1,720,996 research outputs found
A comparative evaluation of biological activated carbon and activated sludge processes for the treatment of tannery wastewater
No full textDepuration methods usually adopted to treat the tanning industry wastewater are based on several technologies, physicochemical or biological, as activated sludge (AS), alone or combined. The AS method faces some difficulties when pollutants toxic are present in the wastewater. The water treatment known as the biological activated carbon (BAC) allows overcoming these limitations by taking advantage of the synergism between activated carbon (AC) and microbacteria. Nevertheless, further investigation about the performance of BAC on real wastewater is much required. For this purpose, an experimental test with BAC in continuous pilot plant with a real tannery wastewater was performed. The same test was performed with AS process and relevant differences from BAC method were observed. The experimental results indicate the good removal of total chromium for both BAC and AS (72-70%). But the main differences are for soluble chromium removal (67% for BAC and 46% for AS) and for COD removal (66% for BAC and 40% for AS). Very good results were also obtained for removal of other pollutants resulting from industrial additives, for BAC (91-100%) and to a lesser extent for AS (28-78%). In every case, the BAC shows faster kinetics removal. Finally, a pseudo-second order model fits the experimental data about soluble chromium. © 2014 Elsevier Ltd
Comparative evaluation of ozonation and stripping methods to treat contaminated groundwater by trichloroethylene. Assessment of effects on the other matrix components
No full textMany methods, that involve several oxidants combined specific catalyst, are commonly utilised for the abatement of organochlorine compounds in natural and waste waters. This study investigates the efficiency of removal of trichloroethylene (TCE) contained in groundwater through oxidation with ozone. The fundamental contribution of the stripping was experimentally measured through tests with nitrogen. For comparative purposes, the same experimental tests were performed on a model solution containing TCE. A dedicated experimental apparatus was specifically designed. The treatment under investigation showed a good efficiency dependent on the ozone dose and initial pollutant concentration. Experimental data, obtained from stripping and oxidation tests performed both with groundwater and model solution, were fitted by models. Finally, the effects of the ozone treatment on other groundwater components, as bromide and organic and inorganic nitrogen, together with the formation of undesired by-products were also taken into account. ᄅ 2014 Elsevier Ltd
Surface water - Groundwater connectivity implications on nitrate cycling assessed by means of hydrogeologic and isotopic techniques in the Alento river basin (Salerno, Italy): Preliminary data
No full textThe knowledge of the mechanisms regulating the concentration of nutrients in rivers is of fundamental importance in maintaining the ecological functioning of streams. In particular, in the riverbed sediments, where the biogeochemical activity is enhanced, the study of retention mechanisms becomes crucial in order to determine the restoring capacity of a watercourse. In case of groundwater inflow, hot-spots in the recycling of nutrients within the riparian and hyporheic zones can be observed, influencing the nutrient load transported into the stream depending on retention mechanisms. Hence, the study of biotic and abiotic factors affecting retention and transport of nutrients in a riverine ecosystem at different spatial scales (from reach to catchment) becomes fundamental to understand the mechanisms regulating the concentration of nutrients, and in particular nitrates, in streams. The present work is developed within the framework of the IAEA Coordinated Research Project (CRP) "Environmental Isotopes and Age Dating Methods to Assess Nitrogen Pollution and Other Quality Issues in Rivers". The main scope is to find a reliable methodology to, spatially and temporally, quantify groundwater inflows to a river in order to study nitrates contamination of a groundwater dependent river ecosystem. In particular, the overall objectives of the proposed project are: i) the identification and quantification of spatiotemporal variation of the connectivity between groundwater and surface water; ii) the identification of the nitrate contamination sources of shallow groundwater; iii) the study of the nitrates retention and recycling mechanisms in riverbed sediments in critical effluent river reaches (key sites) in order to determine the importance of hyporheic and riparian zones. Here, the preliminary results of the hydrogeological, chemical and isotopic (222Rn, δ18O, δD) monitoring are presented and discussed. Società Geologica Italiana, Roma 2016
