Corn and Soybean Growth as Affected by Wastewater-Derived Struvite-Phosphorus Sources and Irrigation Water Types

Struvite (MgNH4PO4·6H2O) produced synthetically from a stock solution of known phosphorus (P) and nitrogen (N) concentrations has been shown to be an effective, alternative fertilizer-P source for various crops, but little is known about the potential agronomic effectiveness of struvite created from an actual municipal wastewater source. The objective of this study was to evaluate the effects of soil [i.e., Creldon silt loam (Oxyaquic Fragiudalf) and Calloway silt loam (Aquic Fraglossudalf) series], fertilizer-P source [i.e., synthetically produced electrochemically precipitated struvite (ECSTsyn), real-wastewater-derived ECST (ECSTreal), chemically precipitated struvite (CPST), monoammonium phosphate (MAP), and an unamended control (UC)], and irrigation water type (i.e., tapwater and struvite-removed wastewater) on corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] growth and N, P, and magnesium (Mg) uptake in a 60-day, greenhouse potted-plant study. Crop growth and N, P, and Mg uptakes for the struvite treatments (i.e., CPST, ECSTsyn, and ECSTreal) were generally similar to or at least 1.2 times greater than MAP. The ECSTsyn material commonly had up to five times greater N, P, and Mg uptake in corn and soybean than any other fertilizer-P source. Struvite-removed wastewater resulted in at least 1.3 times lower dry matter and N, P, and Mg uptake than tapwater. Similar corn and soybean results from the struvite fertilizers among the various soil-water type combinations compared to MAP suggest that struvite generates similar crop responses as at least one widely used, commercially available, multi-nutrient fertilizer-P source.

Soil Chemical Property Changes over Time from Struvite Compared to Other Fertilizer-Phosphorus Sources in Multiple Soils

Studies have shown that phosphorus (P) recovered from wastewater as the mineral struvite [MgNH4PO4·6(H2O)] may be a viable alternative fertilizer-P source. This study aimed to compare the effectiveness of electrochemically precipitated struvite (ECST), reclaimed from synthetic wastewater, to other commercial fertilizer-P sources in cultivated soils from Arkansas [AR;silt loam (SiL) and loam (L)], Missouri (MO;SiL), and Nebraska [NE;SiL and sandy loam (SL)]. A plant-less, moist-soil incubation experiment, including ECST, chemically precipitated struvite (CPST), monoammonium phosphate (MAP), triple superphosphate (TSP), and an unamended control (UC), was conducted to quantify soil pH, nitrate (NO3-N), ammonium (NH4-N), and Mehlich-3 (M3)-P, -Ca, -Mg, and -Fe concentrations at 0.5, 1, 2, 4, and 6 months. All measured soil properties differed (P ·kg-1 for AR-L-TSP after 1 month and NE-SiL-MAP after 6 months, respectively. Soil M3-P ranged from -29.6 mg·kg-1 in the AR-L-UC after 1 month to 429 mg·kg-1 AR-SiL-TSP after 0.5 months. Results showed that, over time, ECST had comparable pH and soil NO3-N, NH4-N, and M3-P, -Ca, -Mg, and -Fe behavior compared to CPST, MAP, and TSP across various soil textures.

Effects of heavy metal ions Cu^(2+)/Pb^(2+)/Zn^(2+)on kinetic rate constants of struvite crystallization

Struvite(MAP)crystallization technology is widely used to treat ammonia nitrogen in waste effluents of its simple operation and good removal efficiency.However,the presence of heavy metal ions in the waste effluents causes problems such as slow crystallization rate and small crystal size,limiting the recovery rate and economic value of the MAP.The present study was conducted to investigate the effects of concentrations of three heavy metal ions(Cu^(2+),Zn^(2+),and Pb^(2+))on the crystal morphology,crystal size,average growth rate,and crystallization kinetics of MAP.A relationship was established between the kinetic rate constant Ktcalculated by the chemical gradient model and the concentrations of heavy metal ions.The results showed that low concentrations of heavy metal ions in the solution created pits on the MAP surface,and high level of heavy metal ions generated flocs on the MAP surface,which were composed of metal hydroxides,thus inhibiting crystal growth.The crystal size,average growth rate,MAP crystallization rate,and kinetic rate constant Ktdecreased with the increase in heavy metal ion concentration.Moreover,the Ktdemonstrated a linear relationship with the heavy metal concentration ln(C/C~*),which provided a reference for the optimization of the MAP crystallization process in the presence of heavy metal ions.

