Microscopic Visualization Technique to Predict the Permeation of Organic Solvents through PVC Pipes in Water Distribution Systems

Organic contaminants may permeate through plastic pipes in water distribution systems and adversely affect the quality of drinking water. In this study, we developed a microscopic visualization technique to investigate the permeation of common organic contaminants (benzene, toluene, ethylbenzene, xylene, and trichloroethene) through polyvinyl chloride (PVC) pipes. By observing the propagation of organic moving fronts in the pipe materials with a light microscope, the technique was able to predict the permeation breakthrough times through PVC pipes that were determined in the pipe-bottle test. The advance of an organic moving front was found to be linearly dependent on the square-root of time and the propagation rate increased with an increase in the external organic chemical activity. Permeation of organic mixtures into PVC pipes was found to be additive in proportion to the permeation rates and volume percents of each component. In combination with a 2-year pipe-bottle test for PVC pipes exposed to premium gasoline, mathematical extrapolations based on the microscopic visualization tests predicted that PVC pipe are likely to resist permeation by commercial gasoline for the service life of the pipe.     

Estimation of water diffusivity parameters on grape dynamic drying

A computer program was developed, aiming at estimating water diffusivity parameters in a dynamic drying process with grapes, assessing the predictability of corresponding non-isothermal drying curves. It numerically solves Fick’s second law for a sphere, by explicit finite differences, in a shrinking system, with anisotropic properties and changing boundary conditions.     

Thick mesoporous TiO2 films through a sol–gel method involving a non-ionic surfactant: Characterization and enhanced performance for water photo-electrolysis

A method for the preparation of TiO₂ thick films made of anatase nanocrystallites and featuring a mesoporous structure is described. Modification of a typical sol–gel synthesis that uses Titanium (IV) isopropoxide (TTIP) as precursor, through both the incorporation of a non-ionic surfactant (Tween 20) and the optimization of thermal treatments, allows to increase the thickness of each spin-coated layer, and to obtain by successive runs porous, transparent, homogeneous and crackless films with thickness up to 1.2 μm. The effect of the changing the Tween 20/TTIP ratio (R, ranging from 0.25 to 1.00) on the crystallographic, morphological and optical properties has been studied by X-ray Diffraction, N₂ adsorption, UV–Visible Spectroscopy and Field Emission Scanning Electron Microscopy, in both powder and film form. The size of particles decreases slightly with increasing R, while the specific surface area increases somewhat. For all the R values, including R = 0, nanoparticles behave as direct semiconductors, in contrast with bulk anatase: changes in the band gap extent caused by the porous structure are negligible. Photo-electrochemical performance and carrier dynamics were studied using the films as anodes for the water photo-electrolysis reaction by means of Linear Sweep Voltammetry, Amperometry and Electrochemical Impedance Spectroscopy. Increasing R values improves the photo-catalytic performance of the TiO₂ films and leads to a comprehensive faster charge transfer at the oxide–solution interface, so that those with R = 1 offer highest performance, due to the combination of both higher thickness and improved quality of the material.     

Sediment Oxygen Demand and Nutrient Fluxes for a Tropical Reservoir in Singapore

Sediment oxygen demand (SOD) and nutrient flux studies were conducted for a tropical reservoir in Singapore in order to determine the approximate SOD and nutrient release rates from the sediments. SOD values obtained from laboratory experiments ranged from 1.4 to 3.3?g?O2/m2-day. Similar results were also obtained by calculating SOD values from in situ DO measurements taken in the field. The nutrient flux study was performed in the laboratory at a constant temperature of 25°C in oxic and anoxic columns. Except for nitrate+nitrite, higher nutrient release rates were generally observed under anoxic conditions. The ammonium release rate was 0.06?g?O2/m2-day under oxic conditions and 0.117?g?O2/m2-day under anoxic conditions. The nitrate flux rate was 0.17?g?O2/m2-day under oxic conditions but was negligible under anoxic conditions. Orthophosphate flux results were negative throughout the oxic incubation implying that sediments acted as a sink. The release rate of orthophosphate was 0.007?6?g?O2/m2-day under anoxic conditions.     

