The Use of Reverse Osmosis in the Removal of PAHs from Municipal Landfill Leachate

Polycyclic aromatic hydrocarbons (PAHs) are relatively well-known organic pollutants and due to their carcinogenic and mutagenic properties their presence in the environment still attracts a lot of attention.

According to literature reports and own research, PAHs presence in wastewaters is common. It was confirmed that PAHs are the components of municipal landfill leachate. Membrane techniques are one of the most interesting ways of removing PAHs from leachate.

The purpose of this article is to monitor PAHs concentration changes during the membrane (reverse osmosis - RO) leachate treatment processes. In the first stage of testing leachates were filtrated on the sand bed (pre-filtration). After the pre-filtration they were directed to the membrane module for the main filtration.

Sixteen PAHs listed by EPA were analyzed. The results with information on PAHs concentration in leachate samples were presented using HPLC with fluorescence detection (FLD). The changes in PAHs concentration were determined in leachate samples before and after pre-filtration as well as after RO. The decrease of PAHs concentration in the samples was observed after these processes. The total concentration of 16 PAHs in raw municipal landfill leachates amounted to 23.64–26.95 μg/L. The research confirmed the high efficiency in removal of PAHs while using a reverse osmosis (59–72%). Including the pre-filtration, the overall level of removed PAHs reached 81–86%. The average PAHs concentration after pre-filtration and RO was in the 4.46–4.99 μg/L range. The municipal landfill leachate with a high concentration of PAHs should be cleaned before it is discharged into the environment.     

Erratum to: Evaluation of the Particle Bonding for Aluminum Sample Produced by Spark Plasma Sintering

Journal of Materials Engineering and Performance -     

Evaluation of the Particle Bonding for Aluminum Sample Produced by Spark Plasma Sintering

Journal of Materials Engineering and Performance - Spark plasma sintering (SPS) is a powder metallurgy process that sinters powder materials within a short time by simultaneous application...     

Theoretical and empirical assessment of evaluation methods of the electric charge transference in welding with covered electrodes

The present work is based on an assessment of experimentally obtained results from the application of different methods of evaluation, reported in the specialised literature, of the electrical charge transference stability in the arc. A simple factorial design, taking the welding current as independent variable, was applied to the process with an AWS A5.1 E6013 electrode. The welds were carried out in the flat position by a gravity device. It was possible to obtain criteria to classify the electrical charge transference stability of the process by digital signal processing and a statistical technique. The outcome was based on visual inspection and morphologic studies. It was concluded that amongst the considered parameters, the average value of the arc conductivity during reignition peaks and the quantity of reignition peaks are the more representative indices, both from statistics and from phenomenological points of view. This finding is validated by the fact that the bead morphology and the stability analysis of the electrical charge transference process coincides with the fact that the 160 A (for 4 mm-diameter electrodes) is the most stable regime.     

Evaluation of mass loss of weld-deposited hardfacing with cored wire Ti-FeCrC alloy

In this article, we have studied the mass loss of hardfacing applied by flux-cored arc welding. Heat input, shielding gas and number of layers of coating were changed to application of Fe–Cr–Ti–C self-shielded tubular wire. Overlapping beads were deposited on plates of carbon steel AISI 1020 to analyse the mass loss, hardness and microstructure. For the analysis of mass loss, beads were deposited forming overlapping layers of coatings. Hardness measurements were performed on the surface of the specimens of wear. A rubber wheel abrasion tester was used to access the mass loss of coatings. The coatings had retained austenite and martensite microstructure with carbides finely dispersed in the matrix. The main factors that contributed to the increase in mass loss were the cracks due to higher cooling rate of the samples deposited with low heat input, the dilution in the first layer of all samples also contributed to the increase in mass loss. The smallest mass losses were those deposited coatings with high heat input, the second and fourth layers, the samples AC2, AC4 and AS2. The volume fraction of titanium carbides contributed to the decrease in the mean free path between the particles of carbides and increased the wear resistance of the coatings.