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Dissertation

Efficiency of chemical free cleaning for fouling control in membrane processes : influence of fouling properties

28 Nov 2019-
About: The article was published on 2019-11-28 and is currently open access. It has received None citations till now. The article focuses on the topics: Forward osmosis & Fouling.
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Journal ArticleDOI
TL;DR: The functions, properties and constituents of the EPS matrix that make biofilms the most successful forms of life on earth are described.
Abstract: The microorganisms in biofilms live in a self-produced matrix of hydrated extracellular polymeric substances (EPS) that form their immediate environment. EPS are mainly polysaccharides, proteins, nucleic acids and lipids; they provide the mechanical stability of biofilms, mediate their adhesion to surfaces and form a cohesive, three-dimensional polymer network that interconnects and transiently immobilizes biofilm cells. In addition, the biofilm matrix acts as an external digestive system by keeping extracellular enzymes close to the cells, enabling them to metabolize dissolved, colloidal and solid biopolymers. Here we describe the functions, properties and constituents of the EPS matrix that make biofilms the most successful forms of life on earth.

7,041 citations


"Efficiency of chemical free cleanin..." refers background in this paper

  • ...Membrane biofouling has been recorded at length in the literature, [78-82] however in terms of initial membrane bioadhesion, little work has been done so far, [79, 83, 84]....

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  • ...It is primarily composed of polysaccharides and proteins, [78]....

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Journal ArticleDOI
20 Mar 2008-Nature
TL;DR: Some of the science and technology being developed to improve the disinfection and decontamination of water, as well as efforts to increase water supplies through the safe re-use of wastewater and efficient desalination of sea and brackish water are highlighted.
Abstract: One of the most pervasive problems afflicting people throughout the world is inadequate access to clean water and sanitation. Problems with water are expected to grow worse in the coming decades, with water scarcity occurring globally, even in regions currently considered water-rich. Addressing these problems calls out for a tremendous amount of research to be conducted to identify robust new methods of purifying water at lower cost and with less energy, while at the same time minimizing the use of chemicals and impact on the environment. Here we highlight some of the science and technology being developed to improve the disinfection and decontamination of water, as well as efforts to increase water supplies through the safe re-use of wastewater and efficient desalination of sea and brackish water.

6,967 citations


"Efficiency of chemical free cleanin..." refers background or methods in this paper

  • ...As with the case of organic fouling with RO, this result shows that flux performance alone cannot indicate how effective membrane cleaning is and highlights the importance of surface imaging to obtain a true representation of cleaning efficiency....

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  • ...As with the case of organic fouling with RO, this result shows that flux restoration alone cannot indicate how effective membrane cleaning is....

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  • ...However, as with RO, the calcium interacted with the organic fouling layer and therefore this backwashing method was not effective....

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  • ...55 In RO, osmotic backwashing can be induced by introducing a pulse of high concentration solution to the feed side causing the osmotic pressure on the feed side to exceed the hydraulic pressure applied to the membrane and thus the permeate flow is reversed....

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  • ...In RO, the initial membrane flux is determined by the operating pressure....

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Journal ArticleDOI
TL;DR: The results reviewed in this article indicate that the formation of biofilms serves as a new model system for the study of microbial development.
Abstract: ▪ Abstract Biofilms can be defined as communities of microorganisms attached to a surface. It is clear that microorganisms undergo profound changes during their transition from planktonic (free-swimming) organisms to cells that are part of a complex, surface-attached community. These changes are reflected in the new phenotypic characteristics developed by biofilm bacteria and occur in response to a variety of environmental signals. Recent genetic and molecular approaches used to study bacterial and fungal biofilms have identified genes and regulatory circuits important for initial cell-surface interactions, biofilm maturation, and the return of biofilm microorganisms to a planktonic mode of growth. Studies to date suggest that the planktonic-biofilm transition is a complex and highly regulated process. The results reviewed in this article indicate that the formation of biofilms serves as a new model system for the study of microbial development.

