1,720,970 research outputs found
Control of fouling in MBRs through nanospheres addition
No full textIn the last decade, the membrane bioreactor (MBR) industry expanded and nowadays this technology is diffused worldwide for wastewater treatment. Nevertheless, membrane fouling is still a critical issue and most research is focused on this aspect in order to control the fouling phenomenon, such as the definition of foulant agents, which are mainly extracellular polymeric substances. One of the main drawbacks related to fouling in MBRs is the sudden jump of the transmembrane pressure, often attributed to the collapse of the fouling layer, which in turn leads to a reduction of the pores size. A potential solution to this problem can be the addition of particles as to reduce the compressibility of the fouling layer through the engineering of the cake structure. Aim of the present work is to test this hypothesis through the addition of nanospheres of different diameter in a hollow fiber MBR unit at lab scale. The nanospheres are inert and non-compressible, and have been chosen for their capability to form well-structured layers. In order to analyze the MBR filtration performance, a synthetic solution has been prepared, in which a foulant agent (sodium alginate) has been spiked. A filtration model has been provided as to interpret the results and their eventual dependence on diameter and concentration of the nanospheres. Results obtained at constant flux in dead-end mode show that the presence of particles changes cake resistance and leads to the formation of non-compressible fouling. However, the addition of particles leads to better filtration performances, no matter what the diameter or concentration may be. Nevertheless, further research is required with the aim of testing the hypothesis with real wastewater. This study may, therefore, enlarge the choice of membrane fouling reducers by taking into consideration their ability to form more structured fouling. © 2015 Balaban Desalination Publications
Membrane Technology in Wastewater Treatments
No full textWater shortage is rapidly becoming a global problem, as climate change and increasing urban population are defining more waterstressed areas. This leads, in turn, to a lower water quality since a higher demand arises. Therefore, novel systems are required in order to provide safe water: one option can be wastewater reclamation through the implementation of membrane filtration. Nowadays, membranes are present in wastewater treatment both in biological oxidation as an hybrid system known as Membrane BioReactor (MBR), and in advanced treatment as pure membrane filtration. For instance, new large treatment plants have been installed in the last years, such as in Singapore, Israel and Spain
Sustainable power plants: A support tool for the analysis of alternatives
No full textShortage of fossil fuels and global oil crisis are leading many national energy authorities to switch from traditional fuels to other renewable ones. On the other hand, in several western countries – due to an increasing environmental awareness – public acceptance of traditional power plants (e.g., coal or fired oil) is steadily decreasing, mostly because of their significant environmental pressures. Decision makers’ activities need to be supported by objective tools, which must be designed to be able to select the best alternative in order to achieve some prefixed goals. Therefore, in the present study, a tool is proposed to support decision makers: it is based on Life Cycle Assessment data from seven different power plants (coal, fired oil, fired gas, nuclear, wind, solar and hydroelectric), to understand what is taken into in terms of material fluxes, and how much it costs in a specific context. Consequently, an Analytic Hierarchy Process has been proposed to select which one might be the best alternative in function of the considered scale and ten environmental criteria. The proposed procedure aims to evaluate different power plants and identify the most environmentally sustainable one in function of plant construction and operation phases
Enhanced drinking water supply through harvested rainwater treatment
No full textDecentralized drinking water systems represent an important element in the process of achieving the Millennium Development Goals, as centralized systems are often inefficient or nonexistent in developing countries. In those countries, most water quality related problems are due to hygiene factors and pathogens. A potential solution might include decentralized systems, which might rely on thermal and/or UV disinfection methods as well as physical and chemical treatments to provide drinking water from rainwater. For application in developing countries, decentralized systems major constraints include low cost, ease of use, environmental sustainability, reduced maintenance and independence from energy sources. This work focuses on an innovative decentralized system that can be used to collect and treat rainwater for potable use (drinking and