Impact of initial biodegradability on sludge anaerobic digestion enhancement by thermal pretreatment

Abstract

Thermal treatments with temperature ranging from 60 to 210°C were applied to 6 waste-activated sludge samples originating from high or medium load, extended aeration wastewater treatment processes that treated different wastewaters (urban, urban and industrial or slaughterhouse). COD sludge solubilisation was linearly correlated with the treatment temperature on the whole temperature range and independently of the sludge samples. Sludge batch mesophilic biodegradability increased with treatment temperature up to 190°C. In this temperature range, biodegradability enhancement or methane production increase by thermal hydrolysis was shown to be a function of sludge COD solubilisation but also of sludge initial biodegradability. The lower the initial biodegradability means the higher efficiency of thermal treatment.

Keywords:

• Thermal hydrolysis
• methanization
• biogas
• biodegradability
• waste-activated sludge

Acknowledgments

Authors want to thank ADEME for financial contributions.