Struvite Precipitation Research Articles

The Feasibility Evaluation of Nitrogen Recovery from Tannery Sludge Leachate Combined with Phosphogypsum Leachate by the Struvite Precipitation

The Feasibility Evaluation of Nitrogen Recovery from Tannery Sludge Leachate Combined with Phosphogypsum Leachate by the Struvite Precipitation

Recovering phosphorus as struvite from anaerobic digestate of pig manure with ferrochrome slag as a magnesium source

The circular economy initiative has driven the agriculture and agro-based industry to beneficiate from waste,thus closing the material loop towards enhancing economic and environmental performance. In this study, the aim was to recover phosphorus from anaerobic digestate of piggery wastewater (ADPW) using ferrochrome slag (FCSL) as the magnesium source to improve the environmental and economic sustainability of struvite precipitation. This was achieved by leaching 100 g L−1 of ferrochrome slag with 5 M HCl where 14.02 g L−1 of magnesium ions were extracted, and this acid-leachate of ferrochrome slag also contained 2650 mg L−1 of total iron. To simultaneously remove both high concentrations of organic matters in ADPW and iron in FCSL which are known to be detrimental to struvite precipitation, hydrogen peroxide (H2O2) at an H2O2/Fe molar ratio of 0.75 and pH 4.0 was added to the mixture of ADPW and FCSL. After the Fenton reaction, removal efficiencies of chemical oxygen demand (COD) and total iron reached 95.06% and 94.00%, respectively. Then COD and an iron-reduced mixture of ADPW and FCSL were added with a satisfying Mg:N:P molar ratio of 1.2:1:1.15 at pH 9.5 to produce struvite in 1 h. From 1 L of ADPW (2.6 g NH3–N), 0.5 L of FCSL (5.34 g Mg2+), and 6.62 g of PO43− P, were consumed to produce 45.57 g of struvite precipitate. Additionally, the economic feasibility of ferrochrome slag was assessed by estimating the chemical costs of FCSL against that of magnesium chloride which is commercially used. It was observed that using FCSL was cheaper as compared to using commercial MgCl2. Response surface methodology coupled with the central composite design was applied as a statistical tool to determine the effects of the key parameters (N:P; Mg:PO4; pH) on phosphorus recovery. Second-order polynomial equations were determined to correlate the parameters. ANOVA was applied and showed that p values for all the investigated parameters were less than 0.05 showing that they had a statistically significant effect on the phosphorus recovery. The study confirmed that it was possible to recover phosphorus as struvite from anaerobic digestate of pig manure with ferrochrome slag as a magnesium source.

Optimization of phosphorus recovery using electrochemical struvite precipitation and comparison with iron electrocoagulation system.

A batch monopolar reactor was developed for total phosphorus (TP) recovery using electrochemical struvite precipitation. This study involves the optimization of factors using response surface methodology to maximize the TP recovery. The optimal parameters for this study were found to be a pH of 8.40, a retention time of 35 min, a current density of 300 A/m2 , and an interelectrode distance of 0.5 cm, resulting in 97.3% of TP recovery and energy consumption of 2.35 kWh/m3 . A kinetic study for TP removal revealed that at optimum operating conditions, TP removal follows second-order kinetics (removal rate constant(K) = 0.0117 mg/(m2 ·min)). The system performance was compared to the performance of an iron electrocoagulation system. The composition of the precipitate obtained during the optimal runs were analyzed using X-ray diffraction and EDS analysis. X-ray diffraction analysis of the magnesium precipitate revealed the presence of struvite as the only crystalline compound. PRACTITIONER POINTS: Electrochemical struvite precipitation has the potential to recover total phosphorus from anaerobic bioreactor effluent. Optimum conditions for phosphorus recovery was found at a pH of 8.4, retention time of 35 min, current density of 300 A/m2, and interelectrode distance of 0.5 cm. The quadratic model predicted complete (100 %) TP recovery under optimized conditions, whereas 97.3 % recovery was observed under experimental conditions. TP removal under optimum conditions followed second-order rate equation (removal rate constant(K) = 0.0117 mg/(m2 ·min)). XRD analysis of the precipitate revealed struvite as the only crystalline compound.

