To Do Class A or Not? What To Do To Enhance Sludge Processing?

Recently, more and more wastewater treatment plants (WWTPs) are upgrading their conventional solids treatment systems which produce Class B biosolids to produce Class A biosolids. This trend has triggered rapid growth of not only new sludge treatment technologies but also conventional treatment modification technologies. The main focus of this paper is on anaerobic digestion process modification techniques to produce Class A biosolids or enhanced digestion to achieve multiple solids processing objectives. The paper is based on information collected from various WWTPs throughout the US on practices and trends to enhance sludge digestion, worldwide literature review, and from technology vendors. A systematic analysis (case studies) of 4 WWTPs to evaluate and shortlist alternatives to enhance the existing solids thickening-anaerobic digestion-dewatering complex into either Class A or enhanced solids processing system as well as estimation of the operational carbon footprint (OCF) of each of the alternatives are presented in this work.