Runoff-Water Properties from Various Soils as Affected by Struvite-Phosphorus Source and Water Type

Struvite (MgNH4PO4?6H2O) can be produced from municipal wastewater and has been shown to be an alternative fertilizer-phosphorus (P) source for various crops, but little is known about the runoff-water-quality implications from soil-applied struvite. The objective of this study was to evaluate the effects of soil [Creldon (Oxyaquic Fragiudalfs), Dapue (Fluventic Hapludolls), Roxana (Typic Udifluvents), and Calloway (Aquic Fraglossudalfs) series], fertilizer-P source [synthetically produced electrochemically precipitated struvite (ECSTsyn), real-wastewater-derived ECST (ECSTreal), chemically precipitated struvite (CPST), and monoammonium phosphate (MAP)], and water source (rainwater, groundwater, and struvite-removed real wastewater) over time on runoff-water-quality parameters from laboratory-conducted, rainfall-runoff simulations. Mesh tea bags containing each soil-fertilizer treatment combination were rained on with each water source (Trial 1), incubated for 6 months, and rained on again (Trial 2) to evaluate runoff-water quality. Struvite fertilizers had similar runoff-water-quality properties to those from MAP. In Trial 1, runoff total P (TP) concentration differences (i.e., soil-fertilizer-water-type response minus control response minus blank response) from ECSTsyn or ECSTreal were 1 to 5 times larger than MAP and CPST for all water-soil-fertilizer-P source treatment combinations, except for the Creldon-groundwater and Roxana-wastewater combinations. In both trials, runoff TP decreased over time in all water-soil and soil-fertilizer-P source treatment combinations, except for the Roxana-CPST combination where TP increased over time by 46%. The similar water-quality responses from the struvite fertilizers among the various soils and water types compared to MAP suggest that struvite has similar runoff-water-quality implications as at least one widely used, commercially available fertilizer-P source.

Struvite Effects on Rice Growth and Productivity under Flood-Irrigation in the Greenhouse

In recent years, electrochemical precipitation has gained interest as an alternative method for the synthesis of various minerals, including struvite, from waste streams that can serve as an alternative fertilizer. Studies in lowland cultivations, specifically rice (Oryza sativa) under flood-irrigated conditions, evaluating struvite as a possible alternative phosphorus (P) fertilizer source have been limited. The objective of this study was to evaluate rice response to electrochemically precipitated struvite (ECST) compared to triple superphosphate (TSP), diammonium phosphate (DAP), a chemically precipitated struvite (CPST), and an unamended control (UC), grown under flooded-soil conditions in the greenhouse. Aboveground vegetative dry matter (DM) P concentration was greatest from the UC (0.18%) and was lowest from DAP (0.08%). Root DM Mg concentration was greatest from ECST (0.13%) and was lowest from TSP (0.10%). Grain yield was greatest from DAP (11.2 Mg•ha−1) and was lowest from the UC (4.0 Mg•ha−1). Grain N, P, K, and Mg uptake were consistently greatest from DAP and consistently lowest from the UC. Grain N concentration was 1.1 times greater from CPST than from ECST, while all other measured rice properties did not differ between the struvite-P sources. The many similar rice responses between struvite materials (ECST and CPST) and TSP and DAP demonstrate that struvite, particularly ECST, is a valid alternative fertilizer-P source for rice-production systems. Further studies should evaluate potential environmental implications (i.e., runoff water quality and greenhouse gas emissions) from struvite use that could affect agricultural sustainability.

Struvite Recovery from Swine Waste Biogas Digester Effluent through a Stainless Steel Device under Constant pH Conditions

Objective To investigate the struvite precipitation under constant and non-constant pH conditions and to test a stainless steel device under different operating regimes to maximize the recovery of struvite. Methods The molar ratio of NH4^＋： Mg^2＋ PO43 was adjusted to 1： 1.2：1.2 and pH was elevated to 9.0. The absorbance measurement was used to trace the process of struvite crystallization. Wastewater and precipitate analysis was done by standard analytical methods. Results The pH constant experiment reported a significantly higher struvite precipitation （24.6±0.86 g） than the non-constant pH experiment （19.8±1.86 g）. The SAR ranged from 5.6 to 8.2 g m^-2h^-1 to 3.6-4.8 g m^-2h^-1 in pH constant and non-constant experiments, respectively. The highest struvite deposit on the device was found in regime 3 followed by in regimes 2 and 4. The highest PO4^3- （97.2%） and NH4^＋ （71%） removal was reported in the R1 regime. None of the influent Cu^2＋ or Zn^2＋ was precipitated on the device. Conclusion A higher struvite yield is evident in pH constant experiments. Moreover, the stainless steel device facilitates the isolation of heavy metal free pure （around 96%） struvite from swine waste biogas digester effluent contaminated with Cu^2＋ and Zn^2＋ and the highest yield is attainable with the device operating at 50 rpm with agitation by a magnetic stirrer.