Combining GIS and FAO's crop water productivity model for the estimation of water footprinting in a temporary river catchment
No full textIn the arid and semi-arid areas such as those in southern Europe, the correct management of water is of fundamental importance as well as the estimation of water consumption associated with human activities. Considering a temporary river catchment, the Water Footprint (WF) methodology allows direct and indirect estimation of water consumption required for the production of a given product. Furthermore, the WF estimation often involves the use of Geographic Information Systems (GIS) that allows to process climate, land use and soil type data. With the intent of strengthening existing methodologies applied at basin scale, this study deals with the estimation of WF in a temporary river catchment combining GIS and FAO's (Food and Agriculture Organization of the United Nations) crop water productivity model. In detail, with reference to each municipality in the Candelaro catchment area (2330 km2, Southern Italy), the blue and green component of WF was calculated for the agricultural products. Additionally, the role of treated wastewater, intended as a strategy of water deficit compensation at basin scale, was addressed. Results showed a WF of 686 Mm3/year with a greater contribution from the green than the blue component. The wheat was the cultivation that required the largest quantity of rainwater while tomato was the product that contributed to the increased demand for irrigation water, which accounted for about 50% of the blue component. The other agricultural products that contributed to the demand for blue water were grapes and olive trees. Finally, the treated wastewater can substantially contribute to covering the water deficit; results showed a contribution of 30%–40% of water savings. © 2018 Institution of Chemical Engineer
UV treatment for the removal of bromate formed during ozonation of groundwater. Influence of the oxidation process on the removal efficiency
No full textThe presence of bromide ions in waters treated with ozone can lead to bromate ions and brominated compounds formation, potentially carcinogenic. This poses a need to remove the bromates through other treatment, as UV. In this work the effects of the water composition, and the corresponding variation due to oxidation, on the UV efficiency for the reduction of bromate to bromide ions in groundwater (GW) were investigated. For this purpose an experimental apparatus was specifically designed and experimental tests with ozone and with a UV lamp 6 W were performed. The experimental results show that the reduction of the bromates to bromides by UV is max 41% in GW, depending on ozone dose and initial bromate concentration. The experimental data were fitted with a first order model and the kinetic constant determined. The effects of the ozone and UV treatment on others groundwater components, as TOC and inorganic nitrogen, were taken into account and the corresponding influence on the bromate removal efficiency was evaluated. To this aim, comparative tests with UV in purified water (PW) (reagent grade) and GW spiked with controlled amount of bromates were performed. It was verified that the removal efficiency of bromate by UV increases with increasing of ammonia concentration, but decreases with increasing of TOC and when intermediate bromide species, produced by ozonation, are presents. © 2016 Elsevier Ltd. All rights reserved
Photocatalytic degradation of atenolol in aqueous suspension of new recyclable catalysts based on titanium dioxide
No full textPhotocatalytic degradation of atenolol in aqueous suspensions using specifically synthetized mesoporous based TiO2 materials as photocatalysts under UVC (254 nm) irradiation was investigated. A batch reactor and a UV lamp 16 W power were used to test the ATL removal with several initial concentrations of ATL (4.5 - 30 mg/L) and four synthetized TiO2 photocatalysts, characterized by different BET surface areas and average pore sizes. Moreover, the effect of solution pH (4.8 - 9.0) and of the oxygen presence were investigated. The performances of the synthetized photocatalysts were compared with commercial Degussa P25. The atenolol degradation was studied using different concentration of catalyst (50 and 1000 mg/L) showing a maximum removal efficiency of 65%. Although the new catalysts showed a lower efficiency when compared to commercial P25, they can be easily recovered from water being in the form of micro-aggregate, and then reused without remarkable changes. The experimental data were fitted using a pseudo first order kinetic model. © 2017 Elsevier Ltd. All rights reserved
