1,720,994 research outputs found
Drinking Water Denitrification in Membrane Bioreactor/Membrane Contactor Systems
No full textThe results of an experimental study, developed on a membrane bioreactor/membrane contactor pilot plant, aimed at drinking water denitrification are presented and discussed. In the adopted configuration the water, contaminated by nitrates, flows inside the fibres of a membrane unit. Due to the existing concentration gradient, nitrates migrate through the membrane and are reduced to nitrogen gas by the autotrophic biomass attached on the exterior of the fibres, and fed with an external source of organic carbon. Data obtained varying influent flow values and nitrate influent concentrations, confirm the potentiality of the system and show the possibility of full-scale applications. A new mathematical model, useful for both simulation and design of the system is also presented. The model is based on simple mass balances in the flow direction, and through the membrane. Each fibre is considered a plug-flow reactor, and nitrate concentration outside the fibres is assumed to be always zero. To obtain an explicit expression useful for simulation and design of membrane bioreactors/membrane contactors, steady-state conditions are supposed. Experimental data are in good agreement with the model's results, and confirm its applicability
Development and application of a planning support tool in the municipal wastewater sector: The case study of Italy
No full textFinancing investment needs during the next 20 years for Integrated Water Service facilities which includes aqueducts, sewers, drinking water as well as wastewater treatment plants (WWTPs), is a significant challenge for government institutions all over the world. There is an urgent need for new approaches to help decisions makers in order to evaluate the quality and efficiency of these infrastructures and consequently planning investments in the best possible way. Taking into account only the municipal wastewater sector in Italy, the aim of this study was to develop and apply a planning support tool to numerous WWTPs based on secondary biological processes, able to: (i) assess the plants efficiency identifying also their environmental and technological critical issues; (ii) propose technical solutions through the definition of appropriate Action Plans; (iii) simulate WWTPs improvements quantifying the results of the proposed upgrade and; (iv) extend the results of the WWTPs efficiency evaluation on a regional scale comparing the performance of each District by means of specific indices (technological equipment, legal requirement compliance, treatment capacity). Our main hypothesis was that the evaluation of quality as well as the efficiency of the wastewater treatment facilities is the basis for the estimation of investments. We applied this methodology to large Italian municipal WWTPs with a treatment capacity greater than a 50,000 population equivalent (PE) even though it is possible to consider smaller facilities (excluding small wastewater treatment systems generally with a PE less than 2000 inhabitants). Our results demonstrate that the tool can be implemented using official data such as those provided by the National Institute of Statistics (ISTAT) although some verification is required. Finally, the paper addresses the policy implications due to the methodology application highlighting the importance of having well-defined planning support tools especially for those areas needing further social cohesion policies. The developed case study shows the suitability of our proposal for governmental institutions and water utility companies in Italy, however it could also be extended to other countries. © 2014 Elsevier Ltd
Drinking Water Denitrification in Membrane Bioreactor/Membrane Contactor Systems
No full textThe results of an experimental study, developed on a membrane bioreactor/membrane contactor pilot plant, aimed at drinking water denitrification are presented and discussed. In the adopted configuration the water, contaminated by nitrates, flows inside the fibres of a membrane unit. Due to the existing concentration gradient, nitrates migrate through the membrane and are reduced to nitrogen gas by the autotrophic biomass attached on the exterior of the fibres, and fed with an external source of organic carbon. Data obtained varying influent flow values and nitrate influent concentrations, confirm the potentiality of the system and show the possibility of full-scale applications. A new mathematical model, useful for both simulation and design of the system is also presented. The model is based on simple mass balances in the flow direction, and through the membrane. Each fibre is considered a plug-flow reactor, and nitrate concentration outside the fibres is assumed to be always zero. To obtain an explicit expression useful for simulation and design of membrane bioreactors/membrane contactors, steady-state conditions are supposed. Experimental data are in good agreement with the model's results, and confirm its applicability
Removal of Nitrate from Contaminated Water Sources Using Membrane Bioreactor/Membrane Contactor Systems
No full textThe use of membrane bioreactor/membrane contactor (MBR/MC) systems is proposed as a promising alternative far nitrate removal from drinking water. The results of an experimental study, developed on a MBR/MC pilot plant, are presented and discussed, and a new mathematical model is introduced for the design of these systems. The model is then applied to the pilot plant to simulate its performance, and the obtained results are compared with the experimental data. Uncontrolled activities related to agriculture and farming are causing a wide contamination of groundwater sources used far drinking supply. The most dramatic situations are related to nitrate contamination, being well know the risk of nitrate assumption in high doses. To face the problem and treat the water, membrane separation processes can be used, but the resulting operational costs are usually very high. Biological denitrification is much cheaper, but it is usually regarded with great suspicion because of the possible contamination caused by the contact between the water and the biomass. The special configuration of the bioreactor adopted in the experimental study described in the paper, allows to avoid this contact, while maintaining low the operational costs. An ultrafiltration membrane, in fact, is used to keep separated the biomass and the water, while the biological process takes place. Hollow fibres are chosen as membrane units for the pilot plant, and the biological process is demanded to the biofilm developed on the exterior of the fibres. The experimental results, obtained varying the influent flow and the nitrate influent concentration, confirm the system potentiality and show the possibility of full-scale applications of the system. The trend of nitrate removal rate and the corresponding values of carbon source consumption operated by the heterotrophic biomass, revel also the risk of parasite processes development. These processes compete with the denitrification one and reduce the overall efficiency of the treatment. The model, proposed for the design and the simulation of MBR/MC systems and presented in the paper, is based on simple mass balances in the flow direction and through the membrane. To obtain a closed solution of these equations, steady-state conditions are supposed, and each fibre is considered as a plug-flow reactor. Moreover it is hypothesed that the biofilm is able to remove, instantaneously, all the nitrates diffusing through the membrane, so that nitrate concentration outside the fibres is always zero. Data obtained with the pilot plant do not contradict the formulated hypotheses and the experimental data are almost always in good agreement with the results obtained applying the simulation model, which results to be an useful tool for future full scale application of MBRIMC systems
