Membrane biofouling by chlorine resistant Bacillus spp.: effect of feedwater chlorination on bacteria and membrane biofouling

In this study, bacteria isolated from a lake were characterised for their chlorine resistivity and the effects of chlorination on growth, mortality, protein expression and attachment propensity towards membranes. Biofouling and membrane performance were analysed. All isolated chlorine resistant strains, characterised by 16s rRNA gene sequencing, belonged to the genus Bacillus. Chlorination caused limited effects on bacterial growth and mortality. B. safensis and B. lechinoformis suffered the maximum effects due to chlorination. Live-to-dead ratios immediately after chlorination were above 1.3, with some exceptions. The membrane pure water flux recovery was highly strain dependent. Irreversible membrane fouling was observed with B. aquimaris. Membrane flux decreased substantially during ultrafiltration of water containing chlorine resistant bacteria.     

Life Cycle Assessment of Water Production Technologies - Part 1: Life Cycle Assessment of Different Commercial Desalination Technologies (MSF,MED, RO) (9 pp)

- Preamble. This series of two papers analyses and compares the environmental loads of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment with the present state of the art of the technology. Further, it is also presented an estimation of the potential environmental loads that the considered technologies could provoke in future, taking into account the most suitable evolution of the technology. - Part 1 presents the assessment of most commercial desalination technologies which are spread worldwide: Reverse Osmosis, Multi Effect Desalination and Multi Stage Flash. Part 2 presents the comparative LCA analysis of a big hydraulic infrastructure, as is to be found in the Ebro River Water Transfer project, with respect to desalination. - DOI: http://dx.doi.org/10.1065/lca2004.09.179.1 - Intention, Goal and Background. In this paper, some relevant results of a research work are presented, the main aim of which consists of performing the environmental assessment of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment of potable water supply to the end users. That is, the scope of this paper is mostly oriented to the comparative Life Cycle Assessment of different water production technologies instead of presenting new advancements in the LCA methodology. In Part 1, the environmental loads associated with the most widespread and important commercial desalination technologies all over the world - Reverse Osmosis (RO), Multi Effect Desalination (MED) and Multi Stage Flash (MSF) – are compared. The assessment technique is the Life Cycle Analysis (LCA), which includes the entire life cycle of each technology, encompassing: extraction and processing raw materials, manufacturing, transportation and distribution, operation and final waste disposal.- Methods and Main Features. The software SimaPro 5.0, developed by Dutch PRé Consultants, has been used as the analysis tool, because it is a well known, internationally accepted and validated tool. Different evaluation methods have been applied in the LCA evaluation: CML 2 baseline 2000, Eco-Points 97 and Eco-Indicator 99. Data used in the inventory analysis of this Part 1 come from: a) existing plants in operation; b) data bases implemented in the SimaPro 5.0 software -BUWAL 250, ETH-ESU 96, IDEMAT 2001. Different scenarios have been analyzed in both parts in order to estimate, not only the potential of reduction of the provoked environmental loads with the present state of the art of technology, but also the most likely future trend of technological evolution. In Part 1, different energy production models and the integration of desalination with other productive processes are studied, while the effect of the most likely technological evolution in the midterm, and the estimation of the environmental loads to the water transfer during drought periods are considered in Part 2. Results and Discussion The main contribution to the global environmental impact of desalination technologies comes from the operation, while the other phases, construction and disposal, are almost negligible when compared to it. Energy is very important in desalination, for this reason the environmental loads change a lot depending on the technology used for providing the energy used in the desalination process. Among the different analyzed technologies, RO is the least aggressive desalination technology (one order of magnitude lower than the thermal processes, MSF and MED) for the environment. When integrating thermal desalination with other productive processes taking advantage of the residual heat, the environmental loads of thermal desalination technologies is highly reduced, obtaining similar loads to that of RO. The environmental loads of desalination technologies are significantly reduced when an energy model based on renewable energies is used. Taking into account the technological evolution, which is experiencing the RO, a reduction of its environmental load by about 40% is to be expected in the mid-term. Conclusion The main conclusion of Part 1 is that, with the present state of the art of the technology, RO is clearly the desalination technology with a reduced environmental load (one order of magnitude lower than the thermal processes, MSF and MED). In the case of thermal desalination technologies, their environmental load can be highly reduced (about 1,000 times less) when integrated with other industrial processes. In the case of RO, the scores and the airborne emissions obtained from an electricity production model based on renewable energies are about 65-70 times lower than those obtained when the electricity production model is mainly based on fossil fuels. Recommendations and Outlook Although desalination technologies are energy intensive and provoke an important environmental load, they present a high potential in being reduced since: a) in the mid-term, it is to be expected that the different technologies could improve their efficiency significantly, b) the environmental loads would be highly reduced if the energy production models were not mainly based on fossil fuels and c) the energy consumption, particularly in the case of thermal desalination, can be drastically reduced when integrating desalination with other productive processes. The results presented in this paper indicate that a very interesting and promising field of research is available in order to reduce the environmental load of these vigorous and increasing desalination technologies.     

