Initial Phosphate Concentration Research Articles

Simultaneous sequestration of nitrate and phosphate from wastewater using a tailor‐made bacterial consortium in biofilm bioreactor

AbstractBACKGROUNDMunicipal wastewater usually contains nitrate and phosphate as major contaminants, and if discharged untreated affects the health of the environment and human population. Currently available treatment technologies to treat municipal wastewater lose the essential growth nutrients ‘P’ and ‘N’ during treatment. This paper presents a strategy of simultaneous sequestration of nitrate and phosphate in biomass, by using a tailor‐made consortium in a biofilm reactor.RESULTSThe consortium comprising of three novel Bacillus strains in a fixed bed biofilm bioreactor maintained at ambient temperature showed reduction up to 94% of nitrate, 68% of phosphate, 93% of chemical oxygen demand, 97% of biochemical oxygen demand, 73% in total organic carbon while maintaining an effluent pH of 6.8 ± 0.02. Response surface methodology revealed maximum reduction at a flow rate of 1.97 L h‐1 with 306.04 mg L‐1 and 19.62 mg L‐1 of initial nitrate and phosphate concentrations respectively. The system was scaled up from 4.5 L to 220 L with the same retention time of 2 h and operated with consistent performance for over 212 days.CONCLUSIONThe treated wastewater met the criterion for reuse as non‐potable water for applications like irrigation and aquaculture, hence making it the fastest microbial process for simultaneous nitrate and phosphate removal from wastewater. © 2017 Society of Chemical Industry

Preparation and testing of a tetra-amine copper(II) chitosan bead system for enhanced phosphate remediation

A tetra-amine copper(II) chitosan bead system (TAC@CS composite beads) was developed by grafting tetra-amine copper(II) (TAC) with chitosan (CS) and utilized for phosphate removal. The prepared TAC@CS composite beads possess enhanced phosphate sorption capacity (SC) of 41.42 ± 0.071 mg/g than copper grafted chitosan (Cu@CS) composite, TAC and chitosan which were found to be 37.01 ± 0.803, 33.20 ± 0.650 and 7.24 ± 0.059 mg/g respectively. In batch mode, various adsorption influencing parameters like contact time, initial phosphate concentration, solution pH, co-anions and temperature were optimized for maximum phosphate sorption. The prepared adsorbents were characterized by FTIR, XRD, UV–Visible, SEM and EDAX analysis. The adsorption isotherms and thermodynamic parameters of the adsorbent were studied. The feasible phosphate uptake mechanism of TAC@CS biocomposite beads was reported. The reusability studies of TAC@CS composite beads were carried out using NaOH as elutant. The suitability of TAC@CS composite beads at field conditions was tested with phosphate contaminated field water samples collected from nearby areas of Dindigul district.

A facile synthesis of magnetic particles sprayed gelatin embedded hydrotalcite composite for effective phosphate sorption

The magnetic composite possess added advantages like high sorption capacity (SC), selectivity and quick separation. The eco-friendly, gelatin (Gel) encapsulated hydrotalcite (HT) GelHT composite was synthesized by dispersing HT in Gel polymeric matrix for phosphate removal. The magnetic biocomposite was synthesized by impregnating iron oxide (Fe3O4) on GelHT composite namely Fe3O4@GelHT composite for phosphate remediation. The developed Fe3O4@GelHT composite hold enhanced phosphate SC of 32.73mg/g whereas phosphate SCs of GelHT composite, Fe3O4@HT composite, HT and Fe3O4 were found to be 25.91, 18.35, 15.37 and 5.15mg/g respectively. The adsorption influencing parameters include contact time, adsorbent dosage, initial phosphate concentration, solution pH, co-existing anions and temperature were optimized in batch mode. The synthesized adsorbents were characterized using FTIR, PXRD, BET, SEM and EDAX with mapping analysis. The feasible phosphate uptake mechanism of magnetic biocomposite was reported. The adsorption equilibrium data were adapted to various suitable isotherm models. Thermodynamic parameters indicate the spontaneous and endothermic of phosphate adsorption. The aptness of the biocomposites at field conditions was examined with collected field water. The reuse of synthesized Fe3O4@GelHT composite was carried out using NaOH solution and it can be reused upto 4 cycles.

