Recovery of extracellular polymers from wastewater treatment residuals as a new circular biopolymer (REThiNk)

Biological wastewater treatment plants (WWTPs) produce large quantities of waste biomass comprising microbes glued together by extracellular polymeric substances (EPS), i.e. activated sludge. The waste sludge mass amounts to approx. 30 kg/person/year, corresponding to 175,000 tonnes per year for Denmark of which EPS form up to 30%. This waste biomass is a problematic
byproduct requiring costly disposal, or additional treatment for biogas production - a low-value product.

To valorize one of our largest bio-solid wastes, we outline here a new resource recovery strategy for biomass centered on the EPS, which has a high intrinsic value arising from structural complexity and diverse functionality. The EPS is extracted and manufactured into new sustainable biopolymers with broad application. The concept stands alongside existing infrastructure, and extraction enhances digestibility of residual biomass, reduces overall waste production, and drastically improves the economy and carbon footprint of wastewater treatment. We aim to tailor polymer composition by elucidating the relation between microbial community structure and the composition and functions of EPS.

We have assembled a team comprising the world-leading experts in WWTP engineering, EPS extraction and characterization, microbial community profiling, biostatistics, genome-centric metaomics, and biomaterial fabrication and application. We will establish a predictive model for extracted EPS by linking the physiology of individual microbes, overall microbial community composition, and environmental factors to the identity and properties of extracted EPS. The EPS will be formulated into biomaterials, where the special functionality of EPS is preserved, and serves as a market differentiator, in viable EPS bio-products. This creates an entry point for activated sludge into the global biopolymer market, increases WWTP sustainability, and generates a new, abundant and cheap raw material for the circular economy.

Activated sludge is the most widely used biological treatment process for wastewater, and it produces >10% of all biowaste in the western world. We present a new strategy for turning these biosolids into valuable biopolymers via extraction of extracellular polymeric substances (EPS) that are secreted from
bacteria in the activated sludge. The EPS has high intrinsic value and can be recycled into new sustainable biomaterials and replace oil-based polymers. There is a lack of understanding of the microorganisms that produce the EPS and their relevant properties. We will establish a predictive model for declaration of extracted EPS by linking the bacterial physiology, overall community composition, and properties of extracted EPS. The EPS will be formulated into biomaterials and create an entry point for activated sludge into the global biopolymer market, with the goal to develop a new resource recovery strategy and increase the sustainability and profitability of wastewater treatment.