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PubMed2006

Enhancing struvite precipitation potential for ammonia nitrogen removal in municipal landfill leachate.

This study was conducted to improve struvite precipitation for NH4-N removal purpose in landfill leachate. For this purpose, we evaluated the effect of the feeding sequence of precipitating reagents (magnesium, orthophosphate, and buffering reagent) on NH4-N removal by forming struvite deposits. Struvite precipitation effectively proceeded by an addition of excess magnesium and phosphate sources followed by an addition of the buffering reagent, in which condition the local formation of inappropriate deposits or the contamination of the desired struvite was minimized. We also tested the effect of struvite addition as the seeding materials on NH4-N removal. Seed addition would increase the potential for the struvite crystal growth, which enhanced NH4-N removal performance in landfill leachate treatment.

Ammonia↗

PubMed2003

Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg:P ratio and determination of rate constant.

Because of increased concern about surface water eutrophication from nutrient-enriched agricultural runoff, many swine producers are encouraged to decrease application rates of waste-based P. Precipitation and subsequent removal of magnesium ammonium phosphate (MgNH(4)PO(4) x 6H(2)O), commonly known as struvite, is a promising mechanism for N and P removal from anaerobic swine lagoon effluent. The objectives of this research were to (i) quantify the effects of adjusting pH and Mg:P ratio on struvite precipitation and (ii) determine the rate constant pH effect for struvite precipitation in anaerobic swine lagoon liquid. Concentrations of PO(4)-P in liquid from two anaerobic swine lagoons were determined after 24 h of equilibration for a pH range of 7.5-9.5 and Mg:P ratios between 1:1 and 1.6:1. Struvite formation reduced the PO(4)-P concentration in the effluents to as low as 2 mgl(-1). Minimum concentrations of PO(4)-P occurred between pH 8.9 and 9.25 at all Mg:P ratios. Struvite precipitation decreased PO(4)-P concentrations by 85% within 20 min at pH 9.0 for an initial Mg:P ratio of 1.2:1. The rate of PO(4)-P decrease was described by a first-order kinetic model, with rate constants of 3.7, 7.9, and 12.3 h(-1) at pH 8.4, 8.7 and 9.0 respectively. Our results indicate that induced struvite formation is a technically feasible method to remove N and P from swine lagoon liquid and it may allow swine producers to recover nutrients for off-farm sale.

Anaerobiosis↗

PubMed2006

Exploring the determination of struvite solubility product from analytical results.

The solubility of magnesium ammonium phosphate hexahydrate (struvite) was determined in different water and wastewater solutions, by using the analytical results of the solubility tests conducted in the Environmental Engineering Lab at the University of British Columbia. The various factors affecting the struvite solubility such as pH, ionic strength and the temperature of the solutions were also studied in this project. The struvite solubility product values were found to vary significantly from one solution to another and over the range of the experimental conditions as well. For instance, the solubility product (Ksp) determined at 20 degrees C for anaerobic digester supernatant from the Penticton, B.C. Advanced Wastewater Treatment Plant, was found to vary from 8.46 x 10(-15) (pKsp =14.07) to 1.3 x 10(-13) (pKsp =12.89), over a pH range 6.45 to 8.97; while in the case of distilled water, with the same struvite crystals and at the identical temperature, it was found to vary from 5.21 x 10(-15) (pKsp=14.28) to 2.12 x 10(-13) (pKsp =12.67) over a pH range of 7.01 to 9.62. These results explore the possible reasons for widely varying struvite solubility reported in the literature. A possible correlation was also developed to correlate struvite solubility product with varying temperature. Furthermore, an attempt was made to establish a correlation between conductivity and calculated ionic strength of the solutions. A significant gap, between the values predicted by the correlation developed in this study and those predicted by the existing correlation, was also observed.

Bacteria, Anaerobic↗

PubMed2004

Evaluation of effects of dietary carbohydrate on formation of struvite crystals in urine and macromineral balance in clinically normal cats.

