Search Results (34)

A modern approach to the organization of wastewater disposal systems ensures the sustainable development of resort areas. Warm mineral springs (WMSs) located in suburban areas are not only recreational facilities for the population, but also sources of used mineral and communal wastewater. Preventing or reducing the discharge of pollutants in this type of liquid waste can reduce the anthropogenic impact on the environment. The article proposes a method for the chemical precipitation of ammonium ions in a mixture of mineral and domestic wastewater, and the production of struvite, a complex agricultural fertilizer. Three series of experiments were conducted: (1) on a model solution of ammonium ions; (2) on a mixture of a model solution and real mineral water; and (3) on real wastewater and spent mineral water taken from a thermal resort. As a result of an experiment with water samples at an initial concentration of no more than 85 mg/L, optimal doses of reagents were identified: 5.67 g/L of sodium hydrophosphate and 3.21 g/L of magnesium chloride to achieve a residual concentration of ammonium ions in purified water of no more than 1.5 mg/L at pH = 9–10. In the case of mixing of domestic wastewater and used mineral water, it was possible to reduce the use of magnesium chloride by 80%. At the same time it was possible to obtain the amount of sediment containing struvite, which is a valuable agricultural fertilizer. With the introduction of this technology, it is possible to reduce the expenses of reagents and reduce the damage caused by the discharge of liquid waste from a thermal resort, while the profit earned through the sale of fertilizer can partially offset the cost of wastewater disposal. Full article

Phosphorus is an essential and finite resource critical for global food production, yet its inefficient use and discharge from wastewater systems contribute to eutrophication and resource depletion. The transition from conventional wastewater treatment plants to water resource recovery facilities has intensified interest in technologies that enable phosphorus recovery within a circular economy framework. This review provides a critical and up-to-date synthesis of phosphorus recovery strategies from wastewater, with primary emphasis on struvite (MgNH₄PO₄·6H₂O) crystallization as one of the most mature and practically implemented recovery routes. The occurrence and chemical forms of phosphorus in wastewater streams are discussed alongside conventional approaches, such as enhanced biological phosphorus removal and chemical precipitation, in order to position struvite recovery within the broader phosphorus management landscape. In addition to struvite crystallization, selected competing and complementary recovery pathways, including electrochemical systems, biochar-assisted processes, and sludge ash recovery, are discussed to compare technological maturity, recovery potential, and practical applicability. Particular attention is given to reactor configurations, full-scale applications, and commercial technologies to assess operational reliability, recovery performance, and fertilizer product quality. Life-cycle assessment results and regulatory developments are also discussed to contextualize sustainability claims, technology selection, and market integration. The review identifies key technical and economic challenges, particularly regarding magnesium supply, competing ions, wastewater matrix effects, and the feasibility of mainstream application. Overall, controlled sidestream struvite crystallization appears to offer the most favorable balance between recovery efficiency, operational reliability, and fertilizer product quality under suitable plant conditions. Full article

Infection urinary stones account for approximately 10–15% of all urinary stones worldwide, with a rising incidence observed in recent decades, particularly in countries with a high Socio-Demographic Index (SDI). This trend has been partially attributed to dietary changes, including increased consumption of processed foods. Heavy metals belong to a group of substances, the source of which can be both food and the human environment. Among many heavy metals, in this study, we focus on copper and investigate its influence on the nucleation and growth of struvite crystals, the primary component of infection urinary stones. Experiments were conducted in artificial urine, both in the presence and absence of Proteus mirabilis, a urease-producing bacterium commonly associated with infection urinary stones. In a bacteria-free system, bacterial urease activity was mimicked by the addition of aqueous ammonia solution. Our results demonstrate that the presence of copper in artificial urine induces a slight shift in the struvite crystallization toward lower pH values, indicating that crystal formation initiates earlier compared to a control test. Additionally, the amount of precipitated struvite increases modestly in the presence of copper. Struvite crystals formed in copper-containing artificial urine are larger and exhibit altered habit and morphology. Energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses confirm that copper does not incorporate into either the bulk or surface structure of the struvite crystals. X-ray diffraction (XRD) data show that struvite remains the sole crystalline phase, consistent with the control samples. Microbiological assays reveal that copper, at the concentrations tested, does not affect the viability of P. mirabilis, indicating an absence of bacteriostatic or bactericidal effects. To elucidate the physicochemical mechanisms underlying copper’s influence on nucleation and growth of struvite, speciation analysis of chemical complexes was performed. This revealed the formation of various copper complexes in artificial urine, including Cu(OH)⁺, CuCit⁻, CuC₂O₄, Cu(OH)₂, CuHPO₄, Cu(NH₃)²⁺, Cu(NH₃)₂²⁺, and Cu(NH₃)₃²⁺. These chemical complexes modulate the equilibrium and formation of complexes with Mg²⁺ and PO₄³⁻ (e.g., MgHCit, MgCit⁻, MgOH⁺, MgC₂O₄, MgSO₄, MgHPO₄), contributing to the observed shift in struvite crystallization to lower pH values. Full article