Life cycle assessment of a novel strategy based on hydrothermal carbonization for nutrient and energy recovery from food waste

In this work, a novel strategy for food waste valorization was evaluated from an environmental life-cycle perspective. A system based on acid-assisted hydrothermal carbonization of food waste combined with the exploitation of hydrochar by combustion and process water through nutrient recovery stage and subsequent anaerobic digestion, was assessed and compared with stand-alone anaerobic digestion as the reference system. This combination of processes aims to recover both nutrients in a stage of struvite precipitation from process water and energy through hydrochar and biogas combustion. Both systems were modeled in Aspen Plus® to identify and quantify their most relevant input and output flows and subsequently evaluate their environmental performance through the life cycle assessment methodology. The novel combined system was found to generally involve a more favorable environmental performance than the reference stand-alone configuration, which would be closely linked to the substitution of hydrochar for fossil fuels. In addition, the impacts associated with soil application of the struvite produced in the integrated process would also be reduced compared to the use of the digestate generated in the stand-alone anaerobic digestion process. Following these results and the evolving regulatory framework for biomass waste management, mainly in the field of nutrient recovery, combined process based on acid-assisted hydrothermal treatment plus nutrient recovery stage and anaerobic digestion is concluded to be a promising circular economy concept for food waste valorization.

A comparison of struvite precipitation thermodynamics and kinetics modelling techniques.

Solution thermodynamics and kinetic modelling applied to struvite crystallisation-precipitation were reviewed from diverse references to determine proximity between predicted and cited experimental measurements. These simulations show the expected variability range of struvite saturation calculation when only limited solution compositional information is given, showing acceptable agreement between predicted and experimental struvite mass. This work also compares results from struvite crystallisation kinetic studies on liquid phase species depletion, crystallisation induction time, primary nucleation, secondary nucleation, crystal growth, and crystal aggregation. Large inconsistencies between reported kinetics were observed in many scenarios. Variations in species depletion models highlighted that they are only suitably applied to the specific system from which they were regressed. Spontaneous primary nucleation was predicted to occur in the range of SI = 0.237-0.8. Predicted primary nucleation rates vary over at least 10 orders of magnitude (depending on supersaturation) because of uncertainties in interfacial tension and maximum achievable nucleation rate. Secondary nucleation rates are more agreeable, varying over approximately two orders of magnitude. Growth rates varied over five orders of magnitude due to variations in experimental conditions. Aggregation rates are not thoroughly examined enough to make any inferences.

A Unit Process Approach to Nontarget Screening of Organic Contaminants during Urine Treatment

Urine treatment has expanded over the past few decades; however, widespread implementation requires rigorous, generalizable comparisons between selective nutrient separation and organic compound mitigation. This study describes and demonstrates an enrichment ratio framework, defined as the relative concentration changes of nutrients (nitrogen or phosphorus) with organic compounds analyzed via high-resolution mass spectrometry. Nontarget analysis enabled comparison of the effects of urine treatment processes (e.g., ion exchange, freeze–thaw, activated carbon, struvite precipitation) on organic compounds. In total, we considered 14 treatment scenarios, including six unit processes for acidified urine and eight for hydrolyzed urine. Acidified and hydrolyzed urine were characterized longitudinally, and each of the two urine types remained stable in terms of the organic compound profile (>79% similarity) over several weeks. Unit processes with mean enrichment ratios (ER) that involved more than a 2-fold concentration change (ER > 2 or ER < 0.5) were considered high priority and were further separated into cases in which organic compounds were concentrated (ER > 2) or removed (ER < 0.5) for various unit processes. Whereas ER values are typically calculated only for compounds present in both the influent and effluent streams, we also analyzed compounds that were detected in only influent or only effluent added. Results from the target analysis of six compounds generally corroborated the nontarget results. Ultimately, our approach to simultaneously characterizing both nutrients and organic compounds through urine processing steps can inform and advance the implementation of urine resource recovery.