OBJECTIVE: To evaluate effects of dietary carbohydrate on urine volume; struvite crystal formation; and calcium, phosphorus, and magnesium balance in clinically normal cats. ANIMALS: 21 healthy adult cats (15 sexually intact males and 6 sexually intact females). PROCEDURE: Diets containing no carbohydrate source (control diet), control plus starch, or control plus fiber were given in a 3 X 3 Latin-square design. The diets were available ad libitum in study 1 (n = 12) and given under restrictions in study 2 (9) to equalize daily intakes of crude protein among the 3 groups. Formation of struvite crystals and balance of calcium, phosphorus, and magnesium were measured. RESULTS: Urine volume was lower in the starch group and fiber group in study 1, whereas no differences were detected among the groups in study 2. Urinary pH and struvite activity product were higher in the starch group in both studies, and the fiber group also had higher struvite activity product in study 2. In both studies, urinary concentrations of HCl-insoluble sediment were higher in the starch group and fiber group. In the fiber group, a net loss of body calcium, phosphorus, and magnesium was detected in study 2. CONCLUSIONS AND CLINICAL RELEVANCE: Starch and fiber in diets potentially stimulate formation of struvite crystals. Hence, reducing dietary carbohydrate is desirable to prevent struvite urolith formation. In addition, a net loss of body calcium, phosphorus, and magnesium during feeding of the fiber diet suggests that dietary inclusion of insoluble fiber could increase macromineral requirements of cats.

Animals↗

PubMed1981

Canine struvite urolithiasis: problems and their dissolution.

Struvite (magnesium ammonium phosphate) uroliths are found more frequently in the urinary tracts, of dogs than are other types of uroliths. Infection of the urinary tract with urease-producing bacteria, especially staphylococci, plays an important role in urolith formation. An inherited predisposition to urinary tract infection may be associated with the high rat of occurrence of struvite uroliths in some dogs. Diagnosis of struvite urolithiasis should encompass analysis of the mineral composition of calculi and identification of concomitant urinary tract infection. Since urinary tract infections occur as sequelae to abnormalities in local or systemic host-defense mechanisms, appropriate effort should be directed toward detection of these abnormalities. Therapy of struvite urolithiasis should encompass relief of obstruction to outflow when necessary, elimination of existing calculi, eradication or control of urinary tract infection, and prevention of recurrence. Although surgical removal remains as the preferred method to eliminate struvite uroliths from dogs, nonsurgical methods of urolith dissolution should be considered. Recurrence of struvite uroliths may be prevented by various combinations of antimicrobial therapy, administration of urease inhibitors, acidification of urine, and induction of diuresis.

Animals↗

PubMed1994

Effects of choreito consumption on struvite crystal growth in urine of cats.

The effect of a dietary supplement, choreito, on in vitro struvite crystal growth in feline urine was evaluated. Adult specific-pathogen-free cats (4 females, 4 males) considered to be clinically normal on the basis of physical examination findings and normal results of CBC, serum biochemical analyses, and urinalyses obtained before the beginning of the study were used. Before 24-hour urine sample collections were made, cats were fed a commercial canned diet with 0 or 500 mg of choreito supplement/kg of body weight for at least 2 weeks in a cross-over design with 4 cats/treatment. Filtered urine samples were analyzed for urine pH, specific gravity, osmolality, and urine electrolytes. The struvite activity product was calculated, using a statistical software program that calculates urine saturation. Urine samples were placed in wells of cell culture plates, increasing concentrations of ammonium hydroxide were added to adjacent wells to stimulate struvite crystal growth, and the plates were incubated at 37 C. Crystal growth was assessed by determination of number of crystals and supersaturation index by direct visualization, using an inverted microscope. Supplementation of the diet with choreito (at this concentration) did not change urine pH, specific gravity, osmolality, urine electrolyte composition, or calculated struvite activity product. However, supplementation significantly (P < 0.05) reduced crystal number and supersaturation index. These results indicate that direct observation of struvite crystal formation in whole urine may more accurately predict the effects of treatments to prevent or treat struvite urolithiasis than do calculations based on electrolyte concentration that do not account for the effect of urine macromolecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Effects of a high-protein diet on mineral metabolism and struvite activity product in clinically normal cats.

OBJECTIVE: To examine effects of high-protein diets (> 50% crude protein of dry matter) on urinary mineral excretion and struvite activity product ([Mg2+] x [NH4+] x [PO(4)3-]). ANIMALS: 14 clinically normal cats, 4 adult female and male cats for experiments 1 and 2, respectively, and 6 female kittens aged 4 months for experiment 3. PROCEDURE: Relations between dietary protein amount (25.9, 38.3, 51.4, and 65.4% crude protein [dry matter]) and urinary excretion of Mg, P, and Ca were examined in a 4 x 4-Latin square design (experiment 1). Struvite activity product, the index of solubility of struvite crystals, was determined when a high-protein diet (54.9%) was fed (experiment 2). Utilization of minerals in cats fed a high-protein diet long term was examined (experiment 3). RESULTS: Water intake and urine volume increased with increasing dietary protein concentration. Urinary Mg2+ excretion was not affected (experiment 1) or was decreased (experiment 3) by higher protein intake, leading to lower urine Mg2+ concentration in groups fed higher protein amounts. Urine pH was decreased by high-protein intake. As a result, PO(4)3- concentration was decreased by high-protein intake (experiment 2), although total daily urinary excretion of P was increased. Consequently, struvite activity product tended to decrease in cats fed high-protein diets, indicating increase in struvite solubility. High-protein intake decreased Ca and P retention by increasing their fecal and urinary excretions, respectively. CONCLUSION: As a consequence of the increase in urine volume and urine acidification, high-protein diets have potential ability to increase solubility of struvite crystals.