Recovery of Nitrogen and Phosphorous as Struvite From Swine Waste Biogas Digester Effluent

Objective To investigate the feasibility of nitrogen and phosphorus recovery from swine waste biogas digester effluent and the effects of pH and NH4^＋： Mg2^＋： PO4^3- molar ratio on its precipitation. Methods Precipitation experiments with swine waste biogas digester effluent were conducted at pH 7.5, 8.0, 8.5, and 9.0 together with NH4^＋： Mg^2＋： PO4^3- molar ratios 1： 0.2： 0.08, 1： 1： 1, and 1： 1.5： 1.5. Chemical and X-ray diffraction （XRD） analysis were done to determine the composition of the precipitate. Results The highest removal and recovery of NH4^＋ and PO4^3- were achieved at pH 9.0 in each experiment. The elevation of pH to 9.0 alone could decrease the initial PO4^3- concentration from 42 mg L^-1 to 4.7 mg L-1 and 89.2% PO4^3- recovery was achieved. The pH-molar ratio combination 9.0-1： 1.5： 1.5 effected 76.5% NH4^＋ and 68.5% PO4^3- recovery. The molar ratio of 1： 1： 1 together with pH elevation to 9.0 was determined to be the optimum combination for both NH4＋ and PO4^3- removal as it recovered over 70% and 97% of the initial NH4^＋ and PO4^3-, respectively. Conclusions Nitrogen and phosphorus can be recovered from biogas digester effluent as struvite.

Effect of Copper (II) Ions on Quality of Struvite Produced in Continuous Reaction Crystallization Process at the Magnesium Ions Excess

The research results concerning continuous removal of phosphate (V) ions from solutions containing 1.0 or 0.20 mass % of phosphate (V) ions and 0.2 or 0.5 mg/kg of copper (II) ions using magnesium and ammonium ions addition are presented. Continuous reaction crystallization of struvite MgNH4PO4 × 6H2O ran both under stoichiometric conditions and at 20% excess of magnesium ions (pH 9, t 900 s). It was concluded, that presence of copper (II) ions in a process system influenced product quality moderately advantageously. Mean size of struvite crystals enlarged by ca. 6% only. Lower concentration of phosphate (V) ions and excess of magnesium ions caused, that products of ca. 9% - 13% larger crystal mean size (up to ca.40mm) were removed from the crystallizer. Presence of struvite crystals and copper (II) hydroxide were detected analytically in the products (Cu in a product varied from 6 to 90 mg/kg). Presence of copper (II) ions favored crystallization of struvite in the form of tubular crystals.

The Struvite Precipitation Index:A Practical Framework for Predicting Struvite Supersaturation in Water and Wastewater

In wastewater facilities, struvite (MgNH4PO4·6H2O) precipitation and subsequent accumulation within sludge processing can be an expensive nuisance or a pathway to orthophosphate reclamation and beneficial reuse. Predictive solubility models developed in the past have been computationally intensive, highly conservative, and have employed uncertain equilibrium constants for the evaluation of solution saturation. The StrPI (Struvite Precipitation Index) developed in this study is a new, computationally light framework for predicting struvite precipitation based on saturation pH. The model permits process-specific calibration (i.e. StrPI plus a correction pH) to deal with the highly variable characteristics of wastewater streams and to eliminate the pH-independent overprediction inherent in existing solubility models. Verification of this model was performed across a range of waste compositions, ionic strengths, and root-mean-square velocity gradients using data from both synthetic laboratory experiments and field tests. The StrPI framework was found to be an effective and uncomplicated predictor of struvite precipitation in both environments.

