Struvite Crystallization Research Articles

In Vitro Study on the Influence of Proline on Struvite Crystals

This study investigated the effect of amino acid proline, as crystal modifier, on the struvite crystallization in vitro conditions. The struvite crystals were evaluated experimentally through XRD, SEM, and FTIR to determine the structure, morphology, and chemical composition, respectively. XRD analysis pointed out that struvite crystals belonged to the orthorhombic Pmn21 space group. SEM analysis depicted that proline had a significant influence on the morphology as well as the particle size of the struvite. Moreover, the length and width of struvite crystals varied with different concentrations of proline. The length of struvite crystals decreased, and their width thickened in the presence of the crystal modifier. The negativity of the zeta potential value became less negative in the presence of proline and the values were determined to be –6.10 mV and -4.00 mV for 25 and 100 ppm, respectively. According to BET analysis results, the surface area of the struvite decreased in the proline media when compared with the crystals formed without the crystal modifier. In addition, the thermal degradation of the formed crystals was examined. Regarding the results of the thermodynamic analysis, the average ∆H , ∆G , and ∆S were 92.17 kJ/mol, 197.85 kJ/mol, and −254.63 J/mol K, respectively. As a result, this study could provide a potential crystal modifier for the inhibition of struvite stones.

Recovery of Phosphate and Ammonium from Dairy Cow Urine by Struvite Crystallization with Vertical Reactor

Excess phosphate (PO43-) and ammonium (NH4+) in wastewater can cause environmental damages, such as pollutants and eutrophication in water. Dairy cow urine is a dangerous liquid waste that contains high amounts of phosphate and ammonium. The removal of PO4 and NH4 components can be done by crystallizing them into struvite fertilizers. Struvite (MgNH4PO4.6H2O) is a mineral formed from magnesium, ammonium, and phosphate with the equimolar ratio. The crystallization process of struvite is carried out using a vertical reactor. MAP solution (magnesium ammonium phosphate) is prepared by reacting MgCl2, H3PO4, and dairy cow urine with MAP molar ratio of 1 : 1 : 1 and KOH 1N. The study run in pH 8; 8.5; 9; 9.5; 10 and temperature variations of 25, 30, 35, 40, 45˚C in vertical reactor continuously. The struvite precipitate was filtered and dried, it is analyzed by XRF to determine the struvite composition and SEM to determine the morphology of the struvite. The results showed that the best percentage of phosphate and ammonium was at 45˚C and pH 9.5, it was 33.2% and 27.9%.

A model of extracellular polymeric substances on crystal growth and morphogenesis of struvite: Effects of sodium alginate

Struvite crystallization has been regarded as a sustainable route to recover phosphorus from wastewaters. In this study, sodium alginate (SA) was chosen as model extracellular polymeric substances (EPS) to investigate its impact on struvite crystallization. The experimental results demonstrate that SA can remarkably influence struvite morphogenesis, resulting from the selective adsorption and binding of SA molecules onto the crystal faces with higher Mg content. SA concentration-dependent experiments show that SA significantly inhibits struvite growth, and the growth inhibition is caused by the adsorption of SA onto struvite surface, thus blocking the active growth sites. We also found that the elevation in Mg/P ratio or initial pH (pHi) can promote struvite growth, thus compensating the adverse effect of SA. Considering that SA is model EPS, our results provide a new insight into the role of EPS on struvite crystallization from wastewater. This will help to improve struvite crystallization technique.

Simultaneous hydrogen production and struvite recovery within a microbial reverse-electrodialysis electrolysis cell

In this research, a novel Microbial reverse-electrodialysis electrolysis struvite-precipitation cell (MRESC) was developed for energy recovery through struvite (MgNH4PO4·6H2O) crystallization and hydrogen production concurrently in a single process without any electrical-grid energy consumption. This hybrid system can effectively transfer the salinity gradient energy to electrical energy as a driving force to produce hydrogen gas coupled with struvite recovery and organic wastewater degradation. A MRESC containing 10 pairs of RED cells, supplied solutions typical of high concentration (600mM NaCl) and low concentration (12mM NaCl) at 1.0mL/min, was operated in the fed-batch mode. The rates of hydrogen production and struvite crystallization were determined to be 0.71m3-H2/m3-Van/d and 7.62g/m2/h, respectively. The gas produced was >92% H2. The Coulombic efficiency was close to or above 100% with a COD removal of 84±6%, and an overall energy efficiency of 28%. The morphology and structure of the main component of accumulated crystal at the cathode were verified by a scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction. These results showed that the MRESC system could be used as an effective bioelectrochemical method for energy recovery in the form of pure hydrogen gas and struvite simultaneously.

