Advances in Mechanical Dewatering of Wastewater Sludge Treatment

What is it about?

Dewatering of wastewater sludge is a difficult process. The difficulty has been attributed mainly to the fact that particles are very fine, colloidal in nature and possess a gel-like structure due to polymeric flocculation. In order to tackle the limitations in wastewater sludge dewatering, new technologies have been developed in recent years. Some technologies, such as wastewater sludge digestion, wastewater sludge mineralisation or peroxidation, allow to reduce the amount of wastewater sludge to be dewatered, or the dewaterability of the sludge, by changing the biochemical composition. Nevertheless, wastewater sludge remains hard to dewater, and therefore, an improvement in the conventional dewatering equipments is desirable. Therefore, current research tends to propose potential alternatives to enhance the dewatering ability of conventional processes, to increase the final dry solids content, and to accelerate the dewatering process with low energy consumption compared to thermal drying. Different options have been investigated to enhance the wastewater sludge dewatering. Some of the new developments to be assimilated and assembled in this chapter include intensification of the dewatering process which combines (1) mechanical and thermal effects, (2) mechanical force and an electric field, (3) the superimposition of ultrasounds and/or magnetic fields, (4) the combined fields (e.g. electric and ultrasonic) applied simultaneously, (5) both shear and compressive forces, (6) and microwave-assisted dewatering. This chapter focuses on the scientific and practical aspects of the application of an additional force field in laboratory/industrial dewatering and discusses this in relation to conventional dewatering techniques in terms of water content/or dry solids content and energy consumption. Indeed, the aim of this chapter is to provide a fundamental understanding of the different process variables and configurations in order to identify potential improvements and future innovative technologies for dewatering enhancement. Following a detailed outline of research in one of the most promising alterative techniques, the electrically assisted dewatering of wastewater sludge, experimental data obtained by the authors are presented in this chapter.

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