Agrotechnical Assessment of Struvite Application

Agrotechnical assessment of struvite produced by a lab-scale sedimentation unit is performed. As a source of phosphates and ammonia, liquor obtained through dewatering of Мunicipal wastewater treatment plant sludge was in use. The range of phosphates and ammonia was in the range of 130 - 250 and 380 - 560 mg/L, respectively. Seawater brine with a magnesium concentration of around 60 g Mg2+/L was applied as a source of magnesium. The agrotechnical characteristics of struvite obtained were compared to ammonium nitrate and carbamide in regards to the productivity effects on maize hybrid P9241. The results show that the effectiveness of struvite and some commercial fertilizers is quite close. The highest yield in the experiment was achieved with the application of carbamide plus ammonium nitrate (56.64 kg/ha), while in applying struvite solely it is 54.60 kg/ha. The highest protein content of maize (9.7%) was observed in the case of struvite/ammonium nitrate application.

Chemically Precipitated Struvite Dissolution Dynamics over Time in Various Soil Textures

Phosphorus (P) is a fundamental nutrient in agricultural production and is one of three major components in common fertilizers. The majority of fertilizer-P sources are derived from phosphorus rock (PR), which has finite abundance;thus a sustainable source of P is imperative for future agricultural productivity. A potential sustainable P source may be the recovery of the mineral struvite (MgNH4PO4·6H2O) from wastewater treatment plant effluent, but struvite behavior in soils of varying texture is not well characterized. The objective of this study was to assess the dissolution dynamics of a commercially available, wastewater-recovered struvite product over time in a plant-less, moist-soil incubation experiment with multiple soil textures. Chemically precipitated struvite (Crystal Green;CG) from municipal wastewater in pelletized and finely ground forms were added to soil cups at a rate of 24.5 kg∙P∙ha−1 containing soils of varying texture (i.e. loam, silty clay loam, and two different silt loams) from agricultural field sites in Arkansas. Soil cups were destructively sampled five times over a 6-month period to examine the change in water-soluble (WS) and weak-acid-extractable (WAE) P, K, Ca, Mg, and Fe concentrations from their initial concentration. After 0.5 months, both WS-P and WAE-P concentrations increased (P < 0.05) more from initial concentrations of the finely ground CG in all soils, which averaged 76.2 and 158 mg∙kg−1, respectively, than in the pelletized CG treatment, which averaged 14.0 and 12.2 mg∙kg−1, respectively, across all soils. Over the course of the 6-month incubation, WS- and WAE-P concentrations generally increased over time in the pelletized and decreased over time in the finely ground treatment, confirming the slow-release property of pelletized CG that has been previously reported. The results of this study provide valuable insight regarding struvite-P behavior in various soils and provide further supporting evidence for the utilization of struvite as a potential alternative, sustainable fertilizer-P source.

Continuous Reaction Crystallization of Struvite in a DTM Type Crystallizer With Jet Pump of Ascending Suspension Flow in a Mixing Chamber–Kinetic Approach of the Process

Reaction crystallization of struvite in water solutions containing 0.20 mass % of phosphate(V) ions by magnesium and ammonium ions addition was investigated experimentally. Process was carried out in DTM type crystallizer with liquid jet pump device in 298 K assuming stoichiometric conditions. Struvite crystals of mean size Lm 5.2-23.0 μm were produced depending on pH (9-11) and mean residence time of suspension in a crystallizer τ (900-3600 s). Under these conditions linear growth rate of struvite crystals (SIG MSMPR kinetic model) decreased 2-time with the increase in pH and 3-time with the elongation of mean residence time of crystal suspension from 7.11×10-9 m/s (pH 9, τ900 s) to 1.65×10-9 m/s (pH 11, τ3600 s). Nucleation rate varied within the 7.9×108-1.8×1010 1/(sm3) limits. Struvite product of maximal linear size exceeded 100 μm with 10 vol. % of < 3 μm fraction corresponded to pH 9 and τ3600 s.

Precipitation and Crystallization of Struvite from Synthetic Wastewater under Stoichiometric Conditions

Phosphate (V) ions were continuously removed from synthetic wastewater containing inorganic impurities using magnesium and ammonium ions. The product was magnesium ammonium phosphate (V) hexahydrate, struvite, MgNH4PO4 × 6H2O. Research ran in stoichiometric conditions in DT MSMPR type crystallizer with internal circulation of suspension. Increase in process environment pH from 9 to 11 resulted in 3-time decrease of mean struvite crystals size (from 40.1 to12.6mm). Elongation of mean residence time of suspension in a crystallizer up to 3600 s resulted in improvement of the product quality. Mean size of struvite crystals enlarged up to50.2mm. Based on kinetic calculations results (SIG MSMPR model) it was concluded, that linear struvite crystal growth rate varied within 5.04 × 10–9 – 1.69 × 10–8 m/s range, whereas nucleation rate within 1.4 × 107 – 1.7 × 1010 1/(s m3) limits. In solid product, besides struvite, also all impurities present in wastewater were identified analytically as hydroxides, phosphates and other salts.

