Suspended Solid Phase Research Articles

Ecotoxicological Properties of Pure and Phosphorus-Containing Graphene Oxide Bidimensional Sheets in Daphnia magna.

In this work, the synthesis and structural, thermal, vibrational, morphological, and electronic characterization of 2D-like pure graphene oxide (GO) and phosphorus-containing graphene oxide (GOP) sheets were investigated. The average thicknesses of GO and GOP were 0.8 μm and 3.1 μm, respectively. The electron energy-loss spectroscopy spectra were used to analyze the differences in the C-K and O-K energy edge bands between GO and GOP. In addition, colloidal stability was studied using dynamic light scattering and zeta potential physicochemical techniques, determining that as the concentration increases, the hydrodynamic diameter and electrostatic stability of GO and GOP increase. The colloidal stability was quite important to ensure the interaction between the suspended solid phase and the biomarker. The 2D-like materials were used to determine their ecotoxicological properties, such as the medium lethal concentration, a crucial parameter for understanding ecotoxicity. Acute ecotoxicity experiments (24 h) were conducted in triplicate to obtain robust statistics, with corresponding mean lethal concentration (LC50) of 11.4 mg L-1 and 9.8 mg L-1 for GO and GOP, respectively. The morphological parameters of GO and GOP were compared with a negative control. However, only the case of GO was analyzed, since the Daphnia magna (D. magna) set exposed to GOP died before completing the time required for morphological analysis. The results indicate that the GOP sample is more toxic than the GO, both during and after exposure. Furthermore, the morphological parameters with the greatest statistically significant changes (p<0.05) were associated with the heart and body, while the eye and tail showed less significant changes.

Nitrogen and phosphorus removal performance of sequential batch operation for algal cultivation through suspended-solid phase photobioreactor

Nitrogen (N) and phosphorus (P) absorbed by algae in the suspended-solid phase photobioreactor (ssPBR) have emerged as an efficient pathway to purify the effluent of wastewater treatment plants (WWTPs). However, the key operational parameters of the ssPBR need to be optimized. In this study, the stability of the system after sequential batch operations and the efficiency under various influent P concentrations were evaluated. The results demonstrated that the ssPBR maintained a high N/P removal efficiency of 96 % and 98 %, respectively, after 5 cycles. When N was kept at 15 mg/L and P ranged from 1.5 to 3.0 mg/L, the system yielded plenty of algae products and guaranteed the effluent quality that met the discharge standards. Notably, the carriers were a key contributor to the high metabolism of algae and high performance. This work provided theoretical ideas and technical guidance for effluent quality improvement in WWTPs.

Ecotoxicological investigations of milking cow slurry and changes of oestrogenic compounds in the solid and liquid phase

Due to the appearance of intensive livestock-rearing systems since the 1970s, a vast amount of liquid manure (slurry) has been produced. The application and utilization are partly regulated for this special substance, which contains urine, excrement, process water, and other chemicals, such as insecticides and disinfectants. Our research was conducted on a slurry management system of a dairy cattle farm, focusing on the investigation of the presence of oestrogenic substances and toxicity of slurry before and after using a separator technology. Yeast oestrogen screen shows in this study that the separation of the liquid and solid phases of slurry contributes to the reduction in oestrogenic substances. Based on the toxicological studies, the growth inhibition of algae was 93%, and the inhibition of the germination of higher plant seeds was 25%, without separation. After separation of the phases, growth and germination were comparable with the negative control; moreover, some stimulation was detected. Consequently, harmful substances were removed with the suspended solid phase. From the present study, we can conclude that stakeholders should support separation technology in intensive livestock-rearing systems, and ecotoxicological investigations obviously help the risk management of slurry utilization. To our best knowledge, this is the first paper presenting detailed and complex toxicological study on slurry samples.

