Role of Bioflocculation on Chemical Oxygen Demand Removal in Solids Contact Chamber of Trickling Filter/Solids Contact Process

The trickling filter/solids contact (TF/SC) process was developed in the late 1970s to improve the quality of the final effluent from existing trickling filter plants, to be able to meet stricter Environmental Protection Agency effluent requirements. Although this process has successfully achieved this objective, it is still not completely understood, there is limited information regarding the flocculation phenomena occurring in the solids contact chamber (SCC), and no information could be found on the relationship between flocculation and organic matter removal kinetics. To better understand the kinetics of biological flocculation in a continuous flow SCC, a long-term experimental program was conducted using a TF/SC pilot plant constructed at the Marrero, La., wastewater treatment plant. This program started in January 1998 and has continued through date. The present article will focus on two major areas: (1) the kinetics of bioflocculation in the SCC; and (2) effect of bioflocculation on chemical oxygen demand (COD) removal. Analysis of the wastewater composition revealed that, on the average, only 18.7% of the total COD in the SCC influent is truly dissolved. Therefore, most of the total COD removal observed in the SCC must be due to a physical process, such as flocculation. The experimental data confirmed that flocculation of the particulate COD contained in the trickling filter effluent explains the high total COD removal observed at the SCC. Both total and colloidal COD removals are well explained by the first-order flocculation model.     

Effect of Hanger Flexibility on Dynamic Response of Suspension Bridges

Linearized continuum models of a suspended span with unloaded backstays and of a symmetric three-span suspension bridge are used to study the effects of the flexibility of the hangers on the vertical vibrations of suspension bridges. The models include elastic parabolic cables, flexible distributed hangers with variable length, and a stiffening girder represented by an elastic beam. It is shown that the free vibrations of a suspended span with unloaded backstays are controlled by five dimensionless parameters, while six dimensionless parameters control the response of a symmetric three-span suspension bridge. The results indicate that the flexibility of the hangers has a significant effect on the natural frequencies of the higher modes only when the relative stiffness of the girder is very high. The effects of hanger flexibility on the response of a suspension bridge to localized impulsive loads are also found to be small. These findings confirm the traditional, albeit previously untested, assumption of inextensible hangers. Finally, the threshold amplitudes of free vibrations that would result in the incipient slackening of the hangers are determined.     

Mechanical properties of iron processed by severe plastic deformation

In the present study, the mechanical properties of Fe processed via severe plastic deformation (equal-channel angular pressing (ECAP)) at room temperature were investigated for the first time. The grain size of annealed Fe, with an initial grain size of about 200 μm, was reduced drastically during ECAP. After eight passes, the grain size reaches 200 to 400 nm, as documented by means of transmission electron microscopy (TEM). The value of microhardness during pressing increases 3 times over that of the starting material after the first pass and increases slightly during subsequent pressing for higher-purity Fe. Examination of the value of microhardness after eight passes as a function of post-ECAP annealing temperature shows a transition from recovery to recrystallization, an observation that resembles the behavior reported for heavily deformed metals and alloys. The tensile and compression behaviors were examined. In tension, a drop in the engineering stress-engineering strain curve beyond maximum load was observed both in the annealed Fe and the ECAP Fe. This drop is related to the neck deformation. The fracture surface, examined by scanning electron microscopy (SEM), shows vein patterns, which is different from the dimples found on the fracture surface of annealed Fe. In compression, an initial strain-hardening region followed by a no-strain-hardening region was observed in the ECAP Fe. The yield strength in tension of the ECAP Fe was observed to be higher than that in compression. The strengthening mechanisms and softening behavior are discussed.     

Defining Phonological Awareness and Its Relationship to Reading Skills in Low-Literacy Adults.

The main purpose of the study reported here was to investigate the relative importance of complexity of syllable structure and task differences in measuring phonological awareness in low-literacy adults. This study is a replication of a study with children conducted by S. A. Stahl and B. A. Murray (1994). Results indicated that the complexity of syllable structure did indeed better describe the construct of phonological awareness in low-literacy adults. At the same time, the authors also found some differences in the pattern of literacy acquisition for their Spanish adults in comparison with child literacy acquisition in English. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Carotenoid composition and vitamin A value of Brazilian loquat (Eriobotrya japonica Lindl.)

Six sample lots of loquat commercialized in Campinas, Brazil were analyzed for their carotenoid composition beta-carotene (7.8 micrograms/g), zeta-carotene (0.1 micrograms/g), neurosporene (1.1 micrograms/g), beta-cryptoxanthin (4.8 micrograms/g), 5,6-monoepoxy-beta-cryptoxanthin (0.6 micrograms/g), violaxanthin (1.6 micrograms/g), (0.8 micrograms/g) and auroxanthin (0.9 micrograms/g) were identified beta-Carotene and beta-cryptoxanthin were the principal pigments, being responsible for 44% and 27%, respectively, of the total carotenoid content (17.6 micrograms/g). Both were also the principal contributors to the vitamin A value of 175 RE/100g. The carotenoid composition of the Brazilian loquat resembles that of the Japanese loquat variety Tanaka.     

Analytical expression for the non-isothermal effectiveness factor: the nth-order reaction in a slab geometry

The problem of calculating the effectiveness factor for a porous slab of catalyst pellet under non-isothermal conditions has been revisited. An exact formal analytical solution was obtained for a nth-order (integer n?0), exothermic and irreversible chemical reaction. Numerical calculations where performed, and an analytical formula was obtained for the very fast reaction limit. In addition, a fairly simple formula, which was called the low beta approximation, was developed and tested to be valid for low values of the thermicity group β?0.1.     

Carotenoid composition and antioxidant activity of the raw and boiled fruit mesocarp of six varieties of Bactris gasipaes

Total carotenoid content and composition of carotenoids of six varieties of Bactris gasipaes were determined by spectrophotometry and HPLC, with photodiode array detector. Significant differences in total carotenoid content (1.1 to 22.3 mg/100g) were detected among these varieties. Boiling the fruits for 30 minutes did not affect total carotenoid content, but did change the amount of some specific carotenoids, mainly by the production of Z-isomers. Peach palm varieties had the same carotenoids, but in different proportions, presenting mainly, all E-beta-carotene (26.2% to 47.9%), Z-gamma-carotene (18.2% to 34.3%) and Z-lycopene (10.2% to 26.8%). When antioxidant activity was evaluated using DPPH, it was observed that the variety with higher percentages of beta-carotene (54.1%) presented the higher activity. This is one of the first reports in carotenoid content and antioxidant activity in well typified varieties of Bactris gasipaes, whose results could have a positive impact in the consumption of certain peach palm varieties.