Encrusted Urinary Tract Infections Due to Corynebacteria Species

IntroductionEncrusted pyelitis and cystitis are peculiar disorders characterized by the calcification of the vesical, the pyelic, and/or the ureteral walls. These calcifications are composed of struvite and calcium carbonate‒apatite due to the presence of Corynebacterium urealyticum.MethodsWe have identified the clinical features and outcomes of 17 patients with encrusted pyelitis (n = 15) or encrusted cystitis (n = 2). Diagnosis was based on computed tomography scan and sonography including thickening and calcified lesions of the urinary tract.ResultsThe main clinical presentation was suggestive of subacute urinary tract infection with fever and urologic symptoms, mostly gross hematuria. Biologic features were characterized by the presence of struvite crystals and alkaline urine. Acute kidney injury was reported in 70.6% of cases. Predisposing factors were mostly due to urologic background (82.4%) with a history of urologic procedure (71%) and prior exposure to antibiotics (59%). All patients received appropriate antibiotherapy and 15 were treated with topical urinary acidification. A significant reduction of encrusted calcifications was observed in 88% of cases. Renal function improved in 71% of the patients. Nevertheless, poor tolerance of the treatment and side effects were common, affecting 71% of patients, with Gram-negative bacilli urinary tract infections (53%) being the most frequent. At last follow-up, 4 patients (23.5%) progressed to end-stage renal disease and only 1 had a clinical relapse.ConclusionsEncrusted urinary tract infections are rare, characterized by a severe renal and overall prognosis in the absence of appropriate treatment. Topical urinary acidification and appropriate antibiotherapy are efficient but may be burdened by significant adverse events.

A constant composition technique for quantifying the effect of As(V) on struvite crystallization under various operational conditions

Struvite crystallization was one of the most promising techniques for nutrient recovery from nutrient-rich wastewater. However, As(V) derived from the wastewater has been proved to adversely affect struvite crystallization. Constant composition technique was employed to quantify the effect of As(V) on struvite crystallization in the presence of As(V) under various operational conditions such as supersaturation, pH and ionic strength. Subsequently, the interaction mechanisms between As(V) and struvite crystals were further elucidated by means of XPS and FTIR. Interestingly, the roles of adsorption and coprecipitation in the interaction under various operational conditions were primarily evaluated. At a supersaturation of 0.4, pH 8.5 and 0.1 mol/L NaCl, the crystal growth rate of struvite was substantially reduced from (14.2 ± 0.3) × 10−6 to (7.6 ± 0.1) × 10−6 mol/min with As(V) concentration increasing from 0 to 10 mg/L. Nevertheless, As(V) scarcely changed the surface diffusion growth mechanism of struvite. Moreover, the adsorption and coprecipitation of As(V) accounted for its interaction with struvite. Thereinto, the adsorption mechanism was triggered by the bidentate inner-sphere surface complexes and the electrostatic interaction between As(V) and struvite. Furthermore, the influence of supersaturation and ionic strength on the inhibitory effect was found to be highly dependent of the adsorption of As(V), whereas the coprecipitation of As(V) is mainly responsible for the impact of pH. The finding herein provided a novel approach to elucidate the inhibitory mechanisms of heavy metals on struvite crystallization, which facilitated to obtain pure struvite crystals from the wastewater contaminated by heavy metals.

Dissolving the high-cost with acidity: A happy encounter between fluidized struvite crystallization and wastewater from activated carbon manufacture

Production of wood-based activated carbon (WAC) generates large volume of highly acidic and phosphate-rich wastewater. Currently, the routine treatment (i.e. lime precipitation) creates significant secondary pollution, leading to extra economic and environmental burdens. Here, by exploiting the strong acidity of WAC wastewater, we successfully demonstrate fluidized struvite crystallization as a low-cost treatment alternative. Based on a 12 m3/d on-site pilot-scale system, four different fluidized struvite crystallization scenarios are evaluated from technical, economic, and environmental perspectives. The results show that using MgO with MgCl2 supplement saves 42.8% of the reagent cost when treating phosphate-rich wastewater (i.e. P = 3125.2 mg/L), and also maintains ideal P removal rate and struvite product purity. Meanwhile, the internal circulation mode exhibits higher P recovery (99.2%) than the external mode (55.3%-89.3%), while also demonstrates superior economic and environmental benefit because of less chemical consumption. In addition, the struvite morphology can be turned between pellets with strong crushing strength (external mode) to powder (internal mode). By Life cycle cost (LCC) analysis, we find that, on a treatment scale of 500 m3/d, struvite-based technology saves up to 31.33 million Chinese Yuan (CYN) during a 20-year lifespan, with relative payback period of 2.60 year. The technical, economic, and environmental assessments confirm that the struvite technology is a promising alternative in solving the bottleneck of WAC wastewater treatment.

