Greenhouse evaluation and environmental impact assessment of different urine-derived struvite fertilizers as phosphorus sources for plants

A selection of six urine-derived struvite fertilizers generated by innovative precipitation technologies was assessed for their quality and their effectiveness as phosphorus sources for crops. Struvite purity was influenced by drying techniques and magnesium dosage. In a greenhouse experiment, the urine fertilizers led to biomass yields and phosphorus uptakes comparable to or higher than those induced by a commercial mineral fertilizer. Heavy metal concentrations of the different struvite fertilizers were below the threshold limits specified by the German Fertilizer and Sewage Sludge Regulations. The computed loading rates of heavy metals to agricultural land were also below the threshold limits decreed by the Federal Soil Protection Act. Urine-derived struvite contributed less to heavy metal inputs to farmland than other recycling products or commercial mineral and organic fertilizers. When combined with other soil conditioners, urine-derived struvite is an efficient fertilizer which covers the magnesium and more than half of the phosphorus demand of crops.     

工艺条件对鸟粪石晶体的粒径和沉降速度的影响

采用激光粒度仪实验测定了小型套管式空气曝气填料层磷回收装置中不同条件下生成的鸟粪石晶体的体积平均粒径,考察了其变化规律,并结合Stokes公式计算了晶体的沉降速率,同时考虑鸟粪石晶体形状的影响,进行了相应的修正。实验结果表明,鸟粪石的粒径在10—200μm之间,主要集中于20～100μm;在磷回收装置中添加填料并通人空气有利于增大鸟粪石晶体的粒径和沉降速度,无填料无空气时和有填料有空气时的平均粒径分别在30～55μm和40～65μm之间。随着pH值的增大,鸟粪石晶体的粒径和沉降速度逐渐增大,但当pH大于9．0后,鸟粪石晶体的粒径和沉降速度又逐渐减小;氮磷比值从1：1增大到2：1,鸟粪石晶体的粒径和沉降速度小幅度增加,氮磷比进一步增大,鸟粪石晶体的粒径和沉降速度基本不变;镁磷摩尔比在1：1—1．2：1的范围内时,鸟粪石晶体的平均粒径和沉降速度随镁磷比的增大而增大;镁磷摩尔比大于1．2：1后,鸟粪石晶体的平均粒径和沉降速度随镁磷比的增大逐渐减小;初始磷浓度越高,鸟粪石晶体的平均粒径和沉降速度越大。     

Overcoming challenges to struvite recovery from anaerobically digested dairy manure

Recovering struvite from dairy manure has consistently posed problems for researchers. This study separated solids from anaerobically digested dairy manure using a filtration system. Filtrate was rich in free magnesium (160 to 423 mg/L), ammonium (320 to 1800 mg N/L) and orthophosphate (93 to 332 mg P/L). High concentrations of free calcium (128 to 361 mg/L) and alkalinity (3309 to 6567 mg/L as CaCO3), however, may hinder struvite precipitation. Batch precipitation tests were conducted to identify and overcome factors that interfere with struvite formation. Precipitation tests at pH 9 identified calcium and ionic strength as most probable interferences. Calcium addition did not significantly change phosphorus removal efficiency, but decreased struvite purity because of formation of calcium phosphates when Ca:P activity ratio was greater than 0.5 to 1. Batch tests demonstrated effective calcium removal from anaerobically digested dairy manure through precipitation of calcium carbonate at pH 9 to 10 while retaining magnesium and orthophosphate, lessening hindrance to struvite formation.     

Effect of culture conditions on the formation of struvite by Myxococcus xanthus

The amount of struvite (MgNH₄PO₄·6H₂O) produced by Myxococcus xanthus as well as the culture parameter values (pH, total phosphorus, total Kjeldahl nitrogen) were dependent on the culture medium used. Struvite formation started during the exponential phase and the maximum concentration was observed at the beginning of stationary growth phase. The addition of each medium component to the liquid culture influenced the amount of crystal produced. This amount did not depend on the pH increase during the culture period. The moment of the bacterial growth phase, at which each medium component was added, influenced the struvite formation.     

Thermal decomposition of struvite and its phase transition

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.     

