Residual Phosphate Research Articles

Effects of N fertilisation, organic matter, and biofertilisers on the growth and yield of chilli in relation to management of plant-parasitic nematodes

An experiment was conducted at the University Agricultural Research Farm to study the effect of inoculation with biological nitrogen fixers on growth and yield of chilli (Capsicum annum L.) cv. "Pusa Jawala" in relation to disease incidence caused by plant-parasitic nematodes. The growth, yield, and quality parameters of chilli increased significantly with the inoculation of biological nitrogen fixers using Azospirillum and Azotobacter. Performance of Azospirillum was found better as compared to Azotobacter. Simultaneous inoculation with biofertilisers (100% recommended dose of N-fertiliser 100 kg N per ha and farmyard manure 15 t per ha) resulted the maximum growth, yield, and quality parameters. Thus, the associative nature of the above biofertilisers helps to save 25% nitrogenous fertiliser in chilli crop. There was increased content in plant nitrogen, phosphate and potash, leaf chlorophyll and residual available soil nitrogen, phosphate and potash with dual inoculation with the biological nitrogen fixers along with recommended full dose of nitrogen fertiliser. Disease intensity was recorded in decreasing order in all the treatments but more pronounced in those where biofertilisers were added.

Study of the Simultaneous Elimination of Phosphates and Heavy Metals Contained In Dairy Wastewater by A Physical-Chemical and Biological Mixed Process; Consequences on the Biodegradability

The study examines the influence of the presence of heavy metals presence on the elimination of phosphates in dairy wastewater. It focuses on the phosphates precipitation in a stoichiometric dose of ferric chloride and is made of two main parts: Without contribution of heavy metals. With contribution of heavy metals (lead and cadmium). In both parts, the removal was carried out at first in a physical-chemical way by the precipitation of phosphates with ferric chloride; the residual phosphates concentrations were then biologically eliminated by activated sludge taken from an urban wastewater treatment plant. For the tests conducted with heavy metals presence, lead and cadmium concentrations between (10 and 100mg/L) were added to the wastewater kept for our study. The main results show: -Good phosphate precipitation with the use of ferric chloride. - The combination of biological and physical-chemical processes is possible since a removal of 69% in presence of Lead (Pb) and 93% in presence of Cadmium (Cd) were obtained. -Maximum removals of 100% lead (for 100mg/L of Pb) and 94% cadmium (for 50mg/L of Cd) were obtained after phosphates precipitation by the ferric chloride. Moreover, in an attempt to assess the performance of the biological treatment by activated sludge combined to the physical-chemical process on the removal of heavy metals in the water to be treated. The evolution of the Cadmium's concentration according to time was followed in both supernatant and sludge. This was made possible by a kinetic study in batch. In this case, the results show: -Cadmium removal from about 81% in the supernatant. -Good retention of cadmium in the sludge. The synthesis of all the results obtained during this study shows that the combination of physical-chemical and biological processes improves the removal of phosphates in the absence and presence of heavy metals.

Thermal degradation behavior of the compound containing phosphaphenanthrene and phosphazene groups and its flame retardant mechanism on epoxy resin

The flame retardant epoxy resin has been prepared by mixing the flame retardant additive hexa-(phosphaphenanthrene-hydroxyl-methyl-phenoxyl)-cyclotriphosphazene (HAP-DOPO) into diglycidyl ether of bisphenol-A (DGEBA). After cured by 4,4′-Diamino-diphenyl sulfone (DDS), the flame retardant properties of thermosets were characterized by the limited oxygen index (LOI), UL-94 test and cone calorimeter. The results show the lower peak of heat release rate (pk-HRR), the higher flammability rating than that of flame retardant epoxy resin by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), hexa-phenoxyl-cyclotriphosphazene (HPCP) and their mixture cloning the ratio of group component of HAP-DOPO. The degradation route of HAP-DOPO was disclosed by thermogravimetric analysis (TGA), the real time Fourier transform infrared spectra (FTIR), thermogravimetric analysis/infrared spectrometry (TGA-FTIR), pyrolysis gas chromatography mass/spectrometry (Py-GC/MS). During combustion, HAP-DOPO continues to release the PO radicals and o-phenylphenoxyl radical during two degradation stages from 200 °C for its unstable trisubstituted methyl structure of HAP-DOPO, inhibits the chain reaction of decomposition and exerts the flame retardant effect in gas phase. The phosphazene groups link with the residual phosphate from degraded phosphaphenanthrene, which increases the crosslink density of residue, effectively promotes the formation of high-strength, high-yield and phosphorus-rich char layer. The structure of HAP-DOPO shows a remarkable flame retardant molecular structure-effect on enhancing the flame retardant efficiency on thermosets.