Mechanochemical conversion of chrysotile asbestos tailing into struvite for full elements utilization as citric-acid soluble fertilizer

Chrysotile asbestos tailing (CAT) are rich in magnesium and silicon which are of great value for crop growth. In this work, CAT was transformed to struvite and silicate salt for the first time by one-step milling with phosphates (NH4H2PO4, (NH4)2HPO4, KH2PO4 and CaHPO4) for full elements utilization as citric acid soluble fertilizer (CASF). The X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG) and Scanning electron microscopy (SEM) were used to characterize the obtained samples. The nutrients release data revealed that CAT milling with (NH4)2HPO4 and CaHPO4 was optimal for the production of Mg, N, P, and Si compound CASF which released 0% Mg, 9.37% N, 2.02% P, and 9.86% Si in water and 94.54% Mg, 96.79% N, 96.97% P, and 14.02% Si in 2% citric acid. The prepared product held the nutrients by the mechanism of struvite crystallization in water and released the nutrients by acid-dissolution in citric acid solution. Techno-economic analysis proved the feasibility and economic value of the CASF produced by the proposed mechanochemical approach. This facile and environmentally friendly process would surely contribute to the improvement of resource utilization efficiency and create a sustainable and environmental friendly agricultural production system.

Investigation of the impact of hydrodynamic parameters for phosphorus recovery from synthetic anaerobic digester supernatant in a fluidized bed reactor

Recovering phosphorus (P) from wastewater as struvite has been investigated widely as this approach represents a solution to several wastewater-related problems. Some of the typical process units applied in the industry for struvite recovery from wastewater streams include fluidized bed reactors where individual struvite crystals are being agglomerated into spherical granules, or pellets. Various hydrodynamic parameters affect the extent of inter-particle collisions, the intensity of mixing, localized concentrations of ionic species, nature of eddies, etc. which determine the efficiency of the crystal agglomeration. This study evaluated the impact of three key hydrodynamic parameters (up-flow velocity, feed injection nozzle velocity, and nozzle configuration) on P-removal and recovery efficiencies in a newly designed novel fluidized bed reactor (FBR). Lowering up-flow velocities from 60 cm/min to 20 cm/min resulted in higher P-removal and recovery efficiency, whereas high up-flow velocities were favorable for the production of larger pellets and fines. Nevertheless, higher nozzle velocity (18.04 m/s) was responsible for improving P-recovery efficiencies. The nozzle velocity had a strong influence on the morphology of pellets and fines. High nozzle velocity contributed to the formation of the smooth-surfaced pellets and plate-shaped fines. Three different nozzle-configurations generating different flow patterns within the agglomeration zone were studied.

Adsorption and precipitation behaviors of zinc, copper and tetracycline with struvite products obtained by phosphorus recovery from swine wastewater

Few investigations take the combined pollution of heavy metals and antibiotics into consideration during the recovery of phosphorus through struvite crystallization. In this study, the adsorption and precipitation behaviors of Zn(II), Cu(II) and tetracycline (TC) with struvite-loaded zeolite (SZ) were investigated by batch experiments. SZ was obtained through reclaiming phosphate from swine wastewater to MgO-loaded zeolite. Experimental results proved that heavy metals and TC were stored by SZ primarily through precipitation and physical adsorption, respectively, with partition coefficients of 191.9 L/kg for Cu(II), 112.5 L/kg for Zn(II) and 1333 L/kg for TC in ternary-pollutant systems. With the presence of Cu(II), the adsorption capacities of SZ for TC increased by around five times, whilst Zn(II) inhibit TC adsorption onto SZ. Cu(II) precipitation was hindered by TC and Zn(II) resulting in less Cu5(PO4)2(OH)4 formation on SZ. The effects of TC on Zn(II) precipitation by SZ were reversed with the variation of Zn(II) or Cu(II) concentration in solution due to two antagonistic effects—restriction of surface-induced precipitation and alleviation of competition interactions. In addition, high concentrations of dissolved organic matter (DOM) decreased the storage of Zn(II), Cu(II) and TC by SZ through competition effects. This study demonstrated that heavy metals and antibiotics in wastewaters could be simultaneously adsorbed and precipitated by struvite products, which was greatly affected by the complexing species and competing ions of the pollutants in wastewater.

