This work explores the possibility of harvesting biopolymers with practical applications from wastewater sludge. Wastewater sludge, also known as activated sludge or wastewater biosolids, is a by-product from biological wastewater treatment processes. The current views about activated sludge is that it is waste and entails costly disposal practices. However, wastewater sludge can be an important source of carbon and carbon based compounds, mainly biopolymers such as proteins and polysaccharides.

In this presentation, the alkaline and cation exchange methods of extraction of biopolymers from activated sludge are compared in terms of extraction yield, extraction kinetics, and the properties of the extracted polymers. Based on this comparison, the alkaline extraction method produced higher and faster extraction yields if the pH of the solution is adjusted to 12.0 or higher, reaching 65% to 70% yield by the 4th hour of treatment.

It was observed that the alkaline extracts are able to achieve an average surface tension of 38 mN/m with an average TOC content of 3.2 g/L, which is comparable to commercial products that reach 35mN/m at ~3 g/L. In addition, the surface tensions of alkaline treated extracts remain similar at a wide range of pH (2 to 12) and a wide range of concentrations (4g/L to 0.3 g/L). Further, Viscosity measurements and size exclusion chromatograms of the resulting polymer solution suggest that the alkaline extraction induce the hydrolysis of various proteins and polysaccharides.

The extracts are also analyzed as emulsifiers/detergents and adhesives. For this, the standardized testing methods for commercial products are applied and the performance of each chemical type is compared to already existing products that are either petrochemical or biologically based.