Comparing alkaline and thermal disintegration characteristics for mechanically dewatered sludge

Abstract

Thermal drying is one of the advanced technologies ultimately providing an alternative method of sludge disposal. In this study, the drying kinetics of mechanically dewatered sludge (MDS) after alkaline and thermal disintegration have been studied. In addition, the effect of total organic carbon (TOC) on specific resistance to filtration and sludge bound water content were also investigated on freshly collected sludge samples. The combined effect of pH and TOC on the thermal sludge drying rate for MDS was modelled using the two‐factorial experimental design method. Statistical assessment of the obtained results proposed that sludge drying potential has increased exponentially for both increasing temperature and lime dosage. Execution of curve fitting algorithms also implied that drying profiles for raw and alkaline‐disintegrated sludge were well fitted to the Henderson and Pabis model. The activation energy of MDS decreased from 28.716 to 11.390 kJ mol⁻¹ after disintegration. Consequently, the unit power requirement for thermal drying decreased remarkably from 706 to 281 W g⁻¹ H₂O.

Keywords:

• bound water content
• dewatered sludge
• disintegration, drying kinetics
• specific resistance to filtration
• total organic carbon