3,321 citations


"Efficiency of chemical free cleanin..." refers background in this paper

  • ...Biofouling is the accumulation of bacteria and other microorganisms in the membrane surface and it is particularly severe in membrane processes due to the strong adhesion of the microorganisms to each other and to the membrane surface and the excretion of exopolymeric substances (EPS) resulting in the formation of a biofilm [8, 88]....

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Journal ArticleDOI
TL;DR: The brominated DBPs were the most genotoxic of all but have not been tested for carcinogenicity and highlighted the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer.
Abstract: Disinfection by-products (DBPs) are formed when disinfectants (chlorine, ozone, chlorine dioxide, or chloramines) react with naturally occurring organic matter, anthropogenic contaminants, bromide, and iodide during the production of drinking water. Here we review 30 years of research on the occurrence, genotoxicity, and carcinogenicity of 85 DBPs, 11 of which are currently regulated by the U.S., and 74 of which are considered emerging DBPs due to their moderate occurrence levels and/or toxicological properties. These 74 include halonitromethanes, iodo-acids and other unregulated halo-acids, iodo-trihalomethanes (THMs), and other unregulated halomethanes, halofuranones (MX [3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone] and brominated MX DBPs), haloamides, haloacetonitriles, tribromopyrrole, aldehydes, and N-nitrosodimethylamine (NDMA) and other nitrosamines. Alternative disinfection practices result in drinking water from which extracted organic material is less mutagenic than extracts of chlorinated water. However, the levels of many emerging DBPs are increased by alternative disinfectants (primarily ozone or chloramines) compared to chlorination, and many emerging DBPs are more genotoxic than some of the regulated DBPs. Our analysis identified three categories of DBPs of particular interest. Category 1 contains eight DBPs with some or all of the toxicologic characteristics of human carcinogens: four regulated (bromodichloromethane, dichloroacetic acid, dibromoacetic acid, and bromate) and four unregulated DBPs (formaldehyde, acetaldehyde, MX, and NDMA). Categories 2 and 3 contain 43 emerging DBPs that are present at moderate levels (sub- to low-mug/L): category 2 contains 29 of these that are genotoxic (including chloral hydrate and chloroacetaldehyde, which are also a rodent carcinogens); category 3 contains the remaining 14 for which little or no toxicological data are available. In general, the brominated DBPs are both more genotoxic and carcinogenic than are chlorinated compounds, and iodinated DBPs were the most genotoxic of all but have not been tested for carcinogenicity. There were toxicological data gaps for even some of the 11 regulated DBPs, as well as for most of the 74 emerging DBPs. A systematic assessment of DBPs for genotoxicity has been performed for approximately 60 DBPs for DNA damage in mammalian cells and 16 for mutagenicity in Salmonella. A recent epidemiologic study found that much of the risk for bladder cancer associated with drinking water was associated with three factors: THM levels, showering/bathing/swimming (i.e., dermal/inhalation exposure), and genotype (having the GSTT1-1 gene). This finding, along with mechanistic studies, highlights the emerging importance of dermal/inhalation exposure to the THMs, or possibly other DBPs, and the role of genotype for risk for drinking-water-associated bladder cancer. More than 50% of the total organic halogen (TOX) formed by chlorination and more than 50% of the assimilable organic carbon (AOC) formed by ozonation has not been identified chemically. The potential interactions among the 600 identified DBPs in the complex mixture of drinking water to which we are exposed by various routes is not reflected in any of the toxicology studies of individual DBPs. The categories of DBPs described here, the identified data gaps, and the emerging role of dermal/inhalation exposure provide guidance for drinking water and public health research.

2,668 citations


"Efficiency of chemical free cleanin..." refers background in this paper

  • ...High levels of TOC in water can react in the disinfection process resulting in the formation of dangerous disinfection by-products [114]....

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Journal ArticleDOI
TL;DR: Key parameters of an RO process and process modifications due to feed water characteristics are brought to light by a direct comparison of seawater and brackish water RO systems.

2,665 citations


"Efficiency of chemical free cleanin..." refers background in this paper

  • ...waste waters and seawater RO plants are mainly fouled by organic material, [115]....

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