Lanthanum oxide nanorods for enhanced phosphate removal from sewage: A response surface methodology study

Lanthanum-based adsorbents are ideal candidates for phosphate removal because of their excellent affinity to phosphate. However, their application in the removal of trace-levels of phosphate from sewage is still unsatisfactory due to the limited adsorption capacity and inadequate optimization of the operational parameters. To overcome these drawbacks, we have developed a novel lanthanum hydroxide (LH), using a facile precipitation and hydrothermal process that involves a nanorod-like structure with the lengths ranging from 124 to 1700 nm, depending on the La/OH molar ratio. The phosphate adsorption capacity of the developed LH is up to 170.1 mg-P g−1 in synthetic water, while a slightly lower adsorption capacity of 111.1 mg-P g−1 is observed in a sewage sample. A polynominal model consisting of three variables (i.e. dosage, reaction time and initial phosphate concentration) for predicting efficiency of phosphate removal has been successfully developed using a face-centred central composite design (CCD)-based methodology. The results also suggest a strong interactive effect of the dosage with the phosphate concentration, and reaction time, which can significantly affect the optimization of the phosphate removal by LH. Both X-ray photoelectron spectroscopy and X-ray diffraction studies indicate that the inner sphere complexation of phosphate with LH is probably the major mechanism governing phosphate removal.

Calcium phosphates recovery from digester supernatant by fast precipitation and recrystallization

Conditional solubility of dicalcium phosphate dihydrate (DCPD) and hydroxyapatite (HAp) in digester supernatant was determined as a function of pH and was compared to its conditional solubility in distilled water. Conditional solubility of both substances in digester supernatant at pH >5–6 was higher than their conditional solubility in pure water due to the presence of impurities, and this influence is more significant for HAp. Amorphous CaP was precipitated through a fast precipitation process from digester supernatant with initial total phosphate concentration 0.008 mol/L and 0.015 mol/L and Ca/P ratios 2 and 5. The amorphous CaP can be subsequently recrystallized into crystalline CaP. Obtained amorphous products have Ca/P ratio > 1, which allow performing the recrystallization process without further Ca dosing into the system. Batch recrystallization of the amorphous products resulted in crystallization of HAp, DCPD or their mixture depending on the conditions of the process. Maximum achieved P-recovery was 69.5%. The increase of phosphate concentration and the addition of seeding decreased the yield of the process but promoted crystallization of DCPD. The increase of Ca/P ratio had a positive effect on the total P-recovery. Compared with the direct batch crystallization of CaP from digester supernatant, the two-step process with fast precipitation and recrystallization significantly improved the color of the obtained products.

Phosphorus sorption to suspended sediment in freshwater

The effect of flow transport on phosphorus sorption to suspended sediment was investigated by combining field experiments with indoor experiments. The phosphorus distribution was found to be spatially variable and the phosphorus concentration gradient between pore water and overlying water decreased with sediment resuspension in the Huaihe River. Indoor experiments were conducted in a batch reactor and an elongated flume. Flow transport accelerated phosphorus sorption onto suspended sediment and the time to reach quasi-equilibrium decreased with an increase in flow velocity in dynamic water. Both phosphorus sorption amount and sorption rate were affected by the flow velocity, the initial phosphate concentration and suspended sediment concentration. The influence of flow velocity on phosphorus sorption amount was found to be controlled by the variance of the initial phosphate concentration. When compared with other isothermal adsorption models, the Langmuir equation provided the best description of the phosphorus sorption performance of the hydrodynamic experiments. Adsorption and desorption were not exactly equal, and the phosphorus sorption amount fluctuated with time in a quasi-equilibrium state in the flume experiments.

Removal of phosphates from aqueous solution by sepiolite-nano zero valent iron composite optimization with response surface methodology

In this study, sepiolite-nano zero valent iron composite was synthesized and applied for its potential adsorption to remove phosphates from aqueous solution. This composite was characterized by different techniques. For optimization of independent parameters (pH = 3–9; initial phosphate concentration = 5–100 mg/L; adsorbent dosage = 0.2–1 g/L; and contact time = 5–100 min), response surface methodology based on central composite design was used. Adsorption isotherms and kinetic models were done under optimum conditions. The results indicated that maximum adsorption efficiency of 99.43 and 92% for synthetic solution and real surface water sample, respectively, were achieved at optimum conditions of pH 4.5, initial phosphate concentration of 25 mg/L, adsorbent dosage of 0.8 g/L, and 46.26 min contact time. The interaction between adsorbent and adsorbate is better described with the Freundlich isotherm (R 2 = 0.9537), and the kinetic of adsorption process followed pseudo-second-order model. Electrostatic interaction was the major mechanisms of the removal of phosphates from aqueous solution. The findings of this study showed that there is an effective adsorbent for removal of phosphates from aqueous solutions.