Ca-Mg kutnahorite and struvite production by Idiomarina strains at modern seawater salinities

The production of Mg-rich carbonates by Idiomarina bacteria at modern seawater salinities has been investigated. With this objective, four strains: Idiomarina abyssalis (strain ATCC BAA-312), Idiomarina baltica (strain DSM 15154), Idiomarina loihiensis (strains DSM 15497 and MAH1) were used. The strain I. loihiensis MAH1 is a new isolate, identified in the scope of this work. The four moderately halophilic strains precipitated struvite (NH4MgPO4 x 6H2O) crystals that appear encased by small Ca-Mg kutnahorite [CaMg(CO3)2] spheres and dumbbells, which are also regularly distributed in the bacterial colonies. The proportion of Ca-Mg kutnahorite produced by the bacteria assayed ranged from 50% to 20%, and I. abyssalis also produced monohydrocalcite. All precipitated minerals appeared to be related to the bacterial metabolism and, consequently, can be considered biologically induced. Amino acid metabolism resulted in a release of ammonia and CO2 that increase the pH and CO(3)(2-) concentration of the culture medium, creating an alkaline environment that favoured carbonate and struvite precipitation. This precipitation may be also related to heterogeneous nucleation on negatively charged points of biological structures. Because the nature of the organic matrix determines which ion is preferentially adsorbed and, consequently, which mineral phase is formed, the uniquely high content in odd-iso-branched fatty acids of the Idiomarina suggests that their particular membrane characteristics could induce Ca-Mg kutnahorite production. The Ca-Mg kutnahorite, a mineral with a dolomite-ordered structure, production at seawater salinities is noticeable. To date, such precipitation in laboratory cultures, has only been described in hypersaline conditions. It has also been the first time that biomineralization processes have been related to Idiomarina bacteria.     

Effect of soluble maillard reaction products on cadA expression in Salmonella typhimurium

The presence of Maillard reaction products (MRP) in foods and food components is due to the non-enzymatic reaction between protein and carbohydrate residues triggered by thermal steps during food processing. The objective of this study was to assess the effect of MRPs and increasing lysine concentrations on S. Typhimurium growth and the expression of cadA which may be an indirect determinant of Salmonella virulence response. Variations in lysine concentrations (from 0 to 0.5 mM) did not exert any effect either on the final optical density after 6-hour incubation or the growth rates of S. Typhimurium in media containing MRPs. In contrast to the reduced final absorbancy of the bacterial cultures grown with histidine and arginine MRPs supplementations (0.1%), growth rates, in general, remained unaltered by all MRPs at each lysine concentration when compared to the control (M9 pH 5.8, no MRPs added). The induction levels of cadA in media containing 0.1% MRPs were close to cadA induction in the reference media (M9, pH 5.8 and no MRPs) and did not exceed the corresponding values by more than approximately 30%. Although the observed negligible induction of cadA under these conditions complies with the concept of its potential “anti-virulence” function, additional studies involving various concentrations and more refined MRPs are needed.     

Study of the biodegradation process of polychlorinated biphenyls in liquid medium and soil by a new isolated aerobic bacterium (Janibacter sp.)

We have isolated and characterised a novel aerobic bacterial strain, designated MS3-02, belonging to the genus Janibacter sp. The capability of this new strain to degrade polychlorinated biphenyls (PCBs) in a commercial mixture (Aroclor 1242) in liquid medium and in soil (sterile and non sterile soil), under laboratory scale, has been evaluated. MS3-02 was isolated from the soil around of an incinerator, located in the east of Madrid (Spain). Gas-chromatographic analysis showed that MS3-02 was able to reduce most peaks observed in the chromatogram between 70% and 100% after seven days of incubation in a culture mineral medium containing yeast extract, but without the addition of biphenyl. The presence of biphenyl in the culture medium decreased the rate of PCB degradation by this bacterium. Comparing the performance of the MS3-02 in liquid culture medium and in soil, degradation was less efficient in sterile soil and still less efficient in non sterile soil. Under the best conditions (sterile soil and 20 weeks of incubation) MS3-02 was able to reduce, between 50% and 100%, nine of the main gas-chromatographic peaks in Aroclor 1242.     

