Nanotechnology in water treatment
Encyclopedia
Nanotechnology
, the engineering and art of manipulating matter at the nanoscale (1-100 nm), offers the potential of novel nanomaterials for the treatment of surface water, groundwater
and wastewater
contaminated by toxic metal
ions, organic and inorganic solutes and microorganism
s. Due to their unique activity toward recalcitrant contaminants many nanomaterials are under active research and development for use in the treatment of water.
of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. An important challenge is therefore the rapid, specific and sensitive detection of waterborne pathogens. Presently, microbial tests are based essentially on time-consuming culture methods. However, newer enzymatic, immunological and genetic
methods are being developed to replace and/or support classical approaches to microbial detection. Moreover, innovations in nanotechnology and nanosciences are having a significant impact in biodiagnostics, where a number of nanoparticle-based assays and nanodevices have been introduced for biomolecular detection.
s and nanobiocides show potential in the improvement of water filtration membranes. Biofouling
of membranes caused by the bacterial load in water reduces the quality of drinking water and has become a major problem. Several studies showed inhibition of these bacteria after exposure to nanofibers with functionalized surfaces. Nanobiocides such as metal nanoparticles and engineered nanomaterials are successfully incorporated into nanofibers showing high antimicrobial activity and stability in water.
s and causes serious problems in various areas, amongst other, the medical industry, industrial water settings, paper industry and food processing industry. Although various methods of biofilm control exist, these methods are not without limitations and often fail to remove biofilms from surfaces. Biofilms often show reduced susceptibility to antimicrobial
s or chemicals and chemical by-products may be toxic to the environment, whereas mechanical methods may be labour intensive and expensive due to down-time required to clean the system. This has led to a great interest in the enzymatic degradation of biofilms. Enzymes are highly selective and disrupt the structural stability of the biofilm EPS matrix. Various studies have focused on the enzymatic degradation of polysaccharides and proteins for biofilm detachment since these are the two dominant components of the EPS. Due to the structural role of proteins and polysaccharides in the EPS matrix, a combination of various proteases and polysaccharases may be successful in biofilm removal. The biodegradability and low toxicity of enzymes also make them attractive biofilm control agents. Regardless of all the advantages associated with enzymes, they also suffer from various drawbacks given that they are relatively expensive, show insufficient stability or activity under certain conditions, and cannot be reused. Various approaches are being used to increase the stability of enzymes, including enzyme modification, enzyme immobilization, protein engineering and medium engineering. Although these conventional methods have been used frequently to improve the stability of enzymes, various new techniques, such as self-immobilization of enzymes, the immobilization of enzymes on nano-scale structures and the production of single-enzyme nanoparticles, have been developed. Self-immobilization of enzymes entails the cross-linking of enzyme molecules with each other and yields final preparations consisting of essentially pure proteins and high concentrations of enzyme per unit volume. The activity, stability and efficiency of immobilized enzymes can be improved by reducing the size of the enzyme-carrier. Nano-scale carrier materials allow for high enzyme loading per unit mass, catalytic recycling and a reduced loss of enzyme activity. Furthermore, enzymes can be stabilized by producing single-enzyme nanoparticles consisting of single-enzyme molecules surrounded by a porous organic-inorganic network of less than a few nanometers thick. All these new technologies of enzyme stabilization make enzymes even more attractive alternatives to other biofilm removal and control agents.
is a new type of pressure driven membrane process and used between reverse osmosis and ultrafiltration membranes. The most different speciality of nanofiltration membranes is the higher rejection of multivalent ions than monovalent ions. Nanofiltration membranes are used in softening water, brackish water treatment, industrial wastewater treatment and reuse, product separation in the industry, salt recovery and recently desalination as two pass nanofiltration system.