Stability of Mg-based anode in electrochemical struvite precipitation using pure Mg vs. AZ31 vs. AZ91D

Struvite (MgNH4PO4·6H2O) electrochemical precipitation method is a compelling new way to recover phosphorus from wastewater. In this study, a suite of common magnesium materials on the market is tested to understand the effect of anode composition on the electrochemical performance of electrolysis reactors with single and batch modes. The pure magnesium anode demonstrated the fast phosphorus removal efficiency and best Mg2+ releasing among three alloys, but it cannot be sustained and must be replaced frequently. Large amounts of brucite were mixed into precipitates, decreasing their purity during the pure Mg anode electrolysis reaction. The Mg anode materials influenced the elemental composition of struvite produced from the electrolysis reactor, which was not standard 1: 1: 1 (Mg: P: N). Al element is the most significant contaminant released from AZ31 and AZ91D among three impurities (Al, Mn, Zn). The Mg anode, which had higher Al content, released more Al3+ into the electrolyte, which was easy to be adsorbed by struvite precipitates with the cycle. The Al3+ concentration in the effluents also decreased with the experiment prolonged. Results showed that AZ31 could support Mg2+ stable production in batch mode without as large impurity ions releasing as AZ91D in the electrolyte or the precipitated struvite.

Combined application of microbes immobilized carbon reactor and the reactive struvite system for the management of tannery deliming wastewater.

This present study investigated the removal of COD and ammoniacal nitrogen (NH4+-N) from tannery deliming wastewater (TDLWW) through microbesimmobilized carbon consisted a bioreactor (MICCR) and reactive struvite crystallization process. Initially, 90% of the organic content of TDLWW was removed using a MICCR reactor at 24 h retention time. Nanoporous carbon (NPC) was used as the carrier matrix for the MICCR reactor. SEM and AFM images of NPC used in the MICCR reactor identify different microorganisms on its surface. The microbial profile of NPC used in the MICCR was analyzed, and the relative abundance is phyla Firmicutes, 25.64%; Proteobacteria, 43.68%; Bacteroidetes, 6.58%; Cyanobacteria, 2.22%; Actinobacteria, 2.34% reason for organic removal. The removal of organics follows the pseudo-second-order rate kinetics with the rate constant of 1.75×10-3L COD-1 h-1. For the reactive struvite crystallization, MgO and Na2HPO4.2H2O were taken as the precipitating agents. The optimum molar ratio for the maximum conversion of NH4+-N into struvite was obtained as 1:1.4:1.4 (NH4+-N:MgO:Na2HPO4.2H2O). The volume of struvite precipitate was 48.5mL/L of TDLWW, and the dry weight was 8.89 g/L. More than 93% of NH4+-N was converted as the struvite fertilizer. The conversion of NH4+-N into struvite follows the pseudo-first-order rate kinetics with the rate constant of 1.67×10-2 min-1. Despite the conversion of NH4+-N into struvite, COD removal was observed, which confirms the conversion of organic nitrogen into struvite. The struvite was evaluated using SEM, XRD, TGA, DSC, and FT-IR spectroscopic analysis. Hence, the integrated MICCR and the reactive struvite crystallization process can be applied to manage tannery deliming wastewater.

Usage of phosphoric acid plant's circulate pond waters in struvite precipitation—Effect of conditions

AbstractStruvite is a suitable fertilizer, and electrochemical precipitation of nutrients from industrial waters provides one answer to the circular economy. Molar ratio between ammonium and phosphate is crucial: Water suitable for the precipitation includes more or at least the same amount ammonium than phosphate. That kind of water typically does not exist in industry. Therefore, ammonium‐rich industrial water was mixed with phosphorus‐rich water to obtain a suitable molar ratio for struvite precipitation. Parameters were studied to determine their effect on removal‐% and struvite yield. 100% struvite yield was obtained under several conditions even without pH control with pH 7–9. The highest phosphate removal (99.7%) was occurred with the molar ratio 1.7:2:1 for Mg:NH4:PO4 (pH 9.0). Waters dilution prevents magnesium anode corrosion. Formed struvite has potential as recycled fertilizer due to low bioavailability of metals and high leachability of nutrients studied by four‐stage sequential leaching.

