Low plant available phosphorus limits legume growth and biological nitrogen fixation (BNF). This study examined, under controlled conditions, the relationship between soil phosphorus and alfalfa and soybean BNF on two contrasting low-P soils (Ontario and Nova Scotia) from organic dairy farms. Soluble P was applied up to 135 mg P kg-1. An optimum range of 45 to 90 mg kg-1 applied P increased soybean plant growth, nodulation, N and P uptake and BNF. Significant effects of soil type reflected greater N supplying ability and lower P sorption for the Ontario soil. Alfalfa response to soluble P application was not as apparent. In addition three potentially organically acceptable amendments (MSW compost, Crystal Green® struvite and partially solubilized rock phosphate) were evaluated as alternate sources of plant available P. Compost and struvite, applied at moderate rates, sufficiently supplied P to increase plant growth and BNF comparably to that found for soluble P fertilizer.

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Magnesium oxide (MgO) is a cost-effective and environmentally sustainable alternative to magnesium chloride (MgCl2) and sodium hydroxide (NaOH) used for sidestream struvite recovery from anaerobically digested supernatant (centrate) through the Pearl® process. MgO is produced from magnesite (MgCO3) calcination, and different calcination conditions can alter the quality and characteristics of the MgO product. It was hypothesized that the insolubility of MgO could provide a "slowly available" form of Mg2+ in the reactor and consequently allow the reactor to be operated beyond design phosphorus (P) reactor loading. MgO has been utilized in other P recovery technologies, e.g. the Phospaq™ Process, but operation and performance of MgO using a full-scale Pearl® 500 fluidized bed reactor was investigated. Performance at rated reactor loading utilizing MgO was initially comparable to baseline conventional MgCl2 reactor operation, ≥50% struvite yield (P recovered/theoretical P recovery) and ≥70% total phosphorus (TP) removal. However, the pilot reactor operated at 2X reactor loading showed comparable results to baseline performance at 1.5X reactor loading. During the full-scale pilot, optimization of the reactor utilizing MgO was limited by the struvite product size that the struvite post-processing equipment could effectively harvest. Additionally, the MgO characteristics due to calcination conditions were hypothesized to affect struvite precipitation kinetics. In struvite precipitation jar testing, MgO products were used to analyze the saturation index, measure precipitation kinetics, and understand the effect that MgO hydration and reactivity had on struvite precipitation. Jar testing showed that initial P removal increased with increasing MgO product reactivity. The most reactive MgO used, Timab AK98, showed 1-40% P removal and substantial decrease in solution saturation index immediately after dosing MgO to centrate. The slower P removal and decrease in saturation index observed with the less reactive material suggests that MgO can provide a "slowly available" Mg2+ reserve throughout the struvite precipitation reaction. / Master of Science / Phosphorus is an essential element for human, plant and animal health. Necessary bodily functions cannot be performed without inputting phosphorus to cell metabolic pathways, such as cell repair and formation of nucleic acids, bone mineral and stored energy. Phosphates are the most common form of phosphorus found in the environment and are a component of many common substances, such as detergents, fertilizers, food and urine. Due to the increasing population and food demand the need for phosphorus-based fertilizers has soared since the 1940s. In 2018, 240 megatons of phosphate rock were mined, and 17 megatons of phosphorus were extracted from mined ore. 15 megatons of the extracted phosphorus were used in fertilizer production. Because of phosphorus loss from the soil and inefficient agro-practices, only 20% of the extracted phosphorus is consumed by humans and animals from food and little is then recycled from our waste systems. There is a major gap in the agricultural phosphorus cycle that is necessary to address with sustainable practices (Oster, M. et al. 2018). Phosphorus can be recovered from wastewater in the form of struvite, which is a mineral that can be utilized a slow-release fertilizer. Conventional methods of phosphorus recovery from wastewater have the potential to be costly. By utilizing an alternative chemical, struvite recovery can be more cost-effective and environmentally sustainable.

