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Ion exchange equilibria of arsenic in the presence of high sulfate and nitrate concentration
Full text linkThe aim of this work was to develop a quantitative description of the ion exchange equilibria of arsenic on a strong anionic resin, in the presence of nitrates and sulphates. First, the ion exchange equilibrium data of As(V) and NO3- on a strong anionic resin in chloride form were obtained and described with a model based on the mass action law. Namely, assuming ideal behaviour for both solution and resin phase, the thermodynamic constant of the As(V)/Cl- and NO3-/Cl- ion exchange equilibria were estimated by fitting of experimental data. Then, these equilibrium constants were used to predict the ion exchange behaviour of the ternary system As(V)/NO3-/Cl-, providing a rather good agreement with experimental results. The ion exchange equilibria involving sulphate ions were also studied, showing,a very high affinity to the resin phase. This behaviour did not allow a quantitative robust modelling of the equilibrium pattern. The results discussed in this paper represent a first step toward the development of a comprehensive modelling of the ion exchange process for the removal of As(V) from surface and groundwater in the presence of competitive, naturally occurring anions
Studio dei siti per discariche: variazione delle caratteristiche chimico-fisiche indotte dall'interazione tra terreni e prcolati
No full textDenitrification in tertiary filtration: application of an up-flow filter
No full textThe present paper shows the results obtained through an experimental work performed at the wastewater treatment plant of Rome, aimed at studying the performances of a tertiary filter regarding combined removal of suspended solids, COD, and nitrates. The up-flow sand filter was fed by the effluent coming from the secondary settling tank of the plant. The filter bed height was of 80 cm of silica sand. After a start up period, a study of particulate and soluble COD removal process was made, to establish the need of methanol in the denitrification process. Total COD removal efficiency was 60% on average, 55% due by soluble COD removal and 5% by particulate one. In the last phase of the experimental activity methanol was fed as carbon source, sodium sulfite was supplied to produce anoxic environment within the filter and the denitrification efficiency was studied. Nitrates removal rates after an acclimation period of 10 days increased up to 60%, with an effluent NO3-N of 8 mg/L. Denitrification rate was 2.4 kg/m3 d for water temperatures of 25 degrees C. Regarding methanol demand and biologic kinetics, the biomass yield coefficient was 0.3 kg(COD-X)/kg(me). Consequently 2.7 kg of methanol was required per kilogram of denitrified nitrogen
Riutilizzo di ceneri volanti da inceneritori per RSU e tests di cessione su materiali inertizzati
No full textReattori Biologici a Letto Fluido: Validazione di Modello Numerico per la Determinazione del Profilo di Concentrazione del Substrato nel Reattore
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L'impatto delle attività antropiche sulle acque sotterranee dell'area di Malagrotta (Roma- Italy)
No full textFull-Scale evaluation of UV and peracetic acid as alternative disinfecting agents to chlorine in WWTPs
No full textLo studio riporta i risultati sperimentali di una ricerca condotta su impianti di depurazione in piena scala per valutare l'efficacia di agenti disinfettanti quali radiazioni ultraviolette e acido peracetico a confronto con il cloro.Experimental studies were carried out with the aim of improving the disinfection process efficiency of the final effluents from wastewater treatment plants of the city of Rome. Two different agents were tested and compared to sodium hypochlorite (SH): (1) ultraviolet (UV) radiation with the aim of achieving a final effluent suitable to be reused according to the Italian legislation in force (D.M. 185/2003); (2) peracetic acid (PAA). Several tests under different operating conditions (dosage and contact times) were carried out in full-scale wastewater treatment plants (WWTPs) where the UV and PAA disinfection systems were installed. The study on UV disinfection showed removal efficiency of Escherichia coli ranging from 99.9% to 90%, with an average value of 97%. The use of PAA allowed to achieve removal efficiency of E. coli always about 99%; the optimal dose, and therefore the economical convenience of PAA with respect to the use of SH, was found to be strongly dependent on the E. col
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