Environmental Benefits and Burdens of Phosphorus Recovery from Municipal Wastewater

Zenah Bradford-Hartke, Joe Lane, Paul Lant, Gregory Leslie

The environmental benefits and burdens of phosphorus recovery in four centralised and two decentralised municipal wastewater systems were compared using life cycle assessment (LCA). In centralised systems, phosphorus recovered as struvite from the solids dewatering liquid resulted in an environmental benefit except for the terrestrial ecotoxicity and freshwater eutrophication impact categories, with power and chemical use offset by operational savings and avoided fertiliser production. Chemical-based phosphorus recovery, however, generally required more resources than were offset by avoided fertilisers, resulting in a net environmental burden. In decentralised systems, phosphorus recovery via urine source separation reduced the global warming and ozone depletion potentials, but increased terrestrial ecotoxicity and salinization potentials due to application of untreated urine to land. Overall, mineral depletion and eutrophication are well-documented arguments for phosphorus recovery; however, phosphorus recovery does not necessarily present a net environmental benefit. While avoided fertiliser production does reduce potential impacts, phosphorus recovery does not necessarily offset the resources consumed in the process. LCA results indicate that selection of an appropriate phosphorus recovery method should consider both local conditions and other environmental impacts, including global warming, ozone depletion, toxicity and salinization, in addition to eutrophication and mineral depletion impacts.