Sludge accumulation, characteristics, and pathogen inactivation in four primary waste stabilization ponds in central Mexico

To support the development of safe and feasible sludge management strategies, the accumulation rates of sludge and its characteristics were studied in four primary wastewater stabilization ponds (WSPs) in central Mexico (three facultative and one anaerobic). The accumulation rates and distribution of sludge were determined by measuring the thickness of the sludge layer at 8-40 locations throughout each pond. The average, per capita sludge accumulation rates ranged from 0.021 to 0.036m(3)/person/yr. In the anaerobic pond the sludge distribution was uniform throughout the pond, whereas in the three facultative ponds most of the sludge accumulated directly in front of the inlet. To measure the horizontal and vertical variation in the sludge characteristics, sludge cores were collected from 3 to 7 locations in three of the ponds. Each core was divided into 4 sub-samples in which various physical, chemical, and microbiological parameters were measured. In addition, the inactivation of several pathogen indicator organisms was studied in a batch of sludge for 7 months. Based on the microbiological results, it is concluded that reasonable estimates of the inactivation of fecal coliform bacteria, fecal enterococci, F+ coliphage, somatic coliphage, and Ascaris eggs in WSP sludge in central Mexico can be made using first-order rate constants of 0.1, 0.1, 0.01, 0.001, and 0.001d(-1), respectively. From the observed changes in the concentrations of total solids and the volatile to fixed solids ratio, empirical equations were developed to describe anaerobic degradation and compression, which are the two most important processes affecting the volume of sludge after its deposition.     

Kinetic and equilibrium studies in removing lead ions from aqueous solutions by natural sepiolite

The capacity of sepiolite for the removal of lead ions from aqueous solution was investigated under different experimental conditions. The Langmuir and Freundlich equations, which are in common use for describing sorption equilibrium for wastewater-treatment applications, were applied to data. The constants and correlation coefficients of these isotherm models for the present system at different conditions such as pH, temperature and particle size were calculated and compared. The equilibrium process was well described by the Langmuir isotherm model and the maximum sorption capacity was found to be 93.4 mg/g for the optimal experimental condition. The thermodynamic parameters (DeltaG(o), DeltaH(o) and DeltaS(o)) for lead sorption on the sepiolite were also determined from the temperature dependence. The influences of specific parameters such as the agitation speed, particle size and initial concentration for the kinetic studies were also examined. The sorption kinetics were tested for first order reversible, pseudo-first order and pseudo-second order reaction and the rate constants of kinetic models were calculated. The best correlation coefficients were obtained using the pseudo-second order kinetic model, indicating that lead uptake process followed the pseudo-second order rate expression.     

Porous PZT ceramics for receiving transducers

PZT-air (porous PZT) and PZT-polymer (polymer impregnated porous PZT) piezocomposites with varying porosity/polymer volume fractions have been manufactured. The composites were characterized in terms of hydrostatic charge (d/sub h/) and voltage (g/sub h/) coefficients, permittivity, hydrostatic figure of merit (d/sub h/.g/sub h/), and absolute sensitivity (M). With decreasing PZT ceramic volume, g/sub h/ increased, and d/sub h/.g/sub h/ had a broad maximum around 80 to 90% porosity/polymer content. The absolute sensitivity was also increased. In each case, PZT-air piezocomposites performed better than PZT-polymer piezocomposites. Hydrophones constructed from piezocomposites showed slightly lower measured receiving sensitivities than calculated values for piezocomposite materials, which was due to the loading effect of the cable and the low permittivity associated with the piezocomposites.     

A new model for the hazardous waste location-routing problem

Hazardous waste management involves the collection, transportation, treatment and disposal of hazardous wastes. In this paper a new multiobjective location-routing model is proposed. Our model also includes some constraints, which were observed in the literature but were not incorporated into previous models. The aim of the proposed model is to answer the following questions: where to open treatment centers and with which technologies, where to open disposal centers, how to route different types of hazardous waste to which of the compatible treatment technologies, and how to route waste residues to disposal centers. The model has the objective of minimizing the total cost and the transportation risk. A large-scale implementation of the model in the Central Anatolian region of Turkey is presented.     

Combining molecular imprinted nanoparticles with surface plasmon resonance nanosensor for chloramphenicol detection in honey

The focus of this article is to develop a surface plasmon resonance (SPR) nanosensor to determine chloramphenicol (CAP) using the molecularly imprinted nanoparticles. The CAP imprinted nanoparticles were prepared by miniemulsion polymerization method. Then, the nanoparticles were attached onto the SPR nanosensor surface via temperature‐controlled evaporation. Surface characterization studies were performed with atomic force microscopy and contact angle measurements. Kinetic studies were performed with CAP solutions in the concentration range of 0.155–6.192 nM. Florphenicol (FLP) and thiamphenicol (TAP) having similar chemical structures to the template (i.e., CAP) were chosen as competitors to determine selectivity of the nanoparticles. Selectivity constants were observed as 8.86 for CAP/TAP and 8.36 for CAP/FLP. The detection limit was calculated as 40 ng/kg honey sample. In the light of these results, it was emphasized that the SPR nanosensor is able to recognize CAP selectively and has a potential for real‐time CAP detection in honey sample. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A novel microbial BOD biosensor developed by the immobilization of P. Syringae in micro‐cellular polymers