Fibroblast Growth Factor 23 in Patients Undergoing Peritoneal Dialysis

Fibroblast growth factor 23 (FGF23) is an independent risk factor for mortality in patients with ESRD. Before FGF23 testing can be integrated into clinical practice of ESRD, further understanding of its determinants is needed. In a study of 67 adults undergoing peritoneal dialysis, we tested the hypothesis that longer dialysis vintage and lower residual renal function and renal phosphate clearance are associated with higher FGF23. We also compared the monthly variability of FGF23 versus parathyroid hormone (PTH) and serum phosphate. In unadjusted analyses, FGF23 correlated with serum phosphate (r = 0.66, P < 0.001), residual renal function (r = -0.37, P = 0.002), dialysis vintage (r = 0.31, P = 0.01), and renal phosphate clearance (r = -0.38, P = 0.008). In adjusted analyses, absence of residual renal function and greater dialysis vintage associated with higher FGF23, independent of demographics, laboratory values, peritoneal dialysis modality and adequacy, and treatment with vitamin D analogs and phosphate binders. Urinary and dialysate FGF23 clearances were minimal. In three serial monthly measurements, within-subject variability accounted for only 10% of total FGF23 variability compared with 50% for PTH and 60% for serum phosphate. Increased serum phosphate, loss of residual renal function, longer dialysis vintage, and lower renal phosphate clearance are associated with elevated FGF23 levels in ESRD patients undergoing peritoneal dialysis. FGF23 may be a more stable marker of phosphate metabolism in ESRD than PTH or serum phosphate.

Biotic and Abiotic Pathways of Phosphorus Cycling in Minerals and Sediments: Insights from Oxygen Isotope Ratios in Phosphate

A key question to address in the development of oxygen isotope ratios in phosphate (δ(18)O(p)) as a tracer of biogeochemical cycling of phosphorus in ancient and modern environments is the nature of isotopic signatures associated with uptake and cycling of mineral-bound phosphate by microorganisms. Here, we present experimental results aimed at understanding the biotic and abiotic pathways of P cycling during biological uptake of phosphate sorbed to ferrihydrite and the selective uptake of sedimentary phosphate phases by Escherichia coli and Marinobacter aquaeolei. Results indicate that a significant fraction of ferrihydrite-bound phosphate is biologically available. The fraction of phosphate taken up by E. coli attained an equilibrium isotopic composition in a short time (<50 h) due to efficient O-isotope exchange (between O in PO(4) and O in water; that is, actual breaking and reforming of P-O bonds) (biotic pathway). The difference in isotopic composition between newly equilibrated aqueous and residual sorbed phosphate groups promoted the ion exchange (analogous to isotopic mixing) of intact phosphate ions (abiotic pathway) so that this difference gradually became negligible. In sediment containing different P phases, E. coli extracted loosely sorbed phosphate first, whereas M. aquaeolei preferred Fe-oxide-bound phosphate. The presence of bacteria always imprinted a biotic isotopic signature on the P phase that was taken up and cycled. For example, the δ(18)O(p) value of loosely sorbed phosphate shifted gradually toward equilibrium isotopic composition. The δ(18)O(p) value of Fe-oxide-bound phosphate, however, showed only slight changes initially but, when new Fe-oxides were formed, coprecipitated/occluded phosphate retained δ(18)O values of the aqueous phosphate at the time of formation of new Fe oxides. Concentrations and isotopic compositions of authigenic and detrital phosphates did not change, suggesting that these phosphate phases were not utilized by bacteria. These findings support burgeoning applications of δ(18)O(p) as a tracer of phosphorus cycling in sediments, soils, and aquatic environments and as an indicator of paleo- environmental conditions.