Currently, researchers are exploring alternative phosphorus sources for agricultural production that are more sustainable than rock phosphate. In this context, the recovery of phosphorus from organic wastes as struvite can constitute an important tool for promoting circular economy practices and reducing the risk of phosphorus contamination through eutrophication. Struvite recovery has been widely developed using different organic wastes with high concentrations of N and P, such as industrial, municipal and animal wastes, mainly in the form of effluents. However, little information is available concerning phosphorus recovery in the form of struvite from sewage sludge samples, these processes being mainly based on chemical procedures. Therefore, the main aim of this work was to study phosphorus recovery from three sewage sludge samples from different wastewater treatment plants (SS1, SS2 and SS3), in comparison with the solid fraction of pig manure (M), through an optimized bioacidification process, as well as to evaluate the potential for struvite precipitation from the recovered P-rich supernatants. Protein recovery through alkaline treatment of the remaining precipitates was also studied. The results obtained showed the feasibility of the optimized bioacidification process for P recovery, especially in the samples M and SS3, which showed the highest P recovery yields (65.7% and 69%, respectively) and the best results regarding struvite formation. In addition, the protein recovery efficiency of the remaining solid residues ranged from 59.3% to 67.4%, without showing a clear influence of the type of organic waste used. Full article

Research into alternative phosphorus (P) fertilizer sources that may be able to supplement P resources is necessary. Struvite (MgNH₄PO₄ · 6H₂O) can be made by removing excess nutrients from waste sources and may reduce greenhouse gas (GHG) emissions from cropping systems. This study sought to quantify GHG [i.e., methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂)] fluxes, season-long emissions, and net GHG emissions from chemically precipitated struvite (CPST) and synthetic and real-wastewater-derived electrochemically precipitated struvite (ECST) compared to monoammonium phosphate (MAP) and an unamended control (UC) from flood-irrigated rice (Oryza sativa) grown in P-deficient, silt loam soil in a greenhouse. Gas samples were collected weekly over a 140-day period in 2022. Methane and CO₂ emissions differed (p < 0.05) among P fertilizer sources, while N₂O emissions were similar among all treatments. Methane, CO₂, and N₂O emissions from MAP-fertilized rice were the greatest (98.7, 20,960, and 0.44 kg ha⁻¹ season⁻¹, respectively), but they were similar to those of CH₄ and CO₂ for CPST and those of N₂O for all other P fertilizer sources. Season-long CH₄, CO₂, and N₂O emissions and net GHG emissions did not differ between ECST materials. This study’s results emphasized the potential that wastewater-recovered struvite has to reduce GHG emissions in rice production systems. Full article

