An Overview of Treatment Approaches for Handling of Common Effluent Treatment Plant’s Sludge

Abstract

Abstract The common effluent treatment plant (CETP) receives untreated effluent generated from different types of industries for their treatment. During treatment, the sludge is separated in a clarifier and sent for consolidation in a dewatering unit (filter press, centrifuge, or sludge drying beds). This consolidated sludge contains organic/inorganic compounds, heavy metals, and other toxic or hazardous materials. The direct disposal of untreated sludge may cause contamination of soil, groundwater and may also adversely affect the environment. Therefore, there is an urgent need to handle this contaminated sludge to avoid its harmful impacts on soil, groundwater, and the environment. The present study reviews various sludge handling approaches used in CETPs, their advantages, applications, limitations, effectiveness, cost efficiency, and environmental impacts associated with them. It includes mechanical (consolidation or dewatering processes), various thermal (incineration, thermal plasma gasification, pyrolysis), and biological treatment (composting, vermicomposting, and anaerobic digestion) processes of sludge treatment/handling. The results shows that the CETP’s toxic sludge can be well treated by the thermal plasma gasification technique because this technique has many advantages, such as fewer emissions of carbon dioxide (CO2), producing syngas (electricity generation), minimising ash generation, cost effective, etc., as compared to other techniques. The concluding remarks of the present study state that the suitability of the sludge handling approach depends on the characteristics and composition of the consolidated sludge.