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- An integrated approach combining chemical analysis and an in vivo bioassay to assess the estrogenic potency of a municipal solid waste landfill leachate in qingdao. [Journal Article]
- PLoS One 2014; 9(4):e95597.
Various adverse effects related to landfill leachate have made leachates an important issue in past decades, and it has been demonstrated that landfill leachate is an important source of environmental estrogens. In this study, we employed chemical analysis of some already evaluated estrogenic substances, in combination with a bioassay using several specific biomarkers (e.g., plasma vitellogenin and sex steroids, enzyme activity of gonad gamma-glutamyl transpeptidase, and gonadosomatic index) to evaluate the estrogenic activities in outlets from different stages of the leachate treatment process. The results indicated that 5 environmental estrogens (4-t-octylphenol, bisphenol A, di-ethyl phthalate, di-n-butyl phthalate, and diethylhexyl phthalate) were detected by a gas chromatography-mass spectrometry, and the concentrations in leachate samples were 6153 ng/L, 3642 ng/L, 2139 ng/L, 5900 ng/L, and 9422 ng/L, respectively. Leachate (1∶200 diluted) induced the synthesis of plasma vitellogenin and led to decreased enzyme activity of gonad gamma-glutamyl transpeptidase and gonadosomatic index in male goldfish (Carassius auratus) after a 28-day exposure, while increased circulating 17β-estradiol level was also observed in males exposed to treated effluent. Although the target EEs were partially removed with removal rates varying from 87.2% to 99.77% by the "membrane bioreactor+reverse osmosis+aeration zeolite biofilter" treatment process, the treated effluent is still estrogenic to fish. The method combined chemical techniques with the responses of test organisms allowing us to identify the group of estrogen-like chemicals so that we were able to evaluate the overall estrogenic effects of a complex mixture, avoiding false negative assessments.
- Marine Yeast Isolation and Industrial Application. [JOURNAL ARTICLE]
- FEMS Yeast Res 2014 Apr 17.
Over the last century, terrestrial yeasts have been widely used in various industries, such as baking, brewing, wine, bioethanol and pharmaceutical protein production. However, only little attention has been given to marine yeasts. Recent research showed that marine yeasts have several unique and promising features over the terrestrial yeasts, e.g. higher osmosis tolerance, higher special chemical productivity and production of industrial enzymes. These indicate that marine yeasts have great potential to be applied in various industries. This review gathers the most recent techniques used for marine yeast isolation as well as the latest applications of marine yeast in bioethanol, pharmaceutical and enzyme production fields. This article is protected by copyright. All rights reserved.
- Electro-osmotic flow in disordered porous and fractured media. [JOURNAL ARTICLE]
- Phys Rev E Stat Nonlin Soft Matter Phys 2014 Mar; 89(3-1):033007.
Electro-osmosis phenomena are studied in a two-dimensional (2D) model disordered porous medium. The flow passages are represented by a network of spatially distributed rectangular channels with random orientations. The channels may represent microfractures in fractured porous media or in a network of interconnected microfractures, pores in a porous medium, or fibers in a fibrous porous material. The linearized equations of electrokinetics are solved numerically in a single channel, and in the 2D network of the channels. The macroscopic electrical conductivity σ and electro-osmotic coupling coefficient β are computed as functions of the electrical surface potential ζ and such geometrical parameters of the network as the channels' number density and widths, as well as the porosity of the medium. Despite the complexity of the phenomena and the model of porous media that is used, both σ and β appear to depend on the characteristics of the phenomena and porous media through very simple relations.
- Impacts of sludge retention time on sludge characteristics and membrane fouling in a submerged osmotic membrane bioreactor. [JOURNAL ARTICLE]
- Bioresour Technol 2014 Mar 21.:340-347.
Sludge retention time (SRT) is a feasible method to alleviate the salt accumulation in the osmotic membrane bioreactor (OMBR) by discharging the waste activated sludge. In this study, effects of SRT on sludge characteristics and membrane fouling were investigated using a submerged OMBR under two SRTs of 10 and 15d. The results showed that the lower SRT was helpful for alleviating the salt accumulation and flux decline. Besides that, the removal of NH3-N was significantly influenced by SRT. SRT also had a strong effect on soluble microbial products (SMP) and microbial activity due to the variation of salinity. Microbial diversity analysis indicated that the high salinity environment in the OMBR significantly affected the microbial communities. The flux decline in the OMBR was mainly attributed to the reduced driving force resulting from the salt accumulation, and the reversible fouling was the dominant forward osmosis (FO) membrane fouling in the OMBR.
