The present review provides an understanding of principles of struvite crystallization and examines the techniques and processes experimented to date by researchers at laboratory, pilot, and full-scale to maximize phosphorus removal and reuse as struvite from wastewater effluents. Struvite is mainly known as a scale deposit causing concerns to wastewater companies. Indeed, struvite naturally occurs under the specific condition of pH and mixing energy in specific areas of wastewater treatment plants (e.g., pipes, heat exchangers) when concentrations of magnesium, phosphate, and ammonium approach an equimolar ratio 1:1:1. However, thanks to struvite composition and its fertilizing properties, the control of its precipitation could contribute to the reduction of phosphorus levels in effluents while simultaneously generate a valuable by-product. A number of processes such as stirred tank reactors and air-agitated and -fluidized bed reactors have been investigated as possible configurations for struvite recove...

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Phosphorus Recovery from Wastewater by Struvite Crystallization: A Review

Phosphorus (P) is an essential element for all life on earth. However, natural P resources (phosphate rock) are depleting. The authors describe the current situation and a forecast for future phosphate production and reserves. The current depletion of phosphate reserves and the increasingly stringent discharge regulations have led to the development of various P-recovery techniques from wastewater. Existing full-scale P-recovery techniques from the liquid phase, sludge phase, and sludge ash are reviewed. Although the full-scale P-recovery techniques have been shown to be technologically feasible, the economical feasibility, legislation and national policies are the major reasons why these techniques are not yet operational worldwide.

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Global Phosphorus Scarcity and Full-Scale P-Recovery Techniques: A Review

Phosphorus (P) is a critical, geographically concentrated, nonrenewable resource necessary to support global food production. In excess (e.g., due to runoff or wastewater discharges), P is also a primary cause of eutrophication. To reconcile the simultaneous shortage and overabundance of P, lost P flows must be recovered and reused, alongside improvements in P-use efficiency. While this motivation is increasingly being recognized, little P recovery is practiced today, as recovered P generally cannot compete with the relatively low cost of mined P. Therefore, P is often captured to prevent its release into the environment without beneficial recovery and reuse. However, additional incentives for P recovery emerge when accounting for the total value of P recovery. This article provides a comprehensive overview of the range of benefits of recovering P from waste streams, i.e., the total value of recovering P. This approach accounts for P products, as well as other assets that are associated with P and can be recovered in parallel, such as energy, nitrogen, metals and minerals, and water. Additionally, P recovery provides valuable services to society and the environment by protecting and improving environmental quality, enhancing efficiency of waste treatment facilities, and improving food security and social equity. The needs to make P recovery a reality are also discussed, including business models, bottlenecks, and policy and education strategies.

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Total Value of Phosphorus Recovery

Production of slow release crystal fertilizer from wastewaters through struvite crystallization – A review

Maximum use of resources present in domestic "used water".

An economic evaluation of phosphorus recovery as struvite from digester supernatant

An approach of estimating struvite growth kinetic incorporating thermodynamic and solution chemistry, kinetic and process description

Phosphorus (P) scarcity and eutrophication have triggered the development of new approaches for phosphorus recovery. This study investigated the impact of calcium-doped biochar, produced from biosolids via microwave pyrolysis at 700 °C for 20 min, on phosphorus recovery. The phosphorus removal isotherms, removal kinetics and the impact of initial pH of phosphorus solution on phosphorus recovery were studied. The phosphorus recovery was proportional to the calcium content in biochar, leading predominantly to the production of brushite. Precipitation was the main mechanism of phosphorus removal by calcium-doped biochar. Phosphorus removal capacity of biochar reached equilibrium after 8 h of contact time and was described by a pseudo-second-order kinetic model. The Langmuir isotherm model fitted the experimental data well with a maximum adsorption capacity of 147 mg-P/g for biochar BC20 (20 wt% Ca(OH)2). The results of phosphorus removal from a real wastewater demonstrated that using Ca-doped biochar for phosphorus removal from contaminated streams is a promising alternative for phosphorus recovery as well as for biosolids management. Heavy metal leaching from Ca-doped biochar was much lower than from undoped biochar, and decreased as the amount of calcium in biochar increased.

Isotherms, kinetics and mechanism analysis of phosphorus recovery from aqueous solution by calcium-rich biochar produced from biosolids via microwave pyrolysis

Philip A. Schneider

Papers

An economic evaluation of phosphorus recovery as struvite from digester supernatant

An approach of estimating struvite growth kinetic incorporating thermodynamic and solution chemistry, kinetic and process description

Isotherms, kinetics and mechanism analysis of phosphorus recovery from aqueous solution by calcium-rich biochar produced from biosolids via microwave pyrolysis

A fed-batch design approach of struvite system in controlled supersaturation

Biochar produced from biosolids using a single-mode microwave: Characterisation and its potential for phosphorus removal.