Struvite precipitation as a technology to be integrated in a manure anaerobic digestion treatment plant – removal efficiency, crystal characterization and agricultural assessment

Abstract

BACKGROUNDThe formation of struvite (MgNH4PO4 6H(2)O) from digested slurry is an opportunity to recover nutrients as a slow-release fertilizer. A series of batch and continuous experiments were conducted to assay the influence of operational parameters, total solids and organic matter content on the quality and size of struvite crystals formed. Finally, the agronomic bioavailability of struvite was assessed in a greenhouse experiment.; RESULTSIn terms of process conditions an optimum pH of 9 was found, while changes in temperature (from 25 degrees C to 36 degrees C) showed to exert no influence whatsoever. On the other hand, though the presence of Na+ didn't affect the efficiency, high amounts of Ca2+ decreased the percentage of Mg2+ and NH4+ removed. CO2 stripping presented a reduction in the reagents required (NaOH) to raise the pH, with a similar removal efficiency and good quality of the struvite obtained. Nevertheless, the presence of organic matter resulted in a reduction on the size of struvite crystals. Agronomic assays showed that struvite P availability is similar to that of synthesis ammonium phosphate fertilizers.; CONCLUSIONSThe results point to struvite precipitation as a good strategy to recover nutrients from digested manure and to improve nutrient management. (c) 2014 Society of Chemical IndustryPostprint (published version

New perspectives for the design of sustainable bioprocesses for phosphorus recovery from waste

“…Similar to sewage sludge, the solid fraction of manure can be incinerated to produce bio-energy and P can be recovered from the ash (Schoumans et al, 2015). One of the major challenges is the high content of organic compounds present in manure and AD effluents, negatively influencing the precipitation or crystallization process (Cerrillo et al, 2014). From currently published literature, it can be inferred that P can be recovered from manure at high rates of up to 95% through struvite precipitation (Siciliano and De Rosa, 2014) or up to 90% as calcium containing P precipitate (Szögi et al, 2015).…”

Sustainability of phosphorus fertilisation: sources and forms of phosphate

“…In addition higher yields were obtained when using animal manures as a P source compared with equivalent amounts of mineral fertiliser (Reddy et al 1999(Reddy et al , 2000Whalen et al, 2000;Horta et al, 2014a). Experiments with struvite show that it's a source of P to crops with a P slow release effect which is a benefit for pastures (Thompson et al, 2012;Katanda et al, 2013;Cerrillo et al, 2015). Nevertheless to use struvite as a fertiliser is still needed more research to develop efficiency and scale of recovered struvite from sewage and to formulate appropriate fertilisers (P-REX policy brief, March 2015).…”

Effect of suspended solids and its role on struvite formation from digested manure

“…Few studies on struvite recovery from digested manure have been performed, and mainly they have been focused on proving the viability of struvite recovery from manure . They have highlighted the content of solids in the influent used as one of the main limitations for struvite recovery from manure.…”

“…Few studies on struvite recovery from digested manure have been performed, and mainly they have been focused on proving the viability of struvite recovery from manure. [10][11][12][13][14] They have highlighted the content of solids in the influent used as one of the main limitations for struvite recovery from manure. Nevertheless, the role of solids during struvite crystallization was not specifically targeted, and for this reason, more knowledge is considered to be essential to overcome the challenges that a complex matrix such as as manure represents.…”