Association of gastrointestinal illness and recreational water exposure at an inland U.S. beach

Recent epidemiology studies examining U.S. recreational water exposure and illness relationships have focused primarily on coastal and Great Lakes beaches. Human-made lakes in the U.S. have received little attention in epidemiology studies despite contributing to more waterborne disease epidemics annually than coastal U.S. waters. In a comprehensive beach cohort study, we examined relationships between water quality indicators and reported adverse health outcomes among users of a beach at an inland U.S. lake. Human health data was collected over 26 swimming days during the 2009 swimming season in conjunction with water quality measurements. Adverse health outcomes were reported 8-9 days post-exposure via a phone survey. Wading, playing or swimming in the water was observed to be a significant risk factor for GI illness (adjusted odds ratio (AOR) of 3.2; CI 1.1, 9.0). Among water users, Escherichia coli density was significantly associated with elevated GI illness risk where the highest E. coli quartile was associated with an AOR of 7.0 (CI 1.5, 32). GI illness associations are consistent with previous freshwater epidemiology studies. Our findings are unique in that our observations of positive associations with GI illness risk are based upon a single daily E. coli measurement. Lastly, this study focused on an understudied issue, illness risk at inland reservoirs. Our results support the usefulness of E. coli as a health-relevant indicator of water quality for this inland U.S. beach.     

南水北调工程中段用大跨度开沟机设计

根据南水北调工程中段工程需要而设计的大跨度开沟机,适合一般混填土的开沟施工。本文通过对其执行机构、桁架机构的设计进行分析,得出结论:其适用最大跨度为23m,最大坡度为1:3,开沟最大深度600mm,开沟速度100~300m/h。该设备生产周期短、投资小、效率高。     

Electrodialytic remediation of soil fines (<63 μm) in suspension—Influence of current strength and L/S

Current treatment of the remaining soil fines from soil wash is onerous and expensive, and therefore, in this work, we investigated the feasibility of electrodialytic remediation (EDR) as an alternative treatment. The study focuses on EDR efficiency as a function of current strength, liquid-to-solid-ratio (L/S), pH and time. We found out that during the experiments, Pb was easily dissolved by the acidification resulting from water splitting at the anion-exchange membrane. When higher currents and/or higher L/S ratios were applied, it was found that water splitting occurring at the cation-exchange membrane increased the pH, and this resulted in decreased remediation efficiency. It was shown that complete remediation of the soil-fines is possible, with the majority of the Pb being transported into the catholyte and precipitated at the cathode. Based on the results it is recommended that EDR is implemented using a number of reactors in series, where the initial reactor works at the highest possible removal rate, and the final reactor works at the target Pb-concentration.     

Sorption characteristics of foam concrete

Knowledge of sorption characteristics like absorption and sorptivity of building materials are of importance as they affect the durability and other properties. In the case of lightweight concrete like aerated and foam concrete, the moisture movement behaviour becomes more complex as such concretes contain much larger volume of air voids. This paper is aimed at investigating the sorption-related properties of foam concrete as affected by its composition and pore structure. Water absorption by complete immersion and sorptivity are measured for various mixes with different fly ash replacement levels for sand and different foam volume. It was found that sorption values are lower than the corresponding base mix (without foam) and the values reduce with increase in foam volume. It is also found that sorption depends on the filler type, density and pore structure and also on permeation mechanisms.     

Horizons and future of water desalination in Libya

A premature study has been conducted to overlook the viability and feasibility of the future of desalination in Libya, by estimating the water situation in several locations in the country. A simplified review of the spectrum of well-known desalination techniques and a presentation of these analysis of the water situation would be highlighted to guideline the planners on how, why and when to embark on desalination to resolve the water shortage problem that would be faced at any moment in the future. Finally the methods to resolve shortage problem alongside their economical evaluation would be considered briefly.     

Practical Assessment of Electronic Water Treatment for the Prevention of Fouling

Fouling or scaling, i.e., the occurrence of deposits on tubes, heat exchangers, and other devices, is a common problem in industrial and domestic processes. Many anti‐fouling techniques exist, both chemically and non‐chemically. The efficiency of non‐chemical methods is still controversial, although the use of these devices is already widespread in industry. In this contribution, a case study is presented in which the operation of such a device is demonstrated. The electronic water treatment device under study was connected to a 2 m‐long copper tube immersed in a water bath with a temperature of 65 °C. A short‐term experiment revealed that the device did not alter the water chemistry and that locally, fouling was prevented by the device. However, the potential for fouling further downstream was not reduced. A long‐term experiment further confirmed the findings of the short‐term experiment showing that locally, the device has an anti‐fouling action as a significant increase in weight was observed when the device was switched off and a significant decrease in weight was observed when the device was switched on.