(hyperfiltration) and nanofiltration
are important in water treatment applications. Reverse osmosis is based on the basic principle of osmotic pressure, while nanofiltration makes use of molecule size for separation. Recent advances in the field of nanotechnology are opening a range of possibilities in membrane technologies. These include: new membrane preparation and cleaning methods, new surface and interior modification possibilities, the use of new nanostructured materials, and new characterization techniques.
is a highly versatile technique that can be used to create ultrafine fibres of various polymer
s and other materials, with diameters ranging from a few micrometers down to tens of nanometres. The nonwoven webs of fibers formed through this process typically have high specific surface areas, nano-scale pore sizes, high and controllable porosity and extreme flexibility with regard to the materials used and modification of the surface chemistry of the fibres. A combination of these features is utilized in the application of electrospun nanofibres to a variety of water treatment applications, including filtration, solid phase extraction and reactive membranes.
s and nanomaterials is of key importance for the continuous development in the new field of nanotechnology. Humans are increasingly being exposed to nanoparticles and nanomaterials, placing stress on the development and validation of reproducible toxicity tests. Tests currently used include genotoxicity and cytotoxicity tests, and in vivo toxicity models. The unique characteristics of nanoparticles and nanomaterials are responsible for their toxicity and interaction with biological macromolecules within the human body. This may lead to the development of diseases and clinical disorders. A loss in cell viability and structure can also occur in exposed tissues as well as inflammation and granuloma formation. The future of nanotechnology depends on the responsible assessment of nanoparticles and nanomaterials.
Nanotechnology
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
, the engineering and art of manipulating matter at the nanoscale (1-100 nm), offers the potential of novel nanomaterials for the treatment of surface water, groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
and wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
contaminated by toxic metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
ions, organic and inorganic solutes and microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s. Due to their unique activity toward recalcitrant contaminants many nanomaterials are under active research and development for use in the treatment of water.
Detection of microbial pathogens
An adequate supply of safe drinking water is one of the major prerequisites for a healthy life, but waterborne diseases is still a major cause of death in many parts of the world, particularly in young children, the elderly, or those with compromised immune systems. As the epidemiologyEpidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
of waterborne diseases is changing, there is a growing global public health concern about new and reemerging infectious diseases that are occurring through a complex interaction of social, economic, evolutionary, and ecological factors. An important challenge is therefore the rapid, specific and sensitive detection of waterborne pathogens. Presently, microbial tests are based essentially on time-consuming culture methods. However, newer enzymatic, immunological and genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
methods are being developed to replace and/or support classical approaches to microbial detection. Moreover, innovations in nanotechnology and nanosciences are having a significant impact in biodiagnostics, where a number of nanoparticle-based assays and nanodevices have been introduced for biomolecular detection.
Nanofibers and nanobiocides
Electrospun nanofiberNanofiber
Nanofibers are defined as fibers with diameters less than 1000 nm nanometers. They can be produced by interfacial polymerization and electrospinning...
s and nanobiocides show potential in the improvement of water filtration membranes. Biofouling
Biofouling
Biofouling or biological fouling is the undesirable accumulation of microorganisms, plants, algae, or animals on wetted structures.-Impact:...
of membranes caused by the bacterial load in water reduces the quality of drinking water and has become a major problem. Several studies showed inhibition of these bacteria after exposure to nanofibers with functionalized surfaces. Nanobiocides such as metal nanoparticles and engineered nanomaterials are successfully incorporated into nanofibers showing high antimicrobial activity and stability in water.
Biofilm removal
Sessile communities of bacteria encased in extracellular polymeric substances (EPS) are known as biofilmBiofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
s and causes serious problems in various areas, amongst other, the medical industry, industrial water settings, paper industry and food processing industry. Although various methods of biofilm control exist, these methods are not without limitations and often fail to remove biofilms from surfaces. Biofilms often show reduced susceptibility to antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
s or chemicals and chemical by-products may be toxic to the environment, whereas mechanical methods may be labour intensive and expensive due to down-time required to clean the system. This has led to a great interest in the enzymatic degradation of biofilms. Enzymes are highly selective and disrupt the structural stability of the biofilm EPS matrix. Various studies have focused on the enzymatic degradation of polysaccharides and proteins for biofilm detachment since these are the two dominant components of the EPS. Due to the structural role of proteins and polysaccharides in the EPS matrix, a combination of various proteases and polysaccharases may be successful in biofilm removal. The biodegradability and low toxicity of enzymes also make them attractive biofilm control agents. Regardless of all the advantages associated with enzymes, they also suffer from various drawbacks given that they are relatively expensive, show insufficient stability or activity under certain conditions, and cannot be reused. Various approaches are being used to increase the stability of enzymes, including enzyme modification, enzyme immobilization, protein engineering and medium engineering. Although these conventional methods have been used frequently to improve the stability of enzymes, various new techniques, such as self-immobilization of enzymes, the immobilization of enzymes on nano-scale structures and the production of single-enzyme nanoparticles, have been developed. Self-immobilization of enzymes entails the cross-linking of enzyme molecules with each other and yields final preparations consisting of essentially pure proteins and high concentrations of enzyme per unit volume. The activity, stability and efficiency of immobilized enzymes can be improved by reducing the size of the enzyme-carrier. Nano-scale carrier materials allow for high enzyme loading per unit mass, catalytic recycling and a reduced loss of enzyme activity. Furthermore, enzymes can be stabilized by producing single-enzyme nanoparticles consisting of single-enzyme molecules surrounded by a porous organic-inorganic network of less than a few nanometers thick. All these new technologies of enzyme stabilization make enzymes even more attractive alternatives to other biofilm removal and control agents.