PHOSPHATE REMOVAL FROM WATER AND RECOVERY USING IRON (Fe+3)OXIDE/HYDROXIDE NANOPARTICLES-BASED AGGLOMERATES SUSPENSION (AggFe) AS ADSORBENT

An iron(Fe+3) oxide/hydroxide nanoparticles-based agglomerates (AggFe) suspension adsorbent was synthesized for efficient, cost-effective phosphate removal. A strong effect of AggFe concentration and pH level of water containing phosphate on removal efficiency was shown. It was found that phosphate adsorption onto the AggFe suspension may be described by pseudo-secondorder reaction kinetics and the Langmuir isotherm model. The unique adsorption properties of synthesized AggFe adsorbent are demonstrated. This technique achieved a residual phosphate concentration of less than 0.05ppm as PO4 (<20 ppb as P), which is acceptable by water quality regulations, and at least 95-99% regeneration efficiency of the phosphate with the proposed adsorbent. The phosphate adsorption capacity on the AggFe at an equilibrium concentration of 0.1ppm as P in the solution is about 1.5-1.9 times higher than these values for granulated ferric hydroxide (fraction <63 m) and more than one order of magnitude higher than other values reported in the literature. This technique enables recovery of the adsorbent while producing a concentrated phosphate solution that may be treated further to obtain phosphate crystals while recovering the cleaning solution.

Threshold of Soil Olsen-P in Greenhouses for Tomatoes and Cucumbers

Phosphorus (P) accumulation is a common phenomenon in greenhouse soil for vegetables. Excessive P accumulation in soil usually decreases the yield and quality of vegetables as well as potentially polluting water environments. Ninety-eight tomato and 48 cucumber greenhouses were investigated in the eight main vegetable production areas of Hebei Province, China. Soil Olsen-P, the electrical conductivity (EC), the pH value, the organic matter of the soil, and the cropping years of these greenhouses were investigated and analyzed in order to better understand the status of soil P accumulation and positively find effective ways to solve the excessive phosphate accumulation problem. The investigation showed that the ratio was above 70% for all of the greenhouses where the soil Olsen-P exceeded 90 mg·kg−1 (upper bound of soil Olsen-P optimum value in greenhouse) in the 0–20 cm surface soil in the investigated greenhouses. There was a significant positive correlation between the soil Olsen-P content and the soil EC, between the soil Olsen-P and the cropping years, and the Olsen-P had a significant negative correlation with the soil pH value. It is concluded that supplying phosphate fertilizer excessively induced the soil EC to ascend and the pH value to descend, which increases the possibility of the soil secondary salinization and soil degeneration. The significant positive correlation between the soil organic content and the soil Olsen-P contents suggests that supplying organic fertilizer might mobilize soil residual phosphate. This also provides a good way to solve the problem of soil P accumulation. In order to further explore the threshold content of soil Olsen-P demanded by tomato and cucumber under the high soil Olsen-P condition, two tomato greenhouses (T1, T2) in Dingzhou and two cucumber greenhouses (C1, C2) in Wuqiang were researched. All of the greenhouses had ranges of soil Olsen-P content that were between 150 and 300 mg·kg−1, which far exceeded the 90 mg·kg−1 ideal. The P fertilizer application rates showed positive correlations with the soil Olsen-P contents and EC values in cucumber and tomato greenhouses in the current season. Analyzing T1 and T2 results showed that tomato was sensitive to the high soil Olsen-P contents ranging from 230.64 to 729.42 mg kg−1 at the seedling stage (15 days after transplanting; DAT) and from 199.41 to 531.42 mg kg−1 at the fruiting stage (90 DAT), because the yields correlated negatively with soil Olsen-P contents at each growth stage. It is suggested that the maximum soil Olsen-P threshold content for tomato should be lower than 230 mg·kg−1 at the seedling stage and lower than 199 mg·kg−1 at the fruiting stage. But cucumber yield did not change significantly as soil Olsen-P content rose from 248.75 to 927.62 mg kg−1, 212.40 to 554.07 mg kg−1, 184.48 to 455.90 mg kg−1, and 128.42 to 400.96 mg kg−1 at the seedling stage (15 DAT), early fruiting stage (50 DAT), middle fruiting stage (140 DAT), and late fruiting stage (235 DAT), respectively, suggesting that the maximal soil Olsen-P threshold content was lower than 249, 212, 185, and 128 mg·kg−1 at each growth stage, respectively. The relationship between fruit qualities and soil Olsen-P contents at each growth stage was not evident. Activities of soil alkaline phosphatase (ALP) decreased as soil Olsen-P supply was raised in T1, T2, and C1 at the seedling stage. It is concluded that in an excess soil Olsen-P condition tomato yield decreases strongly as soil ALP activity decreases, whereas ALP activity has little direct effect on cucumber yield.