Synthesis of novel magnesium ferrite (MgFe2O4)/biochar magnetic composites and its adsorption behavior for phosphate in aqueous solutions

In this work, magnesium ferrite (MgFe2O4)/biochar magnetic composites (MFB-MCs) were prepared and utilized to remove phosphate from aqueous solutions. MFB-MCs were synthesized via co-precipitation of Fe and Mg ions onto a precursor, followed by pyrolysis. Characterization results confirmed that MgFe2O4 nanoparticles with a cubic spinel structure were successfully embedded in the biochar matrix, and this offered magnetic separability with superparamagnetic behavior and enabled higher phosphate adsorption performance than that of pristine biochar and sole MgFe2O4 nanoparticles. Batch experiments indicated that phosphate adsorption on the MFB-MCs is highly dependent on the pH, initial phosphate concentration, and temperature, while it was less affected by ionic strength. Analysis of activation and thermodynamic parameters as well as the isosteric heat of adsorption demonstrated that the phosphate adsorption is an endothermic and physisorption process. Lastly, highly efficient recyclability of the MFB-MCs suggested that they are a promising adsorbent for phosphate removal from wastewater.

Adsorptive Removal of Phosphate from Groundwater Using Granular Activated Carbon

The objective of this work is to study the phosphate adsorption from natural waters by using a granular activated carbon (GAC). Experiments were carried out with synthetic solutions of phosphate prepared using groundwater (mineralized drinking water). Batch tests were carried out in order to study different operating parameters such as the effect of contact time, pH, initial phosphate concentration and adsorbent dosage. In addition, the adsorption kinetic data were simulated using the pseudo first order, the pseudo second-order and the intra-particle diffusion model. The sorption equilibrium was analyzed by Langmuir, Freundlich and Dubinin–Radushkevich isotherms model. Results show that the phosphate adsorption was reversible and the quantity adsorbed reached its maximum value (2.82 mg/g) after 30 min. It was also found that phosphate uptake was affected by variation of pH, initial concentration of phosphate and granular activated carbon dosage. The adsorption improved with increase in pH values, initial concentration and adsorbent dosage. The results of kinetic studies revealed that pseudo-second-order model adequately described the adsorption phosphate on GAC and the intra-particle diffusion involved in the adsorption mechanism. Also, isotherm study showed that Langmuir isotherm best fit the data and the adsorption was a physical type.

Aminopropyl-functionalized mesoporous carbon (APTMS-CMK-3) as effective phosphate adsorbent

Abstract Excess phosphate discharge into water bodies can lead to severe eutrophication. Adsorption has been considered as one of the most effective approaches for phosphate removal and recovery. A new aminopropyl-functionalized mesoporous carbon CMK-3 (denoted as APTMS-CMK-3) was prepared and the materials were used as adsorbents for the removal of phosphate in water. The structure, functional groups and surface charge of the materials were characterized by X-ray powder diffraction, transmission electron microscope, N2 adsorption-desorption, elemental analysis, Fourier transform infrared spectra, X-ray photoelectron spectroscopy and zeta potential measurements. The effects of contact time, initial phosphate concentration, solution pH, coexisting anions and dissolved humic acid were studied. The adsorption capacity of APTMS-CMK-3 was 38.09 mg g−1 at the equilibrium concentration of 49.06 mg L−1, and the adsorption data were well fitted with the Freundlich model. As for the reuse of APTMS-CMK-3, a relatively stable adsorption performance was observed after five adsorption-desorption cycles. Therefore, the way of grafting aminopropyl groups on the CMK-3 efficiently enhanced the capability for phosphate adsorption, indicating that it could be used as potential adsorbents for the removal of phosphate in water.

Triethylene Tetramine Functionalized Magnetic Graphene Oxide Chitosan Composite with Superior Capacity for the Removal of Phosphate

A novel triethylene tetramine-functionalized magnetic graphene oxide chitosan composite material (TETA-MGO/CS) with a high adsorption capacity for the phosphate was prepared by chemical coprecipitation and subsequently modified by triethylene tetramine. TETA-MGO/CS was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction, thermogravimetry, and Brunauer–Emmett–Teller analyses. The adsorption experiments of phosphate on TETA-MGO/CS were compared with MGO, MGO/CS, and TETA-MGO. Effects of pH, initial concentration of phosphate, adsorption time, and adsorption temperature were studied. The results indicated that the adsorption capacity of the four adsorbents were highly pH dependent and reached optimum at pH 3.0. Adsorption processes reached the equilibrium within 50 min. The adsorption data of the four adsorbents were well-fitted with the Langmuir isotherm. The maximum adsorption capacities of MGO, MGO/CS, TETA-MGO, and T...

