Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2003
Publication Date: 11/1/2003
Citation: Vanotti, M.B., Szogi, A.A., Hunt, P.G. 2003. Extraction of soluble phosphorus from swine wastewater. Transactions of the American Society of Agricultural Engineers. 46(6):1665-1674.
Interpretive Summary: We have devised a way to remove phosphorus from swine-production wastewater and turn it into a solid, marketable fertilizer. The process also converts leftover effluent into a liquid crop fertilizer that is more environmentally friendly than manure. 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 process destroys disease-causing pathogens present in the leftover liquid. Meanwhile, the effluent contains a nitrogen-to-phosphorus ratio greater than 12 to 1--ideal for crop irrigation, which requires an 8-to-1 ratio. Regular manure offers a nitrogen-to-phosphorus ratio of 4 to 1. This higher nitrogen-phosphorus ratio translates into less excess phosphorus on land on which the treated wastewater is applied.
Technical Abstract: Manure phosphorus (P) in excess of the assimilative capacity of land available on farms is an environmental concern often associated with confined livestock production. A wastewater treatment process was developed for removal of phosphorus from livestock wastewater. It includes nitrification of wastewater and increasing the pH of the nitrified wastewater by adding an alkaline earth metal-containing compound to precipitate phosphorus to form an effluent having a specified nitrogen:phosphorus ratio that is useful as a balanced fertilizer or a low P fertilizer for remediation of contaminated soils. The presence of infectious microorganisms is reduced in the useable effluent. The precipitated phosphorus is recovered in a marketable form.