Chapter One - Sewage Sludge Generation and Characteristics

Abstract

Sewage sludge, one of the main by-products from wastewater biological treatment process, is being continuously generated. It contains a myriad of toxic substances including pathogens such as viruses and worm eggs, heavy metals, and some organic contaminants, which create odors and hygiene concerns. Improper disposal and reuse of sewage sludge causes severe environmental impacts and health hazard to the public. The water industry is facing unprecedented economic and environmental constraints because of not only large amounts of sewage sludge produced but more stringent regulations. The processing of sewage sludge is one of the expensive items in a wastewater treatment plant, usually accounting for up to 50% of the total operating costs of the plant. Thus, the promotion of economically feasible treatment methods represents one of the most critical missions for environmental researchers. Nowadays, there have been several representative techniques for sewage sludge disposal applied in practice, for example, dewatering, composting, drying and incineration, anaerobic digestion, sanitary landfill, land application, and recycling as building materials. The technical feasibility of one method is dependent upon not only the degree of sludge stabilization, but also energetic and environmental benefits. In this chapter, sewage sludge production, special features of sewage sludge, and general processes of pollution control and resource recovery for sewage sludge are introduced; a deep comparison among dewatering, drying, incineration, composting, and sanitary landfill is made.