Sustainability of Activated Sludge Processes

Recent studies revealed that two-thirds of US coastal systems are moderately to severely impaired because of excess nutrient loading, particularly nitrogen and phosphorus, and, therefore, the need for more efficient treatment procedures for wastewater is greater than ever. Activated sludge process has been used for a century for municipal and industrial wastewater treatment. This process can achieve high efficiency of biochemical oxygen demand, chemical oxygen demand, and nutrient removal. In order to improve the effluent wastewater quality and reduce the point-source nutrient loading on the water bodies, adequate information and knowledge must be acquired. Sustainable solutions to the wastewater treatment technologies can reduce the carbon footprint and the use of chemicals, and save energy and operational cost. The sustainability of activated sludge processes depends upon efficient nutrient and organic carbon removal and efficient sludge/biomass handling and processing. This chapter will introduce readers to the background information on the nutrients and their effects on the environment, different sustainable removal practices for nitrogen and phosphorus from municipal wastewater, and the microbiology of biological nitrogen and phosphorus removal, and finally, the chapter will conclude with a discussion on the need for process optimization and resource recovery.