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Ndounla J.,Ecole Polytechnique Federale de Lausanne | Ndounla J.,Institute International Dingenierie Of Leau Et Of Lenvironnement | Pulgarin C.,Ecole Polytechnique Federale de Lausanne
Applied Catalysis B: Environmental | Year: 2013

Iron photo-assisted inactivation of wild enteric bacteria (total coliforms/E. coli and Salmonella spp.) was carried out in water from the Sahelian wells having different pH (W1: 4.9 and W2: 6.3) and a natural iron content of 0.07mg/L. We evaluate the efficiency of the disinfection on different systems containing both or only one Fenton reagent (H2O2/Fe2+): (i) H2O2/Fe2+/hv, (ii) Fe2+/hv, (iii) H2O2/hv, and (iv) only light irradiation (hv) at lab and field scale. Generally, 0.6mg/L of Fe2+ and/or 8.5mg/L of H2O2 were used in the Fenton reagent. The systems H2O2/Fe2+/hv and H2O2/hv led to total inactivation of Salmonella and E. coli. The natural iron content (0.07mg/L) was enough to drive an efficient photo-Fenton process leading to total bacterial inactivation. Our results show that: (i) the iron salt present in Sahelian water is enough to perform a photo-Fenton disinfection of drinking water when adding H2O2, (ii) addition of external iron salts at near neutral pH has no additional effect on the bacterial photo-Fenton inactivation process. After one week of storage, no enteric bacteria re-growth was observed in treated waters. Mechanistic suggestions are presented to explain the observed results. © 2012 Elsevier B.V. Source

N'Tsoukpoe K.E.,Luneburg University | N'Tsoukpoe K.E.,Institute International Dingenierie Of Leau Et Of Lenvironnement | Schmidt T.,Luneburg University | Rammelberg H.U.,Luneburg University | And 2 more authors.
Applied Energy | Year: 2014

In this paper, the potential energy storage density and the storage efficiency of salt hydrates as thermochemical storage materials for the storage of heat generated by a micro-combined heat and power (micro-CHP) have been assessed. Because salt hydrates used in various thermochemical heat storage processes fail to meet the expectations, a systematic evaluation of the suitability of 125 salt hydrates has been performed in a three-step approach. In the first step general issues such as toxicity and risk of explosion have been considered. In the second and third steps, the authors implement a combined approach consisting of theoretical calculations and experimental measurements using Thermogravimetric Analysis (TGA). Thus, application-oriented comparison criteria, among which the net energy storage density of the material and the thermal efficiency, have been used to evaluate the potential of 45 preselected salt hydrates for a low temperature thermochemical heat storage application. For an application that requires a discharging temperature above 60°C, SrBr2·6H2O and LaCl3·7H2O appear to be the most promising, only from thermodynamic point of view. However, the maximum net energy storage density including the water in the water storage tank that they offer (respectively 133kWhm-3 and 89kWhm-3) for a classical thermochemical heat storage process are not attractive for the intended application. Furthermore, the thermal efficiency that would result from the storage process based on salt hydrates without condensation heat recovery appears also to be very low (lower than 40% and typically 25%). Even for application requiring lower discharging temperature like 35°C, the expectable efficiency and net energy storage density including the water storage remain low. Alternative processes are needed to implement for salt hydrates in low temperature thermochemical heat storage applications. © 2014 Elsevier Ltd. Source

Py X.,University of Perpignan | Azoumah Y.,Institute International Dingenierie Of Leau Et Of Lenvironnement | Olives R.,University of Perpignan
Renewable and Sustainable Energy Reviews | Year: 2013

Conventional Concentrating Solar Power (CSP) technologies have been mainly developed during the eighties. They can be considered as similar to conventional thermal power processes in which the boiler has been replaced, at least partially, by a concentrated solar field producing the heat. After more than 20 years of reduced activity, they have recently taken advantage of an impressive removal at the beginning of the new XXIst century and are subjected today to an increasing industrial interest. Based on the inherited technologies, companies build currently plants in the range of 10-20 MWe for central receiver CSP and 50 MWe for solar trough CSP. According to the IEA, at least 630 GWe of CSP should be installed in 2050 for only 700 MWe available today and preferably in areas of high solar potential (the so-called solar belt). Before this high potential, major issues have still to be overcome to enhance the performances and to adapt the technologies to the up to date constraints. In the present paper, the history and the technologies of the current CSP are presented, the major innovative issues described and the applicability to West African countries discussed. CSP standards proposed by developed countries are compared to the actual needs and potentials of West African countries. © 2012 Elsevier Ltd. All rights reserved. Source

