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M C M Van Loosdrecht - One of the best experts on this subject based on the ideXlab platform.
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Struvite formation for enhanced dewaterability of digested wastewater sludge
Environmental Technology, 2014Co-Authors: B J C Bergmans, M C M Van Loosdrecht, A M Veltman, J B Van Lier, L C RietveldAbstract:One of the main advantages of controlled Struvite formation in digested sludge is an improvement in dewaterability of the digested sludge, which eventually leads to lower volumes of dewatered sludge that need to be transported. The effects of the control parameters for Struvite formation, magnesium concentration and pH, on digested sludge dewaterability were investigated and are discussed in relation to the efficiency of Struvite formation. Laboratory experiments with digested activated sludge were performed in a 20 L batch reactor. CO2 was stripped from the digested sludge using a bubble aerator and magnesium chloride was added to induce Struvite formation. The dewaterability of the sludge was determined by gravity filtration tests. In the experiments, either the pH or the molar magnesium to phosphate ratio (Mg:PO4) was varied. The results confirm improved sludge dewaterability after Struvite formation. Magnesium to phosphate ratios above 1.0 mol/mol did not further improve dewaterability. The addition o...
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the contribution of exopolysaccharides induced Struvites accumulation to ammonium adsorption in aerobic granular sludge
Water Research, 2012Co-Authors: Yuemei Lin, Joao Paulo Bassin, M C M Van LoosdrechtAbstract:Aerobic granular sludge from a lab-scale reactor with simultaneous nitrification/denitrification and enhanced biological phosphorus removal processes exhibited significant amount of ammonium adsorption (1.5 mg NH4+-N/g TSS at an ammonium concentration of 30 mg N/L). Potassium release accompanied ammonium adsorption, indicating an ion exchange process. The existence of potassium magnesium phosphate (K-Struvite) as one of potassium sources in the granular sludge was studied by X-ray diffraction analysis (XRD). Artificially prepared K-Struvite was indeed shown to adsorb ammonium. Alginate-like exopolysaccharides were isolated and their inducement for Struvite formation was investigated as well. Potassium magnesium phosphate proved to be a major factor for ammonium adsorption on the granular sludge. Struvites (potassium/ammonium magnesium phosphate) accumulate in aerobic granular sludge due to inducing of precipitation by alginate-like exopolysaccharides.
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phosphate and potassium recovery from source separated urine through Struvite precipitation
Water Research, 2007Co-Authors: J A Wilsenach, Cornelis Anthonius Hubertus Schuurbiers, M C M Van LoosdrechtAbstract:Phosphate can be recovered as Struvite or apatite in fluidised bed reactors. Urine has a much higher phosphate concentration than sludge reject water, allowing simpler (and less expensive) process for precipitation of phosphates. A stirred tank reactor with a special compartment for liquid solid separation was used to precipitate Struvite from urine. Magnesium ammonium phosphate as well as potassium magnesium phosphate are two forms of Struvite that were successfully precipitated. Liquid/solid separation was very effective, but the compaction of Struvite was rather poor in the case of potassium Struvite. Crystals did not form clusters and maintained the typical orthorhombic structure. Ammonium Struvite had slightly lower effluent phosphate concentrations, but an average of 95% of influent phosphate was removed regardless of ammonium or potassium Struvite precipitation. Fluid mechanics is believed to be important and should inform further work.
Naoko Ellis - One of the best experts on this subject based on the ideXlab platform.
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fluidisation behaviour of Struvite recovered from wastewater
Journal of Environmental Engineering and Science, 2014Co-Authors: Md Saifur Rahaman, Donald S Mavinic, Naoko EllisAbstract:A comprehensive characterisation of Struvite particles produced from the Edmonton, AB, Canada, wastewater treatment plant was performed. The characterisation of Struvite particles included the dete...