Life Cycle Assessment of Water Production Technologies - Part 2: Reverse Osmosis Desalination versus the Ebro River Water Transfer (9 pp)

- Preamble. This series of two papers analyses and compares the environmental loads of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment with the present state of the art of technology. Further, an estimation of the potential environmental loads that the considered technologies could provoke in future is also presented, taking into account the most suitable evolution of the technology. - Part 1 presents the assessment of most commercial desalination technologies which are spread worldwide: Reverse Osmosis, Multi Effect Desalination and Multi Stage Flash. Part 2 presents the comparative LCA analysis of a big hydraulic infrastructure, as is to be found in the Ebro River Water Transfer project, with respect to desalination. - Intention, Goal and Background. In this paper some relevant results of a research work are presented, the main aim of which consists of performing the environmental assessment of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment for supplying potable water to the end users. The scope of this paper is mostly oriented to the comparative Life Cycle Assessment of different water production technologies instead of presenting new advancements in the LCA methodology. Based on the results obtained in Part 1 (LCA of most widespread commercial desalination technologies), the particular case of a big hydraulic project, which is the Ebro River Water Transfer (ERWT) considered in the Spanish National Hydrologic Plan, versus the production by desalination of the same amount of water to be diverted, is compared in Part 2. The assessment technique is the Life Cycle Analysis (LCA), which includes the entire life cycle of each technology, encompassing: extraction and processing raw materials, manufacturing, transportation and distribution, operation and final waste disposal. Methods and Main Features. The software SimaPro 5.0, developed by Dutch PRé Consultants, has been used as the analysis tool, because it is a well known, internationally accepted and validated tool. Different evaluation methods have been applied in the LCA evaluation: CML 2 baseline 2000, Eco-Points 97 and Eco-Indicator 99. Data used in the inventory analysis of this Part 2 come from: a) desalination: data obtained for existing plants in operation; b) ERWT: Project approved in the Spanish National Hydrologic Plan and its Environmental Impact Evaluation and; c) data bases implemented in the SimaPro software – BUWAL 250, ETH-ESU 96, IDEMAT 2001. Different scenarios have been analyzed in both parts in order to estimate not only the potential of reduction of the provoked environmental loads with the present state of the art of technology, but also the most likely future trend of technological evolution. In Part 1, different energy production models and the integration of desalination with other productive processes are studied, while the effect of the most likely technological evolution in the midterm, and the estimation of the environmental loads to the water transfer during drought periods are considered in Part 2. Results and Discussion As proven in Part 1, RO is a less aggressive desalination technology for the environment. Its aggression is one order of magnitude lower than that of the thermal processes, MSF and MED. The main contribution to the global environmental impact of RO comes from the operation, while the other phases, construction and disposal, are almost negligible when compared to it. In the case of the ERWT, the contribution of the operation phase is also the most important one, but the construction phase has an important contribution too. Its corresponding environmental load, with the present state of the art of technology, is slightly lower than that provoked by the RO desalination technology. However, the results obtained in the different scenarios analyzed show that the potential reduction of the environmental load in the case of the ERWT is significantly lower than that in the case of the RO. The effect of drought periods in the assessed environmental loads of the water transfer is not negligible, obtaining as a result an increasing environmental load per m3 of diverted water. Conclusion The environmental load associated with RO, with the present state of the art of technology, is slightly higher than that provoked by the ERWT. However, considering the actual trend of technological improvement of the RO and the present trend of energy production technology in the address of reducing the fossil fuels\ contribution in the electricity production, the environmental load associated with RO in the short mid-term would be likely to be lower than that corresponding to the ERWT. Recommendations and Outlook Although desalination technologies are energy intensive and provoke an important environmental load, as already explained in Part 1, they present a high potential of reducing it. In respect to ERWT, the results indicate, when the infrastructure of ERWT is completed (by 2010–2012), that the LCA of RO will be likely to be against the water transfer. With the present technological evolution of water production technologies and from the results obtained in this paper, it seems, from an environmental viewpoint, that big hydraulic projects should be considered the last option because they are rigid and long-term infrastructures (several decades and even centuries of operation) that provoke important environmental loads with only a small margin for reducing them.     