Ndounla J.,Ecole Polytechnique Federale de Lausanne | Ndounla J.,Institute International Dingenierie Of Leau Et Of Lenvironnement | Pulgarin C.,Ecole Polytechnique Federale de Lausanne
Science of the Total Environment | Year: 2014

The photo-disinfection of water from two different wells (W1, pH: 4.6-5.1±0.02) and (W2 pH: 5.6-5.7±0.02) was carried out during the rainy season at Ouagadougou-Burkina Faso, West Africa. The weather variation during the rainy season significantly affects the photo-disinfection processes (solar disinfection and photo-Fenton). The dilution of the water by rainwater highly affected the chemical composition of the wells' water used in this study; very low iron contents Compared to the ones recorded during the dry season were recorded in all water samples. Both photo-disinfection processes were used to treat 25L of water in a compound parabolic collector (CPC). None of them have shown the total inactivation of both wild enteric bacteria strains (total coliforms/E. coli and Salmonella spp.) involved in the treatment. However, the total coliforms/E. coli strains were totally inactivated during the exposure under most of the photo-Fenton treatment. Also, the remaining strains, especially those of Salmonella spp. were achieved during the subsequent 24h of dark storage under the action of the Fenton process. Under uniquely solar radiation, total inactivation was recorded only in the total coliforms/E. coli strains. The impact of the available irradiance on the efficiency of the photo-Fenton disinfection of natural water was highlighted during the exposure under high intermittent solar radiation. The impact of the HCO3- concentration of both wells' water on the evolution of the pH during the photo-disinfection was recorded. Drastic decrease was noticed after the initial fast increase in presence of low HCO3- concentration while a steady state was observed after the increase in presence of higher concentration. The redox activities of the nitrogen components of the water during both photo-disinfection processes have led to increased concentration of nitrite in all the cases and variations were noticed in that of nitrate and ammonia. 2014 Elsevier B.V. Source

Ndounla J.,Ecole Polytechnique Federale de Lausanne | Ndounla J.,Institute International Dingenierie Of Leau Et Of Lenvironnement | Wethe J.,EAA WSA CREPA | Pulgarin C.,Ecole Polytechnique Federale de Lausanne
Applied Catalysis B: Environmental | Year: 2014

The inactivation of total coliforms/E. coli (104CFU/mL) and Salmonella spp. (105CFU/mL) in well water naturally containing dissolved (Fe2+/3+) and solid iron forms (e.g. iron oxides) was carried out by photo Fenton treatment (Fe2+, 3+/H2O2/hv). In a preliminary run under simulated solar radiation, beyond 4mg/L of added H2O2, the enteric bacteria were totally inactivated after 90min. Thereafter, 25L of well water were treated in the compound parabolic collector (CPC) under direct solar radiation. Three irradiation periods (i) 8 am to 2 pm (8-14h), (ii) 10 am to 4 pm (10-16h) and (iii) 12 pm to 6 pm (12-18h) were evaluated for assessing the impact of different solar irradiances (Wm-2) on the enteric bacterial inactivation rates. Both studied strains were totally inactivated under sole exposure to solar radiation in the CPC when the experiments were conducted from 8 to 14h or 10 to 16h. However, Salmonella spp. strains regrowth was noticed after the 24h dark storage in all the samples previously treated with bare solar radiation. As the treated water contained Fe, the photo-Fenton disinfection at field scale in the CPC was carried out with the addition of H2O2 (10mg/L). Significant enhancement of the enteric bacteria inactivation rate was therefore recorded comparatively to the one obtained under bare solar treatment. No regrowth was observed in water treated by photo-Fenton disinfection one week after the treatment. The comparative evaluation of photo-Fenton disinfection rate as a function of different irradiation periods was based on the monitoring of the effective disinfection time (EDT), or required time to acquire the total inactivation of targeted bacteria in defined conditions. Therefore, significant impact of the irradiance on the process was noticed. High average irradiance (AI) of 35Wm-2 led to the total inactivation of Salmonella spp. in an EDT of 45min and a dose of 26Whm-2; while low irradiance of 20Wm-2 required an EDT of 180min for a dose 60Whm-2. Thus, the experiments revealed that lower irradiance level leads to higher doses to achieve the bacterial disinfection. pH, as well as nitrite and nitrate concentration, increased during the photo-disinfection processes, while depletion was recorded for aqueous ammonia concentration. © 2013 Hirofumi Shimomura The Authors. Source

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