Enhanced simultaneous removal of nitrogen, phosphorous, hardness, and methylisothiazolinone from reverse osmosis concentrate by suspended-solid phase cultivation of Scenedesmus sp. LX1

The disposal of reverse osmosis (RO) concentrate (ROC) is a critical challenge impeding the application of RO-based wastewater reclamation. Herein, we proposed an enhanced biotreatment approach for the simultaneous removal of nitrogen, phosphorous, hardness, and methylisothiazolinone (MIT) from ROC by suspended-solid phase cultivation of Scenedesmus sp. LX1. Repeated carrier addition, guided by the developed optimal carrier addition model, efficiently enhanced algal growth and contaminant removal through dynamically controlling the suspended algal density by cell attachment. The maximum algal growth rate (212.2 mg/(L∙d)) increased by 41% compared with the control, and the time needed for reaching the maximum algal biomass (906.7 mg/L) was shortened by 1 d, attributing to the mitigation of density restriction. 91.8% of nitrogen (30.2 mg/L) was removed with 5.5 mg/(L∙d) accelerating removal rate, and phosphate (3.7 mg/L) was completely removed within 1 d. Hardness precursors calcium and inorganic carbon were also removed in large amounts, 268.4 and 128.2 mg/L, respectively. Moreover, suspended-solid phase cultivation significantly mitigated the growth inhibition caused by MIT toxicity, enabled the algae to completely biodegrade MIT of extremely high concentrations (4.7 mg/L and 11.4 mg/L) in a short time. Our results demonstrate the feasibility of suspended-solid phase algal cultivation for simultaneously and effectively removing multiple main contaminants from ROC.

Buoyancy-induced convection from a pair of heated and cooled horizontal circular cylinders inside an adiabatic tilted cavity filled with alumina/water nanofluids

Purpose This paper aims to investigate numerically buoyancy-induced convection from a pair of differentially heated horizontal circular cylinders set side by side in a nanofluid-filled adiabatic square enclosure, inclined with respect to gravity so that the heated cylinder is located below the cooled one, using a two-phase model based on the double-diffusive approach assuming that the Brownian diffusion and thermophoresis are the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. Design/methodology/approach The system of the governing equations of continuity, momentum and energy for the nanofluid, and continuity for the nanoparticles, is solved by a computational code based on the SIMPLE-C algorithm. Numerical simulations are performed for Al2O3 + H2O nanofluids using the average volume fraction of the suspended solid phase, the tilting angle of the enclosure, the nanoparticle size, the average nanofluid temperature and the inter-cylinder spacing, as independent variables. Findings The main results obtained may be summarized as follows: at high temperatures, the nanofluid heat transfer performance relative to that of the pure base liquid increases with increasing the average volume fraction of the suspended solid phase, whereas at low temperatures it has a peak at an optimal particle loading; the relative heat transfer performance of the nanofluid has a peak at an optimal tilting angle of the enclosure; the relative heat transfer performance of the nanofluid increases notably as the average temperature is increased, and just moderately as inter-cylinder spacing is increased and the nanoparticle size is decreased. Originality/value The two-phase computational code used in the present study incorporates three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity and the coefficient of thermophoretic diffusion, all based on a high number of literature experimental data.

The growth model and its application for microalgae cultured in a suspended-solid phase photobioreactor (ssPBR) for economical biomass and bioenergy production

Attached cultivation could achieve the convenient recovery of microalgae cells during the microalgae-based biomass and bioenergy production. However, this cultivation pattern has a light/nutrient transfer problem in biofilms, which decreases the microalgae growth rate. A combination of attached and suspended microalgae cultivation patterns, i.e., a suspended-solid photobioreactor (ssPBR), has been proposed for the potential of economical biomass production. It was demonstrated that the increase in attached microalgae biomass was mainly attributed to the attachment of suspended microalgae cells rather than to the regrowth of attached microalgae. A specific growth model for the microalgae in an ssPBR was constructed based on the Logistic model, which provided a good fit to the experimental data (R2>0.93, p < 0.05). Therefore, the cultivation strategy was proposed as periodically recovering attached microalgae by capturing carriers and keeping the suspended microalgae at the fastest growth rate (half of the maximum suspended microalgal density). The results indicated that the addition of carriers with an attaching capability of 1.31 × 107 cells/mL into the 105 m3 ssPBR when the suspended Scenedesmus density was at 5.87 × 106 cells/mL and removing them after 5.15 d could achieve the large profit of 146 K dollars/d with an annual production of 3600 t microalgae biomass. In this way, high productivity and energy-saving recovery of microalgae could be achieved.