Zwitterionic polymers functionalised nanoporous graphene for water desalination: a molecular dynamics study

In this paper, one nanoporous graphene grafting several zwitterionic polymer chains was designed as the osmosis membrane for seawater desalination. Using molecular dynamics simulation, the efficiency and mechanism of salt rejection were discussed. The simulated results showed that the zwitterionic polymer chains on nanoporous graphene can form the charge channel to block Na⁺ and Cl^? ions pass through, and the slat rejection efficiency of functionalised graphene can reach to about 90%. In the simulation, the steric hindrance and electrostatic interaction are the main factors for the salt rejection. With time evolution, the charge channel formed by the soft polymer chains can decrease the effective pore area of membrane, leading to the increase of steric hindrance; the positive and negative centres of polymer chains can adsorb Na⁺ and Cl^? ions under electrostatic interaction in the solution, contributing into the increase of charge density above the membrane. These conclusions are consistent with experimental report. Our designed osmosis membrane about the graphene is helpful for improving the potential application of defect graphene in water desalination and reducing the trouble of obtaining appropriate graphene sheet with small aperture.     

Nature of the water channels in the internodal cells ofNitellopsis

Summary The hydraulic resistance was measured on internodal cells ofNitellopsis obtusa using the method of transcellular osmosis. The hydraulic resistance was approximately 2.65 pm^–1 sec Pa, which corresponds to an osmotic permeability of 101.75 m sec^–1 (at 20°C).p-Chloromercuriphenyl sulfonic acid (pCMPS) (0.1–1mm, 60 min) reversibly increases the hydraulic resistance in a concentration-dependent manner.pCMPS does not have any effect on the cellular osmotic pressure.pCMPS increases the activation energy of water movement from 16.84 to 32.64 kJ mol^–1, indicating that it inhibits water movement by modifying a low resistance pathway.pCMPS specifically increases the hydraulic resistance to exosmosis, but does not influence endosmosis. By contrast, nonyltriethylammonium (C₉), a blocking agent of K⁺ channels, increases the hydraulic resistance to endosmosis, but does not affect that to exosmosis. These data support the hypothesis that water moves through membrane proteins in characean internodal cells and further that the polarity of water movement may be a consequence of the differential gating of membrane proteins on the endo- and exoosmotic ends.     

甘草腺体结构及对渗透胁迫的调节作用

甘草叶片上的腺体是其特殊的耐旱形态学结构,通过腺体分泌多糖调节叶肉细胞渗透势是其耐旱的重要生理特征。甘草叶片处于两面对称叶尚未展开期,部分腺体头部已分泌积累呈球状的多糖液,约占总腺体数的13.0%;部分腺体开始分泌多糖液,约占总腺体数的11.6%;75.3%的腺体尚未开始分泌多糖液,表明该期的腺体已有部分开始参与渗透调节。甘草发育成熟的功能叶上的所有腺体头部都分泌有呈球状的多糖液,表明该期所有的腺体都通过向外分泌多糖参与渗透调节。15%PEG+Hoagland培养的渗透胁迫比Hoagland培养的非渗透胁迫,叶内多糖增加了59.8%(P<0.01)。甘草通过腺体向腺体外分泌多糖液的作用,维持叶肉细胞适合的渗透势是甘草一种主动调节过程和方式。     

