Abating the Effects of Calcium on Struvite Precipitation in Liquid Dairy Manure

Phosphorus recovery as struvite from farm, municipal and industrial waste: Feedstock suitability, methods and pre-treatments

“…Some inexhaustible and easily accessible natural P sinks such as animal manure and urine represent potential sources for struvite production in addition to some industrial wastes with high P concentrations (for example, carmine dye industry, semiconductor industry, fertilizer industry, Cola beverage industry and wastewater. However, some sources need to undergo pre-treatment in order to release P into an available form to make the recovery process effective (Shen et al, 2011) ( Table 1 Sources used for recovery of struvite and process conditions)…”

“…P recovery efficiency is generally high and often >90% (Table 1) with municipal wastewater averaging 95% (Pastor et al, 2010;Uysal et al, 2010) and landfill leachate (Iaconi et al, 2010), human urine (Ganrot et al, 2007) and carmine dye industry (Chimenos et al, 2003) wastewater processes reporting 100% recovery. Struvite also captures NH 4 + with recovery efficiency as high as 98% for municipal wastewater and semiconductor wastewater (Suschka and Poplawski, 2003;Kim et al, 2009 (Demirer et al, 2005;Zhao et al, 2010;Shen et al, 2011), swine manure (Burns et al, 2001(Burns et al, , 2003Nelson et al, 2003;Suzuki et al, 2007;Perera et al, 2007;Ryu and Lee, 2010;Liu et al, 2011;Zhang et al, 2012), poultry manure (Yetilmezsoy et al, 2009) and cattle urine (Prabhu and Mutnuri, 2014 The high P content of manure makes it a suitable source, however its available P fraction remains only in the range of 35% (poultry manure) to 63% (dairy manure) of total P (Barnett, 1994). P predominantly present in particulate form remains unavailable for recovery (Sharpley and Moyer, 2000;Chapuis-Lardy et al, 2003).…”

“…P availability is affected by the pH and composition of the material (Stark, 2005). Lowering the pH of anaerobically digested dairy manure to pH 3.8 increased P availability by 500% , whilst a lesser decrease to pH 4.5 resulted in 43-100% of the total P present in dairy manure becoming available (Shen et al, 2011). Szogi et al (2008) demonstrated that 60-80% of the total P in poultry manure was released from organically bound P following acid treatment.…”

“…In mechanically separated liquid dairy manure, EDTA sequesters calcium thereby suppressing formation of calcium phosphate compounds (Shen et al, 2011) resulting in higher concentrations of available P. The ligands react with Ca-PO 4 to form Ca-EDTA complexes and PO 4 3-is released . In digested dairy manure, use of EDTA increased available P up to 93% (Zhang et al, 2012).…”

“…P is readily fixed by other chemical constituents (e.g. Ca, Fe, Al, Mg, K) making it a key limiting factor in soils globally (Shen et al, 2011), with consequences including reduced yields, delayed maturity and lowered disease resistance across 40% of the world's arable soils (Vance, 2001). Agro-ecosystems account for 80-total P consumption (Childers et al, 2011) with 41.8Mt of P fertiliser consumed in 2013…”