Removal of nitrogen and phosphate from wastewater by addition of bittern

Removal of nitrogen and phosphate through crystallization of struvite (MgNH(4)PO(4).6H(2)O) has gained increasing interest. Since wastewaters tend to be low in magnesium relative to ammonia and phosphates, addition of this mineral is usually required to effect the struvite crystallization process. The present study evaluated the feasibility of using bittern, a byproduct of salt manufacture, as a low-cost source of magnesium ions. High reaction rates were observed; the extent of nitrogen and phosphorus removals did not change beyond 10 min. Phosphorus removals from pure solutions with bittern added were equivalent to those obtained with MgCl(2) or seawater. Nitrogen removals with bittern were somewhat lower than with the alternate Mg(2+) sources, however. Application of bittern to biologically treated wastewater from a swine farm achieved high phosphate removal, but ammonia removals were limited by imbalance in the nitrogen:phosphorus ratio.     

Effect of culture conditions on the formation of struvite by Myxococcus xanthus

The amount of struvite (MgNH₄PO₄·6H₂O) produced by Myxococcus xanthus as well as the culture parameter values (pH, total phosphorus, total Kjeldahl nitrogen) were dependent on the culture medium used. Struvite formation started during the exponential phase and the maximum concentration was observed at the beginning of stationary growth phase. The addition of each medium component to the liquid culture influenced the amount of crystal produced. This amount did not depend on the pH increase during the culture period. The moment of the bacterial growth phase, at which each medium component was added, influenced the struvite formation.     

Effects of zinc on the structure and growth dynamics of a natural freshwater phytoplankton assemblage reared in the laboratory

The response of a natural phytoplankton assemblage to different concentrations of Zn(2+) was evaluated by means of a static laboratory bioassay. Aliquots of surface water, taken in autumn from a non-polluted point of the Reconquista River (Buenos Aires, Argentia), were incubated in mineral nutrient media containing 2.5, 10 or 25 mg litre(-1) of Zn(2+) (as zinc chloride). The comparative structure and dynamics of the communities were followed through periodic physico-chemical and biological analyses of samples taken during 24 days of incubation. Under the experimental conditions of the bioassays, the existence of several Zn(2+) tolerant algal species was shown: the most important of them were Chlorella vulgaris Beij. (Chlorophyceae, Chlorococcales), Nitzschia palea (Kütz.) Smith and Gomphonema parvulum (Kütz.) Kütz. (Bacillariophyceae). It was also demonstrated that the algal responses to Zn(2+) were selectively concentration dependent: at 2.5 and 10 mg litre(-1) a stimulatory effect was observed in the diatoms; at 25 mg litre(-1), diatom toxicity occurred. In contrast, Chlorophyceae growth was stimulated at the maximal Zn level. In general, the diversity, richness and equitability of the community were adversely affected by Zn in a concentration-dependent fashion.     

Precipitation of carbonates by Nesterenkonia halobia in liquid media

We investigated the precipitation of carbonates by Nesterenkonia halobia in a liquid medium at different concentrations of salts and incubation times. N. halobia only produced crystals at salt concentrations of 2.5%, 7.5% and 15%. At 20% salt concentration no crystal formation was observed. Calcite, aragonite and dolomite were precipitated in different quantities, depending on the salinity of the medium and incubation time. Scanning and transmission electron microscopy, microanalysis and electron diffraction were all used to study in detail the morphology, composition and internal structure of the bioliths. We propose a mechanism for biolith formation involving both biological and inorganic processes.     

Optimum conditions for microbial carbonate precipitation

The type of bacteria, bacterial cell concentration, initial urea concentration, reaction temperature, the initial Ca(2+) concentration, ionic strength, and the pH of the media are some factors that control the activity of the urease enzyme, and may have a significant impact on microbial carbonate precipitation (MCP). Factorial experiments were designed based on these factors to determine the optimum conditions that take into consideration economic advantage while at the same time giving quality results. Sporosarcina pasteurii strain ATCC 11859 was used at constant temperature (25°C) and ionic strength with varying amounts of urea, Ca(2+), and bacterial cell concentration. The results indicate that the rate of ureolysis (k(urea)) increases with bacterial cell concentration, and the bacterial cell concentration had a greater influence on k(urea) than initial urea concentration. At 25 mM Ca(2+) concentration, increasing bacterial cell concentration from 10(6) to 10(8)cells mL?1 increased the CaCO(3) precipitated and CO(2) sequestrated by over 30%. However, when the Ca(2+) concentration was increased 10-fold to 250 mM Ca(2+), the amount of CaCO(3) precipitated and CO(2) sequestrated increased by over 100% irrespective of initial urea concentration. Consequently, the optimum conditions for MCP under our experimental conditions were 666 mM urea and 250 mM Ca(2+) at 2.3×10? cells mL?1 bacterial cell concentration. However, a greater CaCO(3) deposition is achievable with higher concentrations of urea, Ca(2+), and bacterial cells so long as the respective quantities are within their economic advantage. X-ray Diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray analyzes confirmed that the precipitate formed was CaCO(3) and composed of predominantly calcite crystals with little vaterite crystals.     

