Modern techniques for sludge dewaterability improvement

Since sludge mitigation requires new strategies for enhanced dewaterablity, several scientific and technological advancements in conditioning, dewatering and drying technologies for a variety of sludges are being developed continuously. Grappling with the problem of ever-increasing sludge volume, it is important to critically assess the new concepts to assist in rapid technological developments in this area. This paper provides a concise state-of-the-art discussion focused on the effects of the key parameters including affected dewatering performance according to the sludge type, source and its physicochemical characteristics, rheological factors, particle size distribution, floc surface charge and endogenic polymeric substances (EPS), on the dewatering performance. Since initial conditioning is highly critical on the following dewatering and drying steps, innovative methods, e.g., physical conditioning, sonication, hydrodynamic cavitation, thermal treatment, microwave, electrical treatment, photocatalytic treatment and chemical coagulation/flocculation have been included in this review. Furthermore, latest developments in dewatering and drying technologies are also discussed in terms of their advantages/disadvantages and energy demands. This paper includes a capsule discussion of control of industrial sludges and the application of advanced oxidation processes (AOP(s)) in sludge conditioning and dewatering.