Molecular Modeling of Chemicals Products Inhibitors of Growth Struvite Crystal

Struvite (MgNH4PO46H2O) crystals were produced by infection associated with urea generating organ- isms.The aim of this study is to examine the interactions between the enzyme urease and two inhibitors, the first is an inhibitor monoatomic: Aluminum and the second is a polyatomic: Citrate by the methods of molecular modeling: molecular mechanics, molecular dynamics (MM+, AMBER) and molecular docking (FleX). Supersaturated solutions induce crystallization by nucleation and subsequent crystal growth .The mechanisms for the formation of calcium phosphate urinary stones are still not understood. Chemicals prod- uct has been studied extensively as inhibitors and has been observed in the attachment of crystals to in vitro study. As a complement we have using an electron microscope Hitachi TM1000, we examined specimens of crystals struvite. The various figures show a set of grains of sizes of the order of 20 μm. The majority of these particles present regular forms. This suggests the crystal growing. This result to an alteration in the expression of these faces and the development of a characteristic architectural struvite morphology. Similar changes were observed in the presence of identical concentrations of citrate acid, and Alluminuium, emphasizing the unique interaction of phosphocitrate with the struvite crystal.

Phosphorus recovery from wastewater by struvite crystallization:Property of aggregates

Struvite crystallization is a promising method to remove and recover phosphorus from wastewater to ease both the scarcity of phosphorus rock resources and water eutrophication worldwide. To date, although various kinds of reactor systems have been developed, supporting methods are required to control the stmvite fines flushing out of the reactors. As an intrinsic property, aggregation is normally disregarded in the struvite crystallization process, although it is the key factor in final particle size and therefore guarantees phosphorus recovery efficiency. The present study developed a method to analyze the characteristics of struvite aggregates using fractal geometry, and the influence of operational parameters on struvite aggregation was evaluated. Due to its typical orthorhombic molecular structure, struvite particles are prone to crystallize into needle or rod shapes, and aggregate at the comers or edges of crystals. The determined fractal dimension （Dpf） of struvite aggregates was 1.52-1.31, with the corresponding range of equivalent diameter （d0.5） at 295.9-85.4 Ixm. Aggregates formed in relatively low phosphorus concentrations （3.0-5.0 mmol/L） and mildly alkaline conditions （pH 9.0-9.5） displayed relatively compact structures, large aggregate sizes and high aggregation strength. Increasing pH values led to continuous decrease of aggregate sizes, while the variation of Dpf was insignificant. As to the aggregate evolution, fast growth in a short time followed by a long steady stage was observed.

Recovery of phosphorus as struvite from sewage sludge ash

Phosphorus （P） is an element vital for all living organisms, yet the world＇s reserves of phosphate rock are becoming depleted. This study investigated an effective P recovery method from sludge ash via struvite precipitation. Results showed that more than 95% of the total P content was extracted from sludge ash by applying 0.5 mol/L HC1 at a liquid/solid ratio of 50 mL/g. Although heavy metal leaching also occurred during P extraction, cation exchange resin efticiently removed the heavy metals from the P-rich solution. Orthogonal tests showed that the optimal parameters for P precipitation as struvite would be a Mg：N：P molar ratio of 1.6：1.6：1 at pH 10.0. X-ray diffraction analysis validated the formation of struvite. Further investigations revealed that the harvested precipitate had a high struvite content （97%）, high P bioavailability （94%）, and low heavy metal content, which could be considered a high quality fertilizer.

Selection of cost-effective magnesium sources for fluidized struvite crystallization

Struvite crystallization has been considered a promising approach to recover phosphorus from wastewater. However, its practical application is limited, probably because of the high cost of magnesium（Mg）. In this study, a comprehensive economic analysis was conducted using five Mg sources（MgCl2, MgSO4, MgO, Mg（OH）2, and bittern） during the operation of a pilot-scale fluidized bed reactor（FBR）, using swine wastewater as the case matrix. First, the economic operating conditions were investigated, and subsequently, the performance and the costs of the five Mg sources were compared. The results indicated that the FBR could be operated most economically at pH of 8.5 and Mg to phosphorus（Mg/P） molar ratio of 1.5. Under these conditions, no significant differences in phosphorus removal and product quality could be found between the five Mg sources. Selecting the most economical Mg source was thus highly dependent on the prices of the reagents and Mg sources. Low-solubility Mg sources were preferable when NaOH was priced higher, while high-solubility Mg sources proved more economical when HNO3 was expensive. The bittern was the most economical choice only when the distances for total inorganic orthophosphate removal and struvite recovery were shorter than 40 and 270 km, respectively. The current study provides an overview of the economic selection of an Mg source, which can help reduce the cost of struvite crystallization.