Animals↗

PubMed1990

A simple technique for studying struvite crystal growth in vitro.

Struvite urolithiasis forms as a consequence of a urinary tract infection by urease-producing species of bacteria such as Proteus mirabilis. Ammonia, produced by the enzymatic hydrolysis of urea, elevates urine pH causing a supersaturation and precipitation of Mg++ as struvite (NH4MgPO4). Calcium often precipitates as well, forming the mineral carbonate-apatite (Ca10(PO4)6CO3). We have developed a procedure based on direct observation by light microscopy whereby struvite crystal growth can be quickly monitored in response to chemical changes in urine. As struvite crystals assume a characteristic shape or crystal habit based on their growth rate, the effect of urine chemistry and the action of various crystallization or urease inhibitors on struvite formation can be quickly shown. In addition preliminary effects of alkaline pH, or the presence of toxic compounds on bacteria can also be shown through their loss of motility.

Crystallization↗

PubMed1997

Crystal growth and molecular modeling studies of inhibition of struvite by phosphocitrate.

The inhibition by phosphocitrate of struvite crystal formation and growth has been examined in the present study. Crystal growth in a gel matrix was controlled by phosphocitrate in a dose-dependent manner. The effects of inhibition were followed using scanning electron microscopy, optical microscopy, and single crystal X-ray analysis. The presence of phosphocitrate induced very strong, crystal face specific inhibition of struvite, leading to total cessation of crystal growth when sufficient concentration of the inhibitor was made available. Crystal growth studies and results from molecular modeling indicated strong affinity of phosphocitrate to (101) faces of struvite. This in turn led to an alteration in the expression of these faces and the development of a characteristic arrowhead struvite morphology. Similar changes were not observed in the presence of identical concentrations of citrate, acetohydroxamic acid, and N-sulfo-2 amino tricarballylate (an analog of phosphocitrate), emphasizing the unique interaction of phosphocitrate with the struvite crystal lattice.

Citrates↗

PubMed2004

Formation and transformation of struvite and newberyite in aqueous solutions under conditions similar to physiological.

The precipitation of magnesium phosphates in the system MgCl(2)-NH(4)H(2)PO(4)-NaOH-H(2)O was studied at a wide range of reactant concentrations at 37 degrees C and an initial pH(i) of 7.4. Precipitates were aged for 24 h and characterized by means of optical and scanning electron microscopy, x-ray diffractometry, FT-IR spectroscopy and thermogravimetry. Struvite was found to precipitate in nearly the whole concentration region investigated. Pure newberyite and a mixture of struvite and newberyite were obtained in a narrow range only with a pH(24 h)<6.4. The transformation of struvite into newberyite was studied by following changes in the liquid and solid phases. Thus, the changes of pH and the content of struvite in the precipitate as a function of time were recorded. The influence of the initial pH(i) and temperature on the transformation process is discussed. Analysis of the experimental data suggests a solution mediated transformation process as a possible mechanism of struvite transformation.

Chemical Precipitation↗

PubMed2005

An economic evaluation of phosphorus recovery as struvite from digester supernatant.

Phosphorus can be recovered from wastewater through crystallisation of struvite, MgNH(4)PO(4).6H(2)O. Approximately 1 kg of struvite can be crystallised from 100 m(3) of wastewater. Crystallisation is profitable compared to chemical and biological removal of phosphorus due to savings from the reduction in (i) chemicals used for precipitation and sludge disposal; and (ii) downtime for cleaning unwanted struvite formed during chemical and biological removal. The struvite produced annually from a wastewater treatment plant that processed 100 m3/d, would be sufficient to apply on 2.6 ha of arable land, as fertilizer. If struvite were to be recovered from wastewater treatment plants worldwide, 0.63 million tons of phosphorus (as P(2)O(5)) could be harvested annually, reducing phosphate rock mining by 1.6%. Therefore, this technology could provide opportunities to recover phosphorus sustainably from waste streams and preserve phosphorus reserves.