Removal and recovery of phosphate from water by a magnetic Fe3O4@ASC adsorbent

The removal and recovery of phosphate from water by Fe3O4@alkali-treated calcium-silicate composite (Fe3O4@ASC) was investigated. The adsorbent was characterized by XRF, BET, XRD and zeta-potential analyses. The characterization results showed the successful synthesis of Fe3O4@ASC with a high specific surface area (129m2/g). In batch experiments, the kinetic data and isotherm data fitted well to the pseudo-second-order model and Langmuir model, respectively, and the maximum adsorption capacity calculated by Langmuir model was 128mg/g. The phosphate adsorption of Fe3O4@ASC performed well over a wide pH range from 2.5 to 13 and exhibited a good selective property even with 10 times higher molar concentration of other anions. Fe3O4@ASC could remove nearly 100% phosphate from real lake solution with phosphate concentration of 10mg/L at the dosage of 0.25g/L. In the column experiment, the breakthrough point of Fe3O4@ASC column was nearly 6000mL for the initial phosphate concentration of 18.02mg/L. Experimental data showed a good agreement with Yoon and Nelson model and Thomas model, the saturation adsorption capacity was 92mg/g. Phosphate fractionation, XRD, and FTIR spectra analysis indicated that Ca-P precipitation generated during the phosphate adsorption process. Besides, the adsorbed phosphate could be successfully recovered by 2% citric acid solution, which implied that recovered phosphate could be reused as fertilizer.

Removal of phosphate from aqueous solution by activated siderite ore: Preparation, performance and mechanism

Abstract Activated siderite ore (ASO) was prepared by annealing siderite ore at different temperatures for different durations. The performance of ASO on the removal of phosphate from aqueous solution and the effects of particle size, contact time, pH, initial phosphate concentration, temperature, and coexisting anions on phosphate removal were investigated. X-ray diffractometer, thermogravimetric analyzer (TGA), transmission electron microscopy (TEM), surface area analyzer, Fourier transformed infrared spectra and other techniques were utilized to characterize ASO before and after adsorption. The results showed that a large amount of CO2 was released meanwhile the siderite began to transform to hematite when the annealing temperature increased to 450 °C. The specific surface area of annealed product increased from 4.17 m2/g to 57.5 m2/g as the temperature came to 470 °C. Phosphate can be removed efficiently by ASO in a relatively wide pH range between 3.0 and 11.0. The effects of coexisting anions were not significant within the experimental concentration ranges except HCO3−. The adsorption process of phosphate on ASO fitted pseudo-second order kinetics model. ASO showed a high-efficient adsorption capacity of 9.24 mg/g estimated from Langmuir isotherm at 30 °C. Results of TEM and FTIR analysis suggested that under the condition of pH = 6.5 and phosphate concentration (100 mg/L), two different monoprotonated phosphate complexes exist at ASO, with one surface complex coordinated in a monodentate binuclear (bridging) fashion, and the other as a monodentate mononuclear complex. A small amount of co-precipitation is most likely to be another mechanism for the removal of phosphate. These fundamental data indicate that siderite is a promising precursor for preparing porous material at least for adsorption of phosphate.

Akaganeite nanorods decorated graphene oxide sheets for removal and recovery of aqueous phosphate

The increased amount of phosphate in water results in the depletion of dissolved oxygen levels and becomes detrimental to aquatic organism. The waste generated from industries contains large quantity of phosphates and needed effective treatment before reaching to the fresh water. In this study we report synthesis of a nanocomposite containing akaganeite nanorods (β-FeOOH) and graphene oxide sheets (GO) via chemical route and used as a low-cost potential adsorbent for removal of phosphate dissolved in the water. In the presence of graphene oxide β-FeOOH nanorods showed enhanced aspect ratio of rods from 5 to 7. The influence of adsorbent dose, adsorption time, solution pH, and initial phosphate concentration on the phosphate removal capacity were studied. The second order kinetics model fitted better compare to the first and solid diffusion model. The adsorption isotherm was best fitted with Langmuir model compare to Freundlich isotherm indicates formation of monolayer of phosphate on the surface of adsorbent. The β-FeOOH nanorods/GO nanocomposite showed maximum phosphate adsorption capacity 45.2mg/g at pH 7 and room temperature 30°C.

