (around 60-70% in lab scale), and to obtain high methane production rates (0.25 Nm3/kgVSfed) without negative impacts on digester stability.