Recent advances in sludge dewatering and drying technology

Sewage sludge is an inevitable by-product of biological wastewater treatment process and contains various toxic substances such as pathogens, heavy metals and organic contaminants, which may cause serious pollution risks without appropriate disposals. Dewatering and drying technology play significant roles in minimizing sludge volume, facilitating transportation, increasing calorific value and reducing the leachate production in landfill sites. Various new technologies are emerging and existing ones are always evolving because of sharp growth of sewage sludge in the last decade. This paper presents a comprehensive review on recent advances in related to dewatering and drying of sewage sludge. The influencing factors of sludge dewatering are addressed out firstly. And then the conditioning methods to improve sludge dewatering performance are summarized and compared in terms of applicable occasions, material consumption, energy and environmental impacts etc. The dewatering technology is classified into common, deep and high-dry dewatering based on the degree of moisture content, and the drying method is divided into convective drying, conduction drying, radiation drying and other new drying. The present dewatering and drying technologies are reviewed and compared in order to provide useful guidelines for sludge disposal. The future demands and opportunities for sludge dewatering and drying are pointed out from industrial perspective.