Effects of Waste Activated Sludge Extracellular Polymeric Substances (EPS) Composition on Biosorption for Primary Carbon Diversion

Abstract

Extracellular polymeric substances make up a significant fraction of the organic matter in waste activated sludge, strongly influence the sludge’s physicochemical properties, as well as serve biological functions. Biosorption is a physicochemical process in which biomass, such as waste activated sludge, acts as a sorbent which uptakes external nutrients and compounds from a sorbate such as raw wastewater into its cell matrix. This paper characterizes the composition of waste activated sludge extracellular polymeric substances from various treatment processes and analyzes their ability to conduct biosorption when mixed with raw wastewater. Biosorption effectiveness was characterized as the ability to remove the soluble fraction of the organic matter from the wastewater. Due to different waste activated sludge bioaggregate structures, the amount of total organics available in the sludge could not be used as an indicating factor for how effective the sludge was at conducting biosorption. However, a positive correlation was found between the amount of extracellular polymeric substances present in the organic fraction of the sludges and the normalized removal of soluble organic matter. The extracellular polymeric substances, regardless of its chemical composition, removed nearly the same amount of soluble and truly soluble organics removing 1.43±0.15 (n=16) mg of soluble chemical oxygen demand, and 1.20±0.18 (n=16) mg of truly soluble chemical oxygen demand, per mg of cation exchange resin extracted extracellular polymeric substances. Additionally, it was observed that utilizing multiple extraction methods in series could increase extracellular polymeric substances extraction yields and provide a more holistic insight into its composition as well as its biosorption properties.