Liquid-Liquid Extraction for Phosphorus and Nitrogen Nutrient Removal and Recovery/Reuse from Water

Nutrient (nitrogen and phosphorus) concentrations in wastewater effluents can create significant ecological problems. This paper presents the results of using liquid-liquid extraction (LLX) technology for the removal of phosphorus (P) and/or nitrate (NO3) from wastewater and recovery of concentrated, usable products instead of solutions or precipitates requiring disposal. Phosphates (ortho- (o-P) and poly-P) and nitrite/nitrate are recovered in a concentrated aqueous solution as sodium or potassium salts. This “PN-LLX” (for phosphorus and nitrogen removal/recovery) process is applicable to a wide variety of wastewaters, including municipal, industrial, or agricultural aerobically or anaerobically processed liquids or solids. Examples of applications include anaerobically digester supernatant filtrate/centrate; aerobic or anaerobic lagoon clarified effluent; animal feeding operations barn flush water; biologically industrial wastes, e.g. food wastes; industrial wastes with high phosphate or nitrate, e.g. phosphorus mining/phosphoric acid production, nitrations production, etc. Applicability to a wide variety of feed concentrations with achievement of low target final water-phase concentrations have been demonstrated in laboratory LLX screening tests. This paper will illustrate the LLX process as applied to a surrogate water containing o-P and NO3, and to animal (dairy) manure anaerobic digester effluent, and is called AD-LLX.