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modeling phosphorus removal and recovery from anaerobic digester supernatant through Struvite crystallization in a fluidized bed reactor
Water Research, 2014Co-Authors: Md Saifur Rahaman, Donald S Mavinic, Alexandra Meikleham, Naoko EllisAbstract:Abstract The cost associated with the disposal of phosphate-rich sludge, the stringent regulations to limit phosphate discharge into aquatic environments, and resource shortages resulting from limited phosphorus rock reserves, have diverted attention to phosphorus recovery in the form of Struvite (MAP: MgNH 4 PO 4 ·6H 2 O) crystals, which can essentially be used as a slow release fertilizer. Fluidized-bed crystallization is one of the most efficient unit processes used in Struvite crystallization from wastewater. In this study, a comprehensive mathematical model, incorporating solution thermodynamics, Struvite precipitation kinetics and reactor hydrodynamics, was developed to illustrate phosphorus depletion through Struvite crystal growth in a continuous, fluidized-bed crystallizer. A thermodynamic equilibrium model for Struvite precipitation was linked to the fluidized-bed reactor model. While the equilibrium model provided information on supersaturation generation, the reactor model captured the dynamic behavior of the crystal growth processes, as well as the effect of the reactor hydrodynamics on the overall process performance. The model was then used for performance evaluation of the reactor, in terms of removal efficiencies of Struvite constituent species (Mg, NH 4 and PO 4 ), and the average product crystal sizes. The model also determined the variation of species concentration of Struvite within the crystal bed height. The species concentrations at two extreme ends (inlet and outlet) were used to evaluate the reactor performance. The model predictions provided a reasonably good fit with the experimental results for PO 4 –P, NH 4 –N and Mg removals. Predicated average crystal sizes also matched fairly well with the experimental observations. Therefore, this model can be used as a tool for performance evaluation and process optimization of Struvite crystallization in a fluidized-bed reactor.
Donald S Mavinic - One of the best experts on this subject based on the ideXlab platform.
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fluidisation behaviour of Struvite recovered from wastewater
Journal of Environmental Engineering and Science, 2014Co-Authors: Md Saifur Rahaman, Donald S Mavinic, Naoko EllisAbstract:A comprehensive characterisation of Struvite particles produced from the Edmonton, AB, Canada, wastewater treatment plant was performed. The characterisation of Struvite particles included the dete...
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modeling phosphorus removal and recovery from anaerobic digester supernatant through Struvite crystallization in a fluidized bed reactor
Water Research, 2014Co-Authors: Md Saifur Rahaman, Donald S Mavinic, Alexandra Meikleham, Naoko EllisAbstract:Abstract The cost associated with the disposal of phosphate-rich sludge, the stringent regulations to limit phosphate discharge into aquatic environments, and resource shortages resulting from limited phosphorus rock reserves, have diverted attention to phosphorus recovery in the form of Struvite (MAP: MgNH 4 PO 4 ·6H 2 O) crystals, which can essentially be used as a slow release fertilizer. Fluidized-bed crystallization is one of the most efficient unit processes used in Struvite crystallization from wastewater. In this study, a comprehensive mathematical model, incorporating solution thermodynamics, Struvite precipitation kinetics and reactor hydrodynamics, was developed to illustrate phosphorus depletion through Struvite crystal growth in a continuous, fluidized-bed crystallizer. A thermodynamic equilibrium model for Struvite precipitation was linked to the fluidized-bed reactor model. While the equilibrium model provided information on supersaturation generation, the reactor model captured the dynamic behavior of the crystal growth processes, as well as the effect of the reactor hydrodynamics on the overall process performance. The model was then used for performance evaluation of the reactor, in terms of removal efficiencies of Struvite constituent species (Mg, NH 4 and PO 4 ), and the average product crystal sizes. The model also determined the variation of species concentration of Struvite within the crystal bed height. The species concentrations at two extreme ends (inlet and outlet) were used to evaluate the reactor performance. The model predictions provided a reasonably good fit with the experimental results for PO 4 –P, NH 4 –N and Mg removals. Predicated average crystal sizes also matched fairly well with the experimental observations. Therefore, this model can be used as a tool for performance evaluation and process optimization of Struvite crystallization in a fluidized-bed reactor.
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nucleation and growth kinetics of Struvite in a fluidized bed reactor
Journal of Crystal Growth, 2008Co-Authors: Iqbal M H Bhuiyan, Donald S Mavinic, Roger BeckieAbstract:Kinetics of Struvite crystallization were studied to gain a better understanding of intentional Struvite formation in fluidized bed reactors. Mechanisms controlling nucleation were studied in the laboratory by induction time experiments. pH monitoring proved to be an effective method of induction time determination, during the induction period. The induction period, when nucleation was the controlling process for Struvite crystal formation, was found to be primarily reaction controlled, with minor transport influence. The metastable region for Struvite was explored in this study. The solubility and supersolubility curves, which are the boundaries of the metastable region, were observed to be almost parallel straight lines in the concentration range studied. The growth rate of Struvite determined in a fluidized bed reactor was mainly transport controlled. With the determination of the mass-transfer coefficient and surface-reaction coefficient for a specified condition, a two-step linear growth rate model for Struvite growth determination in a fluidized bed reactor has been proposed.