Effect of Ca:Mg ratio and high ammoniacal nitrogen on characteristics of struvite precipitated from waste activated sludge digester effluent

This study revealed the relationship between the presence of calcium impurities and ammoniacal nitrogen concentration upon crystallization of struvite.The research hypothesis was that the presence of both calcium and high concentrations of ammoniacal nitrogen(328–1000 mg/L)in waste activated sludge may influence the struvite quality and acid stability.Hence,we studied the impact of Ca:Mg ratio upon morphology,particle size,purity and dissolution of struvite,in the presence of varying levels of excess ammoniacal nitrogen.X-ray diffraction revealed that up to 31.4%amorphous material was made which was assigned to hydroxyapatite.Increasing the ammoniacal nitrogen concentration and elevation of the Mg:Ca ratio maximized the presence of struvite.Struvite particle size was also increased by ammoniacal nitrogen as was twinning of the crystals.Tests with dilute solutions of organic acid revealed the sensitivity of struvite dissolution to the physical characteristics of the struvite.Smaller particles(21.2μm)dissolved at higher rates than larger particles(35.86μm).However,struvite dissolved rapidly as the p H was further reduced irrespective of the physical characteristics.Therefore,addition of struvite to low p H soils was not viewed as beneficial in terms of controlled nutrient release.Overall,this study revealed that waste activated sludge effluent with high ammoniacal nitrogen was prospective for synthesis of high quality struvite material.

Study on the mechanism of copper-ammonia complex decomposition in struvite formation process and enhanced ammonia and copper removal

Heavy metals and ammonia are difficult to remove from wastewater,as they easily combine into refractory complexes.The struvite formation method（SFM） was applied for the complex decomposition and simultaneous removal of heavy metal and ammonia.The results indicated that ammonia deprivation by SFM was the key factor leading to the decomposition of the copper-ammonia complex ion.Ammonia was separated from solution as crystalline struvite,and the copper mainly co-precipitated as copper hydroxide together with struvite.Hydrogen bonding and electrostatic attraction were considered to be the main surface interactions between struvite and copper hydroxide.Hydrogen bonding was concluded to be the key factor leading to the co-precipitation.In addition,incorporation of copper ions into the struvite crystal also occurred during the treatment process.

Enhanced struvite recovery from wastewater using a novel cone-inserted fluidized bed reactor

The feasibility of struvite recovery at low （12.5 mg/L） and high （120 mg[L） phosphorus concentrations was studied by constructing a novel fluidized bed reactor with cones （FBRwc） and without cones （FBRwoc）. The crystallization process was continuously operated for 133 days under different hydraulic retention times （HRT = 1-10 hr）, pH （7.5-10）, and molar ratios of Mg/P （0.75-1.75）, N/P （1-10） and Ca/Mg （0-2）. The optimum operating conditions of HRT, pH, Mg/P and N/P molar ratios were found to be 2 hr, 9, 1.25, and 7.5, respectively. Under these optimum conditions, the phosphorus precipitation efficiencies of FBRwc were 93% for low and 98% for high phosphorus influent; however, the efficiencies were 78% and 81% for FBRwoc, respectively. Due to crystal losses at each junction （17%-31%）, the crystal recovery efficiency of FBRwoc was relatively low （47%-65%） for both influent concentrations. However, the losses were minimal in FBRwc, which showed 75% and 92% crystal recovery for low and high phosphorus concentrations, respectively. At low calcium concentration, crystal chemical analysis showed the product to be pure struvite （〉 99%）. The scanning electron microscope and X-ray diffraction results further confirmed that the crystal recovered from FBRwc contained pure struvite, which could be considered a high quality fertilizer. Except HRT, all parameters （pH, Mg/P, N/P and Ca/Mg） were found to be influencing factors for FBRwc performance. Overall, inserting cones in each part of the reactor played a significant role in enhancing struvite recovery from a wide range of phosphorus-containing wastewater.