Buoyancy-induced convection of water-based nanofluids from an enclosed heated cylinder

PurposeLaminar natural convection of nanofluids in a square cooled cavity enclosing a heated horizontal cylinder is studied numerically. This paper aims to investigate in what measure the nanoparticle size and average volume fraction, the cavity width, the cylinder diameter and position, the average temperature of the nanofluid and the temperature difference imposed between the cylinder and the cavity walls, affects the basic heat and fluid flow features, as well as the thermal performance of the nanofluid relative to that of the base liquid.Design/methodology/approachThe four-equation system of the mass, momentum and energy transfer governing equations has been solved using a computational code incorporating three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity and the coefficient of thermophoretic diffusion, all based on a high number of experimental data available in the literature. The SIMPLE-C algorithm has been used to handle the pressure-velocity coupling. Simulations have been performed using Al2O3 + H2O, for different values of the average volume fraction of the suspended solid phase in the range 0-0.04, the diameter of the nanoparticles in the range 25-75 nm, the temperature difference imposed between the cylinder and the cavity walls in the range 5-20 K, the average nanofluid temperature in the range 300-330 K, the ratio between the cylinder diameter and the cavity width in the range 0.1-0.5 m, the ratio between the distance of the cylinder axis from the bottom wall and the cavity width in the range 0.2-0.8 and the ratio between the distance of the cylinder axis from the left sidewall and the cavity width in the range 0.2-0.5.FindingsThe main results obtained may be summarized as follows: the overall solid phase migration from hot to cold results in a cooperating solutal buoyancy force which tends to compensate the friction increase consequent to the viscosity growth due to the dispersion of the nanoparticles into the base fluid; the effect of the increased thermal conductivity consequent to the nanoparticle dispersion into the base fluid plays the major role in determining the heat transfer enhancement of the nanofluid, at least in the upper range of the investigated average temperatures; at high temperatures, the nanofluid heat transfer performance relative to that of the pure base liquid increases with increasing the average volume fraction of the suspended solid phase, whereas at low temperatures, it has a peak at an optimal particle loading; the relative heat transfer performance of the nanofluid increases notably with increasing the average temperature, and just moderately as the imposed temperature difference, the width of the cavity and the distance of the cylinder from the bottom of the cavity, are increased; the relative heat transfer performance of the nanofluid increases as the nanoparticle size, the cylinder diameter and the distance of the cylinder from the sidewall, are decreased; as a consequence of the local competition between the thermal and the solutal buoyancy forces, a periodic flow arises when the cylinder is located in the vicinity of one of the cooled walls of the enclosure.Originality/valueFramed in this general background, a comprehensive numerical study on buoyancy-driven convection of alumina-water nanofluids inside a cooled square cavity containing a heated circular cylinder is executed by the way of a two-phase model based on the double-diffusive approach accounting for the effects of the Brownian diffusion and thermophoresis.

Arsenic and Trace Metals in Three West African rivers: Concentrations, Partitioning, and Distribution in Particle-Size Fractions.