Phosphorus Recovery from Municipal Wastewater: Brucite from MgO Hydrothermal Treatment as Magnesium Source

Crystallization of struvite (MgNH4PO4·6H2O, MAPH) for both N and P recovery from municipal wastewater is an attractive alternative. The low magnesium concentration in municipal wastewater calls for low-cost magnesium sources. In the present work, the precipitation of struvite from supersaturated solutions was investigated. The supersaturated solutions were prepared by the addition of either slurry of Mg(OH)2 (brucite) obtained from the hydrothermal treatment of magnesium oxide (MgO) or using the aqueous solution equilibrated with brucite after separation from the solid. In both cases, in the supersaturated solutions prepared by the addition of ammonium dihydrogen phosphate, the Mg:NH4:P ratio was 1:1:1, pH 7.0–11.0. The apparent order for the precipitation suggested that the dominant mechanism was surface diffusion according to the polynuclear model. The apparent rate constant for struvite precipitation was two orders of magnitude smaller for the slurry prepared supersaturated solution in comparison with the respective prepared from the brucite-equilibrated solution. Simulated wastewater (SWW), was supersaturated with respect to struvite, by inoculation with brucite. The apparent rate constant was two orders of magnitude higher than that corresponding to the supersaturated solutions prepared by the addition of solution equilibrated with brucite. The P recovery from SWW reached 70%.

The implications of pulsating anode potential on the electrochemical recovery of phosphate as magnesium ammonium phosphate hexahydrate (struvite)

A sustainable approach to address the limited availability of rock phosphate is to electrochemically recover phosphorus (P) as struvite (magnesium ammonium phosphate hexahydrate, MgNH4PO4·6H2O) fertilizer. On Mg surfaces, however, magnesium hydroxide (Mg(OH)2) and/or struvite form resistive films that limit the release of divalent Mg ions and reduce struvite precipitation. The present work enhances struvite recovery through the application of a dynamic voltage with a sinusoidal waveform. Compared to a constant potential, our results demonstrated that a dynamic potential could enhance the rupture of the passivating film, and facilitate the release of Mg2+ from the metal anode, thereby overcoming passivation problems. Ammonium dihydrogen phosphate (NH4H2PO4, 10 mM) solutions at neutral pH were used as test solutions. A 160–192 % increase in magnesium release was observed versus constant voltage applications, resulting in a 1.3x increase in phosphate recovery. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations indicated that the precipitate recovered contained struvite. An analysis of electrode surfaces using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) confirms a greater extent of passivating film breakdown under dynamic voltages.

Treatment of engineering waste slurries by microbially induced struvite precipitation mechanisms.

With societal development, the growing scale of engineering construction, and the increase in environmental protection requirements, the necessity of engineering waste mud disposal is becoming increasingly prominent. In this study, microbially induced struvite precipitation (MISP) was introduced to treat engineering waste mud. The study mainly focused on: i) the optimal mineralization scheme for microbially induced struvite precipitation, ii) the feasibility of the process and the effect of reaction parameters on treating engineering waste mud with microbially induced struvite precipitation, and iii) the mechanism of microbially induced struvite precipitation in treating engineering waste mud. The results showed that the waste mud could be well treated with bacteria, 10mM urea, 20mM phosphate buffer, and 25mM at pH 7. The kaolin suspension could be effectively flocculated. The flocculation rate reached approximately 87.2% under the optimum mineralization conditions. The flocculation effect was mainly affected by the concentrations of reactants and heavy metals and the suspension pH. The X-ray diffraction (XRD) patterns showed a strong struvite (MAP) diffraction peak. Scanning electron microscopy (SEM) images indicated that under the optimal mineralization conditions, the crystals were large and showed prismatic shapes tilted at both ends with adhered kaolin particles. In summary, this manuscript provides an effective way to treat engineering waste mud, and the findings should have a positive effect on enhancing soil fertility and preventing secondary pollution.

