Removal of Natural Organic Matter from Groundwater Using Advanced Oxidation Processes at a Pilot Scale Drinking Water Treatment Plant in the Central Banat Region (Serbia)

To improve water quality, a pilot-scale evaluation into upgrading the conventional treatment process was conducted. By following DOC content, UV₂₅₄ absorbance, SUVA and by-products formation, three oxidative pre-treatments were evaluated: pre-ozonation (2.2 g O₃/m³); O₃/H₂O₂ process (2.2 g O₃/m³; H₂O₂:O₃ = 1:2) and O₃/H₂O₂ process (2.2 g O₃/m³; H₂O₂:O₃ = 2:1). The second pre-treatment gave the best results, with a final average DOC content of 0.9 mg C/L, UV₂₅₄ absorbance of 0.06 cm^?1 and the lowest THMFP of 130 μg/L. UV₂₅₄ absorbance can serve as a proper indicator for predicting THM and HAA formation, yielding a correlation coefficient ≥ 0.90.     

Clarification of red raspberry juice using microfiltration with gas backwashing: A viable strategy to maximize permeate flux and minimize a loss of anthocyanins

Red raspberry (Rubus idaeus) juice was produced by maceration of raspberry pulp at 50 °C for 2 h using 400 mg kg^?1 Klerzyme^®150 enzymatic pectolitic preparation followed by raw juice clarification with gelatin and bentonite or cross-flow membrane filtration. A minimal loss of anthocyanins from 630 to 540 mg l^?1 was obtained when the juice was clarified using a ceramic multichannel microfilter (MF) with a pore size of 0.2 μm. A light transmission at 625 nm in MF permeate was above 85% and the residual pectin (900 mg l^?1) was completely removed. During ultrafiltration through ceramic or polysulfone membranes with a molecular weight cut-off of 30–300 kDa, the content of anthocyanins was reduced to 220–370 mg l^?1, but a light transmission at 625 nm was as high as 96%. The permeate flux in MF was maintained at high values above 170 l m^?2 h^?1 at 3 bar for more than 2 h by backwashing the membrane with a compressed air every 6 min for 1 min. The cake compression at high pressures was avoided by short filtration times between backwashing.     

Non-lithographic fabrication of metallic micromold masters by laser machining and welding

A non-lithographic process of rapidly fabricating metallic micromold masters for the manufacture of disposable polymer microfluidic devices is presented in this paper. The developed technique exploits the precision material removal capabilities of industrial lasers to cut accurate profiles of microfeatures (e.g., liquid flow microchannels, reservoirs, passive micromixers) from thin metallic sheets. The machined micropatterns are then laser welded onto a metal substrate to form the final functional mold master. Multiple versions of the functional device are replicated from the assembled master by either soft molding polydimethylsiloxane or hot embossing polymethyl methacrylate. Several metallic micromold masters and polymer replicas are tested for dimensional accuracy and surface roughness to verify the developed microfabrication process.     

Stress enhanced environmental corrosion and lifetime prediction modelling in silica optical fibres

The glass/water interaction is reviewed from early experimental work in bulk samples to the current molecular interpretation of bond rupture in that interaction. The significance of that work to static fatigue in silica optical fibres is discussed. Assumptions concerning the basic equations used to predict the rate of crack propagation, and hence, the lifetime of silica optical fibres, are questioned. Issues such as flaw distribution and the true nature of the crack tip are highlighted along with deficiencies in test methods and data analysis techniques used to obtain fibre lifetime parameters. These factors have resulted in no single fibre lifetime model becoming universally accepted with some 15 published lifetime models currently available. It is suggested that lifetime theory based on large, well-defined cracks in bulk material is no longer entirely sufficient to explain the static fatigue behaviour of the nanometre-sized flaws found in current optical fibres. Instead, the literature indicates a two-stage model consisting of a precursor stage followed by the currently accepted bond-rupture mechanism, to be more appropriate.     

Melting equilibria in the iron-rich corner of the Fe-Ni-Mo system

Isothermal holding tests were carried out in the Fe-Ni-Mo system in the two-phase region between the liquidus (melt) and the solidus (crystal). The δ and γ liquidus surfaces in the iron-rich corner of the Fe-Ni-Fe₃Mo₂-NiMo subsystem, as well as the position of the peritectic line situated between them, could be very accurately established by the experimentally determined isotherms. Based on these results and on the known liquidus lines in the three boundary binary systems, as well as on the known concentration fields of the Fe₃Mo₂-NiMo solid solutions, the melting equilibria could be developed with sufficient accuracy in the entire subsystem.     

Fabrication of metallic micromolds by laser and electro-discharge micromachining

A method of creating metallic micromolds with features that have high-aspect ratios is described in this paper. The proposed manufacturing process utilizes laser micromachining to cut the negative two-dimensional profiles of the desired microfeatures and fluidic network patterns on a 100 μm thick brass sheet. The positive relief of the cut pattern is then created by using electro-discharge micromachining (micro-EDM) die-sinking the metallic mask onto a brass substrate. The final substrate with the desired relief pattern becomes the molding tool used for either elastomer casting or thermoplastic hot embossing. To validate the proposed fabrication methodology and evaluate the quality of surface finishes, a brass mold master of a T-channel micromixer (50 μm width, 25 μm height) is developed and multiple replicated devices are cast on this mold using poly-di-methyl-siloxane (PDMS). The surface finish of both the original micromold master and final molded channels on PDMS are measured using an optical profiler and found to have a roughness of approximately 400 nm Ra. The ability of the proposed fabrication technique to create high-aspect ratio features is illustrated by manufacturing a Y-channel micromixer with an aspect ratio of 4. Experimental results are discussed and suggestions for improvement are presented.