Technical and economic feasibility of phosphorus recovery from wastewater in Sao Paulo's Metropolitan Region

Phosphorus can be recovered from wastewater in the form of marketable fertilizers. That can be profitable for municipal facilities, alleviate the eutrophication of urban rivers, and ease further polishing the effluent to produce reclaimed water. In this work, it is assessed the viability of recovering phosphorous in the treatment plants of a large metropolitan region. It is proposed the production of struvite granules from sludge liquors by adding magnesium in a reactor (fluidified bed or stirred). Previously, an anaerobic tank would stimulate the action of microorganisms to release phosphorus from the sludge before its digestion. Applying such process in the five largest treatment facilities of the Metropolitan Region of Sao Paulo would recover 5.3 tons/day of phosphorous and yield 38.0 tons/day of struvite granules. A preliminary viability assessment was conducted, considering operational expenses and potential revenues. Results indicate the economic viability of this nutrient recovery scheme in this particular region.