Modeling and optimization of struvite recovery from wastewater and reusing for heavy metals immobilization in contaminated soil

Abstract

BACKROUND Few studies have been carried out to connect nutrients recovery from wastewater and heavy metals immobilization in contaminated soil. To achieve the goal, ammonia nitrogen (AN) and phosphorus (P) were recovered from rare‐earth wastewater by using the formation of struvite, which was used as the amendment with plant ash for copper, lead and chromium immobilization. RESULTS AN removal efficiency and residual P reached 95.32 ± 0.73% and 6.14 ± 1.72 mg L−1 under optimal conditions: pH=9.0, n(Mg): n(N): n(P) = 1.2:1:1.1, which were obtained using response surface methodology (RSM). The minimum available concentrations of Cu, Pb and Cr (CPC) separately reduced to 320.82 mg kg−1, 190.77 mg kg−1 and 121.46 mg kg−1 with increasing immobilization time at the mass ratio of phosphate precipitate (PP)/plant ash (PA) of 1:3. Humic acid (HA) and fulvic acid (FA) were beneficial to immobilize Cu, both of which showed no effect or even a negative effect on Pb and Cr immobilization. CONCLUSION Building up a suitable ‘bridge’ to connect and achieve recovery of nutrients and reuse of struvite. © 2016 Society of Chemical Industry

Optimized Phosphate Recovery Through MAP Precipitation in an Air Agitated Column Reactor

“…The pH solution (8, 9 and 10) was adjusted by injection of 1 N KOH from the bottom mixed with air. The estimated retention time within the reactor was to be 13,17,20,25,31 minutes, while the reaction temperature was fixed at 30 O C. In this study, pH was observed every 5-min intervals. Then the crystalline solid was formed in the bottom of the reactor, whereas the liquid left from the conical part of the reactor owing to an overflow system.…”

“…Here, the change of reaction crystallization in the recovery of struvite due to the presence of calcium ions has been demonstrated in a batch crystallizer 13 and in a continuous crystallizer 14,15 . Correspondingly, reaction crystallization of struvite for recovery of phosphate ions from wastewaters is a complex technological challenge 16,17,18 . This requires fully controlled conditions for struvite production and partly purifying wastewater systems 17 , while desirable amounts of precipitated struvite can be recovered by typically control of the precipitating process in the reactor system.…”

“…Correspondingly, reaction crystallization of struvite for recovery of phosphate ions from wastewaters is a complex technological challenge 16,17,18 . This requires fully controlled conditions for struvite production and partly purifying wastewater systems 17 , while desirable amounts of precipitated struvite can be recovered by typically control of the precipitating process in the reactor system. Also, successful recovery of phosphate as mineral fertilizer in agriculture requires struvite crystals with prismatic or needle-like morphology, and the grain should be homogeneous in size and possibly large 19,20 .…”

Fate of Copper in Saline–Alkali Soil with Long-Term Application of Biogas Residue

“…Illite is a layered silicate mineral with high cation exchange capacity and specific surface area and strong adsorption capacity of heavy metals [14,15]. Struvite contains N, P, Mg and other nutrients needed by plants [16], and it has the potential to stabilise heavy metals in soil [17]. Pyroxene is a silicate mineral produced by reaction of CaO, MgO and SiO 2 at high temperature [18].…”

Investigation of fluorapatite crystallization in a fluidized bed reactor for the removal of fluoride from groundwater

“…The saturation index (SI) was calculated according to Eqn (1): 27,28 where log IAP is the logarithm of the ion activity product calculated from the stoichiometry; Ks is the temperature-corrected thermodynamic solubility product; and SR is the supersaturation ratio. A SI greater than zero indicates that the solution is supersaturated, and a SI value 0 indicates the solution is in equilibrium or undersaturated.…”