BACKGROUND: A biochemical oxygen demand (BOD) sensor, based on an immobilized Pseudomonas syringae in highly porous micro‐cellular polymer (MCP) in combination with a dissolved oxygen electrode, has been developed for the analysis of biodegradable organic compounds in aqueous samples. Microorganisms were immobilized in a molded MCP disk and a wastewater sample was injected into the biocomposite disk by a flow injection system. Dissolved oxygen (DO) changes as a measure of soluble BOD was read with a DO probe placed into a flow cell carrying biocatalytically activated disk. RESULTS: Optimal response of the MCP BOD sensor was obtained at pH 6.8 and 25 °C with a typical response time of 3–5 min for a 2 mm thick molded polymeric disk. The sensor showed detection linearity over the range 5–100 mg L^?1 BOD₅ (r² > 0.99) at a flow rate of 0.6 mL min^?1. The repeatability and reproducibility of the sensor response were found to be 3.08% and 7.77%, respectively. BOD values produced with this biosensor for various municipal and industrial wastewaters correlated well with those determined by the conventional 5‐day BOD test. CONCLUSION: This new biosensor was different from present amperometric BOD biosensor configurations in which the biocatalyst (microbial/enzymatic) is placed between cellulose and Teflon membranes installed on a DO probe. The use of a molded MCP disk coniainng microbial activity offers better stability and lifetime for commercial use in environmental monitoring. Copyright © 2008 Society of Chemical Industry     

Carbon nanotube/boehmite-derived alumina ceramics obtained by hydrothermal synthesis and spark plasma sintering (SPS)

Preparation, structure and properties of hydrothermally treated carbon nanotube/boehmite (CNT/γ-AlOOH) and densification with spark plasma sintering of Al₂O₃ and CNT/Al₂O₃ nanocomposites were investigated. Hydrothermal synthesis was employed to produce CNT/boehmite from an aluminum acetate (Al(OH)(C₂H₃O₂)₂) and multiwall-CNTs mixture (200 °C/2 h.). TEM observations revealed that the size of the cubic shape boehmite particles lies around 40 nm and the presence of the interaction between surface functionalized CNTs and boehmite particles acts to form ‘nanocomposite particles’. Al₂O₃ and CNT/Al₂O₃ compact bodies were formed by means of spark plasma sintering (SPS) at 1600 °C for 5 min using an applied pressure of 50MPa resulting in the formation of stable α-Al₂O₃ phase and CNT–alumina compacts with nearly full density. It was also found that CNTs tend to locate along the alumina grain boundaries and therefore inhibit the grain coarsening and cause inter-granular fracture mode. The DC conductivity measurements reveal that the DC conductivity of CNT/Al₂O₃ is 10^?4 S/m which indicate that there is a 4 orders of magnitude increase in conductivity compared to monolithic Al₂O₃. The results of the microhardness tests indicate a slight increase in hardness for CNT/Al₂O₃ (28.35 GPa for Al₂O₃ and 28.57 GPa for CNT/Al₂O₃).     

The role of human factors in flexibility management: A survey

Flexibility can be defined as the ability to respond effectively to the ever‐changing and increasing needs of the customer. For this demand to be satisfied, flexibility should be built into the total chain of acquisition, processing, and distribution stages. As a result, there is an increasing interest in flexibility and flexibility enabling mechanisms/parameters to achieve the best strategy for obtaining the right and desired output. Although quite a number of flexibility definitions and mechanisms can be found in the literature, flexibility remains poorly understood and utilized in practice. That is due to the lack of standardization in the terminology about the flexibility definitions and mechanisms. This article presents the finding of an extensive literature survey to determine the Intra flexibility mechanisms/parameters. These mechanisms/parameters are then classified, according to their contribution to the supply chain stages and their interaction with Inter Flexibility mechanisms (e.g., Organizational structure flexibility, Technology flexibility, Information system flexibility, and Human resource flexibility). In addition, the crucial role of human factors and its relationship with flexibility mechanisms are investigated, and related flexibility mechanisms are identified. © 2002 John Wiley & Sons, Inc.     

Right Hemisphere Sensitivity to Word- and Sentence-Level Context: Evidence From Event-Related Brain Potentials.

Researchers using lateralized stimuli have suggested that the left hemisphere is sensitive to sentence-level context, whereas the right hemisphere (RH) primarily processes word-level meaning. The authors investigated this message-blind RH model by measuring associative priming with event-related brain potentials (ERPs). For word pairs in isolation, associated words elicited more positive ERPs than unassociated words with similar magnitudes and onset latencies in both visual fields. Embedded in sentences, these same pairs showed large sentential context effects in both fields. Small effects of association were observed, confined to incongruous sentences after right visual hemifield presentation but present for both congruous and incongruous sentences after left visual hemifield presentation. Results do not support the message-blind RH model but do suggest hemispheric asymmetries in the use of word and sentence context during real-time processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depressive symptoms among amphetamine and cocaine users before and after substance abuse treatment.

This study examined whether higher rates of depressive symptoms among amphetamine compared with cocaine users result from amphetamine use itself, polydrug use, or experiencing a major lifetime depressive episode and whether depressive symptoms among amphetamine users are more likely to persist 12 months after treatment. The association between amphetamine use and depressive symptoms disappears when controlling for polydrug use and lifetime major depressive episode. Polydrug use and lifetime depressive episode are significantly related to depressive symptoms in the year preceding treatment. Amphetamine use at intake does not predict depressive symptoms among individuals who are abstinent at follow-up, and amphetamine users are no more likely than cocaine users to report depression at a 12-month follow-up. (PsycINFO Database Record (c) 2010 APA, all rights reserved)