- Impact of spacer thickness on biofouling in forward osmosis. [JOURNAL ARTICLE]
- Water Res 2014 Mar 27.:223-233.
Forward osmosis (FO) indirect desalination systems integrate wastewater recovery with seawater desalination. Niche applications for FO systems have been reported recently, due to the demonstrated advantages compared to conventional high-pressure membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Among them, wastewater recovery has been identified to be particularly suitable for practical applications. However, biofouling in FO membranes has rarely been studied in applications involving wastewater effluents. Feed spacers separating the membrane sheets in cross-flow systems play an important role in biofilm formation. The objective of this study was to determine the influence of feed spacer thickness (28, 31 and 46 mil) on biofouling development and membrane performance in a FO system, using identical cross-flow cells in parallel studies. Flux development, biomass accumulation, fouling localization and composition were determined and analyzed. For all spacer thicknesses, operated at the same feed flow and the same run time, the same amount of biomass was found, while the flux reduction decreased with thicker spacers. These observations are in good agreement with biofouling studies for RO systems, considering the key differences between FO and RO. Our findings contradict previous cross-flow studies on particulate/colloidal fouling, where higher cross-flow velocities improved system performance. Thicker spacers reduced the impact of biofouling on FO membrane flux.
- Hybrid Pressure Retarded Osmosis - Membrane Distillation System for Power Generation from Low-Grade Heat: Thermodynamic Analysis and Energy Efficiency. [JOURNAL ARTICLE]
- Environ Sci Technol 2014 Apr 11.
We present a novel hybrid membrane system that operates as a heat engine, capable of utilizing low-grade thermal energy, which is not readily recoverable with existing technologies. The closed-loop system combines membrane distillation (MD), which generates concentrated and pure water streams by thermal separation, and pressure retarded osmosis (PRO), which converts the energy of mixing to electricity by a hydro-turbine. The PRO-MD system was modeled by coupling the mass and energy flows between the thermal separation (MD) and power generation (PRO) stages for heat source temperatures ranging from 40 to 80 C and working concentrations of 1.0, 2.0, and 4.0 mol/kg NaCl. The factors controlling the energy efficiency of the heat engine were evaluated for both limited and unlimited mass and heat transfer kinetics in the thermal separation stage. In both cases, the relative flow rate between the MD permeate (distillate) and feed streams is identified as an important operation parameter. There is an optimal relative flow rate that maximizes the overall energy efficiency of the PRO-MD system for given working temperatures and concentration. In the case of unlimited mass and heat transfer kinetics, the energy efficiency of the system can be analytically determined based on thermodynamics. Our assessment indicates that the hybrid PRO-MD system can theoretically achieve an energy efficiency of 9.8% (81.6% of the Carnot efficiency) with hot and cold working temperatures of 60 °C and 20 °C, respectively, and a working solution of 1.0 M NaCl. When mass and heat transfer kinetics are limited, conditions that more closely represent actual operations, the practical energy efficiency will be lower than the theoretically achievable efficiency. In such practical operations, utilizing a higher working concentration will yield greater energy efficiency. Overall, our study demonstrates the theoretical viability of the PRO-MD system and identifies the key factors for performance optimization.
- Chaotic induced-charge electro-osmosis. [Journal Article]
- Phys Rev Lett 2014 Mar 28; 112(12):128302.
We present direct numerical simulations of the coupled Poisson-Nernst-Planck and Navier-Stokes equations for an electrolyte around a polarizable cylinder subject to an external electric field. For high fields, a novel chaotic flow phenomenon is discovered. Our calculations indicate significant improvement in the prediction of the mean flow relative to standard asymptotic models. These results open possibilities for chaos-enhanced mixing in microdevices and provide insight into barriers to efficient electrokinetic micropumps with broad applications in electrochemical and lab-on-a-chip systems.
- Membrane scaling and flux decline during fertiliser-drawn forward osmosis desalination of brackish groundwater. [JOURNAL ARTICLE]
- Water Res 2014 Mar 27.:172-182.
