Municipal wastewater treatment plants are under increasing pressure to meet low discharge limits for nitrogen and phosphorus, while aging infrastructure and changing precipitation patterns causes a wet weather burden. A new process, referred to as granular sludge applications, offers a solution to these challenges since slow-growing microbial populations capable of nutrient removal are maintained in dense particles that can be retained under high loading and flow conditions. In the proposed research, settling of the particles will be determined for an optimum granule diameter and density will be investigated and criteria to select for desired particles will be developed.
To date, granular sludge units have been pioneered in Europe using column-type sequencing batch reactors that utilize a fast settling time and continuous washout of biomass in order to maintain granular sludge, typically resulting in high effluent suspended solids. This reactor geometry and dependence on internal settling selection limits the adoption of granular technology by existing wastewater treatment plants, which have a tremendous infrastructure already built that should be utilized as plants expand. This proposal is framing sludge particle formation and selection in terms of balancing Fick?s and Stoke?s Law. The PIs hypothesize that low-strength municipal wastewater can supply a minimum organic surface loading of readily-biodegradable substrate required for extracellular polymeric substances and granule formation, as well as the selection of phosphorus accumulating organisms, when a fermentation pretreatment is performed. While current research on granular formation focuses on selecting granular sludge and out-selecting flocs, the PIs hypothesize that: 1) balancing the two sludge structures will provide the maximum reactor performance, and 2) the application of external settling selectors to preferentially retain good settling biomass and PAOs will alleviate the high effluent suspended solids burden typical of column-type granular reactors, and stabilize biological phosphorus removal. The research has the potential to transform the US water sector by developing approaches for granular sludge within existing infrastructure. The proposed project will center on promoting industry-utility-university partnerships to the wastewater profession. DC Water and Hampton Roads Sanitation District have been early adopters of granular sludge technology within the United States, having performed anammox granule pilot research for the past five years at their wastewater treatment plants. The Co-PIs will develop a Water Environment Federation workshop that promotes utility-university partnerships, highlighting how these hasten new technology adoption.