Adsorptive removal of phosphate using nano cobalt hydroxide as a sorbent from aqueous solution; multivariate optimization and adsorption characterization

A unique application of Cobalt hydroxide nanoparticles is proposed in the current study. Particles were synthesized and used for removal of phosphate in a batch system. Here, the main variables e.g. pH, sorbent dosage (m), and initial concentration of phosphate (CP) were considered with an assumption that they were likely to be influential on both removal efficiency (R %) and capacity uptake (q). Response surface methodology (RSM) involving Box-Behnken design (BBD) was employed to optimize effective factors and subsequently to propose an appropriate regression model of adsorption system. Apart from that, the kinetic and thermodynamic studies of phosphate adsorption onto the nano-adsorbent were carried out. Second-order kinetic model shows more favorability for dynamic behavior of current adsorption process. The thermodynamic parameters such as ΔG, ΔH and ΔS were determined and results testified that the adsorption procedure is spontaneous and endothermic in its nature. FT-IR, energy dispersive X-ray microanalysis (EDX) for elemental analysis/composition, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) were applied to characterize bare and adsorbed materials. FT-IR analysis imparted a confirmation that the surface of sorbent is involved in the adsorption process. Desirable potential of nano-sized cobalt hydroxide was reported for removal of phosphate from aqueous medium as an entire result.

Adsorption of phosphate from aqueous solution using electrochemically modified biochar calcium-alginate beads: Batch and fixed-bed column performance

Batch and continuous fixed-bed column studies were investigated using electrochemically modified biochar calcium-alginate beads (EMB-CABs) as an adsorbent for the removal of phosphate from aqueous solutions. Batch experiments revealed that the phosphate adsorption behavior of EMB-CABs and its structural characteristics were highly dependent on pH condition. Also, kinetics and equilibrium isotherms studies demonstrated that the experimental data correlated well with the pseudo-second-order and Sips isotherm models, respectively. The effects of different operating parameters such as bed height, initial phosphate concentration, and flow rate were investigated in a continuous fixed-bed column, and the experimental data were fitted to three different breakthrough models, the Adams-Bohart, Thomas, and Yoon-Nelson models. The results suggested that the Yoon-Nelson model showed better agreement with the breakthrough curves than other models. Lastly, the design parameters for a large-scale column were calculated via the scale-up approach using the breakthrough parameters obtained from lab-scale column tests.

Carbon-dioxide biofixation and phycoremediation of municipal wastewater using Chlorella vulgaris and Scenedesmus obliquus.

The pure cultures of microalgae Chlorella vulgaris ATCC 13482 and Scenedesmus obliquus FACHB 417 were grown in municipal wastewater in 7-L airlift bubble column photobioreactor supplied with 5% CO2/air (v/v). Batch experiments were conducted at 25°C with 14-h light/10-h dark cycle for a period of 10days. The CO2 capture efficiencies for both the microalgae were monitored in terms of their respective biomass productivities, carbon contents, and CO2 consumption rates. In the present study, the initial concentration of ammonia (43.7mgL-1) was decreased to 2.9 and 3.7mg L-1 by C. vulgaris and S. obliquus, respectively. And, the initial concentration of phosphate (18.5mgL-1) was decreased to 1.1 and 1.6mgL-1 by C. vulgaris and S. obliquus, respectively. CO2 biofixation rates by C. vulgaris and S. obliquus, cultivated in municipal wastewater, were calculated to be 140.91 and 129.82mgL-1day-1, respectively. The findings from the present study highlight the use of microalgae for wastewater treatment along with CO2 uptake and biomass utilization for pilot scale production of biodiesel, biogas, feed supplements for animals, etc., thus minimizing the production costs.

