Chapter 20 - Sludge treatment: an approach toward environmental remediation

Abstract

The generation and handling of sewage sludge produced during the treatment of sewage is one of the major drawbacks that needs to be managed very carefully for overall environmental protection and sustainability. Being a nutrient resource, the sewage sludge potentially replaces the chemical fertilizers in the global market, but the presence of heavy metals and pathogens in the sludge holds back the land application of the untreated sewage sludge. To cut down the nuisance caused by raw sludge, it has to be treated or digested before utilizing for soil amendment and disposal. From the perspective of the economical and ecological sustainability, the biological sewage sludge treatment methods, especially, composting, vermicomposting, and anaerobic digestion, have become very popular over the last few decades. In the case of vermicomposting, the produced vermicompost can be utilized as fertilizer as it is very rich in nutrients and soil-friendly microbes, whereas anaerobic digestion promotes the concept of circular bioeconomy through the generation of energy from the produced biogas. Moreover, these treatment methods cut down the greenhouse gas emission to a great extent. In this chapter, the needs of treating sewage sludge and comparison between the different biological sludge treatment methods have been emphasized from the perspective of economical soundness and environmental sustainability.