Biodegradation, Environmental↗

PubMed2006

Agglomeration of struvite crystals.

Struvite crystallisation is widely studied as a way to remove phosphorus from wastewater effluents and simultaneously generates a valuable product for the fertiliser industry. However, to date, some crystallisation processes experimented at either pilot/or full scale face problems linked to the formation of fines. This paper presents results on the investigation of struvite agglomerative properties and the possible application of coagulants and/or flocculants to remove fines. Coagulants investigated were hydrolysing metals salts (Al(3+) and Fe(3+)), calcium compounds and a cationic polymer, polydiallyldimethylammoniumchloride (polyDADMAC). The effects of a natural flocculant (alginate) have also been tested. Results demonstrated that destabilisation of struvite particles by chemical addition was feasible and identified polyDADMAC as a good option for the agglomeration of struvite particles. However, optimisation of its dosage under typical pH conditions for struvite formation showed floc formation to be very pH sensitive.

Alginates↗

PubMed1990

Influence of chondroitin sulfate, heparin sulfate, and citrate on Proteus mirabilis-induced struvite crystallization in vitro.

Struvite crystals were produced by Proteus mirabilis growth in artificial urine, in the presence of a number of naturally occurring crystallization inhibitors. The use of phase contrast light microscopy enabled the effects of added chondroitin sulfate A, chondroitin sulfate C, heparin sulfate, or sodium citrate, on struvite crystal growth rates to be rapidly monitored as changes in crystal habit. Struvite crystals formed as a consequence of the urease activity of P. mirabilis under all chemical conditions. In the absence of inhibitor, early crystal development was marked by large quantities of amorphous precipitate, followed immediately by the appearance of rapidly growing X-shaped or planar crystals. Addition of the glycosaminoglycans, chondroitin sulfate A, chondroitin sulfate C, or heparin sulfate to the artificial urine mixture had no effect on the rate of crystal growth or appearance. When sodium citrate was present in elevated concentrations, crystal appearance was generally slowed, and the crystals assumed an octahedral, slow growing appearance. None of the added compounds had any influence on bacterial viability, pH, or urease activity. It is therefore likely that the inhibitory activity displayed by sodium citrate might be related to its ability to complex magnesium or to interfere with the crystal structure during struvite formation. From these experiments it would appear that citrate may be a factor in the natural resistance of whole urine to struvite crystallization.

Chondroitin Sulfates↗

PubMed2005

Laboratory and pilot-scale phosphate and ammonium removal by controlled struvite precipitation following coagulation and flocculation of swine wastewater.

To reduce the suspended solids load to a trickling filter installation, raw swine effluent was pre-treated with ferric chloride and a cationically charged polyacrylamide coagulant resulting in unexpected struvite accumulation downstream of this post-separation process. Using this pre-treated swine manure, struvite precipitation studies were carried out as a function of pH at laboratory and pilot batch and continuously operated scales. An optimal reaction time of 30 min was established for struvite precipitation in the pre-treated swine wastewater at pH 8.5, minimizing the co-precipitation of interfering minerals. Ferric chloride addition resulted in magnesium solubilization, such that no external additional source of magnesium was required for struvite formation. Aeration alone did not result in significant pH increases, so base addition was required for pH adjustment. X-ray diffraction revealed that the only crystalline phase produced was struvite. Removal of phosphate and ammonium attained 98% and 17% respectively in laboratory scale experiments. At the pilot-scale, removal attained 99% and 15% of phosphate and ammonium in both batch and continuously HRT = 1h) operated reactors.

Animals↗

PubMed2006

Rat strains differ in susceptibility to Ureaplasma parvum-induced urinary tract infection and struvite stone formation.

Individuals with struvite uroliths are susceptible to recurrent urinary tract infections (UTI), sepsis, and renal disease. Unfortunately, little is known about the host-specific factors that predispose to this disease. In order to develop a rodent model that can address this problem, we inoculated female Fischer 344 (F344), Lewis (LEW), Sprague-Dawley (SD), and Wistar (WIS) rats with a host-adapted strain of Ureaplasma parvum. Animals were necropsied at 2 weeks postinoculation; 100% of F344, 42% of SD, 10% of LEW, and 10% of WIS rats remained infected. Severe bladder lesions and struvite calculi were seen in 64% of F344 rats; in other rat strains, bladder lesions were mild or absent. F344 rats with struvite uroliths had the highest urinary levels of proinflammatory cytokines, such as GRO/KC, interleukin-1alpha (IL-1alpha), and IL-1beta. F344 rats without struvite stones at necropsy had milder bladder lesions and significantly lower urinary levels of proinflammatory cytokines but a more prominent inflammatory response than did other rat strains. Based on our results, struvite stone formation is linked to a robust inflammatory response that does not resolve UTI but instead promotes damage to surrounding tissues.