Ensuring the safety of drinking water, treating wastewater, and remediating soil are ongoing global concerns. Adsorption is a favorable substitute for traditional methods including coagulation, precipitation, membrane separation, and ion-exchange in water purification. Biochar-based sorbents are cheap and effective due to high density surface functional groups, which can retain a wide range of chemicals. This dissertation focused on three main projects involving magnetite (Fe3O4) and struvite/struvite-K (MgNH4PO4.6H2O/MgKPO4.6H2O) deposited high surface area Douglas fir biochar (DFBC) based engineered material for water and soil remediation. Chapter II focuses on toxic arsenic (V) contaminated wastewater remediation using magnetite particles dispersed Douglas fir biochar. This chapter highlights the effect of pH, adsorption kinetics, isotherms, particle sizes, ionic strength, the impact of competitive ions and fixed-bed column sorption on As(V) removal and redox transformation of As(III) to As(V) during the adsorption in a wide range of pHs. Moreover, Mössbauer spectroscopy was used to analyze the composition of Fe3O4 particles formed on Fe3O4/DFBC. Furthermore, X-ray photoelectron spectroscopy studies were conducted to study As(V) adsorption onto Fe3O4/DFBC at a wide range of solution pHs to verify the predominant As adsorption mechanisms. Chapter III focuses on challenging per- and poly-fluoroalkyl substances (PFAS) contaminated water remediation at low concentrations using Fe3O4/DFBC. In this work, we used classical adsorption techniques to purify PFAS contaminated water. Chapter IV is focused on remediation of depleted soil using struvite/struvite-K- modified Douglas fir biochar (BCF). In this study, we examined the leaching rates of PO43-, NH4+, K+, and Mg2+ from BCF in different water matrices, different temperatures, and a wide range of pHs. Greenhouse experiments were conducted to evaluate the performances of BCF.

Struvite and other minerals often form at WRRFs when phosphorus-rich activated sludge from EBPR processes undergo anaerobic digestion. Without proper control, these minerals can cause scale deposits that clog pipes and damage dewatering equipment. However, managing when and where these minerals form allows for phosphorus recovery as a sustainable fertilizer or its sequestration into Class A biosolids, creating a nutrient-rich soil product. This approach can reduce phosphorus recycling in solids handling, prevent scaling issues, and enhance the value of biosolids as a marketable, sustainable product. In a digested solids storage tank that is in between anaerobic digestion and final dewatering, precipitation was removed in a controlled pilot setup by manipulating variables such as mixing, aeration to achieve a low solids retention time (SRT) post aerobic digestion (PAD) and by chemical addition. Optimizing this via pilot testing can reduce struvite buildup, enhance phosphorus removal, and provide additional benefits such as nitrogen and COD removal. The pilot setup at Hampton Roads Sanitation District's Atlantic Treatment Plant (ATP) consisted of four 45-gallon tanks operated as daily batch fed continuously stirred tank reactors with a 3-day SRT. Aeration and chemical addition of Mg(OH)2 and Ca(OH)2 at varying Ca2++Mg2+:P ratios were tested under different aeration settings of constant, pH or dissolved oxygen (DO) setpoints. Results showed that DO setpoint-controlled aeration stabilized pH and DO and enhanced OP-P and NH3-N removal, with maximum OP-P removal of 97 percent achieved at a Ca2++Mg2+:P ratio of 1.3:1. NH3-N removal, mainly from struvite precipitation, averaged 10–20 percent, with no nitrification observed likely due to free ammonia inhibition. Alkalinity reduction exceeded predicted levels, suggesting additional coprecipitation reactions occurred. Aeration and mixing consistently achieved about 20 percent total COD removal across the pilot in microaerobic conditions. The chemical equilibrium model Visual MINTEQ was also explored to determine the effects of pH, temperature, chemical choice and dose on minerology. A validated model could then be used to predict scaling potential and characterize minerals formed at WRRFs to better treat these nuisance scaling minerals and determine their potential for harvesting or sequestration as a nutrient-rich product. With the increasing need to not only remove but recover nutrients for beneficial reuse, it is imperative to deepen the understanding of successful phosphorus precipitation in biosolids and how it can be optimized and modified for various solids handling configurations. / Master of Science / Nutrient removal, particularly phosphorus (P) and nitrogen (N), is essential in wastewater treatment to prevent eutrophication and its harmful impacts on aquatic ecosystems and water quality. Phosphorus, while a pollutant in excess, is also a critical and non-renewable resource essential for food and fertilizer production, with limited global supplies and rising demand. A common phosphorus recovery source the industry has turned to are Water Resource Recovery Facilities (WRRFs), which process billions of gallons of wastewater daily. Enhanced Biological Phosphorus Removal (EBPR) is a process that takes advantage of microorganisms in wastewater to divert phosphorus from the liquid to the solids stream. In solids handling, this excess phosphorus can be recovered in the form of phosphorus minerals, most notably struvite, and can be utilized as a sustainable biosolid product for beneficial land application. However, struvite, if not properly controlled, can lead to costly maintenance issues by forming scale in piping and dewatering equipment. By optimizing phosphorus recovery and directing where these mineral formations occur, WRRFs can reduce scaling risks, recycle phosphorus, and produce a sustainable fertilizer alternative. A pilot setup at Hampton Roads Sanitation District's Atlantic Treatment Plant (ATP) consisted of four 45-gallon tanks operated as daily batch fed continuously stirred tank reactors with a low solids retention time (SRT). Various aeration settings were tested for pH adjustment and the addition of two chemicals were tested, Mg(OH)2 and Ca(OH)2, at varying Ca2++Mg2+:P ratios to supplement phosphorus mineral precipitation. Phosphorus precipitation was successful in each trial and a maximum of 97 percent phosphorus removal was achieved, along with additional benefits such as nitrogen and COD removal. A chemical equilibrium model was also explored to predict scaling potential and characterize minerals formed at WRRFs to better treat these nuisance scaling minerals and determine their potential for harvesting or sequestration as a nutrient-rich product. Optimizing this approach at the pilot scale can improve plantwide efficiency at ATP and provide other WRRFs an optimized operational strategy to prevent nuisance scaling while producing a marketable biosolids product, thereby enhancing the sustainability of phosphorus management in wastewater treatment.