Phosphorus recovery from synthetic biosolid digestion supernatant through lignin-induced struvite precipitation

Phosphorus recovery from wastewater is essential to resolve the problems of the fast depletion of phosphate rocks due to the increasing demand of phosphorus fertilizer and eutrophication caused by excessive phosphorus discharging from wastewater. In this study, the feasibility of adding lignin as seed materials to promote phosphorus recovery through struvite (NH4MgPO4·6H2O) crystallization from synthetic biosolid digestion supernatant was evaluated via batch experiments. Influencing factors including lignin dosage, Mg/P molar ratio, and pH were tested. Lignin addition enhanced phosphorus recovery by 44.6% at a relatively low pH of 7.9 with Mg/P molar ratio of 1.5 and lignin dosage of 6 g/L, improved the quality of recovered struvite crystals by reducing the potential of co-precipitation. The phosphorus recovery improvement became less noticeable and the extent of reducing the potential of co-precipitation became more evident as pH increases from 7.9 to 9.5. The characterizations by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and zeta potential analysis, combined with precipitation modeling by a thermodynamic model software (Visual MINTEQ) were done to understand the process. Struvite-lignin clusters were identified, which likely provide nucleation sites on lignin to enhance struvite crystallization. It can be concluded that the inclusion of Kraft lignin as a seeding material might be a sustainable strategy to enhance struvite formation, improve phosphorus recovery, and yield high-quality struvite.

Engaging a Battle on Two Fronts: Dual Role of Polyphosphates as Potent Inhibitors of Struvite Nucleation and Crystal Growth

Polyprotic acids often serve as effective regulators of inorganic crystallization in natural, biological, and synthetic systems. These molecules or macromolecules can function as efficient modifier...

Phosphorous recovery from septic tank liquor: Optimal conditions and effect of tapered velocity gradient

The growing recognition of the potential of recovery of products from, and recycling of, wastewater is matched by a growing interest in decentralized treatment systems. Sanitation-focused policies and interventions, undertaken by many developing countries, are dominated by septic tanks for septage management. As reserves of phosphate rock continue being depleted, recovery of phosphorus (P) from the waste stream is one of the practical strategies to deal with that depletion. Partial anaerobic digestion of septic tank liquor converts organic P to soluble orthophosphate form, allowing it to be recovered. Factors that influence such recovery, namely pH, the molar ratio of magnesium (Mg) to P, velocity gradient, and mixing duration were tested and optimized for recovering P as struvite. Interactions between the above factors and their possible influence on the efficiency of P recovery were also examined. Under optimal conditions, more than 90% of P could be recovered. The maximum size of struvite crystals was 201 μm. Among the factors that influenced P recovery, pH and the Mg/P ratio affected recovery efficiency whereas the velocity gradient and mixing duration affected the size of struvite crystals. Tapering the velocity gradient not only increased the crystal size significantly, from 280 μm to 371.9 μm, but also reduced energy requirement by 62%. The study showed that new reactors designs can be based on the concept of tapered velocity gradient to improve the properties of struvite crystals.

First Report of Pathogenic Bacterium Kalamiella piersonii Isolated from Urine of a Kidney Stone Patient: Draft Genome and Evidence for Role in Struvite Crystallization.

Uropathogenic bacteria are widely distributed in the environment and urinary tract infection is implicated in kidney stone disease. Here, we report on a urease negative bacterium Kalamiella piersonii (strain YU22) isolated from the urine of a struvite stone (MgNH4PO4·6H2O) patient. The closest species, K. piersonii IIIF1SW-P2T was reported from International Space Station samples. However, there are no earlier reports on its human association. Using whole genome and experimental analysis, its involvement in urinary tract colonization and struvite crystallization was explored. The strain YU22 showed many virulence factors that are needed for host cell invasion and colonization including cell adhesion factors, swimming and swarming motilities, biofilm and siderophore among others. In vitro infection studies in HEK-293T cells demonstrated the host cell attachment and killing. It was able to utilize amino acids as sole carbon source and showed growth in synthetic and healthy urine establishing metabolic adaptation to urinary tract. Increased pH and availability of ammonium ions from amino acid breakdown promoted struvite crystallization. The results from this study support the involvement of urease negative uropathogen in the struvite lithogenesis. Further studies on other isolates of K. peirsonii are warranted to assess its health risks.

