Struvite separation from wastewater and its use with sulfur-oxidizing bacteria improves phosphorus utilization in alkaline soil

Abstract

A major portion of phosphatic fertilizer comes from the limiting natural resource, rock phosphate, which demands a timely alternative. Struvite, a crystalline mineral of low solubility, is a worthwhile alternative. Evaluation of the local wastewater streams for their ability to precipitate struvite and its capability as phosphatic fertilizer under an alkaline soil environment was studied. Two stirring speeds, a pH range of 8.0–11.0, and a constant molar ratio were used to optimize local wastewater streams for struvite precipitation. Struvite was used in five different combinations to assess the release of phosphorus (P), including control (no P source), single superphosphate, struvite, struvite + sulfur, and rock phosphate with or without inoculation of sulfur-oxidizing bacteria (SOB). For struvite precipitation, low stirring speeds are ideal because the precipitates readily sink to the bottom once they form. Furthermore, the amalgamation of SOB with sulfur significantly improved P use efficiency under alkaline soils through increased phosphorus sources solubility and enabled optimum wheat production due to its low solubility in an alkaline soil condition. Due to its capacity to recycle phosphorus from wastewater, struvite is poised to emerge as a sustainable fertilizer and had an opportunity to capture a share of this expanding market. HIGHLIGHTS Wastewater characteristics and effects of increasing pH levels on P and N removal.; The effects of stirring speeds and pH levels on MAP precipitation.; Relationship of pH levels with N and P removal and struvite production.; Various P sources effects on soil pH, both with and without SOB.; Struvite application and its impact.;

Keywords

• alkaline soil
• phosphatic fertilizer
• slow release
• stirring speed
• struvite
• wastewater