Effects of Solution Composition and Polymer Additive on the Crystallization of Struvite

Liu, Yi; Qu, Haiyan

doi:10.1002/ceat.201600719

Cited by 6 publications

(5 citation statements)

References 23 publications

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“…Biological and/or chemical treatment procedures are necessary to meet the discharge limit set by political regulations (de- Bashan and Bashan, 2004). Phosphate recovery/recycling by controlled precipitation of struvite and calcium phosphate precipitation, which remove phosphate from the liquid phase after sludge dewatering, do not exploit the full potential for phosphate recovery (Liu and Qu, 2017;Song et al, 2006;Vasenko and Qu, 2017). Thus, the sludge contains valuable phosphate, but the direct application of sludge to fields is problematic as toxins such as heavy metals, microplastic, and pathogens may be present in critical quantities.…”

Section: Introductionmentioning

confidence: 99%

Layered double hydroxides for phosphorus recovery from acidified and non-acidified dewatered sludge

et al. 2019

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Phosphate, which contains the essential element phosphorous (P), is a necessary fertilizer for agriculture, but the current phosphate deposits are running out and alternative sources are needed. Sludge obtained from wastewater treatment plants contains high concentrations of phosphorus and represents an alternative, sustainable source. In this study, sludge obtained from a wastewater treatment plant with biological and chemical phosphorus removal was acidified (pH = 3, 4, 5 and 6) to release orthophosphate followed by sequestration of the orthophosphate by a zinc aluminum layered double hydroxide (Zn2Al-LDH). Sulfuric acid (H2SO4), nitric acid (HNO3), and hydrochloric acid (HCl) was tested, which showed that only sulfate anions compete with phosphate and results in reduced phosphate recovery (25-35%). The orthophosphate concentration in the liquid phase increased from 20 % (raw sludge) to 75 % of the total phosphorus concentration at a pH of 3, which enhanced the phosphate uptake by the ZnAl-LDH from 1.7±0.2% to 60.3±0.6%. During acidification, the competing anion carbonate is degassed as CO2, which further improved the phosphate uptake. PXRD showed the intercalation of carbonate in the LDH in the raw sludge at pH = 8, whereas orthophosphate was intercalated at lower pH values. 27 Al MAS NMR spectroscopy and powder Xray diffraction (PXRD) proved preservation of the LDH at all pH values. Furthermore, about a third of the Al is present as an amorphous aluminum phosphate (AlPO4) upon exposure to phosphate at low pH (pH = 3 and 2 5) based on 27 Al MAS NMR spectroscopy. At a pH of 6 about a third of the P is present as brushite (CaHPO4•2H20).

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Section: Introductionmentioning

confidence: 99%

Layered double hydroxides for phosphorus recovery from acidified and non-acidified dewatered sludge

et al. 2019

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“…A high concentration of the struvite-forming ions in the inlet-mixed solution can shift the solid−liquid equilibrium to a lower pH. 20,72 The calculated saturation index for experiment L9 M was already higher than zero (0.9) at pH 6.0. This finding indicates the potential of struvite precipitation at a pH lower than 9.0 in the case of HTL byproducts of manure, corresponding with the observation from the experiment.…”

Section: Effect Of Inlet-mixed Solution Composition On Htl-based Stru...mentioning

confidence: 95%

“…Struvite precipitation is widely applied to recover phosphate and/or nitrogen from municipal, farm, and agro-industrial wastes, and the literature regarding the effect of operating parameters on the struvite precipitation from these wastes is extensive; for example, effects of temperature and pH are summarized in reviews. , The molar ratio of the struvite-forming ions in the solution also has a significant effect. Experimental studies on struvite precipitation from solutions of different complexities have indicated that increasing the ammonium-to-phosphate ion molar ratio − and the magnesium-to-phosphate ion molar ratio − over 1:1 favors struvite formation. The presence of non-struvite-forming constituents in the solution (denoted as foreign ions) can influence both the thermodynamics and kinetics of struvite precipitation, which affects the properties of the precipitate.…”

