Biotechnological Approaches to Sludge Dewatering

Sewage treatment plants generate a large volume of waste sludge as a by-product with water content over 95%, which requires further treatment, volume reduction, dewatering, stabilization, and safe disposal. Sludge dewatering is a major issue in sewage treatment as dewatering consumes a large quantity of expensive synthetic chemical flocculants. Moreover, the commercial chemical flocculants create several environmental issues including generation of odor and release of toxic compounds. As an alternative to chemical flocculant-based dewatering, a sustainable and eco-friendly process is necessary. A number of studies have been reported on this aspect using flocculants produced by heterotrophic bacteria, chemolithoautotrophic bacteria, and fungi. A composite flocculant from iron-oxidizing bacteria has been found to be a promising flocculating agent. This chapter presents a comprehensive review of developments in biotechnological approaches to sludge flocculation and dewatering, which includes background on sewage treatment, sludge flocculation, and dewatering methods using microbial flocculants.