cooking purposes) of a single household, or a small community. The experimented treatment system combines in one compact unit a Filtration process with an adsorption step on GAC and a UV disinfection phase in an innovative design (FAD - Filtration Adsorption Disinfection). All tests have been carried out using a full scale FAD treatment unit. The efficiency of FAD technology has been discussed in terms of pH, turbidity, COD, TOC, DOC, Escherichia coli and Total coliforms. FAD technology is attractive since it provides a total barrier for pathogens and organic contaminants, and reduces turbidity, thus increasing the overall quality of the water. The FAD unit costs are low, especially if compared to other water treatment technologies and could become a viable option for developing countries
MBR Technology: its main characteristics and market over the world
No full textA market survey of the Membrane BioReactors (MBRs) industry has been performed, obtaining data from 3 major suppliers of MBR filtration systems and MBR plant constructors. MBR plants constructed up to 2012 have been checked, and about 600 wastewater treatment plants have been listed. On average, the capacity of industrial applications is an order of magnitude smaller than municipal. While several systems are available, this study focuses on flat sheet and hollow fibre membranes, in that their share of the MBR market is consistent. What is more, the predominance of immersed MBR filtration systems in wastewater treatment is undisputed, as they represent 99% of the total installed membrane surface (GE Zenon and Kubota, 2 non-European suppliers, representing 63% and 30% respectively). If the industrial market can be considered as mature and stabilized, the municipal market is expected to witness further growth over the next decade under the combined effects of the acceleration of plant construction and the capacity increase. This provides a commercial opportunity for new MBR suppliers to increase their share in the global market through innovation
Sonochemical degradation of twenty-three emerging contaminants in urban wastewater
No full textThe occurrence and fate of pharmaceuticals in the environment, and in aquatic media in particular,
have received considerable attention by the scientific community during the last two
decades. Pharmaceuticals, which are designed to be biologically active substances, are usually
lipophilic and resistant to biodegradation, thus having the potential for accumulation
and persistence in the environment. Although they are usually present at relatively low concentrations,
ranging between ng/L and lg/L levels, they may cause serious effects on the
environment. In this study, the removal efficiency of sonolysis has been tested on a mixture
of 23 pharmaceuticals. Diclofenac and carbamazepine degradations were tested at different
power densities (100–400 W/L) using low frequency. These compounds were spiked separately
in wastewater at high concentrations (mg/L). Subsequently, low-frequency ultrasound-
induced degradation of a mixture of 23 emerging contaminants with low
concentration (lg/L) in urban wastewater was investigated, working at 100 W/L. It was
found that the pharmaceuticals conversion is enhanced at increased applied power densities.
The reaction rate for different pharmaceuticals is almost the same in the mixtures and the
kinetic regimes are mainly pseudo-first order
River water quality assessment: A comparison of binary- and fuzzy logic-based approaches
No full textEuropean Union defined strategies for surface water quality with the 2000/60/EC, or Water Framework Directive (WFD), in order to safeguard Union's water environment; therefore policies have been implemented and became part of Member States legislations. WFD sets guidelines regarding control of river water quality as well as land use planning. However, there is a real requirement of practical investigating procedures, as well as water quality management tools, to help professionals to properly assess the water quality status. In addition, sampling frequencies can be optimized in order to reduce their costs. One of the possible approaches is substantiated into the fuzzy logic, which allows to consider variables not in a binary code but with a certain degree of membership for each of the described classes. The aim of the present study is to show how fuzzy analysis can be implemented when running a water quality assessment, and then focus on a relevant case study. Fuzzy logic approach is studied in order to manage the subjectivity of the analysis, in which examined indicators are classified after data fuzzification and a subsequent defuzzification. A potential optimization of water quality assessment would then reduce sampling frequencies when downward or steady-state trends are found during monitoring campaigns. Sampling frequency studies and non-parametric tests have also been proposed as possible water quality management tools for the application of the EU directive
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