Fertiliser-drawn forward osmosis (FDFO) desalination has been recently studied as one feasible application of forward osmosis (FO) for irrigation. In this study, the potential of membrane scaling in the FDFO process has been investigated during the desalination of brackish groundwater (BGW). While most fertilisers containing monovalent ions did not result in any scaling when used as an FO draw solution (DS), diammonium phosphate (DAP or (NH4)2HPO4) resulted in significant scaling, which contributed to severe flux decline. Membrane autopsy using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) analysis indicated that the reverse diffusion of DAP from the DS to the feed solution was primarily responsible for scale formation during the FDFO process. Physical cleaning of the membrane with deionised water at varying crossflow velocities was employed to evaluate the reversibility of membrane scaling and the extent of flux recovery. For the membrane scaled using DAP as DS, 80-90% of the original flux was recovered when the crossflow velocity for physical cleaning was the same as the crossflow velocity during FDFO desalination. However, when a higher crossflow velocity or Reynolds number was used, the flux was recovered almost completely, irrespective of the DS concentration used. This study underscores the importance of selecting a suitable fertiliser for FDFO desalination of brackish groundwater to avoid membrane scaling and severe flux decline.
- Experience in using thermal disinfection to remove viable bacteria and endotoxins in centraly distributed reverse osmosis water. [Journal Article]
- Arab J Nephrol Transplant 2014 Jan; 7(1):27-31.
Introduction: The water used for dilution of hemodialysis concentrates has to meet official quality recommendations regarding microbiology and chemical parameters. To avoid chemical use and to simplify treatments, hot water has been used to control microbial contamination of water distribution systems. In this study we evaluated the efficacy of heat disinfection in maintaining the quality of dialysis water generated by reverse osmosis (RO).
Methods:During the first part of the study, we consecutively used (1) continuous water circulation, (2) daily heat disinfection and (3) a combination of daily heat disinfection and weekly chemical disinfection while checking bacterial count and endotoxin level every 4-5 weeks. During the second part of the study, we continued using daily heat disinfection while checking bacterial count and endotoxin level on weekly basis.
Results:The endotoxin levels at all sampling points of the water treatment system were lower than 0.005/ ml throughout the study. The application of heat disinfection alone reduced bacterial levels but an escape phenomenon occurred. After an interval of 21 days, an exponential increase of bacterial count was noted and cultures from the RO unit revealed growth of Pseudomonas fluorescence. The addition of chemical disinfection was successful in eliminating micro-organisms. Throughout this study, micro-organisms and endotoxins were not detectable in dialysate fluid and substitution fluid in dialysis monitors.
Conclusion:The isolation of a thermo-sensitive organism from the RO unit after a period of relying on thermal disinfection suggests the existence of dead space in the RO unit that is not adequately exposed to heat but is accessible to chemical disinfection. Keywords: Chemical disinfection; Dialysis Water; Microbiological Quality; Thermal disinfection.
- An analysis of the effects of osmotic backwashing on the seawater reverse osmosis process. [Journal Article, Research Support, Non-U.S. Gov't]
- Environ Technol 2014 May-Jun; 35(9-12):1455-61.
Fouling control is an important consideration in the design and operation of membrane-based water treatment processes. It has been generally known that chemical cleaning is still the most common method to remove foultants and maintain the performance of reverse osmosis (RO) desalination. Regardless of the chemical membrane cleaning methods applied effectively, however, frequent chemical cleaning can shorten the membrane life. In addition, it also increases operating and maintenance costs due to the waste chemical disposal. As an alternative, osmotic backwashing can be applied to RO membranes by diluting the concentration polarization (CP) layer. In this study, the effects of osmotic backwashing were analysed under different total dissolved salts (TDSs) and backwashing conditions, and the parameters of the osmotic backwashing were evaluated. The results of the analysis based on the properties of the organic matters found in raw water showed that the cleaning efficiency in respect to the fouling by hydrophilic organic matters was the greatest. Osmotic backwashing was carried out by changing the TDS of the permeate. As a result, the backwashing volume decreased with time due to the CP of the permeate and the backwashing volume. The difference in the osmotic pressure between the raw water and the permeate (Delta pi) also decreased as time passed. It was confirmed that when the temperature of the effluent was high, both the cleaning efficiency and the backwashing volume, which inpours at the same time, increased. When the circulation flow of the effluent was high, both the cleaning efficiency and the backwashing volume increased.