Renewable P sources: P use efficiency of digestate, processed animal manure, compost, biochar and struvite

In the attempt to close nutrient cycles, organic fertilizers and soil improvers are getting interest as renewable P sources for crops. However, both the P availability of these compounds for crops and the underlying mechanisms are not fully understood. In this study composts (n = 8), biochars (n = 5), animal manure and processed animal manure (n = 13), digestates and processed digestates (n = 15) and blends of digestates with compost/animal manure/mineral fertilizers (n = 15) were analyzed for chemical composition, organic matter stability and P use efficiency (PUE). Biodegradability (=holocellulose/lignin ratio) proved to be a good indicator for organic matter stability and can successfully replace time-consuming incubation experiments in standard analyses of organic fertilizers. The PUE of digestates, struvites, animal manure products and blends of digestate with compost/animal manure/mineral fertilizers was determined by the NH4+-N, Mg and Fe content of the organic fertilizers. The PUE can be predicted by PUE = 61.34 + 8.59*NH4+-N/P + 42.25*Mg/P – 8.09*Fe/P (R2 = 0.71). As increasing amounts of NH4+-N and Mg stimulate the formation of soluble struvite crystals, increasing PUE is explained by an increasing amount of P as struvite. The PUE of biochars and composts was determined by the Ca/P and Al content of the organic fertilizers. Here, PUE can be predicted by PUE = 88.87–1.07*Ca/P + 6.08*Al/P (R2 = 0.93). As increasing amounts of Ca stimulate the formation of highly stable apatite crystals, increasing PUE is explained by an increasing amount of P in the form of apatite.

Nucleation and crystal growth kinetic parameter optimization of a continuous Poiseuille flow struvite crystallizer using a discretized population balance and dynamic fluid model

Struvite crystallization is an important process in recovering phosphorus from waste streams, but kinetic parameters involve significant uncertainty. In this research a model is developed which includes population balance, fluid flow equations, and kinetic relations. Power law rate coefficients for struvite nucleation (knuc=7.509×107L-1.min-1) and growth (kg=16.72μm.min-1) are optimised by combining a Poiseuille flow reactor model (PFR) and experimental data for phosphorus concentration and particle size distribution (PSD) at the reactor outlet. Nucleation and crystal growth rates were optimized using both filtered and sonicated PSD samples. The model incorporated three key aspects: non-ideal thermodynamics; Poiseuille fluid flow (including advection, diffusion and reaction); and a discretized population balance model (PBM). Sensitivity analysis using deltas (min/max) showed diffusion effects to be negligible and indicated that power law rate constants for both nucleation and growth were more influential on PSD and phosphorus concentration than the associated rate orders. Optimized parameters agreed reasonably well with a previous study conducted by our group under different conditions, using a different model, providing confidence in results. The optimized nucleation rate, knuc, was only 12% lower than that found using a similar model for a seeded system, where secondary nucleation is dominant. Additionally, a primary nucleation model provided a poor fit to experimental data. These two factors indicate that secondary nucleation is an influential mechanism. A 2nd order growth model provided a better fit to data than a previously suggested 5th order growth model. The optimized growth rate coefficient, kg, was higher than in any previous studies, an effect attributed to sonication, which eliminated aggregates.

Struvite crystallization induced the discrepant transports of antibiotics and antibiotic resistance genes in phosphorus recovery from swine wastewater

Struvite (MgNH4PO3·6H2O) crystallization is one of important methods of phosphorus recovery from wastewater. As to livestock wastewater, the high-strength occurrence of antibiotics and antibiotic resistance genes might induce struvite recovery to spread antibiotic resistance to the environment. However, limited information has been reported on the simultaneous transport of antibiotics and ARGs in struvite recovery. In the present study, tetracyclines (TCs) and tetracyclines antibiotic resistance genes (ARGs) were selected as the targeted pollutants, and their discrepant residues in struvite recovery from swine wastewater were investigated. TCs and ARGs were obviously detected, with their contents of 4.88–79.5 mg/kg and 6.99 × 107–2.14 × 1011 copies/g, notably higher than those of TCs 0.550–1.94 mg/kg and ARGs 3.98 × 104–5.66 × 107 copies/g obtained from synthetic wastewater. The correlational relationship revealed that predominant factors affecting TCs and ARGs transports were different. Results from network analyses indicated that among the total edges, the negative correlations between TCs and ARGs predominately occupied 18.0%. The redundancy analysis revealed that mineral components in the recovered products, including struvite, K-struvite and amorphous calcium phosphate, coupling with organic contents, displayed insignificant roles on TCs residues, where heavy metals exerted positive and remarkable functions to boost TCs migration. Unexpectedly, mineral components and heavy metals did not displayed significant promotion on ARGs transport as a whole.