Experimental investigation to evaluate the potential environmental hazards of photovoltaic panels
No full textRecently the potential environmental hazard of photovoltaic modules together with their management as waste has attracted the attention of scientists. Particular concern is aroused by the several metals contained in photovoltaic panels whose potential release in the environment were scarcely investigated. Here, for the first time, the potential environmental hazard of panels produced in the last 30 years was investigated through the assessment of up to 18 releasable metals. Besides, the corresponding ecotoxicological effects were also evaluated. Experimental data were compared with the current European and Italian law limits for drinking water, discharge on soil and landfill inert disposal in order to understand the actual pollution load. Results showed that less than 3% of the samples respected all law limits and around 21% was not ecotoxic. By considering the technological evolutions in manufacturing, we have shown that during the years crystalline silicon panels have lower tendency to release hazardous metals with respect to thin film panels. In addition, a prediction of the amounts of lead, chromium, cadmium and nickel releasable from next photovoltaic waste was performed. The prevision up to 2050 showed high amounts of lead (30 t) and cadmium (2.9 t) releasable from crystalline and thin film panels respectively. © 2015 Elsevier B.V
Modeling and validation of a modular multi-lamp photo-reactor for cetylpyridinium chloride degradation by UV and UV/H2O2 processes
No full textThermal treatment of waste photovoltaic module for recovery and recycling: Experimental assessment of the presence of metals in the gas emissions and in the ashes
No full textThe rapid expansion of the photovoltaic (PV) module market in the last years will determine in the near future a remarkable growth of corresponding waste. Then, the hazardous materials contained in the modules, such as Cd, Pb and Cr, could be released in the environment if the waste panels will not be handled adequately. Recycling processes of silicon crystalline panels, finalized to separate PV cells from the glass, involve the removal of the EVA (Ethylene Vinyl Acetate) layer through different methods, as the thermal treatment. During this treatment, some hazardous components can be released due to thermal degradation process. In this paper the metals released in the gas emissions and in the ashes due to the thermal treatment of modules were evaluated. For this purpose, three samples of crystalline panels were heated in furnace up to 600°C and the complete degradation of the EVA was obtained. A mass balance between the sample and its components, before and after treatment, was performed in order to assess the weight loss percentage. Finally, after thermal treatment a qualitative analysis on the separated PV cell surface was performed by SEM-EDS (Scanning Electron Microscope equipped with Energy Dispersive Spectrometer). © 2015 Elsevier Ltd
Treatment and management of the effluents generated by hydrometallurgical processes applied to End-of-Life Photovoltaic Panels
No full textPhotovoltaic (PV) technology is a low-carbon and efficient option to produce electricity with an expected growing market. In the next years, end-of-life PV panels (EoL PV) will generate a new type of waste whose management implies environmental concerns but also opportunities to recover secondary raw materials. As part of a European project, a 1,500 panels/year capacity pilot plant to recover valuable resources from EoL PV panels using hydrometallurgical processes was operated in real environment. It represents the first time that a hydrometallurgical treatment was applied, at industrial scale, to EoL PV panels. This study focuses on the specific topic of treating the wastewater generated by the end of the hydrometallurgical process. Different chemical and physical tests were tried in laboratory on such streams loaded with metal species. The experimental results indicated that induced precipitation by adding strong acid or alkaline solutions allows obtaining high metal removal rates (greater than 95%). The optimal pH was around neutrality. Results suggested testing whether mixing the two wastewater at different rates could result in similar decontamination effects. pH neutrality was again the optimal condition. A further test at industrial scale was carried out by using a treatment plant specially assembled for the purpose. The study showed as the approach allowed to: 1) achieve a final supernatant to be reused within the recycling panel process; 2) avoid the use of lab-made high-grade solutions to modify pH; 3) minimize the production of waste (less than 60%) avoiding costs for the final out-side treatment and disposal
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