Examining Coagulation and Precoating for Seawater UF/RO System Pretreatment

Ultrafiltration (UF) is gradually becoming the technology of choice for seawater reverse osmosis (RO) pretreatment because of its ability to provide consistent, high-quality RO feed and its small footprint, among other advantages. However, because of the complexity and cost of coagulation sludge handling and disposal, coagulation as a UF pretreatment is a concern for most plant operators. Although efforts are being made to reduce or eliminate coagulation prior to UF, potential benefits may be overlooked. This study focused on the effect of coagulation conditions and modes of application on UF performance as it relates to hydraulic operation and product water quality. Coagulation was performed in two modes—inline coagulation and precoating. Filtration was performed in unstirred cells through membranes in dead-end constant pressure. UF hydraulic performance was evaluated, and UF permeate quality was characterized in terms of residual phosphate. Although precoating improved hydraulic performance, results showed that permeate quality was better when inline coagulation was applied. Furthermore, hydraulic performance for inline coagulation improved considerably when flocculation time was increased. Maximum phosphate removal was achieved in inline coagulation when pH was 6 and flocculation time was 45 min.

Relationship between Olsen P and Ammonium Lactate–Extractable P in Portuguese Acid Soils

The soil phosphorus (P) test in Portugal is based on extraction with ammonium lactate (AL) at acidic pH. Because this test is rarely used in other countries, it is desirable to see whether the AL-P values correlate with the more commonly used P tests. In this work, we compared AL-P with bicarbonate-extractable P (Olsen's method) for a group of 48 samples from Portuguese acidic soils differing widely in P status. Despite their contrasting composition, both reagents extracted phosphate from the same sources, albeit in different proportions. Both Olsen P and AL-P were strongly correlated with resin-extractable and dilute electrolyte-desorbable P, which are respectively related to the soil contents in phytoavailable P and P that can be released to runoff or drainage water. Olsen P and AL-P were strongly correlated (R2 = 0.870), the correlation became stronger when three overfertilized soils were excluded (Olsen P = 2.35 + 0.45 AL-P; R2 = 0.908; P ≤ 0.001, n = 45). No correlation was observed for a group of soils recently fertilized with Gafsa phosphate probably because the acidic AL reagent dissolved residual calcium phosphate, thus overestimating the soil content in desorbable P. On the basis of the present results and the AL-P-based fertility classes used for fertilizer recommendation purposes, Olsen P–based fertility classes were tentatively proposed for Portuguese acidic soils.

Effect of sodium hexametaphosphate concentration and cooking time on the physicochemical properties of pasteurized process cheese

Sodium hexametaphosphate (SHMP) is commonly used as an emulsifying salt (ES) in process cheese, although rarely as the sole ES. It appears that no published studies exist on the effect of SHMP concentration on the properties of process cheese when pH is kept constant; pH is well known to affect process cheese functionality. The detailed interactions between the added phosphate, casein (CN), and indigenous Ca phosphate are poorly understood. We studied the effect of the concentration of SHMP (0.25–2.75%) and holding time (0–20min) on the textural and rheological properties of pasteurized process Cheddar cheese using a central composite rotatable design. All cheeses were adjusted to pH 5.6. The meltability of process cheese (as indicated by the decrease in loss tangent parameter from small amplitude oscillatory rheology, degree of flow, and melt area from the Schreiber test) decreased with an increase in the concentration of SHMP. Holding time also led to a slight reduction in meltability. Hardness of process cheese increased as the concentration of SHMP increased. Acid-base titration curves indicated that the buffering peak at pH 4.8, which is attributable to residual colloidal Ca phosphate, was shifted to lower pH values with increasing concentration of SHMP. The insoluble Ca and total and insoluble P contents increased as concentration of SHMP increased. The proportion of insoluble P as a percentage of total (indigenous and added) P decreased with an increase in ES concentration because of some of the (added) SHMP formed soluble salts. The results of this study suggest that SHMP chelated the residual colloidal Ca phosphate content and dispersed CN; the newly formed Ca-phosphate complex remained trapped within the process cheese matrix, probably by cross-linking CN. Increasing the concentration of SHMP helped to improve fat emulsification and CN dispersion during cooking, both of which probably helped to reinforce the structure of process cheese.