Ammonia removal from low-strength municipal wastewater by powdered resin combined with simultaneous recovery as struvite

Low-strength municipal wastewater is considered to be a recoverable nutrient resource with economic and environmental benefits. Thus, various technologies for nutrient removal and recovery have been developed. In this paper, powdered ion exchange resin was employed for ammonia removal and recovery from imitated low-strength municipal wastewater. The effects of various working conditions (powdered resin dosage, initial concentration, and pH value) were studied in batch experiments to investigate the feasibility of the approach and to achieve performance optimization. The maximum adsorption capacity determined by the Langmuir model was 44.39 mg/g, which is comparable to traditional ion exchange resin. Further, the effects of co-existing cations (Ca2+,Mg2+,K+) were studied. Based on the above experiments, recovery of ammonia as struvite was successfully achieved by a proposed two-stage crystallization process coupled with a powdered resin ion exchange process. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) results revealed that struvite crystals were successfully gained in alkaline conditions (pH = 10). This research demonstrates that a powdered resin and two-stage crystallization process provide an innovative and promising means for highly efficient and easy recovery from low-strength municipal wastewater.

Mitigating rural WWTP impacts: System dynamics modeling of downstream nutrient outputs

A system dynamics modeling approach was used to assess the potential impact of intentional struvite crystallization recovery on wastewater treatment plant (WWTP) allocation of N and P in effluent and biosolids outputs. Struvite crystallization has been used to recover wastewater N and P and produce valuable fertilizer. However, it is often overlooked whether additional benefits may be realized by diverting N and P from other fates. A system dynamics model was used with operational data from three activated-sludge WWTPs in North Florida. Incorporating struvite crystallization reduced the effluent P load by 37 to 100%, dependent upon the WWTP. This may translate into substantial savings for systems facing severe restrictions in effluent P release outside the plant. Additionally, biosolids P load reductions ranged from 17 to 46%. The model also predicted a 37% average increase in the biosolids N:P ratio. Increasing the N:P ratio may allow for greater biosolids land-application rates where P fertilizer restrictions exist. In comparison, the N load reductions were much less dramatic, i.e. below 10% reduction from the effluent and 14% from the biosolids. Most N inputs into an activated-sludge type WWTP are likely lost through denitrification during wastewater processing and struvite does not appear to be a significant means of recovering N from small WWTPs. However, incorporating struvite recovery into even the simplest WWTPs reduces effluent post-treatment needs and results in a more useful biosolids product.

Minimizing heavy metals in recovered struvite from swine wastewater after anaerobic biochemical treatment: Reaction mechanisms and pilot test

Struvite crystallization is a chemicophysical process for nitrogen and phosphorus recovery, and its product can be used as a slow-release fertilizer. Heavy metals (mainly Cu and Zn) present in swine wastewater not only affect the crystallization kinetics, but also increase the product’s ecological risk and make it inadequate for agricultural applications. However, there is currently little research focusing on heavy metal minimization during struvite recovery. This paper is to develop a cost-effective operation strategy, in which minimum process modification and optimum phosphorus recovery could be achieved. The results indicated that the Cu and Zn co-precipitation was mainly controlled by the chemical reaction rather than adsorption during struvite crystallization, making the pre-removal of heavy metals possible. Increasing the ammonia nitrogen concentration could effectively inhibit the co-precipitation of Cu and Zn. When struvite crystallization was performed in synthetic swine wastewater, it was found that the pre-removal of Cu/Zn by chemical precipitation, followed by the increase in initial solution pH, could markedly reduce the Cu and Zn co-precipitation and their contents in the recovered struvite. A pilot-scale test validated such a recommendation. Compared to the conventional struvite crystallization process, the proposed approach could reduce 43.5% Cu and 77.6% Zn in the recovered struvite.