In the context of struvite precipitation, the most significant gap pertains to the transfer of knowledge from scientific research to practical applications. The primary objective of this study is twofold: firstly, to identify the most critical process parameters influencing struvite precipitation and, secondly, to translate these parameters into a pragmatic tool for real-world applications. This study investigates the precipitation of struvite from digestion centrate to obtain information on the appropriate precipitation conditions for different initial chemical compositions. We carried out 24 lab-scale experiments to investigate the effect of varying pH value (7.0–8.5), temperature (5 °C and 33 °C) and initial phosphate concentrations (353; 165; 68 mg/L) on struvite precipitation. Varying the pH had the strongest influence on precipitation efficiencies. Adjusting pH from 7 to 8.5 increased PO₄-P removal from 1.4% to 98.8%, whereas temperature had little impact on PO₄-P removal. Furthermore, we found that a saturation index of at least 1.7 is imperative to precipitate at least 90% of the available PO₄-P. Based on the results, we developed a nomogram showing the resulting saturation index and the associated PO₄-P removal efficiency for variable initial PO₄-P and pH levels. The tool developed in this study enables users to directly identify the so-called ‘sweet spot’, which is the optimal balance between process effectiveness and resource efficiency, for each centrate. Full article

Nutrient recovery from anaerobic digestate has gained increasing importance in recent years due to its potential to reduce resource dependency and to close nutrient cycles. The aim of this work is to evaluate the influence of a previous solid–liquid separation phase on nutrient recovery efficiency using two innovative membrane technologies, namely, gas-permeable membranes (GPM) and electrodialytic (ED) processes, applied individually or in combination. The obtained results were compared with those obtained through the centrifugation of the raw digestate and direct chemical precipitation followed by centrifugation in terms of the efficiency in the recovery of N (nitrogen) and P (phosphorous). A total of nine scenarios of digestate processing were compared. GPM technology allowed for the recovery of 65% of the N content in the raw digestate (41.5 g total solids (TS) kg⁻¹) and 67% of N in the liquid fraction (28.0 g TS kg⁻¹), without any significant difference between the two scenarios. However, the results revealed significant differences in the P recovery with ED from the raw digestate (15%) and the liquid fraction (34%), suggesting that phosphorous extraction can be improved by the application of a prior solid–liquid phase. The recovery of N with the GPM technology also enhanced the further recovery of total P with the ED processes. Furthermore, the combination of these technologies allowed for the recovery of N- and P-rich solutions, which were used to precipitate secondary struvite with an efficiency of up to 85%. This research provides a practical framework for sustainable nutrient management, advancing solutions for resource efficiency and environmental stewardship. Full article

Anaerobically treated palm oil mill effluent (AnT-POME), containing a high concentration of ammoniacal-nitrogen (NH₄⁺-N) and soluble chemical oxygen demand (sCOD) was subjected to sequential processes of struvite precipitation to recover NH₄⁺-N and Fenton oxidation for sCOD removal. The optimization of treatment was conducted through response surface methodology (RSM). Under optimized struvite precipitation conditions (Mg²⁺/NH₄⁺, PO₄³⁻/NH₄⁺ molar ratios: 1; pH 8.2 ± 0.1), NH₄⁺-N concentration decreased to 41 ± 7.1 mg L⁻¹ from an initial 298 ± 41 mg L⁻¹ (78.8 ± 1.6 % removal). Field emission scanning electron microscopy (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDX) confirmed NH₄⁺-N was recovered as struvite. Subsequent Fenton oxidation under the optimized conditions (H₂O₂ dosage: 2680 mg L⁻¹; molar ratio of Fe²⁺/H₂O₂: 0.8; reaction time: 56 min) reduced sCOD concentration to 308 ± 46 mg L⁻¹ from an initial 1350 ± 336 mg L⁻¹ (76.0 ± 1.0 % removal). The transparent appearance of treated AnT-POME validated the removal of sCOD responsible for the initial brownish appearance. Models derived from RSM demonstrated significance, with high coefficients of determination (R² = 0.99). Overall, integrated struvite precipitation and Fenton oxidation effectively removed NH₄⁺-N and sCOD from AnT-POME, contributing to nutrient recovery and environmental sustainability. Full article