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thermal decomposition of Struvite and its phase transition
Chemosphere, 2008Co-Authors: Iqbal M H Bhuiyan, Donald S Mavinic, F A KochAbstract:Intentional crystallization of Struvite, before it forms and accumulates on wastewater treatment equipment, solves an important and costly wastewater treatment problem and on the other hand, provides an environmentally sound and renewable nutrient source to the agricultural industry. Struvite was synthesized in the laboratory; it was also produced as pellets in a pilot-scale, fluidized bed reactor, using real centrate resulting from an anaerobic digester. The thermal decomposition of both synthetic Struvite and Struvite pellets was studied. The decomposition of Struvite was found to be dependent on the rate of heating. Through gradual loss of ammonia and water molecules, ultimately Struvite was found to be transformed into amorphous magnesium hydrogen phosphate. When Struvite was heated in excess water, it was partially transformed into bobierrite, through the gradual loss of ammonia. It was transformed into monohydrate, dittmarite by losing its five water molecules of crystallization, when boiled in excess water.
Tingting Zhang - One of the best experts on this subject based on the ideXlab platform.
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a thermodynamic modeling approach for solubility product from Struvite k
Computational Materials Science, 2019Co-Authors: Yuanquan Yang, Baomin Wang, Tingting ZhangAbstract:Abstract Crystallization of Struvite-k could be an economical and sustainable alternative for potassium and phosphorus recovery from wastewater and ashes of biomass combustion. Knowledge with regards to thermodynamics that are involved in the formation of Struvite-k in reactor is key in determining the optimal conditions for an efficient process. However, less research work has been done on Struvite-k solubility product. A thermodynamic model for Struvite-k precipitation was in this study thus proposed to determine the Struvite-k solubility product, as well as conversion rate for Struvite-k and its accompanying crystal cattiite over a pH value range of 10.5–12.5. The model was based on numerical equilibrium prediction of involved system Mg-K-PO4-H2O. The model was presented by a set of nonlinear equations that were solved by an optimization strategy with a three-step method. The method consists of a preliminary search by Lagarias Simplex search method for initialization, Successive Quadratic Programming (SQP) for resolution of system, and extrapolating calculated data to zero ionic strength for determination of Struvite-k solubility product. A pKStruvite-k value of 10.872 for Struvite-k at 25 °C was obtained in the model. This novel model will provide a theoretical reference for recovery of potassium and phosphate, as well as its possible application in magnesium potassium phosphate cement (MKPC).
M M Rahman - One of the best experts on this subject based on the ideXlab platform.
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production of slow release crystal fertilizer from wastewaters through Struvite crystallization a review
Arabian Journal of Chemistry, 2014Co-Authors: M M Rahman, Mohamad Amran Mohd Salleh, Umer Rashid, Amimul Ahsan, M M Hossain, Chang Six RaAbstract:Abstract Nitrogen and phosphorus in wastewaters are a burning environmental issue of the present world. This review covers the studies conducted on the removal and recovery of phosphorus and nitrogen from wastewaters through Struvite crystallization. Wastewater which contains a high amount of phosphorus and nitrogen would be a good source of Struvite. Struvite is a phosphate fertilizer, although it contains a significant amount of nitrogen and magnesium, and it is an effective alternative source of rock phosphate to maintain the agricultural production system. The present review deals with the principles and concept of Struvite nucleation, crystal growth and the factors that affect on the Struvite quality. Struvite precipitation occurs in an equimolecular concentration of Mg2+, NH 4 + and PO 4 3 − at slightly alkaline conditions. Addition of a source of Mg is essential to maintain the favorable condition of PO4 and Mg. Different factors such as Mg:PO4 molar ratio, pH, aeration rate, reactor types, as well as P and N removal efficiencies were also discussed throughout this review. The slower nutrient leaching loss and its fertilizer quality make Struvite an eco-friendly fertilizer. It is possible to overcome the acute shortage of rock phosphate if all the municipal and livestock wastewaters are connected with the wastewater treatment plants.
