Mixing Effect on Bio-Methanation and Dewaterability of Primary and Secondary Sludge

Abstract

Biomethanation and dewaterability characteristics of primary (PS) and secondary sludge (SS) fractions were assessed after anaerobic stabilization under parallel batch and continuous mixing conditions at 35 degrees C in order to investigate the performance of the separate digestion system. Similar methane conversion/yield values were obtained for PS and SS, while continuous mixing and 35 degrees C have been evaluated as optimal for methane production in PS digestion. Continuous mixing resulted in 50% increased methane yield (600(+/-100) mL/g VSadd.d. SS sludge digestion produced comparable methane yield at 650(+/-100) mL/g VSadd.d showing no effect due to mixing pattern. Settling and dewaterability characteristics of the stabilized PS were superior to stabilized SS samples. A reverse relationship was obtained between settling characteristics and dewaterability for both sludge types.