Overview and description of technologies for recovering phosphorus from municipal wastewater

Over the past years, numerous technologies have been developed to recover phosphorus (P) from waste streams to repair currently broken nutrient cycles. These developments were largely triggered by environmental considerations (sustainability, resource efficiency), concerns regarding the finite and geopolitically concentrated deposits of raw phosphate ore, and phosphate price increases. Municipal wastewater is a promising and viable source to recover P in larger quantities, to re-establish a circular economy and therefore increase net use efficiency. This work compiles the latest knowledge on approaches to recover P from municipal wastewater and related waste flows with a specific focus on the existing well-developed wastewater management infrastructure, available in significant parts of Europe (e.g., secondary treated effluent, digester supernatant, sewage sludge, sewage sludge ash). About 50 technologies were identified at various levels of development (industrial-, full-, pilot- and laboratory scale). The current selection of P recovery processes is broad and ranges from simple precipitation of dissolved P to complex multi-step approaches, and only a few of these displayed potential for full-scale implementation. They are discussed with regard to their technical principles, process parameters, recovery efficiency, resource demand, possible effects on wastewater treatment, waste flows, and fate of pollutants. We also evaluated them with respect to their rates of P removal from wastewater and their access points of P recovery. For selected technologies, material flow models are presented to facilitate the understanding of even complex processes. This work serves as a basis for future integrated comparative assessments of selected recovery approaches according to technical, environmental and economic criteria.