Despite increasing mining activities, and fertilizer and pesticide use in agriculture, little information is available on the status of metal(loid) contamination in rivers in West Africa. Sixty water samples were collected from three significant rivers (the Bandama, Comoé, and Bia Rivers) in Côte d'Ivoire, the world's top cocoa producer, to examine As, Pb, Cu, Fe, Cd, and Zn concentrations, partitioning, and distribution in suspended particle-size fractions. The results showed higher total metal(loid) concentrations during the dry and flood seasons than during the rainy season. Significant As and Pb concentrations, moderate Cu and Fe concentrations, and low Zn concentrations were observed during the flood season. The metal(loid) concentrations decreased upstream to downstream primarily due to increased deposition through flocculation. Inverse or no obvious spatial trends often were observed, indicative of local contamination from anthropogenic activities. The suspended solid phase and the strength of metal affinity to the particles controlled the metal(loid) concentrations. Furthermore, total metal(loid) concentrations increased significantly with decreasing suspended particle-size fractions. The results underline that As and Pb contents in the Comoé and Bia Rivers threaten the health of at least 3million people in southeastern Côte d'Ivoire. Filtering river waters before use will significantly reduce human health risks.

Differences between attached and suspended microalgal cells in ssPBR from the perspective of physiological properties

Attached microalgae cultivation for the algae-based products is considered as a promising approach to simplify biomass recovery processes and reduce the cost. However, as an incipient research field, biomass accumulation is the mainly index for attached microalgal growth evaluation. To break through such limitations, physiological properties of attached microalgae (e.g. the oxygen evolving activity and the main organic composition of cells), which are important for microalgal growth evaluation but are still unclear in most studies, were studied using an attached microalgae culture system, i.e. suspended-solid phase photobioreactor (ssPBR) in this paper. As light, nutrients and other environmental conditions of attached microalgae were different from the suspended microalgae, physiological properties of attached microalgae also varied from the suspended ones. Besides the relatively lower biomass accumulation rate, attached microalgae also had a lower oxygen evolving activity (65% on average) comparing to suspended microalgae. The composition of microalgae changed towards accumulating more protein when suspended microalgae turned to attached status. The relative protein content of attached microalgae (50.1% ± 10.1%) was approximately 30% higher than the suspended algae (36.0% ± 16.1%) on average. The discovery of physiological properties of attached microalgae in this paper could help the production of high-protein microalgae-related products and explain some phenomenon during the production of microalgae-related products.

Effects of nitrogen and phosphorus concentrations on the growth of microalgae Scenedesmus. LX1 in suspended-solid phase photobioreactors (ssPBR)

Attached microalgae cultivation is an effective way to decrease the high harvesting cost in microalgae biomass production. Nitrogen and phosphorus, as the two main nutrients, are hypothesized to influence the attachment efficiency and growth of microalgae. The attached growth of Scenedesmus. LX1 in the suspended-solid phase photobioreactor (ssPBR)1 with feed composed of different total nitrogen (TN) and total phosphorus (TP) concentrations was studied in this paper. The productivity of attached microalgae on Day 3 (3 × 106 cells·cm−3) at the nutrient levels of TN = 15 g m−3 and TP = 5 or 3 g m−3 was approximately 70% higher than that at relatively high-nutrient levels (i.e. TN = 150 g m−3 and TP = 10 or 15 g m−3). Under the nutrient levels of TN = 15 g m−3 and TP = 5, 3, 1.5, 0.5 g m−3, the average TN and TP concentrations in the microenvironment around microalgae biofilm were about 2.1 and 15.5 times higher than those of the bulk media, respectively. The higher nutrient concentration in the surrounding microenvironment of microalgae biofilm improved protein synthesis of attached microalgae compared to the suspended ones within the same reactor, especially at the late stage of batch cultivation.

