Plastic mechanisms for thin-walled cold-formed steel members in eccentric compression.

The Eurocode 3 concerning thin-walled steel members divides members subjected to compression into four classes, considering their ductility. The representatives of the class C4 are short bars, for which the load-capacity corresponds to the maximum compression stresses less than the yield stress. There are bars prone to local buckling in the elastic range and they do not have a real post-elastic capacity. The failure at ultimate stage of such members, either in compression or bending, always occurs by forming a local plastic mechanism. This fact suggests the possibility to use the local plastic mechanism to characterise the ultimate strength of such members. The present paper is based on previous studies and some latest investigations of the authors, as well as the literature collected data. It represents an attempt to study the plastic mechanisms for members in eccentric compression about minor axis and the evolution of plastic mechanisms, considering several types of lipped channel sections

MANAGEMENT PRACTICES OFWASTEWATER SLUDGE

Large amounts of wastewater sludge, a secondary pollutant of wastewater treatment plants, commonly containing over 90% water and pathogens, organic pollutants and heavy metals, are produced daily worldwide.  Main treatment routes of wastewater sludge are: landfill, anaerobic digestion, land application and incineration. Anaerobic sludge digestion is a technology employed worldwide to reduce solids, stabilize organic matter, and destroy pathogens and to produce biogas as a source of energy.Compositing is applied for sludge treatment and conversion of complex biowaste into a stabilized product that can be used as organic fertilizer in agriculture. In this paper we present the main practices employed in the management of wastewater sludge, in order to reduce its volume, to capitalize it and to protect the environment

APPLICATIONS OF ROTATING BIOLOGICAL CONTACTORSIN WASTEWATER TREATMENT

Rotating biological contactors are generally used as secondary treatment of domestic, hospital and industrial wastewater, operating asan aerobic and anaerobic fixed film biological treatment. Rotating biological contactors areeffective in the removal of biodegradable matter,pathogenic bacteria,nitrogen, recalcitrant compounds, heavy metals,emerging contaminants, and dyes from wastewater. In this paper, we present the design and operating principles of rotating biological contactors, and we review some of the most important results related to the applications of rotating biological contactors for the treatment of wastewater originating from different activities

NANOMATERIALS FORHEAVY METALS REMOVAL FROM WASTEWATER

Human, agricultural, industrial, and mining activities generate large quantities of wastewater contaminated with toxic and non-biodegradable heavy metals such as As, Cr, Cd, Co, Cu, Hg, Ni, Pb and Zn.To avoid the harmful effects of heavy metals on terrestrial and aquatic ecosystems and on human health, it is essential to develop and implement innovative technologies for the removal of these toxic and hazardous pollutants from wastewater.In wastewater treatment, and particularly in nanotechnology applications, many efficient, ecological and cost-effective nanomaterials have been developed, having unique functions of heavy metals removal from industrial effluents, surface waters, groundwater and drinking water.Due to their antimicrobial properties, nanoparticles are also used for wastewater disinfection and microbial control

ELECTROCOAGULATION IN WASTEWATER TREATMENT

Within the past decades,water scarcity is one of the greatest challenges faced by humans, sothe treatment and reuse of wastewater generated daily from household, sanitary and industrial activities iswidely practiced and encouraged.Electrocoagulation has emerged as an effectivetechnology for the treatment ofdifferent categories of wastewater. The electrode materials should non-toxic to human health and environment and these usually involve aluminium or iron, but new materials are also used.The efficiency of electrocoagulation depends on current density, gap between anodes and cathodes, electrodes arrangement, composition and shape, initial pollutant concentration, composition and pH of the solution, electrolysis time.This paper aims to reviewthe mechanisms involved in wastewater electrocoagulationand the results of electrocoagulation applied in the treatment of wastewater from different sources

Further insights on predictors of environmental tobacco smoke exposure during the pediatric age

Background: The smoking ban in public places has reduced Environmental Tobacco Smoke (ETS) exposure for non-smokers, but despite this, domestic environments still remain places at high risk of exposure, and, today, about 40% of children worldwide are exposed to ETS at home. The aims of the study are to investigate the contribution of several factors on ETS exposure among a group of Italian children and to evaluate the changes in smoking precautions adopted at home when the smoker is the mother, the father, or both parents, respectively. Methods: A cross-sectional study was performed on a sample of 519 Italian schoolchildren. Information was collected via a questionnaire. Results: 41.4% of the participants lived with at least one smoker. Almost half of the children exposed to ETS lived with one or more smokers who do not observe any home smoking ban. Lower maternal or paternal educational levels significantly increase the risk of ETS exposure at home and the “worst case” is represented by both parents who smoke. Conclusions: More effective preventive interventions are needed to protect children from ETS exposure. Some interventions should be specifically dedicated to smokers with a low educational level and to mothers that smoke

STRUCTURAL STATIC ANALYSIS OF THE CURVED STILT BY FEM USING THE ELCUT PROGRAM

The paper presents a study of the distribution of stresses and strains in the curved stilt of the plough-body, using the ELCUT analysis program by the finite element method. In its public version, the program allows the static structural analysis in three stages of precision. However, there are some limitations on the number of nodes for the discretized structure, depending on its complexity (250 to 500 nodes)

ANALYSIS OF THE STATE OF STRESSES AND STRAINS IN THE CURVED STILT, USING TRIANGULAR FINITE ELEMENTS (CST)

The paper presents a study on the analysis of the distribution of stresses and strains in the curved stilt of the plough-body, using the Finite Element Method. Modeling was performed with the help of triangular finite elements "CST" (Constant Strain Triangle), using a special program for this type of applications “CSTPL.EXE”, developed at University Politehnica of Bucharest, Department of Materials Strength

THE EFFECTS OF WASTEWATER IRRIGATION ON AGRICULTURAL SOILS

In arid and semi-arid areas, wastewater is often recovered for crop irrigation, contributing to the sustainable agriculture. Although positive effects have been observed on crop yields (50-80% growth) due to wastewater nutrients, the reuse of untreated wastewater harms both the environment and human health. Soil is mostly affected by excess salts, sodium, nutrients and heavy metals in wastewater. High salinity affects the upper layer of soil (0–30 cm); sodium and chlorine reduce crop yields by 40%; high content of organic matter in wastewater decreases soil pH, and heavy metals and pathogens enter the food chain. Irrigation technology is also important: sodium and salinity are higher in sprinkler than in furrow or subsurface irrigation; subsurface drip irrigation is more effective in reducing soil pathogens than surface drip irrigation. This paper examines the effects of wastewater irrigation on soil salinity, sodium, heavy metals and pathogen contamination