Control of ammonia toxicity to Hyalella azteca by sodium, potassium and pH

The toxicity of ammonia to Hyalella azteca at constant pH in artificial media was controlled by sodium and potassium, and not by calcium, magnesium, or anions. Small increases in the LC50 for total ammonia (from 0.15 to 0.5 mM) occurred as sodium was increased from 0.1 to 1 mM and above, but major increases in the LC50 (to over 10 mM total ammonia) required the addition of potassium. Potassium was, however, more effective at reducing ammonia toxicity at high (1 mM) sodium than at low (0.1 mM) sodium. Ammonia toxicity was independent of pH at low sodium and potassium concentrations, when ammonia toxicity appeared to be associated primarily with aqueous ammonium ion concentrations. At high sodium and potassium concentrations, the toxicity of ammonia was reduced to the point where un-ionized ammonia concentrations also affected toxicity, and the LC50 became pH dependent. A mathematical model was produced for predicting ammonia toxicity from sodium and potassium concentrations and pH.     

Illuminating reactive microbial transport in saturated porous media: demonstration of a visualization method and conceptual transport model

We demonstrate a method to study reactive microbial transport in saturated translucent porous media using the bacteria Pseudomonas fluorescens 5RL genetically engineered to carry a plasmid with bioluminescence genes inducible by salicylate. Induced bacteria were injected into a cryolite grain filled chamber saturated with a sterile non-growth-promoting (phosphorus limited) chemical mixture containing salicylate as an aromatic hydrocarbon analogue. The amount of light produced by the bacteria serves as an estimator of the relative efficiency of aerobic biodegradation since bioluminescence is dependent on both salicylate and oxygen but only consumes oxygen. Bioluminescence was captured with a digital camera and analyzed to study the evolving spatial pattern of the bulk oxygen consuming reactions. As fluid flow transported the bacteria through the chamber, bioluminescence was observed to initially increase until an oxygen depletion zone developed behind the advective front. Bacterial transport was modeled with the advection dispersion equation and oxygen concentration was modeled assuming bacterial consumption via Monod kinetics with consideration of additional effects of rate-limited mass transfer from residual gas bubbles. Consistent with previous measurements, bioluminescence was considered proportional to oxygen consumed. Using the observed bioluminescence, model parameters were fit that were consistent with literature values and produced results in good agreement with the experimental data. These findings demonstrate potential for using this method to investigate the complex spatial and temporal dynamics of reactive microbial transport in saturated porous media.     

Interaction between water flow and spatial distribution of microbial growth in a two-dimensional flow field in saturated porous media

Bacterial growth and its interaction with water flow was investigated in a two-dimensional flow field in a saturated porous medium. A flow cell (56 x 44 x 1 cm) was filled with glass beads and operated under a continuous flow of a mineral medium containing nitrate as electron acceptor. A glucose solution was injected through an injection port, simulating a point source contamination. Visible light transmission was used to observe the distribution of the growing biomass and water flow during the experiment. At the end of the experiment (on day 31), porous medium samples were destructively collected and analyzed for abundance of total and active bacterial cells, bacterial cell volume and concentration of polysaccharides and proteins. Microbial growth was observed in two stripes along the length of the flow cell, starting at the glucose injection port, where highest biomass concentrations were obtained. The spatial distribution of biomass indicated that microbial activity was limited by transverse mixing between glucose and nitrate media, as only in the mixing zone between the media high biological activities were achieved. The ability of the biomass to change the flow pattern in the flow cell was observed, indicating that the biomass was locally reducing the hydraulic conductivity of the porous medium. This bioclogging effect became evident when the injection of the glucose solution was turned off and water flow still bypassed the area around the glucose injection port, preserving the flow pattern as it was during the injection of the glucose solution. As flow bypass was possible in this system, the average hydraulic properties of the flow cell were not affected by the produced biomass. Even in the vicinity of the injection port, the total volume of the bacterial cells remained below 0.01% of the pore space and was unlikely to be responsible for the bioclogging. However, the bacteria produced large amounts of extracellular polymeric substances (EPS), which likely caused the observed bioclogging effects.     

