Effects of organic substances on struvite crystallization and recovery

Abstract

A B S T R A C TThe effects of organic substances on struvite crystallization and recovery from synthetic wastewater were investigated. Experiments were completed during trials lasting 5 days using a pilot reactor with two concentric stainless steel meshes as seed material. Various concentrations of organics were added to synthetic CO 2 -saturated solutions and the pH was elevated from an initial value of 6.5 using a degassing technique. The results showed the presence of glucose, humic acid, and citric acid could reduce the struvite mass accumulating rates as compared to solutions without organic additives. In addition, glucose as an additive could significantly promote the removal rate of phosphorus as opposed to the other two. The mechanisms of the inhibitory effects are specially focused on the fact citric acid is able to complex with Mg 2+ , and NH þ 4 in solution, while humic acid or glucose are able to adsorb onto the crystal surface. The recovered precipitates were analyzed using X-ray diffraction and were proven to have high purities. The morphologies of the precipitates were examined using scanning electron microscopy and found struvite particles aggregated together showing an irregular block shape, with the exception of particles recovered from solutions with humic acid, which showed a triangle-like shape.

Understanding the growth of the bio-struvite productionBrevibacterium antiquumin sludge liquors

“…The presence of bio-struvite was confirmed with energy-dispersive X-ray spectroscopy. The spectra obtained matched the spectra expected for struvite crystals (Figure 4d), and the morphology of the bio-struvite crystals, observed in the electron microscope, was found to follow characteristic prismatic, tabular, and twinnedcrystal habit (Figure 4) similar to the morphologies found in other published reports on struvite [7,[29][30][31].…”

“…Organic substances as humic and citric acids have been shown to inhibit struvite formation [29,30]. And acetate has been reported to delay the precipitation of struvite at more than 5 mM (equiv.…”

Struvite crystallization combined adsorption of phosphate and ammonium from aqueous solutions by mesoporous MgO⿿loaded diatomite

“…Fig. 7b shows 10 -5 ) [38,42], respectively, which is unfavorable to the reaction of struvite crystallization. ValsamiJones [43] reported that the organic acids could be adsorbed onto the crystal nucleus of struvite, blocking the subsequent growth of struvite crystals and increasing the required supersaturation index for struvite crystallization, which would lead to a decrease of the nutrients removal efficiency.…”

Feedstock-Dependent Phosphate Recovery in a Pilot-Scale Hydrothermal Liquefaction Bio-Crude Production

“…The molar relation between metal ions and phosphate in the HTL solid phase from SPR (Al/P~0.03 and Fe/P~0.07) was lower than that from PSS (Al/P~0.21 and Fe/P~0.08), which can result in less co-precipitation of secondary Al-and Fe-phosphate salts [77]. While citric acid provided a high extraction capacity for HTL-SPR-SP, its application may be limited by its negative effect on subsequent precipitation [79]. Figure 4a conveys that sulfuric acid is more selective to phosphate release compared to other leaching agents.…”