Nanofiltration
NanofiltrationNanofiltration
Nanofiltration is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening and removal of disinfection by-product precursors such as natural organic matter and synthetic organic...
is a new type of pressure driven membrane process and used between reverse osmosis and ultrafiltration membranes. The most different speciality of nanofiltration membranes is the higher rejection of multivalent ions than monovalent ions. Nanofiltration membranes are used in softening water, brackish water treatment, industrial wastewater treatment and reuse, product separation in the industry, salt recovery and recently desalination as two pass nanofiltration system.
Reverse Osmosis
The membrane separation technologies of reverse osmosisReverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...
(hyperfiltration) and nanofiltration
Nanofiltration
Nanofiltration is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening and removal of disinfection by-product precursors such as natural organic matter and synthetic organic...
are important in water treatment applications. Reverse osmosis is based on the basic principle of osmotic pressure, while nanofiltration makes use of molecule size for separation. Recent advances in the field of nanotechnology are opening a range of possibilities in membrane technologies. These include: new membrane preparation and cleaning methods, new surface and interior modification possibilities, the use of new nanostructured materials, and new characterization techniques.
Electrospinning
ElectrospinningElectrospinning
Electrospinning uses an electrical charge to draw very fine fibres from a liquid. Electrospinning shares characteristics of both electrospraying and conventional solution dry spinning of fibers. The process does not require the use of coagulation chemistry or high temperatures to produce solid...
is a highly versatile technique that can be used to create ultrafine fibres of various polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s and other materials, with diameters ranging from a few micrometers down to tens of nanometres. The nonwoven webs of fibers formed through this process typically have high specific surface areas, nano-scale pore sizes, high and controllable porosity and extreme flexibility with regard to the materials used and modification of the surface chemistry of the fibres. A combination of these features is utilized in the application of electrospun nanofibres to a variety of water treatment applications, including filtration, solid phase extraction and reactive membranes.
Potential risks on human health
The risk assessment of nanoparticleNanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s and nanomaterials is of key importance for the continuous development in the new field of nanotechnology. Humans are increasingly being exposed to nanoparticles and nanomaterials, placing stress on the development and validation of reproducible toxicity tests. Tests currently used include genotoxicity and cytotoxicity tests, and in vivo toxicity models. The unique characteristics of nanoparticles and nanomaterials are responsible for their toxicity and interaction with biological macromolecules within the human body. This may lead to the development of diseases and clinical disorders. A loss in cell viability and structure can also occur in exposed tissues as well as inflammation and granuloma formation. The future of nanotechnology depends on the responsible assessment of nanoparticles and nanomaterials.
See also
- NanotechnologyNanotechnologyNanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometres...
- Molecular nanotechnologyMolecular nanotechnologyMolecular nanotechnology is a technology based on the ability to build structures to complex, atomic specifications by means of mechanosynthesis. This is distinct from nanoscale materials...
- BioremediationBioremediationBioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...
- Environmental microbiologyEnvironmental microbiologyEnvironmental microbiology is the study of the composition and physiology of microbial communities in the environment. The environment in this case means the soil, water, air and sediments covering the planet and can also include the animals and plants that inhabit these areas...
- Industrial microbiologyIndustrial microbiologyIndustrial microbiology or microbial biotechnology encompasses the use of microorganisms in the manufacture of food or industrial products. The use of microorganisms for the production of food, either human or animal, is often considered a branch of food microbiology...