Oxidative gating of water channels (aquaporins) in corn roots

An oxidative gating of water channels (aquaporins: AQPs) was observed in roots of corn seedlings as already found for the green alga Chara corallina. In the presence of 35 mM hydrogen peroxide (H2O2)--a precursor of hydroxyl radicals (*OH)--half times of water flow (as measured with the aid of pressure probes) increased at the level of both entire roots and individual cortical cells by factors of three and nine, respectively. This indicated decreases in the hydrostatic hydraulic conductivity of roots (Lp(hr)) and of cells (Lp(h)) by the same factors. Unlike other stresses, the plant hormone abscisic acid (ABA) had no ameliorative effect either on root LP(hr) or on cell Lp(h) when AQPs were inhibited by oxidative stress. Closure of AQPs reduced the permeability of acetone by factors of two in roots and 1.5 in cells. This indicated that AQPs were not ideally selective for water but allowed the passage of the organic solute acetone. In the presence of H2O2, channel closure caused anomalous (negative) osmosis at both the root and the cell level. This was interpreted by the fact that in the case of the rapidly permeating solute acetone, channel closure caused the solute to move faster than the water and the reflection coefficient (sigma s) reversed its sign. When H2O2 was removed from the medium, the effects were reversible, again at both the root and the cell level. The results provide evidence of oxidative gating of AQPs, which leads on to inhibition of water uptake by the roots. Possible mechanisms of the oxidative gating of AQPs induced by H2O2 (*OH) are discussed.     

Biofouling of reverse osmosis membranes used in river water purification for drinking purposes: analysis of microbial populations

Biofouling in water treatment processes represents one of the most frequent causes of plant performance decline. Investigation of clogged membranes (reverse osmosis membranes, microfiltration membranes and ultrafiltration membranes) is generally performed on fresh membranes. In the present study, a multidisciplinary autopsy of a reverse osmosis membrane (ROM) was conducted. The membrane, which was used in sulfate-rich river water purification for drinking purposes, had become inoperative after 6 months because of biofouling and was later stored for 18 months in dry conditions before analysis. SSU rRNA gene library construction, clone sequencing, T-RFLP, light microscope, and scanning electron microscope (SEM) observations were used to identify the microorganisms present on the membrane and possibly responsible for biofouling at the time of removal. The microorganisms were mainly represented by bacteria belonging to the phylum Actinobacteria and by a single protozoan species belonging to the Lobosea group. The microbiological analysis was interpreted in the context of the treatment plant operations to hypothesize as to the possible mechanisms used by microorganisms to enter the plant and colonize the ROM surface.     

Removal of Phthalate Esters by Activated Sludge Inoculated with a Strain of Nocardia erythropolis

Phthalate esters, such as di-2-ethyl hexyl phthalate (DEHP) and di-n-butyl phthalate (DBP), were efficiently removed from wastewater by inoculating viable cells of Nocardia erythropolis, a bacterium capable of rapidly degrading phthalate esters, in activated sludge. When the wastewater containing 1500 ppm of DEHP was treated with the activated sludge inoculated with Nocardia erythropolis, the DEHP was found to be removed at a rate of 98.2% in 1 day and to be gas-chromatographically free on and after the 3rd day. Activated sludges, in particular, when high concentration of substances was used, were efficiently prevented from deflocculation of sludge by inoculation of Nocardia erythropolis, and moreover, the deflocked sludge was restored and recovered by the addition of Nocardia erythropolis.     

Osmotic Forces and Gap Junctions in Spreading Depression: A Computational Model

In a computational model of spreading depression (SD), ionic movement through a neuronal syncytium of cells connected by gap junctions is described electrodiffusively. Simulations predict that SD will not occur unless cells are allowed to expand in response to osmotic pressure gradients and K⁺ is allowed to move through gap junctions. SD waves of [K⁺]_out 25 to 60 mM moving at 2 to 18 mm/min are predicted over the range of parametric values reported in gray matter, with extracellular space decreasing up to 50%. Predicted waveform shape is qualitatively similar to laboratory reports. The delayed-rectifier, NMDA, BK, and Na⁺ currents are predicted to facilitate SD, while SK and A-type K⁺ currents and glial activity impede SD. These predictions are consonant with recent findings that gap junction poisons block SD and support the theories that cytosolic diffusion via gap junctions and osmotic forces are important mechanisms underlying SD.