Anaerobic Digestion, Dewatering, Thermal Hydrolysis, CHP, Steam Explosion

Historically is has been shown on many projects that centrifuges can outperform belt presses in dewatering digested sludge. However results from a number of projects where sludge has been treated before digestion with Cambi thermal hydrolysis process (THP) have shown good results for belt press dewatering - generally greater than 30% DS. The authors propose that the main mechanism in THP is in changing the structure of extracelluar polymer (ECP) that binds water mainly to secondary sludge and limits dewaterability and compressibility of the mixed sludge. The digested sludge after THP is also much finer in structure and this can lead to problems with capture rate, higher polymer rate with some centrifuges. The aim of this work was to aid process selection for final dewatering for future projects to ensure a cake of greater that 30% DS and with a good capture rate.