Time filter

Source Type

Aartselaar, Belgium

Stepanov A.S.,Australian National University | Stepanov A.S.,RAS Institute of Geology and Mineralogy | Korsakov A.V.,RAS Institute of Geology and Mineralogy | Yuryeva O.P.,RAS Institute of Chemistry | And 4 more authors.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

Abstract: We have performed petrographic and spectroscopic studies of brown diamonds from an eclogite xenolith from the Udachnaya pipe (Yakutia, Russia). Brown diamonds are randomly intermixed with colorless ones in the rock and often located at the grain boundaries of clinopyroxene and garnet. Brown diamonds can be characterized by a set of defects (H4, N2D and a line at 490.7 nm) which are absent in colorless diamonds. This set of defects is typical for plastically deformed diamonds and indicates that diamonds were likely annealed for a relatively short period after deformation had occurred. Excitation of brown colored zones with a 632.8 nm He-Ne laser produced the typical diamond band plus two additional bands at 1730 cm -1 and 3350 cm -1. These spectral features are not genuine Raman bands, and can be attributed to photoluminescence at ∼710 nm (1.75 eV) and ∼802 nm (1.54 eV). No Raman peak corresponding to graphite was observed in regions of brown coloration. Comparison with previous reports of brown diamonds from eclogites showed our eclogitic sample to have a typical structure without signs of apparent deformation. Two mechanisms with regard to diamond deformation are proposed: deformation of eclogite by external forces followed by subsequent recrystallization of silicates or, alternatively, deformation by local stress arising due to decompression and expansion of silicates during ascent of the xenolith to surface conditions. © 2011 Elsevier B.V. All rights reserved.

Abdel-Aal M.,University of Bradford | Mohamed M.,University of Bradford | Smits R.,Aquafin | Abdel-Aal R.E.,King Fahd University of Petroleum and Minerals | And 3 more authors.
Water Science and Technology | Year: 2015

A predictive modelling technique was employed to estimate wastewater temperatures in sewer pipes. The simplicity of abductive predictive models attracts large numbers of users due to their minimal computation time and limited number of measurable input parameters. Data measured from five sewer pipes over a period of 12 months provide 33, 900 training entries and 39, 000 evaluation entries to support the models' development. Two simple predictive models for urban upstream combined sewers and large downstream collector sewers were developed. They delivered good correlation between measured and predicted wastewater temperatures proven by their R2 values of up to 0.98 and root mean square error (RMSE) of the temperature change along the sewer pipe ranging from 0.15 °C to 0.33 °C. Analysis of a number of potential input parameters indicated that upstream wastewater temperature and downstream in-sewer air temperature were the only input parameters that are needed in the developed models to deliver this level of accuracy. © IWA Publishing 2015.

Fenu A.,Aquafin | Fenu A.,University of Antwerp | De Wilde W.,AquaPlus | Gaertner M.,Aquafin | And 4 more authors.
Journal of Membrane Science | Year: 2012

The membrane life-time has a strong impact on competitivity and viability of MBRs. This study critically analyzes the membrane life-time concept, approaching it through different assessment methods. A full scale MBR's membrane life-time was assessed on the following: (i) maintaining the permeate flow throughput to the MBR; (ii) the permeability decline; (iii) oxidative aging; (iv) the increase in energy costs; and (v) mechanical aging.The method based on permeability decline provides a membrane life-time estimate up to a theoretical end. It was further elaborated inherently to operations with no long-term flux decline. The increase in operating pressure remains the main end-of-life trigger for deciding when to replace membrane modules.On the contrary, mechanical and permeate flow throughput analysis of the data are not able to provide a clear estimate of the membrane life-time. As for the membrane life-time estimation based on chlorine contact, it was found to be too optimistic. Complete irreversible fouling occurs before maximum contact time with chlorine is reached.At end-of-life operating conditions, the energy consumption raised of 170% due to the reduced flow rate. The cost raise appears high but still affordable. Earlier membrane replacement thus can never be counterbalanced by energy costs saving. © 2012 Elsevier B.V.

Abdel-Aal M.,University of Bradford | Smits R.,Aquafin | Mohamed M.,University of Bradford | De Gussem K.,Aquafin | And 2 more authors.
Water Science and Technology | Year: 2014

Modelling of wastewater temperatures along a sewer pipe using energy balance equations and assuming steady-state conditions was achieved. Modelling error was calculated, by comparing the predicted temperature drop to measured ones in three combined sewers, and was found to have an overall root mean squared error of 0.37 K. Downstream measured wastewater temperature was plotted against modelled values; their line gradients were found to be within the range of 0.9995- 1.0012. The ultimate aim of the modelling is to assess the viability of recovering heat from sewer pipes. This is done by evaluating an appropriate location for a heat exchanger within a sewer network that can recover heat without impacting negatively on the downstream wastewater treatment plant (WWTP). Long sewers may prove to be more viable for heat recovery, as heat lost can be reclaimed © IWA Publishing 2014.

De Gussem K.,Aquafin | Fenu A.,Aquafin | Wambecq T.,Aquafin | Weemaes M.,Aquafin
Water Science and Technology | Year: 2014

This work provides a case study on how activated sludge modelling and computational fluid dynamics (CFD) can help to optimize the energy consumption of a treatment plant that is already equipped with an advanced control based on online nutrient measurements. Currently, aeration basins on wastewater treatment plant Antwerp-South are operated sequentially while flow direction and point of inflow and outflow vary as a function of time. Activated sludge modelling shows that switching from the existing alternating flow based control to a simultaneous parallel feeding of all aeration tanks saves 1.3% energy. CFD calculations also illustrate that the water velocity is still sufficient if some impellers in the aeration basins are shutdown. The simulations of the Activated Sludge Model No. 2d indicate that the coupling of the aeration control with the impeller control, and automatically switching off some impellers when the aeration is inactive, can save 2.2 to 3.3% of energy without affecting the nutrient removal efficiency. On the other hand, all impellers are needed when the aeration is active to distribute the oxygen. © IWA Publishing 2014.

Discover hidden collaborations