Differences in the Soluble, Residual Phosphate Concentrations at Which Coastal Phytoplankton Species Up-regulate Alkaline-Phosphatase Expression, as Measured By Flow-Cytometric Detection of ELF-97® Fluorescence

The enzyme-labeled fluorescence (ELF-97®) substrate produces an insoluble, fluorescent yellow-green product at the site of alkaline-phosphatase (AP) activity. Fifteen coastal phytoplankton species were tested to determine if AP activity could be detected in phosphate- depleted media. All species tested, except Synechococcus bacillaris, expressed AP activity. Subsequently, threshold concentrations of soluble reactive phosphate (SRP) at which AP activity could be detected by ELF-97® were deter- mined for Chaetoceros neogracile, Chlorella autotrophica, Isochrysis sp., Prorocentrum minimum ,a ndTetraselmis chui. Microalgal species differed significantly in the SRP con- centration at which AP activity was first detectable (10.1- 16.4 µM), well above concentrations normally considered limiting for phytoplankton. P. minimum began to express AP activity at a higher SRP concentration than the other algal species; this may be attributable to a relatively high DNA/cell ratio in P. minimum, compared to the other phytoplankton. Thus, phytoplankton species may respond to phosphorus deficiency at high SRP concentrations.

Precipitation flotation of phosphate from water

The removal of phosphate from water by precipitation flotation was examined. Calcium chloride (CaCl 2) was added to induce precipitates. Effects of both molar ratio ([Ca 2+]:[HPO 4 2−]) and pH on precipitation were examined, and experimental results were compared with those from equilibrium modeling by PHREEQC. Molar ratio and pH were the key parameters in determining the residual phosphate concentration, and monetite (CaHPO 4), hydroxyapatite (Ca 5(PO 4) 3OH), and amorphous calcium phosphate precipitates (Ca 3(PO 4) 2· xH 2O) were found to be the dominant solid species. Dispersed air flotation was utilized for the removal of precipitates from water using various collectors. Anionic collector, sodium dodecyl sulfate (SDS) and sodium oleate (NaOl) could become adsorbed onto solid surfaces and facilitated the flotation removal of calcium phosphate precipitates. Neither nonionic collector Brij 35 nor cationic cetyltrimethyl ammonium bromide (CTAB) were effective collector. The ionic strength and the presence of anions affected the removal efficiency of calcium phosphate precipitate when SDS was the collector. However, it increased by increasing the concentration of SDS or by adding SOl.

Optimizing the phosphate level of soils in agroecosystems of opolie regions of Central Russia

The regularities of the effectiveness of systematic application of phosphorus fertilzer in various types of crop rotations have been studied in long-term permanent field experiments on gray forest soils of opolie regions of Central Russia. The main factors determining the degree of use by crops of freshly applied and residual phosphates—the level of phosphorus fertilizer in agroecosystems, nitrogen supply of crops, and characteristics of phosphorus nutrition of the crops being grown—have been established. Depending on the character of interaction of these factors, crops over the course of 9 to 23 years have utilized 12–88% of applied fertilizer.

Strategies to optimize phosphate removal from industrial anaerobic effluents by magnesium ammonium phosphate (MAP) production

AbstractBACKGROUND: Owing to more stringent phosphate discharge requirements and the increasing prices of fertilizers, beneficial recovery and reuse of phosphate from industrial anaerobic effluents is becoming an important issue. Phosphate recovery by struvite or magnesium ammonium phosphate (MAP) permits its recycling in the fertilizer industry because struvite is a valuable slow release fertilizer. Two different approaches to MAP crystallization depending on initial levels of phosphate in the wastewaters were tested and compared.RESULTS: For low‐phosphate‐containing anaerobic effluents (&lt;30 mg PO43−‐P L−1), a novel approach using ureolytic induced MAP formation with MgO addition appeared to be suitable. The residual phosphate concentrations in the effluent ranged from 5 to 7 mg PO43−‐P L−1 and the separated matter contained residual amounts of Mg(OH)2. High‐phosphate‐containing anaerobic effluents (100 to 120 mg PO43−‐P L−1) were treated efficiently using air stripping combined with MgCl2 and NaOH reagents, yielding residual phosphate levels of 8 to 15 mg PO43−‐P L−1 and spherical pure MAP crystals of 0.5 to 2 mm.CONCLUSION: Results show that depending on the initial phosphate concentrations in the wastewaters and the ammonium and magnesium levels, the strategy selected for struvite crystallization is a determinative factor in achieving a cost effective technology. Copyright © 2008 Society of Chemical Industry