La Denitrificazione delle Acque Potabili nei Bioreattori a Membrana Confinati. Parte I: Proposta di un Modello di Progettazione e Verifica
No full textNel lavoro, suddiviso in due parti, vengono presentati i sistemi di denitrificazione biologica in reattori a membrana confinati (MBRC), come valida alternative per l’eliminazione dei nitrati dalle acque destinate all’approvvigionamento idropotabile. In questa prima parte, dopo aver discusso delle possibili configurazioni impiantistiche sperimentate, viene introdotto un modello matematico semplificato, utile per la verifica e la progettazione di reattori che utilizzano membrane a fibre cave. Dall’applicazione , a scopo dimostrativo, del modello, si ricava l’influenza esercitata, sul rendimento depurativo, dalle caratteristiche geometriche del sistema, dalle modalità di gestione operativa dello stesso, nonché dai parametri caratteristici del materiale utilizzato per la realizzazione delle membrane. La validazione del modello è riportata nella seconda parte del lavoro, nella quale vengono altresì discussi i risultati sperimentali ottenuti su impianto pilota
History and technology of Terra Preta sanitation
No full textIn order to reach the Millennium Development Goals for significantly reducing the number of people without access to adequate sanitation, new holistic concepts are needed focusing on economically feasible closed-loop ecological sanitation systems rather than on expensive end-of-pipe technologies. An analysis of a former civilization in the Amazon (nowadays Brazil) highlights the possibility to close the loop with a more sustainable lifestyle integrating soil fertility, food security, waste management, water protection and sanitation, renewable energy. Terra Preta do Indio is the anthropogenic black soil produced by ancient cultures through the conversion of bio-waste, fecal matter and charcoal into long-term fertile soils. These soils have maintained high amounts of organic carbon several thousand years after they were abandoned. Deriving from these concepts, Terra Preta Sanitation (TPS) has been re-developed and adopted. TPS includes urine diversion, addition of a charcoal mixture and is based on lactic-acid-fermentation with subsequent vermicomposting. Lacto-fermentation is a biological anaerobic process that generates a pre-stabilization of the mixture. The main advantage of lacto-fermentation is that no gas and no odor is produced. What makes it particularly interesting for in-house systems even in urban areas. Instead, vermicomposting is an aerobic decomposition process of the pre-digested materials by the combined action of earthworms and microorganisms. It transforms the carbon and nutrients into the deep black, fertile and stable soil that can be utilized in agriculture. No water, ventilation or external energy is required. Starting from ancient Amazonian civilizations traditional knowledge, the aim of this work is to present TPS systems adopted nowadays
Implementation of water efficiency strategies for Italian urban wastewater treatment plants through performance indicators assessment
No full textThe EMWater Project - Promoting Efficient Wastewater Management and Reuse in Mediterranean Countries
No full textGiven the fact of water shortage in the Mediterranean countries, the EMWater project (efficient management of wastewater, its treatment and reuse in the Mediterranean countries) aims to increase the security and safety of water supply through creation of public awareness and implementation of innovative and suitable solutions in wastewater treatment and reuse. The main target countries of this 4-year project are Jordan, Lebanon, Palestine and Turkey. The EMWater project contributes to these goals through training programmes (local, regional and web-based) for technicians, engineers and employees of authorities and non-government organizations; public awareness campaigns; design and construction of pilot plants applying low-cost techniques, as well as through the development of policy guidelines for wastewater treatment and reuse. Such activities will contribute to general objectives of promoting transfer of appropriate wastewater treatment technologies, such as low-cost technologies for rural areas; strengthening local capacities and regional co-operation through the creation of co-operative professional networks; enhancing public awareness of the insufficient and inproper wastewater treatment to the need for hygienically safe disposal, and the potentials of water reuse. The paper is aimed to present the state of implementation of the EMWater project after 3 years, especially focusing on the main steps in pilot plants design and construction activity and in development of guidelines for decision-makers in wastewater management and planning. It further addresses the progress in implementation of capacity building programs
La Denitrificazione delle Acque Potabili nei Bioreattori a Membrana Confinati. Parte II: Sperimentazione su Impianto Pilota e Validazione del Modello Teorico
No full textIl lavoro costituisce la seconda parte di una ricerca finalizzata a presentare i sistemi di denitrificazione biologica in reattori a membrana confinati (MBRC), come possibile alternativa per il trattamento delle acque destinate al consumo umano. Dopo aver introdotto, nella prima parte, un modello matematico semplificato, utile per la verifica e la progettazione di reattori che utilizzano membrane a fibre cave secondo lo schema MBRC, vengono qui presentati i risultati di una serie di sperimentazioni effettuate su impianto in scala pilota. In particolare vengono illustrati i rendimenti depurativi ottenibili in diverse configurazioni idrauliche del sistema, al variare della portata e della fonte di carbonio organico utilizzata per consentire lo sviluppo del processo biologico eterotrofo. I risultati delle sperimentazioni per mettono di individuare le principali problematiche che si possono verificare nella gestione di questi impianti, tra cui, in particolare, lo sviluppo di processi parassiti all’interno del comparto biologico. Essi, inoltre, consentono di valicare il modello matematico proposto, che fornisce valori delle concentrazioni in uscita dal sistema poco distanti da quelli rilevati sperimentalmente
Implementation of water efficiency strategies for Italian urban wastewater treatment plants through performance indicators assessment
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