ARS | Publication request: Method for recovery of phosphorus from animal wastewater

Submitted to: Water Environment Federation Technical Exhibition and Conference (WEFTEC)
Publication Type: Proceedings
Publication Acceptance Date: July 31, 2012
Publication Date: September 29, 2012
Citation: Vanotti, M.B., Garcia, M.C., Szogi, A.A., Hunt, P.G., Millner, P.D. 2012. Method for recovery of phosphorus from animal wastewater. In: Proceedings of the Water Environment Federation Technical Exhibition and Conference, September 29-October 3, 2012, New Orleans, Louisiana.

Technical Abstract: A wastewater treatment process and systems were developed to extract and concentrate phosphates from livestock wastewater. The research was conducted over a 10-year period and went from initial bench studies to pilot module development to full-scale demonstrations of the phosphorus module on swine farms and current licensing and commercialization by industry. The basic process is based on the distinct chemical equilibrium between phosphorus and calcium ions when natural buffers are substantially eliminated, which substantially reduces chemical addition. The precipitated phosphorus is recovered in a marketable form. The concentration grade obtained during full-scale demonstration was 24.4 ± 4.5% phosphorus pentoxide. The recovered calcium phosphate can be recycled into a marketable fertilizer without further processing due to its high content (> 90%) of plant available phosphorus. The process has several positive implications. Removing phosphorus from wastewater can cut down on any excess, which is not absorbed from the soil by plants and instead washes away as runoff into streams and rivers. Large amounts of the nutrient can lead to oxygen depletion in water bodies. During processing, hydrated lime precipitates most of the phosphorus in the wastewater as a solid and converts it into a marketable calcium phosphate fertilizer. This phosphorus could be very useful to the fertilizer industry because world reserves of the nutrient are limited. Another benefit is that the high pH achieved by the P module destroys disease-causing pathogens present in the leftover manure liquid. A second generation system includes simultaneous separation of solids and phosphorus from wastewater and industrial effluents. The combined separation process is more efficient in terms of equipment needs and chemical use. Thus, it reduced installation and operational cost of phosphorus treatment.