A Demonstrative Study on the Two-phase vs. Single-phase Modeling of Buoyancy-driven Flows of Enclosed Nanofluids

ABSTRACTA demonstrative numerical study on natural convection of water-based nanofluids in square enclosures with different boundary conditions imposed at the walls, and different orientations with respect to the gravity vector, is performed using both the single-phase and the two-phase approaches, with the main scope to evaluate in what measure the single-phase approach fails in describing the basic heat and fluid flow features, as well as in determining the thermal performance of nanofluids. The system of the mass, momentum and energy transfer governing equations is solved by way of a computational code based on the SIMPLE-C algorithm. Empirical correlations are used for the calculation of the effective thermal conductivity, the effective dynamic viscosity, and the thermophoretic diffusion coefficient. The following configurations are investigated: a tilted cavity differentially-heated at two opposite walls; a vertical cavity partially-heated at the bottom wall and cooled at both sides; and a vertical cavity differentially-heated at the vertical and horizontal walls. It is found that the non-uniform distribution of the suspended solid phase throughout the enclosure gives rise to a solutal buoyancy force, whose competition with the thermal buoyancy force results in a periodic flow detectable only if the two-phase approach is applied. Moreover, the impact of the dispersion of the nanoparticles into the base liquid, which turns out to be notably higher at higher average temperatures, is found to be systematically underestimated by the single-phase approach.

Buoyancy-Induced Convection of Alumina-Water Nanofluids in Laterally Heated Vertical Slender Cavities

ABSTRACTA two-phase model based on the double-diffusive approach is used to perform a numerical study of natural convection of alumina-water nanofluids in differentially heated vertical slender cavities. In the mathematical formulation, Brownian diffusion and thermophoresis are assumed to be the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. The system of the governing equations of continuity, momentum and energy for the nanofluid, and continuity for the nanoparticles is solved through a computational code relying on the SIMPLE-C algorithm for the pressure-velocity coupling. The effective thermal conductivity and dynamic viscosity of the nanofluid, and the coefficient of thermophoretic diffusion of the suspended solid phase, are evaluated using three empirical correlations based on a high number of experimental data available from diverse sources, and validated by way of literature data different from those used in generating them. Numerical simulations are executed for different height-to-width aspect ratios of the enclosure, as well as different average temperatures of the nanofluid. The heat transfer performance of the nanoparticle suspension relative to that of the base fluid is found to increase as the nanofluid average temperature is increased and, at low to moderate temperatures, the aspect ratio of the enclosure is decreased. Moreover, at temperatures higher than room temperature, a peak at an optimal particle loading is found to exist for any investigated configuration.

Buoyancy-driven convection of nanofluids in inclined enclosures

A two-phase model based on the double-diffusive approach is used to perform a numerical study on natural convection of water-based nanofluids in square cavities differentially heated at two opposite walls, and inclined with respect to gravity so that the heated wall faces upwards. It is assumed that Brownian diffusion and thermophoresis are the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. The system of the governing equations of continuity, momentum and energy for the nanofluid, and continuity for the nanoparticles, is solved through an in-house developed computational code which incorporates three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity, and the thermophoretic diffusion coefficient, all based on literature experimental data. The pressure-velocity coupling is handled by way of the SIMPLE-C algorithm. Numerical simulations are executed for three different nanofluids, using the diameter and the average volume fraction of the suspended nanoparticles, as well as the tilting angle of the enclosure, the enclosure width, the average temperature of the nanofluid, and the temperature difference imposed across the cavity, as independent variables, whose effects are thoroughly analyzed and discussed. The existence of an optimal tilting angle of the enclosure and an optimal particle loading for maximum heat transfer is detected. In addition, a thermophoresis-induced periodic flow at tilting angles larger than 50° is found to occur for low to moderate values of both the nanofluid average temperature and the volume fraction of the suspended solid phase.

Thermophoresis-induced oscillatory natural convection flows of water-based nanofluids in tilted cavities