Pretreatment of Raw Biochar and Phosphate Removal Performance of Modified Granular Iron/Biochar

Biochar is a potential carrier for nutrients due to its porous nature and abundant functional groups. However, raw biochar has a limited or even negative capacity to adsorb phosphate. To enhance phosphate removal and reduce phosphate releases, acidic, alkaline, and surfactant pretreatments, followed by granulation and ferric oxide loading, were applied to raw biochar powder (Bp). The alkaline pretreatment proved to be the most effective method and exhibited significant pore expansion and surface oxidation. Bg-OH-FO showed the highest phosphate removal efficiency at 99.2% (initial phosphate concentration of 20 mg/L) after granulation and ferric oxide loading. Static adsorption results indicated that a pH value of 4 was the most suitable for phosphate adsorption because of the surface properties of Bg-OH-FO and the distribution of P (V) in water. Higher temperatures and a larger initial phosphate concentration led to better adsorption; the adsorption capacity of Bg-OH-FO was 1.91 mg/g at 313 K with an initial phosphate concentration of 50 mg/L. The Bg-OH-FO adsorption process was endothermic in nature. The Freundlich model seemed to be the optimum isotherm model for Bg-OH-FO. Under continuous adsorption, the flow rate and bed depth were changed to optimize the operation conditions. The results indicate that a slow flow rate and high bed depth helped increase the removal efficiency (η) of the fixed bed. The breakthrough curves fitted well with the Yoon–Nelson model.

Enhanced phosphorus reduction in simulated eutrophic water: a comparative study of submerged macrophytes, sediment microbial fuel cells, and their combination

ABSTRACTThe phosphorus reduction in water column was attempted by integrating sediment microbial fuel cells (SMFCs) with the submerged macrophyte Vallisneria spiralis. A comparative study was conducted to treat simulated water rich in phosphate with a control and three treatments: SMFC alone (SMFC), submerged macrophytes alone (macophyte), and combined macrophytes and fuel cells (M-SMFC). All treatments promoted phosphorus flux from the water column to sediments. Maximum phosphorus reduction was obtained in proportion to the highest stable phosphorus level in sediments in M-SMFC. For the initial phosphate concentrations of 0.2, 1, 2, and 4 mg/L, average phosphate values in the overlying water during four phases decreased by 33.3% (25.0%, 8.3%), 30.8% (5.1%, 17.9%), 36.5% (27.8%, 15.7%), and 36.2% (0.7%, 22.1%) for M-SMFC (macrophyte, SMFC), compared with the control. With macrophyte treatment, the obvious phosphorus release from sediments was observed during the declining period. However, such phenomenon was significantly inhibited with M-SMFC. The electrogenesis bacteria achieved stronger phosphorus adsorption and assimilation was significantly enriched on the closed-circuit anodes. The higher abundance of Geobacter and Pseudomonas in M-SMFC might in part explain the highest phosphorus reduction in the water column. M-SMFC treatment could be promising to control the phosphorus in eutrophic water bodies.

Hypophosphatemia after nontraumatic intracranial hemorrhage.

The aim of this study was to assess the incidence and contributing factors of hypophosphatemia and the association with poor long-term outcome after nontraumatic intracranial hemorrhage. This was a prospective, observational study of patients with nontraumatic intracranial hemorrhage (i.e., aneurysmal or perimesencephalic subarachnoid hemorrhage, or spontaneous intracerebral or intraventricular hemorrhage) treated in the intensive care unit (ICU) at our university hospital. Plasma phosphate concentrations were measured serially in 2-day sections during the 6 day study period. The ICU mortality was recorded, 3-month and 1-year outcomes were assessed using the Glasgow Outcome Scale. One hundred patients were enrolled. The frequency of hypophosphatemia (Pi ≤ 0.65 mmol/l) was 70%. Chronic hypertension, acute hydrocephalus, and diffuse brain edema were more common in patients with hypophosphatemia compared with normophosphatemics (44% vs. 21%, P = 0.021; 59% vs. 33%, P = 0.021; and 43% vs. 13%, P = 0.004, respectively). Hypophosphatemic patients had higher maximum SOFA scores [10 (7-11) vs. 7.5 (5.75-10), P = 0.024]. Initial phosphate concentration correlated inversely with APACHE II score on admission (ρ = -0.304, P = 0.002) and SOFA score on the first ICU day (ρ = -0.269, P = 0.008). There was no difference in outcome between hypophosphatemic and normophosphatemic patients. In all five patients with severe hypophosphatemia (Pi < 0.32 mmol/l) the functional outcome was good. Hypophosphatemia was common in this patient population. The outcome was similar between hypophosphatemic and normophosphatemic patients. Chronic hypertension, acute hydrocephalus, diffuse brain edema and higher SOFA scores were more common in patients with hypophosphatemia.