Section: Introductionmentioning

confidence: 99%

“…The HTL process water, which is targeted as an ammonium ion source in the inlet-mixed solution for struvite precipitation, has a high content of organic compounds . The presence of organics can limit struvite precipitation and change the physical properties of the struvite. ,− The mixing condition affects the mass transfer of solutes. A good mass transfer of struvite-forming ions is beneficial for struvite formation and for transport-limited growth .…”

Section: Introductionmentioning

confidence: 99%

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Valorization of Byproducts from Hydrothermal Liquefaction of Sewage Sludge and Manure: the Development of a Struvite-Producing Unit for Nutrient Recovery

2021

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Hydrothermal liquefaction (HTL) presents a promising technology to recover energy from sewage sludge and manure as bio-crude oil. The liquid and solid phases after HTL are considered as byproducts; however, the latter is rich in nutrients, which offers a possibility for nutrient recovery and manufacturing of valuable products. This study focuses on the simultaneous recovery of phosphate and ammoniacal nitrogen as struvite by combining the liquid HTL byproduct and leachate from the solid HTL byproduct. To implement a flexible struvite-producing unit, the effect of an inlet-mixed solution composition on the struvite precipitation was investigated on a laboratory scale and preferable operating conditions were identified. These operating conditions were used afterward to evaluate and adapt an air-agitated system for struvite precipitation subsequent to the HTL production chain. Moreover, the precipitation process in the air-agitated system was evaluated using synthetic model solutions compared to real HTL byproducts to offer insight into the effect of impurities on the product quality. The product, which has a struvite content of more than 75 wt %, was manufactured from the HTL byproducts of manure and sewage sludge as well. It has potential for use as a fertilizer based on its elemental composition but the use of citric acid was found to be effective to improve the quality of the product, especially of sewage sludge. The results showed that the air-agitated system could be effectively implemented in the HTL production chain. It has the potential to enhance features of the product, leading to a ready-to-use fertilizer in shape (particle size) and quality (struvite content).

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“…As a result, the aquatic life is threatened and the water bodies becomes unsightly and unhealthy. The wastewater streams, especially those originating from household, agricultural and animal farming, are characterized by a high level of ammonia and P contents (Liu & Qu, 2017;Mpountas et al, 2017;Deng et al, 2006). Therefore, the effluents must be treated before discharging them into water bodies.…”

Section: Introductionmentioning

confidence: 99%

On precipitation of struvite (MgNH4PO4.6H2O)

Muryanto

2017

JoSSE

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Excessive input of N and P into water bodies causes eutrophication which leads to deterioration of aquatic evironments and has adverse effects naturally and economically. It is therefore urgent to remove N and P from wastewater prior to disposal into inland and coastal waters. Among the various removal methods, controlled struvite precipitation is preferred. Struvite (MgNH4PO4.6H2O) precipitates uncontrollably under the specific conditions producing a scale deposit causing persistent problems in industries and wastewater treatment plants. The scale deposit clogs the piping system and impair plant equipment. On the other hand, thanks to its composition and properties, struvite is a potential fertilizer. In medical field, struvite is a common component of kidney stones. A number of process parameters govern the struvite precipitation. This paper briefly presents these parameters: pH, molar ratios, temperature, mixing, and presence of foreign ions. pH level is considered as the most important variable affecting the precipitation of struvite and the pH level: 9.5 to 10.5 is seen as the optimum. For an effective precipitation the molar ratios of the struvite components, i.e. Mg:N:P should be at least unity. With regard to struvite solubility, the effect of temperature, in the range of 21oC to 49oC, is conflicting, which is probably due to different experimental conditions. Whilst agitation is not regarded as a decisive parameter, the influence of foreign ions, notably divalent metal ions, on struvite morphology and change of crystal phases is significant.

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Effects of Solution Composition and Polymer Additive on the Crystallization of Struvite

Cited by 6 publications

References 23 publications

Layered double hydroxides for phosphorus recovery from acidified and non-acidified dewatered sludge

Layered double hydroxides for phosphorus recovery from acidified and non-acidified dewatered sludge

Valorization of Byproducts from Hydrothermal Liquefaction of Sewage Sludge and Manure: the Development of a Struvite-Producing Unit for Nutrient Recovery

On precipitation of struvite (MgNH4PO4.6H2O)

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