Struvite is a salt that is formed out of  Mg2+,NH4+ and PO43- and it crystallizes in form of MgNH4PO4.6H2O. Struvite‟s (magnesium ammonium phosphate or MAP) precipitation has recently been regarded as an interesting technique to remove phosphate and ammonium from waste water. The high elimination rates and the possibility of recycling the struvite as a direct slow release fertilizer make this process feasible and appealing. However, the costs due to the raw chemicals needed are drawbacks that leave aside the application of the process in some facilities. The MAP biological dissolution makes possible a recycling of magnesium and phosphate, a fact that reduces the process‟s costs and will help making it even more feasible and environmentally friend. This thesis goes also through the parameters, reactions and different techniques that optimize the struvite precipitation process.

Dissolved compounds and ions, including mineral elements and products of microbial metabolism, are present in many cheeses in relatively high concentrations. These dissolved substances may precipitate from the aqueous phase of cheese to form sparingly soluble crystals that can impart a crunchy, gritty, or sandy texture on the cheese. In the present work, optical and diffractometric methods were optimized for use with cheese samples to identify crystal phases in several cheese varieties. These techniques, which included powder X-ray diffractometry (PXRD), single crystal X-ray diffractometry (SCXRD), and petrographic microscopy (PM) have traditionally been used on geological specimens that are quite different from the cheese samples used in the present study. Nonetheless, these techniques were successfully used to gain valuable insight into crystal development in cheese. Powder X-ray diffractometry was optimized to minimize the occurrence of artifacts that may occur due to the high water content and low crystallinity of some cheese samples. The use of enhanced sample preparation techniques facilitated the identification of organic and inorganic crystal phases such as tyrosine, leucine, brushite (CaHPO4·2H2O), and calcite (CaCO3) in hard and soft cheeses. SCXRD was used to determine the crystal structures of ikaite and struvite, which had been tentatively identified in washed-rind cheese using PXRD. PM was used to observe morphological and optical properties of crystals in white mold cheese and washed-rind cheese. In two subsequent aging studies, PXRD was used to determine the approximate timing of crystal nucleation in the rinds of white mold cheese and washed-rind cheese. These observations were paired with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) data to demonstrate that the onset of crystallization in the rinds coincided with a diffusion phenomenon in which mineral ions diffused from the center of the cheese and became concentrated in the rind. PM observations demonstrated that maximum crystal size in the rinds generally increased as aging progressed. These observations will be useful in future work that investigates the impact of crystallization on sensory properties of cheese.