Effects of Salinity on Physicochemical Properties of Alaska Pollock Surimi after Repeated Freeze–Thaw Cycles

The effects of residual salt in surimi on physicochemical properties as affected by various freeze and thaw (FT) cycles were examined. Fresh Alaska pollock surimi was mixed with 4.0% sugar and 5.0% sorbitol, along with 8 combinations of salt (0.4%, 0.6%, 0.8%, and 1.0% NaCl) and sodium polyphosphate (0.25% and 0.5%), vacuum-packed, and stored at -18 degrees C until used. FT cycles (0, 6, and 9) were used to mimic long-term frozen storage. At the time of gel preparation, each treatment was appropriately adjusted to maintain 2% salt and 78% moisture. The pH decreased as residual salt increased during frozen storage. Salt extractable protein (SEP) decreased (P < 0.05) as FT cycles extended from 0 to 9. Regardless of residual salt and phosphate concentration during frozen storage, whiteness value (L*- 3b*) decreased (P < 0.05) as FT cycles extended, except for samples with 0.4% salt/0.5% phosphate and 0.6% salt/0.25% phosphate. Water retention ability (WRA) and texture significantly (P < 0.05) decreased at higher salt content (0.8% and 1.0%) after 9 FT cycles, indicating higher residual salt concentration can shorten the shelf life of frozen surimi. Our study revealed lower residual salt concentration and higher phosphate concentration are likely to extend the shelf life of frozen surimi.

Significance of Design and Operational Variables in Chemical Phosphorus Removal

Batch and continuous experiments using model and real wastewaters were conducted to investigate the effect of metal salt (ferric and alum) addition in wastewater treatment and the corresponding phosphate removal from a design and operational perspective. Key factors expected to influence the phosphorus removal efficiency, such as pH, alkalinity, metal dose, metal type, initial and residual phosphate concentration, mixing, reaction time, age of flocs, and organic content of wastewater, were investigated. The lowest achievable concentration of orthophosphate under optimal conditions (0.01 to 0.05 mg/L) was similar for both aluminum and iron salts, with a broad optimum pH range of 5.0 to 7.0. Thus, in the typical operating range of wastewater treatment plants, pH is not a sensitive indicator of phosphorus removal efficiency. The most significant effect for engineering practice, apart from the metal dose, is that of mixing intensity and slow kinetic removal of phosphorus in contact with the chemical sludge formed. Experiments show that significant savings in chemical cost could be achieved by vigorously mixing the added chemical at the point of dosage and, if conditions allow, providing a longer contact time between the metal hydroxide flocs and the phosphate content of the wastewater. These conditions promoted the achievement of less than 0.1 mg/L residual orthophosphate content, even at lower metal-to-phosphorus molar ratios. These observations are consistent with the surface complexation model presented in a companion paper (Smith et al., 2008).

Mobilization of phosphorus from iron ore by the bacterium Burkholderia caribensis FeGL03

The bacterium Burkholderia caribensis FeGL03, isolated from a Brazilian high-phosphorus iron ore, was used to mobilize the phosphate contained in the same ore. The phosphate-mobilizing ability of the organism was tested in shake-flask cultures containing sterilized crushed iron ore in a chemically-defined liquid culture medium containing glucose (1 g/l) as carbon source and no phosphorus source except the ore itself. Phosphate removal from the ore was determined by measuring the residual phosphate contained in the ore after the bacterial treatment. The time course of the phosphate mobilization process was determined with two different particle sizes (2.0 mm and 0.2 mm mean size) of the crushed ore under conditions of unlimited and limited air exchange. Between 5% and 20% of the phosphorus originally contained in the ore was mobilized in 21 days of treatment. Other variables such as dissolved Fe, pH and cell counts were also monitored throughout the trials. It was also found that this bacterium accumulated gluconic acid in the spent broth. Scanning electron microscopy, revealed biofilms on the ore surface as a result of the production of exopolymeric substances (EPS). Extraction of the EPS from the cultures and its analysis by Fourier transform infrared techniques revealed the presence of molecular functionalities capable of interacting with the ore surface and with the iron dissolved in the medium. It was found that dense biofilms, formed under limited air exchange, resulted in lower phosphate mobilization from the ore than under unlimited air exchange. This was found to be a consequence of a dynamic process of iron and phosphate re-precipitation within the formed biofilms.