Struvite precipitation by the dissolved CO2 degasification technique: impact of the airflow rate and pH

In the present work, struvite precipitation was provoked by the dissolved CO(2) degasification technique where precipitation occurred following the degassing of the CO(2) by atmospheric air. The impact of the airflow rate and initial solution pH on struvite precipitation were assessed. For initial solution pH<6.5, no precipitation was observed. For initial solution pH>6.5, the phosphorus removal through struvite precipitation could be improved by increasing the airflow rate up to 25 L min(-1), or by increasing the initial pH for higher airflow rates. Compared to traditional techniques of struvite precipitation such as stirring and aeration, the dissolved CO(2) degasification technique is promising since a high amount of phosphorus (approximately 78%) could be removed at relatively short experiment time.     

Adsorption and precipitation of tetracycline with struvite.

The interaction of tetracycline with struvite during adsorption and precipitation processes was investigated. Tetracycline removal by adsorption was affected by solution pH, contact time, and struvite concentration. The lowest tetracycline removal (8.4%) was observed at pH 7.7, the dissociation constant (pKa2) of tetracycline. Because of the electrostatic repulsion, the amount of tetracycline adsorbed on the surface was low. The small amount of adsorption was the result of surface complexation between tetracycline ions and metal ions. Calcium (Ca2+) ions in the adsorbent enhanced the binding of tetracycline. Freundlich (KF: 0.04, n: 1.49) and Redlich-Peterson (KR: 0.08, alphaR: 0.98, betaR: 0.49) models best defined the equilibrium data. In the case of struvite precipitation, approximately 22% of tetracycline was removed as a result of binding to struvite alongside struvite formation.     

Comparison of spontaneous antibiotic resistance frequency of Salmonella Typhimurium growth in glucose amended continuous culture at slow and fast dilution rates

The objective of the study was to determine the frequency of spontaneous acquisition of resistance to select antibiotics by Salmonella Typhimurium (ST) when grown in glucose amended continuous flow culture at slow (D = 0.025 h(-1)) or fast (D = 0.27 h(-1)) dilution rates. The bacterium was grown in LB minimal medium (pH 6.25) containing no antibiotics. Upon achieving steady state, samples were plated to tryptic soy agar (TSA) alone or supplemented (per ml) with 2 and 16 microg oxytetracycline, 4 and 16 microg tetracycline, 2 and 64 microg kanamycin, and 0.25 and 2 microg enrofloxacin. Regardless of growth rate, CFU of resistant ST from the TSA containing antibiotics was less than 2 x 10(1) except for 2 microg kanamycin and 0.25 microg enrofloxacin treatments (higher than 1 x 10(9) and 4 x 10(7) CFU of resistant ST for trials 1 and 2, respectively). Frequency of recovering resistant ST from the TSA containing the higher antibiotic concentrations was less than 1 in 10(9) for all antibiotics, but was higher on the media containing 2 microg kanamycin and 0.25 microg enrofloxacin at both slow and fast growth rates. In general, minimal susceptibility differences were detected for isolates from slow and fast dilution rates.     

Phosphate Recovery from Greenhouse Wastewater

A study was conducted to investigate the suitability of phosphate recovery from greenhouse wastewaters by using precipitation/crystallization process. More than 90% of the phosphate could be removed from the greenhouse wastewater. Various calcium phosphate salts were obtained in the process; hydroxyapatite [Ca₅(PO₄)₃OH] could be the main product from the precipitates. Phosphate removal was affected by the presence of magnesium ion in wastewaters. An increase of magnesium concentrations in wastewaters decreased phosphate removal rates. The chemical contents of precipitates in terms of calcium, magnesium and phosphate were affected by calcium to magnesium molar ratio. Higher calcium contents were obtained at wastewaters with high calcium to magnesium molar ratio. An addition of magnesium did not affect the potassium contents in the precipitates. K‐struvite, MgKPO₄·6H₂O, was not the major product in the precipitate, even with addition of a large quantity of magnesium.