Effect of organic loading on a novel hydrogen bioreactor

This study investigated the impact of six organic loading rates (OLR) ranging from 6.5 gCOD/L-d to 206 gCOD/L-d on the performance of a novel integrated biohydrogen reactor clarifier systems (IBRCSs) comprised a continuously stirred reactor (CSTR) for biological hydrogen production, followed by an uncovered gravity settler for decoupling of solids retention time (SRT) from hydraulic retention time (HRT). The system was able to maintain a high molar hydrogen yield of 2.8 mol H₂/mol glucose at OLR ranging from 6.5 to 103 gCOD/L-d, but dropped precipitously to approximately 1.2 and 1.1 mol H₂/mol glucose for the OLRs of 154 and 206 gCOD/L-d, respectively. The optimum OLR at HRT of 8 h for maximizing both hydrogen molar yield and volumetric hydrogen production was 103 gCOD/L-d. A positive statistical correlation was observed between the molar hydrogen production and the molar acetate-to-butyrate ratio. Biomass yield correlated negatively with hydrogen yield, although not linearly. Analyzing the food-to-microorganisms (F/M) data in this study and others revealed that, both molar hydrogen yields and biomass specific hydrogen rates peaked at 2.8 mol H₂/mol glucose and 2.3 L/gVSS-d at F/M ratios ranging from 4.4 to 6.4 gCOD/gVSS-d. Microbial community analysis for OLRs of 6.5 and 25.7 gCOD/L-d showed the predominance of hydrogen producers such as Clostridium acetobutyricum, Klebsiella pneumonia, Clostridium butyricum, Clostridium pasteurianum. While at extremely high OLRs of 154 and 206 gCOD/L-d, a microbial shift was clearly evident due to the coexistence of the non-hydrogen producers such as Lactococcus sp. and Pseudomonas sp.     

Use of low CaO unprocessed steel slag in concrete as fine aggregate

Steel slag, which is produced locally in great amounts, has a negative impact on the environment when disposed. Local steel slag has a low CaO content and has no pozzolanic activity.In this research, local unprocessed steel slag is introduced in concrete mixes. Various mixes with compressive strength ranging from 25 to 45 MPa are studied. The slag is used as fine aggregate replacing the sand in the mixes, partly or totally. Ratios of 0%, 15%, 30%, 50% and 100% are used.Depending on the grade of concrete, the compressive strength is improved when steel slag is used for low sand replacement ratios (up to 30%).When optimum values are used, the 28-day tensile strength of concrete is improved by 1.4–2.4 times and the compressive strength is improved by 1.1–1.3 times depending on the replacement ratio and the grade of concrete. The best results are obtained for replacement ratios of 30–50% for tensile strength and 15–30% for compressive strength.Therefore, the use of steel slag in concrete would enhance the strength of concrete, especially tensile strength, provided the correct ratio is used.     

Three dimensional energy profile:: A conceptual framework for assessing household energy use

The provision of adequate, reliable, and affordable energy has been considered as a cornerstone of development. More than one-third of the world's population has a very limited access to modern energy services and suffers from its various negative consequences. Researchers have been exploring various dimensions of household energy use in order to design strategies to provide secure access to modern energy services. However, despite more than three decades of effort, our understanding of household energy use patterns is very limited, particularly in the context of rural regions of the developing world. Through this paper, the past and the current trends in the field of energy analysis are investigated. The literature on rural energy and energy transition in developing world has been explored and the factors affecting households' decisions on energy use are listed. The and the factors affecting households' decisions on energy use are listed. The gaps identified in the literature on rural household energy analysis provide a basis for developing an alternative model that can create a more realistic view of household energy use. The three dimensional energy profile is presented as a new conceptual model for assessment of household energy use. This framework acts as a basis for building new theoretical and empirical models of rural household energy use.     