N, P, K recovery from hydrolysed urine by Na-chabazite adsorption integrated with ammonia stripping and (K-)struvite precipitation.

This study investigated the recovery of K+ along with NH4+-N and PO43--P from hydrolyzed urine by technical integration. The K adsorption capacities of biochar, clinoptilolite, artificial zeolite and chabazite were firstly compared. Due to the high K recovery efficiency and additional P recovery capacity, Na-chabazite was selected as the adsorbent in this study. Its kinetics and isotherm analysis indicated that the high molarity of NH4+-N seriously hindered the K adsorption onto Na-chabazite in synthetic hydrolyzed urine (SHU). However, this competition between NH4+ and K+ got diminished when their molarity is the same, i.e. in the SHU after ammonia stripping (ASSHU). Based on this key finding, Na-chabazite adsorption was integrated with ammonia stripping and struvite precipitation under different configurations. Simultaneous ammonia stripping was inadequate to diminish the competitive effect of NH4+ on K+ adsorption. Depending on the demand for fertilizer, two sequential configurations were recommended, respectively.

Mechanism of calcium hydroxide-reinforced magnesium-loaded clinoptilolite/phosphoric acid-modified biochar for NH3-N removal from rare earth element tailing wastewater

An efficient composite for NH3-N removal from REE wastewater was developed, removing NH3-N primarily by forming calcium magnesium ammonium phosphate precipitation along with volatilization, adsorption, and struvite precipitation.

Research Progress on the Treatment of High-Concentration Nitrogen and Phosphorus Wastewater by Struvite Precipitation

Aiming at the problems of eutrophication of water bodies and the shortage of phosphorus resources, the struvite method for treating high-concentration nitrogen and phosphorus-containing wastewater has been widely used because of its high efficiency and low consumption. This paper summarizes the research progress on the treatment efficiency, influencing factors and stability of high concentration nitrogen and phosphorus mixed wastewater in recent years, and on this basis, the feasibility and development prospect of MAP method in the treatment of high concentration nitrogen and phosphorus wastewater are proposed.

Treatment of landfill leachate using advanced oxidation process and struvite precipitation processes

Landfill leachate contains high organic matter, heavy metals, ammonia and xenobiotic compounds. It requires potential treatment prior to its discharge. Several treatment methods are reported in the literature with low Chemical Oxygen Demand (COD) and ammonia concentration but most of them were inefficient to treat landfill leachate. In this view, Advanced Oxidation Processes (AOP’s) in combination with chemical precipitation are considered to be more suitable for high COD and ammonia. In this study, an attempt was made to evaluate the application of Fenton and Struvite Precipitation processes for the removal of COD and ammonia. The operational parameters for Fenton and Struvite are optimized. The individual treatment processes by Fenton and struvite achieved % removal of 60% and 25%, 30% and 65% of COD and ammonia respectively. The Fenton and struvite processes were performed in a sequence with the pre-optimized parameters, where the maximum removal of COD and ammonia is observed as 89% and 78%. The kinetic analysis of struvite process fits into the first order kinetics. Hence, the combined fenton process and struvite precipitation processes are reliable, efficient and can be considered as an alternative treatment for the traditional treatment methods thereby reducing its toxicity.

Combined stripping-struvite precipitation process for treating high ammonia-nitrogen wastewater generated by the craft of vanadium extraction

Unlocking Sustainable Solutions! A significant achievement in high-concentration ammonia–nitrogen removal from vanadium extraction wastewater is reported through an innovative combination of stripping and struvite precipitation methods.