A presente pesquisa estudou a viabilidade do emprego de sais de magnésio em estações de tratamento de esgoto sanitário visando a remoção do fósforo, bem como a produção de estruvita, mineral que pode ser utilizado diretamente no solo como fertilizante. As estações estudadas nesta pesquisa foram a Estação de Tratamento de Esgoto Sanitário de Franca-SP e a Estação de Tratamento de Esgoto Sanitário Jardim das Flores, localizada no município de Rio Claro-SP, e a Estação de Tratamento de Esgoto Sanitário Piçarrão, no município de Campinas. No caso da ETE Jardim das Flores (Rio Claro-SP), observou a possibilidade do emprego de sais de magnésio para se remover fósforo no efluente dos reatores UASB. Com ensaios de Jar-Test, atingiu-se cerca 49% de remoção de fosfato na amostra precipitada por gravidade e cerca de 90% na amostra centrifugada. No caso da ETE-Franca-SP, constatou-se, apesar do emprego de sais de magnésio não ter sido viável, verificou-se os benefícios do emprego de cloreto férrico em estações de tratamento de esgoto sanitário. / The present research studied the use of magnesium salts to remove phosphorus. With the phosphorus removal, magnesium salts, produce, as well, struvite, mineral that can be use directly on soil as fertilizer. The wastewater treatment plants objects of studies in this research was Wastewater Treatment Plant of Franca (SABESP) city Wastewater Treatment Plant of Jardim das Flores (Foz do Brasil), at Rio Claro city, and Wastewater Treatment Plant of Piçarrão (SANASA), at Campinas city. All three WWTP\'s are at São Paulo state, Brazil. In WWTP Jardim das Flores/Foz do Brasil (Rio Claro-SP), the results shown the viability of magnesium salts use at effluent of UASB reactors. In Jar-test essays, the phosphorus removal reached among 49% and in centrifuged samples, phosphorus removal was among 90%. In WWTP Franca-SP/SABESP, the results shown the benefits of iron salts in wastewater treatment.

A presente pesquisa estudou a viabilidade do emprego de sais de magnésio em estações de tratamento de esgoto sanitário visando a remoção do fósforo, bem como a produção de estruvita, mineral que pode ser utilizado diretamente no solo como fertilizante. As estações estudadas nesta pesquisa foram a Estação de Tratamento de Esgoto Sanitário de Franca-SP e a Estação de Tratamento de Esgoto Sanitário Jardim das Flores, localizada no município de Rio Claro-SP, e a Estação de Tratamento de Esgoto Sanitário Piçarrão, no município de Campinas. No caso da ETE Jardim das Flores (Rio Claro-SP), observou a possibilidade do emprego de sais de magnésio para se remover fósforo no efluente dos reatores UASB. Com ensaios de Jar-Test, atingiu-se cerca 49% de remoção de fosfato na amostra precipitada por gravidade e cerca de 90% na amostra centrifugada. No caso da ETE-Franca-SP, constatou-se, apesar do emprego de sais de magnésio não ter sido viável, verificou-se os benefícios do emprego de cloreto férrico em estações de tratamento de esgoto sanitário. / The present research studied the use of magnesium salts to remove phosphorus. With the phosphorus removal, magnesium salts, produce, as well, struvite, mineral that can be use directly on soil as fertilizer. The wastewater treatment plants objects of studies in this research was Wastewater Treatment Plant of Franca (SABESP) city Wastewater Treatment Plant of Jardim das Flores (Foz do Brasil), at Rio Claro city, and Wastewater Treatment Plant of Piçarrão (SANASA), at Campinas city. All three WWTP\'s are at São Paulo state, Brazil. In WWTP Jardim das Flores/Foz do Brasil (Rio Claro-SP), the results shown the viability of magnesium salts use at effluent of UASB reactors. In Jar-test essays, the phosphorus removal reached among 49% and in centrifuged samples, phosphorus removal was among 90%. In WWTP Franca-SP/SABESP, the results shown the benefits of iron salts in wastewater treatment.

Hog manure phosphorus (P) can be recovered as struvite or magnesium ammonium phosphate hexahydrate (MgNH4PO4∙6H2O). The recovered struvite has slow-release properties and may be used as a P-source for crops. Two pot experiments were conducted to evaluate the agronomic effectiveness and seedling toxicity of liquid hog manure-recovered struvite for canola (Brassica spp.) and wheat (Triticum aestivum). While wheat was non-responsive to P application, canola dry matter yield (DMY) from struvite (1.9 g kg-1) was similar to that from monoammonium phosphate (MAP) (1.8 g kg-1) and coated-monoammonium phosphate (CMAP) (1.7 g kg-1). Importantly, when P was seed-placed at the higher rate (15 mg kg-1), canola seedling emergence was significantly greater with struvite (90%) and CMAP (85%) than with MAP (60%). The results demonstrate the potential of struvite as an effective P-source for canola in P-deficient soils, which can be safely applied at higher rates than those currently recommended for seed-placed MAP.