1,721,007 research outputs found
Removal of Organics from Landfill Leachate by Heterogeneous Fenton-like Oxidation over Copper-Based Catalyst
Full text linkLandfill leachates are a mixture of high concentration organic and inorganic contaminants and need to be appropriately treated due to their toxicity and severe adverse effects on the environment. Here, we studied the treatment of landfill leachate through a heterogeneous Fenton-like oxidation process using a zirconia supported copper catalyst (Cu/ZrO2). Reaction conditions such as pH, amount of catalyst, oxidant dose, temperature, and reaction time were investigated and their effects on pollutant abatement discussed. AOS (average oxidation state) and COS (carbon oxidation state) parameters were used for the evaluation of the degree of oxidation of the process, obtaining some insight into the formation of oxidized intermediates (partial oxidation) and the total oxidation (mineralization) of the leachate during the reaction. A two-step oxidation process enhanced the overall performance of the reaction with an abatement of organic compounds of 92% confirming the promising activity of a copper-based catalyst for the treatment of liquid waste. Higher catalytic activity was achieved when the following reaction conditions were applied: 70 °C, pH 5, 200 mg/L of catalyst, 30 mL/L of H2O2 dose, and 150 min. In addition, durability of the catalyst under optimized reaction conditions was verified by repeated reaction cycles
Pilot-UASB reactor tests for anaerobic valorisation of high-loaded liquid substrates in friulian mountain area
No full textLa combustione dei rifiuti solidi urbani
No full textLa termovalorizzazione dei RSU, oltre ad occupare un ruolo di significativa importanza all’interno del sistema integrato di gestione dei rifiuti, rappresenta un’interessante strumento per recuperare l’energia contenuta all’interno della grande quantità di materiale che, diversamente, verrebbe avviata a smaltimento perché ritenuta non più utilizzabile.
La relazione proposta descrive i principali sistemi di trattamento termico, con recupero di energia, utilizzati per lo smaltimento dei RSU, nonché alcune delle tecnologie adottate per il controllo delle emissioni da impianti di termovalorizzazione
Sustainability of Domestic Sewage Sludge Disposal
No full textLarge-scale cropland application of municipal wastewater was first practiced about 150 years ago after flush toilets and sewer systems were introduced into cities in Western Europe and North America. Wastewater was discharged without any treatment and receiving watercourses became heavily polluted [1]. Many “sewage farms” were designated as a preferred alternative to the direct discharge of raw sewage into waterways [2]; in 1875, this “land treatment” served England and major cities in Europe and with the new century it has also started in the United States. Sewage farms played a role in decreasing pollution in the receiving streams, and also creating several environmental sanitation problems: hydraulic and pollutant land overloading caused clogging of soil pores, soil water logging, odors and contamination of food crops [1]. This procedure was gradually abandoned with the development of more effective technologies and building municipal sewage treatment systems. Land application of sewage sludge starts with the treatment of municipal wastewater and the consequent production of an end product, a solid waste, consisting in a concentrated suspension of solids high in organics and biodegradable compounds. One of the most widely used process for the treatment of wastewaters from medium to large populations that has found application in almost all of the countries of the world is the activated sludge process. It is a biological treatment which uses a mass of microorganisms to aerobically treat wastewater. It is widely accepted that the original process is attributed to the experimental work undertaken by Dr. Edward Ardern and Mr. William Lockett and carried out at the Davyhulme Sewage Works, which at that time were operated by the Manchester Corporation, with the cooperation of Dr. Fowler in 1914 [3]. The process was developed for the treatment of domestic wastewater and it has since been adapted for removing biodegradable organics from industrial wastewaters [4]. Owing to the physical-chemical processes involved in its treatment, sewage sludge tends to concentrate heavy metals and poorly biodegradable trace organic compounds, as well as potentially pathogenic organisms (viruses, bacteria, etc.) presented in wastewaters [5]. Since the late 1970s, source control and industrial wastewater pretreatment programs were applied to limit the discharge of industrial constituents into municipal sewers resulting in a consistent reduction of trace elements in wastewater and sewage sludge. Over the past 30 years and until now, many studies were started to understand and predict the toxicity and the fate of toxic substances and pathogens in sewage sludge when they are applied to soils [1]. Results constituted a benchmark for the development of guidelines in the United States and in western European countries. For more than 20 years, the sewage sludge directive 86/278/EEC has encouraged the use of sewage sludge in agriculture, suggesting at the same time regulation of its use to prevent possible harmful effects on soil, vegetation, animals and humans. The key concept of the directive is to consider sewage sludge as a valuable resource: in fact it is rich in plant macro and micronutrients and its application can, in the long term, improve soil fertility [6]. In Europe the most pragmatic and environmentally sustainable approach to manage sludge from wastewater treatment plants is actually recycling it on agricultural land [7]
Enhanced Heterogeneous Fenton Degradation of Organic Dyes by Bimetallic Zirconia-Based Catalysts
Full text linkThe qualitative impact of pollutants on water quality is mainly related to their nature and their concentration, but in any case, they determine a strong impact on the involved ecosystems. In particular, refractory organic compounds represent a critical challenge, and several degradation processes have been studied and developed for their removal. Among them, heterogeneous Fenton treatment is a promising technology for wastewater and liquid waste remediation. Here, we have developed mono- and bimetallic formulations based on Co, Cu, Fe, and Mn, which were investigated for the degradation of three model organic dyes (methylene blue, rhodamine B, and malachite green). The treated samples were then analyzed by means of UV-vis spectrophotometry techniques. Bimetallic iron-based materials achieved almost complete degradation of all three model molecules in very short time. The Mn-Fe catalyst resulted in the best formulation with an almost complete degradation of methylene blue and malachite green at pH 5 in 5 min and of rhodamine B at pH 3 in 30 min. The results suggest that these formulations can be applied for the treatment of a broad range of liquid wastes comprising complex and variable organic pollutants. The investigated catalysts are extremely promising when compared to other systems reported in the literature
Catalytic activity of metals in heterogeneous Fenton-like oxidation of wastewater contaminants: a review
Full text linkInnovations in water technology are needed to solve challenges of climate change, resource shortages, emerging contaminants, urbanization, sustainable development and demographic changes. In particular, conventional techniques of wastewater treatment are limited by the presence of poorly biodegradable organic matter. Alternatively, recent Fenton, Fenton-like and hybrid processes appear successful for cleaning of different types of liquid wastewaters. Here, we review the application of metallic catalyst-H2O2 systems in the heterogeneous Fenton process. Each metallic catalyst-H2O2 system has unique redox properties due to metal oxidation state. Solution pH is a major influencing factor. Catalysts made of iron and cerium form stable complexes with oxidation products and H2O2, thus resulting in reduced activities. Copper forms transitory complexes with oxidation products, but copper catalytic activity is restored during the reaction. Silver and manganese do not form complexes. The catalyst performance for degradation and mineralization decreases in the order: manganese, copper, iron, silver, cerium, yet the easiness of practical application decreases in the order: copper, manganese, iron, silver, cerium
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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