ABSTRACTA two-phase model based on the double-diffusive approach is used to perform a numerical study on the natural convection of water-based nanofluids in differentially heated square cavities, inclined with respect to gravity so that the heated wall is positioned below the cooled wall, assuming that Brownian diffusion and thermophoresis are the only slip mechanisms by which the solid phase can develop a significant relative velocity with respect to the liquid phase. The system of the governing equations of continuity, momentum, and energy for the nanofluid, and continuity for the nanoparticles, is solved through a computational code that incorporates three empirical correlations for the evaluation of the effective thermal conductivity, the effective dynamic viscosity, and the thermophoretic diffusion coefficient, all based on several sets of literature experimental data. Pressure–velocity coupling is handled by the way of the SIMPLE-C algorithm. Numerical simulations are executed for tilting angles in the range 50−70 deg, such that the nonuniform distribution of the suspended solid phase gives rise to a nonnegligible solutal buoyancy force, whose effects are investigated using the nanoparticle diameter and average volume fraction, the cavity width, the nanofluid average temperature, and the temperature difference imposed across the cavity, as independent variables. It is found that the competition between the solutal and thermal buoyancy forces results in an oscillatory flow, with an oscillation amplitude that increases on increasing the cavity size and the imposed temperature difference. Moreover, the impact of the nanoparticle dispersion into the base liquid is found to be higher at higher average temperatures, whereas, by contrast, the other variables have moderate or negligible effects.

Flow cytometry based rapid duplexed immunoassay for fusarium mycotoxins.

At small food processing facilities, the most frequently used test to determine if grain-derived mycotoxin concentrations are compliant with legal limits is the enzyme-linked immunosorbent assay (ELISA). Each kit is designed to detect one of the six dangerous mycotoxins. With the increasing occurrence of coinfection of grain with multiple-mycotoxins in the field and/or during storage, ELISA is no longer a cost effective best assay option. With ELISA, each species of mycotoxin requires different sample preparation/extraction and a 45 min incubation. The alternative multiplexed assay presented here, the competitive fluorescent microsphere immunoassay (CFIA), follows current food safety standards. It handles several toxins simultaneously with a single universal extraction protocol. The authors' objective was to modify an existing commercial CFIA kit developed for bench top flow cytometry and extend its utility for point-of-need (PON) applications. The accelerated protocol offers over 60% reduction in total processing time and it detects dual mycotoxin contamination simultaneously. The observed enhanced binding kinetics equations reported here utilizing suspended solid phase particles in liquid phase, are also supported by published theoretical calculations. In the near future portable cytometry may bring rapid multiplexed PON testing to assure the safety of small food processing installations. © 2016 International Society for Advancement of Cytometry.

The precipitation of indium at elevated pH in a stream influenced by acid mine drainage

Indium is an increasingly important metal in semiconductors and electronics and has uses in important energy technologies such as photovoltaic cells and light-emitting diodes (LEDs). One significant flux of indium to the environment is from lead, zinc, copper, and tin mining and smelting, but little is known about its aqueous behavior after it is mobilized. In this study, we use Mineral Creek, a headwater stream in southwestern Colorado severely affected by heavy metal contamination as a result of acid mine drainage, as a natural laboratory to study the aqueous behavior of indium. At the existing pH of ~3, indium concentrations are 6–29μg/L (10,000× those found in natural rivers), and are completely filterable through a 0.45μm filter. During a pH modification experiment, the pH of the system was raised to >8, and >99% of the indium became associated with the suspended solid phase (i.e. does not pass through a 0.45μm filter). To determine the mechanism of removal of indium from the filterable and likely primarily dissolved phase, we conducted laboratory experiments to determine an upper bound for a sorption constant to iron oxides, and used this, along with other published thermodynamic constants, to model the partitioning of indium in Mineral Creek. Modeling results suggest that the removal of indium from the filterable phase is consistent with precipitation of indium hydroxide from a dissolved phase. This work demonstrates that nonferrous mining processes can be a significant source of indium to the environment, and provides critical information about the aqueous behavior of indium.