Tea and coffee consumption in relation to vitamin D and calcium levels in Saudi adolescents

ABSTRACT: BACKGROUND: Coffee and tea consumption was hypothesized to interact with variants of vitamin D-receptor polymorphisms, but limited evidence exists. Here we determine for the first time whether increased coffee and tea consumption affects circulating levels of 25-hydroxyvitamin D in a cohort of Saudi adolescents. METHODS: A total of 330 randomly selected Saudi adolescents were included. Anthropometrics were recorded and fasting blood samples were analyzed for routine analysis of fasting glucose, lipid levels, calcium, albumin and phosphorous. Frequency of coffee and tea intake was noted. 25-hydroxyvitamin D levels were measured using enzyme-linked immunosorbent assays. RESULTS: Improved lipid profiles were observed in both boys and girls, as demonstrated by increased levels of HDL-cholesterol, even after controlling for age and BMI, among those consuming 9--12 cups of coffee/week. Vitamin D levels were significantly highest among those consuming 9--12 cups of tea/week in all subjects (p-value 0.009) independent of age, gender, BMI, physical activity and sun exposure. CONCLUSION: This study suggests a link between tea consumption and vitamin D levels in a cohort of Saudi adolescents, independent of age, BMI, gender, physical activity and sun exposure. These findings should be confirmed prospectively.     

Structure effect of some amine derivatives on corrosion inhibition efficiency for carbon steel in acidic media using electrochemical and Quantum Theory Methods

The structure effect on corrosion inhibition of two amines and their derivatives is the main object of this article. The first amine was 1,8-diaminooctane and its ethoxylated (50 e.o.) 1,8-diaminooctane and propoxylated (50 p.o.) 1,8-diaminooctane. The second amine is the tetraethylenepentamine and its ethoxylated (50 e.o.) and propoxylated (50 p.o.) derivatives. The investigations were carried out by open circuit potential, potentiodynamic polarization, electrochemical impedance, quantum calculations and SEM measurements. The data obtained for the first amine showed the minimum inhibition efficiency (65.5%), meanwhile the maximum inhibition efficiency was 78.9% for its propoxylated derivative. On the other hand the maximium inhibition efficiency was 91% for the second propoxylated amine. The electronic properties; HOMO and LUMO energy levels, energy gap, dipole moment, polarizability, log P, total energy, charge densities, area/molecule and hydration energy have been calculated. The inhibition efficiency was calculated theoretically using the electronic parameters. From the obtained results, there is a significant difference between the inhibition efficiency of the electronic and the inhibition efficiency experimentally. The results were discussed on the light of the chemical structure of the used inhibitors. In general, the inhibition efficiency is affected by the shape and structure of the molecule.     

Thermal performance of different pond cells under actual climatic conditions in Qatar

Experimental work was undertaken to study the thermal performance of three different pond cells under actual climatic conditions of Qatar. The first cell was an open pond. In the second unit, a finned radiator, painted black, was placed over the pond. In the third cell, the water was contained in a polyethylene bag. Experimental results indicated that the exposed pond cell came out best, when considered in terms of how quickly the temperature of the stored water could be reduced, and how low that temperature could be. The water in the exposed pond was cooled directly (by evaporation and radiation to sky) whereas in the case of the finned radiator cell, heat had to be transferred from the stored water to the radiator, and then from the radiator to the surrounding. In the case of water-in-bag cell, evaporation was eliminated and radiative exchange with the sky was reduced due to the partial transparency of the polyethylene bag (in the infrared region).     

Fluorescent dye labeled bacteriophages--a new tracer for the investigation of viral transport in porous media: 1. Introduction and characterization

A new method for the study of pathogen transport in porous media is presented. The method is based on conjugation of fluorescent dyes to target bacteriophages and application of the modified bacteriophages for tracer studies. We demonstrate that the relevant transport determining properties of Rhodamine and several fluorescein-labeled phages are practically identical to those of the native bacteriophages. The advantages of the proposed method relative to direct enumeration of bacteriophages by plaque forming unit method, turbidity, fluorescent microspheres, and other alternative tracers are discussed. Notable advantages include simple quantitation by optical methods, unbiased signals even when virus aggregates are formed, and the ability to decouple inactivation kinetics from transport phenomena. Additionally, the signal reflects the removal and transport of the studied microorganism and not a surrogate.     

Development of an interferometer for measurement of the diffusion coefficient of miscible liquids

A common-path interferometer (CPI) system was developed to measure the diffusivity of transparent liquid pairs by real-time visualization of the concentration gradient profile. The CPI is an optical technique that can be used to measure changes in the gradient of the refractive index of transparent materials. The CPI is a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Molecular diffusivity of liquids can be determined by use of physical relations between changes in the optical path length and the liquid phase properties. The data obtained by this interferometer are compared with similar results from other techniques. This demonstrates that the instrument is reliable for measurement of the diffusivity of miscible liquids and allows the system to be compact and robust. It can also be useful for studies in interface dynamics as well as other applications in a low-gravity environment.