Histologic Analysis of Allograft Mixed With Hydroxyapatite-Tricalcium Phosphate Used in Revision Femoral Impaction Bone Grafting

Failed total hip arthroplasty (THA) often is accompanied by loss of bone stock. In cases in which revision THA becomes necessary, adequate stabilization of the implant can be difficult because of the bone loss. Bone can be reconstructed by using tightly packed morselized cancellous bone graft in combination with a cemented stem. However, worldwide availability of human bone is limited, and risks such as infection and antigenicity are associated with the use of allogeneic bone. These risks have led to the development of synthetic bone graft extenders. The objective of impaction bone grafting is to achieve stability of an implant and subsequently allow the restoration of living bone stock. To reduce the amount of allograft consumed, a mixture of morselized allograft and hydroxyapatite-tricalcium phosphate was used for impaction grafting in a series of 15 patients. In 2 patients who required re-revision arthroplasty, the areas of impacted graft were analyzed histologically. The results showed a complex mixture of residual hydroxyapatite-tricalcium phosphate, necrotic bone (graft), viable bone, and fibrous tissue. Although several pre-clinical studies have described the expansion of allograft with synthetic materials, this article represents the first description of histologic findings in human femoral impaction grafting with a combination of allograft and hydroxyapatite-tricalcium phosphate.

Biological phosphate removal by model based fed-batch cultivation of Acinetobacter calcoaceticus

A simpler phosphate removal process has been proposed involving only aerobic cultivation of Acinetobacter calcoaceticus in a fed-batch mode of treatment. Batch cultivation of A. calcoaceticus was conducted under statistically optimized culture conditions in order to study the kinetics of growth and phosphate uptake. Studies with respect to carbon, nitrogen and phosphate were performed to quantify their inhibitory effect on specific growth rate (if any). Using kinetics/inhibition data, a mathematical model was proposed. The batch model was extrapolated for fed-batch cultivation by incorporating the dilution terms in the model equations so as to predict, suitable nutrient feeding strategy for better phosphate removal. According to the developed feed-strategy, the bioreactor was operated in batch mode for 4 h, after which model based predetermined fresh nutrient feeding (sodium acetate 5.0 g/l) at 2.25 ml/min was started. Model predictions indicated that after 7 h of cultivation process phosphate would be totally consumed. Upon implementation of this model based fed-batch cultivation strategy a biomass accumulation of 4.02 g/l was obtained experimentally against 3.88 g/l concentration predicted by model after 7 h with a residual phosphate concentration of 0.01 g/l. An improvement to 94% phosphate removal efficiency (initial loading 0.175 g/l) in only 7 h was observed in fed-batch cultivation as opposed to 78% (initial loading 0.175 g/l) in 11 h for batch cultivation.

Anaerobic membrane bioreactor treatment of domestic wastewater in Tunisia

An anaerobic cross-flow ultrafiltration membrane bioreactor was investigated for municipal wastewater treatment at 37°C. The removal of the total suspended solid, the soluble chemical oxygen demand and the biochemical oxygen demand were respectively 100%, 90% and 88%. Less than 85 mg l −1 of soluble chemical oxygen demand in the effluent was obtained by ranging the organic loading rate from 0.23 to 2 g COD l −1 d −1. The biomass accumulated in the reactor reached 4.3 to 4.9 g l −1 in terms of MLVSS in the last month of the treatment. The biogas production increased with the increase of the loading rate to reach an average of 28 l after 140 days. The average content of the biogas in methane was practically constant at 70%. The treated wastewater could be considered non phytotoxic since the germination index of Lepidium sativum ranged between 60 and 87%. The quality of the treated wastewater fits largely with Tunisian norm NT 106.03 and World Health Organization Guidelines for the microbiological quality of treated wastewater used in agriculture. However, this treated wastewater should undergo further processes to reduce its contents in residual nitrogen and phosphate and thus to conform with the Tunisian standards NT 106.02, a requirement for acceptance in hydraulic public domain.