Animals↗

PubMed2003

Effects of a high-protein diet versus dietary supplementation with ammonium chloride on struvite crystal formation in urine of clinically normal cats.

OBJECTIVE: To evaluate the effects of a high-protein diet versus dietary supplementation with ammonium chloride (NH4Cl) on struvite crystal formation in the urine of clinically normal cats by measuring the urine concentration of hydrochloric acid (HCl)-insoluble sediment, urine pH, struvite activity product (SAP), number of struvite crystals in urine, and urine volume. ANIMALS: 23 healthy adult cats. PROCEDURE: Urine was fractionated by centrifugation with subsequent extraction of the sediment with 1 N HCl (study 1). Diets containing either 29% crude protein or 55% crude protein were fed to cats in a crossover trial of 3 weeks/period (study 2). Diets supplemented with either sodium chloride (NaCl) or NH4Cl were fed, by use of a 3 x 3 Latin-square design with 3 wk/period (study 3). In studies 2 and 3, urine samples were collected for the last 7 days of each period. RESULTS: The HCl-insoluble sediment contained Tamm-Horsfall glycoprotein (THP; study 1). The high-protein diet (study 2) and dietary supplementation with NH4Cl (study 3) resulted in a decrease in urine pH, SAP, and the number of struvite crystals in urine. However, the high-protein diet decreased urine concentrations of HCl-insoluble sediment containing THP (study 2), in contrast to the NH4Cl supplementation that increased urine volume without a significant effect on the urine concentration of the HCl-insoluble sediment (study 3). CONCLUSIONS AND CLINICAL RELEVANCE: Our results indicate that compared with dietary supplementation with NH4Cl, the high-protein diet is preferable as a urine acidifier for the prevention of struvite crystal formation in clinically normal cats.

Ammonium Chloride↗

PubMed1990

Medical dissolution of feline struvite urocystoliths.

The efficacy of a diet designed to facilitate dissolution of feline magnesium ammonium phosphate (struvite) uroliths was evaluated in 30 cases of urolithiasis, sterile struvite uroliths dissolved in a mean of 36 days after initiation of dietary treatment. In 5 cases of urolithiasis, struvite urocystoliths associated with urease-negative bacterial urinary tract infection dissolved in a mean of 23 days after initiation of dietary and antimicrobial treatment. In 3 cases of urolithiasis, struvite urocystoliths associated with urease-positive staphylococcal urinary tract infection dissolved in a mean of 79 days after initiation of dietary and antimicrobial treatment. Dissolution of uroliths in cats fed the treatment diet was associated with concomitant remission of dysuria, hematuria, and pyuria, and reduction in urine pH and struvite crystalluria. In one case, a urocystolith composed of 100% ammonium urate, and in another case, a urolith composed of 60% calcium phosphate, 20% calcium oxalate, and 20% magnesium ammonium phosphate did not dissolve.

Amoxicillin↗

PubMed1994

Effects of Tamm-Horsfall glycoprotein and albumin on struvite crystal growth in urine of cats.

Tamm-Horsfall protein (THP) was isolated and purified, using pooled urine collections from clinically normal cats. The effects of feline THP and purified feline serum albumin on urine chemical and struvite crystal variables were compared, using an in vitro crystal growth system and 24-hour samples of pooled urine obtained from 4 cats. Urine samples were placed in wells of cell culture plates, increasing concentrations of ammonium hydroxide were added to adjacent wells to stimulate struvite crystal growth, and the plates were incubated at 37 C. The effect of albumin and THP on crystal growth in sample wells was compared with that in control wells, without protein addition, in the same plate. Crystal growth was assessed by determination of number of crystals and supersaturation index, a scale of crystal habit at different degrees of supersaturation, by use of direct visualization with an inverted microscope. Albumin addition did not have significant effect on either crystal number or supersaturation, compared with controls. Addition of THP significantly (P < 0.05) increased crystal number and supersaturation index. It was concluded that THP significantly (P < 0.05) promoted growth of struvite crystals in feline urine, and thus, may have a role in feline struvite uroliths and struvite urethral plug formation.

Ammonia↗