Sludge Production and Settleability in Biofilm-Activated Sludge Process

The sludge production and settleability have been estimated experimentally in a completely mixed biofilm-activated sludge reactor (hybrid reactor). A steady-state hybrid reactor was run at different stages of suspended biomass concentration (X) under constant values of influent substrate concentration (So) and hydraulic retention time (HRT). The values of X were gradually decreased in these stages until the system completely washed out of the suspended biomass and converted to pure biofilm reactor. As a result, the role of biofilm in the treatment gradually increased with an increase in the effluent substrate concentration (S). The experiment was supported by a mathematical expression for describing the sludge yield in the system under the previous conditions. The experimental and theoretical studies in the present work reveal that there is a critical phase of the hybrid system at which the system produces a high rate of excess sludge. That critical phase is found at a specific ratio between the suspended and the attached growth. Avoiding that critical phase enables the sludge production in the hybrid reactor to be reduced and optimized. Further, the minimum sludge production was found when the biofilm is theoretically inactive for chemical oxygen demand (COD) removal (S相似文献   

A study of A2/O process in El-Berka WWTP by replacing the anaerobic selector with UASB and adopting a hybrid system in the oxic zone

ABSTRACT

A multistage system comprising an upflow anaerobic sludge blanket (UASB) followed by anoxic unit and then oxic activated sludge (AS) with biofilm is studied in El-Berka WWTP, Egypt. Different organic loading wastewaters of chemical oxygen demand (COD) less than 500 mg/L till 3000 mg/L are tested during the study. The hydraulic retention time (HRT) varies for each loading from 7.5 to 10 to 15 h. The UASB reactor accomplishes the removal efficiency of 50%–70% of influent COD. The overall system performs the removal efficiency of 95% of influent COD and NH₄-N. Also, the results are verified by a modified mathematical model.     

Total mercury and its distribution in blue crab and deep water pink shrimp from Alexandria coast

Total mercury content and its distribution in muscles and viscera of male and female blue crab (Callinectes sapidus Rothbum) and deep water pink shrimp (Parapenacus longirostris) collected from the 3 main fishing grounds near the Alexandria coast in the Mediterranean sea was estimated. The results indicate that the mercury content in the muscles of both species differ according to fishing areas, size, sex, and species. More than 75% of total mercury were accumulated in the viscera of both species which indicates that the mercury entered in these organisms via the feed chain.     

Analysis of the atomic force microscopy vibration behavior using the Timoshenko theory by multi‐scale method in the air environment

This article deals with the modeling and simulation of the vibration behavior of piezoelectric micro‐cantilever (MC) based on the Timoshenko theory and using multi‐scale (MTS) method in the air environment. In this regard, the results are compared with the previous literature, such as the finite element method and the MTS method. The analysis of the piezoelectric MC vibrating behavior is investigated in a dynamical mode including non‐contact and tapping modes. The dynamics of this system is affected by interferential forces between probe tip and sample surface, such as van der Waals, capillary, and contact forces. According to the results, the forces applied to the probe tip reduce the amplitude and the resonance frequency. The simulation of surface topography in non‐contact mode and tapping for rectangular and wedge‐shaped roughness in the air environment are presented. Various experiments have been conducted in Ara research Company using the atomic force microscopy device in the amplitude mode. In the NSC15 Cantilever, the first natural frequency is derived from the results of the MC simulation based on Timoshenko beam theory, the practical results are 295.85 and 296.12 kHz, and the error rate is 0.09; at higher natural frequencies, the error rate has been increased. The γ _f coefficient is a measure of the nonlinear effects on the system; the effect of the piezoelectric length and width on γ _f coefficient is also investigated.     

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.     

Utilisation of mango seed kernel (Mangifera indica) as a source of oil

Fat extracted from mango seed kernel (Mangifera indica) was analysed for its chemical and physical constants, triglycerides, fatty acids and phospholipids; and these were compared with those of cotton seed oil, cocoa butter and two of its substitutes, namely, Croklaan Special 555 and Wesco Special E. The effects of incorporation of mango seed kernel oil in butterscotch toffee on its organoleptic properties were also studied. It was found that mango kernel oil and cocoa butter were almost identical in several of their constants, triglycerides, fatty acids and effects on taste, odour and texture of the toffee.     

Mercury content in some marine fish from the Alexandria coast

The total Hg of 6 marine fish species, caught from the 3 main fishing grounds along the coast of Alexandria, was determined and the distribution among the different organs was studied. It was found that the total Hg levels in fish differed according to species, size, and organs of fish as well as fishing ground. The highest value was found in large size especially in the viscera of Mullus barbatus obtained from El-Mex fishing ground.     

Infrared study of the interaction of dental polycarboxylate cements with tooth structure and some metals

The interaction of three commercial zinc polycarboxylate cements with tooth structure was investigated by using infrared spectroscopic techniques. The obtained data revealed that the cements interact with enamel and ionic bonds are formed between calcium ions in enamel and carboxyl groups in polycarboxylic acid. The interaction depends on the percentages of ZnO content in the powders and of carboxylic acid in the liquids of these cements. The results provided some evidence that the cements also may interact with dentin but to a lesser extent than with enamel. The interaction of the cements with the metals copper and nickel or with Cr₂O₃, was also studied.     

Temperature dependence of the IR-absorbances of diphenylcarbinol

The temperature dependence of the absorbances of IR-absorption bands corresponding to the fundamental, overtones and combination frequences of diphenylcarbinol in the pure liquid phase is presented. The range of temperature taken in this investigation is between 68 and 298°C. Many difficulties have been met with in trying to find a relation connecting the symmetry of the vibrations and the temperature effect on their absorbances. As shown, in the text, the change in the absorbances of the bands and the temperature variation is linear even for the broad bands.