Struvite is a substance that can be extracted from wastewater and has the potential to replace conventionally manufactured fertilizers and reduce environmental issues. A slow-release fertilizer can more effectively be used by matching the nutrient requirements of plants through the growing period and gradually supplying N and P for crop growth. Struvite is an ecologically friendly fertilizer because of its gradual fertilizer treatment and high quality. Existing research indicates that the solubility and absorption of struvite by plants are equivalent to those of artificial phosphorus fertilizers such as triple superphosphate or potassium phosphate. Struvite is recognized to be an effective fertilizer for grass, tree seedlings, ornamental plants, vegetables, and flower beds. Struvite precipitation removes phosphorus and nitrogen from sewage water, hence alleviating phosphorus shortages from non-renewable phosphorus sources and water eutrophication. Struvite would also be useful in the grasslands and woods where fertilizers are used. However, the agricultural utility of struvite has not been thoroughly investigated. As a result, this work is reported as a pot experiment designed to assess the fertilizer value of struvite. Experimental settings were created, and pot experiments were conducted to establish the optimal amount of struvite based on two factors. The initial pH for struvite synthesis was 9. The formulated struvite fertilizers were compared to standard phosphorus fertilizers in the pot trials. Fourier-transform spectroscopy and Scanning Electron Microscopy (SEM) with Energy-Dispersive X Ray Spectroscopy (EDAX) were employed to support the quantitative findings. To summarize, struvite precipitation is a desirable and effective method for removing phosphate and nitrogen from domestic sewage water and using them as fertilizers. Full article

In recent years, promising developments in the hydrothermal carbonization (HTC) of sewage sludge, as well as the potential to reclaim phosphorus and nitrogen, have emerged. In this study, the HTC of digested sewage sludge (DSS) was investigated for the downstream production of heavy metal (HM)-free fertilizer and the use of freeze concentration (FC) as a novel technology for process water treatment. To obtain clean fertilizer, phosphatic acid extracts were first treated with ion-exchange resins to remove dissolved HM, as well as phosphorus precipitating agents (i.e., aluminum and iron). Over 98% of the aluminum (Al) and 97% of the iron (Fe) could be removed in a single treatment step. The purified extract was then used for the precipitation of HM-free struvite crystals, with P-recovery rates exceeding 89%. Process water (PW) makes up the largest share of the two main HTC-products (i.e., hydrochar and PW) and is very rich in organic compounds. Compared to evaporation or membrane separation, FC is a promising technology for concentrating solutes from PW. Separation experiments resulted in the recovery of over 90% of the dissolved compounds in the concentrate. In our study, the concentrate was later utilized as an ammonium source for struvite precipitation, and the subsequent aerobic digestion of the remaining ice water resulted in an 85% reduction in chemical oxygen demand (COD) in 15 days. Full article

Environmental legislation on waste management coupled with the potential for nutrient recovery are key factors encouraging the use of advanced treatment technologies to manage biosolids waste. In this context, phosphorus recovery from sewage sludge treated by a wet oxidation (WO) process was carried out in this work. High organic matter (up to 85% in COD) and total solids content (up to 75%) removal values were achieved by the WO process at elevated temperature (up to 300 °C) and pressure (up to 200 bar) conditions. The liquid and solid fractions found in the oxidation process effluent contain high amounts of phosphorus that can be recovered. This research aims to maximize its recovery in both liquid and solid fractions. In the liquid effluent, phosphorus was recovered (up to 90 mg P/L) by chemical precipitation as struvite (MgNH₄PO₄∙6 H₂O), a slow-release fertilizer. In this case, P recoveries greater than 95% were achieved. Additionally, the solid fraction, analyzed after filtration and drying (68 mg P/g_solid), was treated by acid leaching, obtaining up to 60% phosphorus recovery. All phosphorus extracted was in orthophosphate form. Full article