OPTIMIZATION OF ALKALINE–THERMAL HYDROLYSIS TO OBTAIN STRUVITE FROM DIGESTED SLUDGE USING A BOX–BEHNKEN DESIGN: SOLUBILIZATION OF NUTRIENTS AND METALS

In this study, we investigated ways by which to optimize metals and nutrients solubilization from sewage sludge using alkaline–thermal hydrolysis and the Box–Behnken design. We also examined through struvite crystallization the recovery of solubilized nutrients from hydrolyzed liquid and determined the effect of NaOH concentration, the liquid/solid ratio, and temperature on the hydrolysis process. Nutrients solubilization was positively affected by decreasing liquid/sludge ratio and increasing NaOH concentration. Ca, Al, and Zn solubilization increased with increasing temperature. The optimum condition for solubilization of nutrients and metals was 0.7 M NaOH and a 5/1 mL/g liquid/solid ratio at 35 °C. EDS analyses of hydrolyzed sludge obtained under optimum conditions showed that the mass percentage of C, P, Fe, Al, and K decreased compared to that of the digested sludge. Under optimum conditions, the removal efficiencies of NH4+ and PO43- from hydrolyzed liquid by struvite precipitation were 57.43 and 79.22% at a N:Mg:P molar ratio of 1:1:1, and 73.31 and 99.02% at a N:Mg:P molar ratio of 1:1.5:1, respectively. XRD analyses of the dry precipitate showed hazenite in addition to struvite formation at a molar ratio of N:Mg:P of 1:1:1.

Microbial phosphorus removal and recovery by struvite biomineralisation in comparison to chemical struvite precipitation in municipal wastewater

Microbial biomineralisation is attracting significant interest as an innovative process to recover nutrients from wastes. Nevertheless, little is understood about the requirements to form struvite using biological pathways in wastewater and how does this compare with conventional chemical processes. To address this gap, Halobacterium salinarum, Bacillus pumilus, Brevibacterium antiquum, Myxococcus xanthus and Idiomarina loihiensis were grown in wastewater to explore the relationships between cell growth, nutrients levels and properties of the recovered precipitates. The microorganisms were capable of removing ortho-phosphate (PO4-P) from municipal wastewater at concentrations ranging from 5.4 to 62.4 mg PO4-P/L. Visible crystals of biological struvite (bio-struvite) (identified by morphology XRD and elemental analysis), were observed at PO4-P ≥ 19.7 mg/L, compared to chemical struvite precipitation at 62.4 mg/L PO4-P (with pH adjustment). The initial nutrient concentrations presented a strong positive correlation with bio-struvite production yields and crystal size distribution. B. antiquum distinguished itself by relatively stable PO4-P removal (68–97%) independent of the initial nutrient concentration, with effluents containing as low as 1 mg PO4-P/L. The recovered bio-struvite presented high purity with low heavy metal contents, meeting regulations for inorganic fertiliser. The microbial processes for phosphorus (P) recovery as bio-struvite presented several key advantages: bio-struvite crystals were released to the wastewater and recoverable by filtration at PO4-P ≥ 19.7 mg/L, no need to adjust pH, bio-struvite crystals had purity equivalent to 11.8–12.3% P and low heavy metal content, which was similar or better than that of chemical struvite (12.6% P). This study validates bio-struvite’s relevance for low nutrient concentrations.

Treatment of Liquid Fraction of Digestate by Integrated Process Struvite Precipitation—Forward Osmosis

The research undertaken in this paper was aimed at determining the effect of struvite precipitation, one of the potential products that can be obtained during digestate management, on the performance of the non-pressurized membrane process—forward osmosis (FO). The effect of using an integrated struvite precipitation—forward osmosis process to treat the digestate liquid on the changes in the properties of organic substances present in the treated solution (particle size distribution, ζ-potential) was analysed as well. The study was conducted for the liquid fraction of municipal waste biogas plant digestate. The obtained results demonstrate the suitability of this process for recovering water from liquid digestate. It was found that forward osmosis conducted for a digestate pre-treated by chemical struvite precipitation leads to higher water flux values and increased salt concentration in the receiving solution (from 0.5 to 3 mol/dm3 NaCl). There is practically no concomitant infiltration of organic substances into the receiving solution. Therefore, the use of 3 mol/dm3 NaCl as a draw solution results in the recovery of the highest volume of water per unit of time. An analysis of the particle size distribution shows that the removal of the macromolecular fraction of organic compounds from the digestate mainly takes place simultaneously with the chemical precipitation of struvite. It was found that an increase in the concentration of the draw solution, which allows for greater water recovery, resulted in the aggregation of the concentrated organic molecules.