Enhanced attached growth of microalgae Scenedesmus. LX1 through ambient bacterial pre-coating of cotton fiber carriers

The role of bacteria/extracellular polymeric substances (EPS) coated carriers on attached microalgae growth in suspended-solid phase photobioreactor (sspBR) was assessed in this study. The results showed that pre-coating cotton with ambient bacteria and their EPS improved the attached microalgal growth by as much as 230% in terms of attached microalgae density. Additionally, the single cell dry weight, chemical composition and oxygen evolving activity of attached microalgae were significantly affected by the presence of bacteria/EPS coating on the cotton carriers. The protein content of microalgae cells cultivated in the ssPBRs with carriers coated by bacteria and sterilized bacteria were on average 26% and 15% more than uncoated carriers, respectively. Through absorbing and immobilizing nutrients from the bulk medium, the bacteria/EPS coating provided the attached microalgae with nitrogen/phosphorus for protein synthesis, especially during the late stages of batch cultivation.

Speciation of inorganic selenium in environmental samples after suspended dispersive solid phase microextraction combined with inductively coupled plasma spectrometric determination

A rapid and effective suspended dispersive solid phase microextraction (SDSPME) was developed for the speciation of inorganic selenium using alumina nanoparticles functionalized with Aliquat-336. The target analytes were preconcentrated and determined by inductively coupled plasma optical emission spectrometry. Alumina nanoparticles were characterized using XRD, BET, SEM and EDX while the functionalized nano-Al2O3 was characterized by FTIR. The effect of pH of the solution on speciation Se in water samples was optimized separately. It was observed that when the pH values of sample solution ranged from 2.0 to 7.0, successful separation of inorganic Se species was achieved. The percentage recoveries for Se (IV) and Se (VI) were >90% and 5%, respectively. The two-level fractional factorial design was used to optimize experimental parameters affecting the preconcentration system. Under optimal conditions, the enrichment factor (EF), limit of detection (LOD) and limit of quantification for Se (IV) were found to be 850, 1.4ngL−1, and 4.6ngL−1, respectively. Furthermore, intra-day and inter-day precisions expressed in terms of relative standard deviation (RSD) were found to be 1.9% and 3.3%, respectively. The effect of coexisting ions on the recovery of Se (IV) was investigated. The accuracy of the developed method was checked by analysis of standard reference material (NIST SRM 1643e). The optimized method was applied for the determination of targets in surface water samples.

A novel suspended-solid phase photobioreactor to improve biomass production and separation of microalgae

A novel suspended-solid phase photobioreactor (ssPBR) was proposed in this paper to solve the problem of microalgal expensive and complex harvest system for biomass/biofuel production. In this ssPBR, solid carriers were added and kept suspended by aeration. Part of microalgae could attach and grow on the carriers. By catching carriers, microalgae could easily be separated from liquid phase. Three kinds of Carriers A, B, C made of cotton, mohair and linen, respectively, were used in this study. Compared with the reactor without carriers, the biomass production in each ssPBR was increased by adding these three kinds of carriers at a dosage of 2g/L, and the maximum increments of biomass were 2.2×10(5) (10.3%), 7.8×10(4) (3.9%) and 4.4×10(5) (20.5%)cells/mL, respectively. By increasing the dosage of Carriers-C to 4g/L, the maximum increment of microalgal biomass could reach up to about 30% in the ssPBR compared with control group.

Paraben-chlorinated derivatives in river waters

This article reports the first identification of paraben-chlorinated derivatives in river water. Parabens are widely used as preservatives in pharmaceuticals and personal care products. Parabens can be easily chlorinated by chlorinated tap water. The resulting chlorinated derivatives might pose a higher potential risk to humans and ecosystems than the corresponding parent parabens. However, the occurrence of such derivatives in rivers remains unknown so far. We studied 23 parabens and their chlorinated derivatives from rivers receiving effluents from sewage treatment plants in Shizuoka city, in the central Pacific region of Japan. The compounds were extracted by solid-phase extraction with a styrene polymer sorbent, trimethylsilyl-derivatized, and then identified by gas chromatography–mass spectrometry. Six chlorinated parabens and their primary degradation products, two chlorinated hydroxybenzoic acids, were found for the first time in river water. Moreover, in river water, chlorinated derivatives preferentially partition into the suspended-solid phase.