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. Full article

Phosphorus (P) recovery from wastewaters as struvite (MgNH₄PO₄·6H₂O) may be a viable alternative fertilizer-P source for agriculture. The objective of this study was to evaluate the economic and environmental implications of struvite as a fertilizer-P source for flood-irrigated rice (Oryza sativa) relative to other commonly used commercially available fertilizer-P sources. A field study was conducted in 2019 and 2020 to evaluate the effects of wastewater-recovered struvite (chemically precipitated struvite (CPST) and electrochemically precipitated struvite (ECST)) on rice yield response in a P-deficient, silt–loam soil in eastern Arkansas relative to triple superphosphate, monoammonium and diammonium phosphate, and rock phosphate. A life cycle assessment methodology was used to estimate the global warming potentials associated with rice produced with the various fertilizer-P sources. Life cycle inventory data were based on the field trials conducted with and without struvite application for both years. A partial budget analysis showed that, across both years, net revenues for ECST and CPST were 1.4 to 26.8% lower than those associated with the other fertilizer-P sources. The estimated greenhouse gas emissions varied between 0.58 and 0.70 kg CO₂ eq kg rice⁻¹ from CPST and between 0.56 and 0.81 kg CO₂ eq kg rice⁻¹ from ECST in 2019 and 2020, respectively, which were numerically similar to those for the other fertilizer-P sources in 2019 and 2020. The similar rice responses compared to commercially available fertilizer-P sources suggest that wastewater-recovered struvite materials might be an alternative fertilizer-P-source option for flood-irrigated rice production if struvite can become price-competitive to other fertilizer-P sources. Full article

While phosphorus is a limited resource that is essential for agriculture, its release to the environment adversely impacts water quality. At the same time, animal wastewaters contain significant quantities of phosphorus and nitrogen that can be recovered for beneficial use. Phosphorus uptake experiments were performed with magnesium-treated corn-cob char and with magnesium silicate prepared using silicate from rice straw at pH 8 and 9. The concentration of dissolved phosphorus as a function of total added ammonium chloride (NH₄Cl) was determined, and chemical equilibrium modeling was used to investigate the concentration trends of dissolved and mineral species. According to chemical equilibrium modeling, carbonate alkalinity exerted a significant magnesium demand, with approximately half of all added magnesium forming magnesite (MgCO₃(s)). As total added NH₄Cl increased, excess Cl⁻ complexed with dissolved Mg²⁺ in competition with orthophosphate, freeing orthophosphate to precipitate, mainly as the mineral struvite (NH₄MgPO₄·6H₂O(s)). As the concentration of added NH₄Cl increased by a factor of ten, measured concentrations of dissolved phosphorus decreased by a factor of ten, meaning that ionic composition has the potential to significantly impact the amount of phosphorus that can be recovered from wastewaters for beneficial use. Full article

As the population continues to rise, the demand for resources and environmentally friendly management of produced wastes has shown a significant increase in concern. To decrease the impact of these wastes on the environment, it is important to utilize the wastes in producing and/or recovering usable products to provide for the sustainable management of resources. One non-renewable and rapidly diminishing resource is phosphorus, which is used in several products, the most important being its use in manufacturing chemical fertilizer. With the increase in demand but reduction in availability of naturally occurring mineral phosphorus, it is important to investigate other sources of phosphorus. Phosphorus is most commonly recovered through struvite (magnesium ammonium phosphate) precipitation. The recovery of phosphorus from various wastewater has been well established and documented with recovery rates mostly above 90%. However, one of the major drawbacks of the recovery is the high cost of chemicals needed to precipitate the phosphorus. Since the external magnesium needed to achieve struvite precipitation accounts for around 75% of the total chemical cost, applicability of low-cost magnesium sources, such as bittern or seawater, can help reduce the operational cost significantly. This paper investigates the different magnesium sources that have been used for the recovery of phosphorus, highlighting the different approaches and operating conditions investigated, and their corresponding phosphorus recovery rates. An investigation of the economic aspects of the magnesium sources used for removal/recovery show that costs are dependent on the raw waste treated, the source of magnesium and the location of treatment. A review of published articles on the economics of phosphorus removal/recovery also indicates that there is a lack of studies on the economics of the treatment processes, and there is a need for a comprehensive study on life cycle assessment of such processes that go beyond the technical and economical aspects of treatment processes. Full article