1. Nanotechnology and Water Treatment: Applications and Emerging Opportunities

Jacques Theron, Joseph Adrian Walker and Thomas Eugene Cloete

Nanotechnology, the engineering and art of manipulating matter at the nanoscale (1-100 nm), offers the potential of novel nanomaterials for treatment of surface water, groundwater and wastewater contaminated by toxic metal ions, organic and inorganic solutes, and microorganisms. Due to their unique activity toward recalcitrant contaminants and application flexibility, many nanomaterials are under active research and development. Accordingly, literature about current research on different nanomaterials (nanostructured catalytic membranes, nanosorbents, nanocatalysts and bioactive nanoparticles) and their application in water treatment, purification and disinfection is reviewed. Moreover, knowledge regarding toxicological effects of engineered nanomaterials on humans and the environment is presented.

2. Current Molecular and Emerging Nanobiotechnology Approaches for the Detection of Microbial Pathogens

Jacques Theron, Thomas Eugene Cloete and Michele de Kwaadsteniet

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 epidemiology 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. Accordingly, current and emerging molecular approaches for the detection of microbial pathogens as well as nanobiotechnologies that that will extend the limits of current molecular diagnostics are discussed.

3. The Potential of Nanofibers and Nanobiocides in Water Purification

Marelize Botes and Thomas Eugene Cloete

Electrospun nanofibers 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. Research on the applications of nanofibers and nanobiocides in water purification, the fabrication thereof and recently published patents are reviewed in this article.

4. Nanozymes for Biofilm Removal

Melanie Richards and Thomas Eugene Cloete

Sessile communities of bacteria encased in extracellular polymeric substances (EPS) are known as biofilms 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 antimicrobials 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.

5. Nanofiltration for Water and Wastewater Treatment

Ismail Koyuncu and Mehmet Cakmakci

Nanofiltration (NF) is a new type of pressure driven membrane process and used between reverse osmosis and ultrafiltration membranes. The most different speciality of NF membranes is the higher rejection of multivalent ions than monovalent ions. NF 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 NF system. In this chapter, a general overview of nanofiltration membranes, membrane materials and manufacturing techniques, principles such as performance and modelling, module types, membrane characterization and applications on water and wastewater treatment were given.

6. Reverse Osmosis: Membranes, Materials, Applications and Nanotechnology

Jesus Hierrezuelo, Elena Garrido and J. Manuel López-Romero

This chapter provides a review about the membrane separation technologies focusing on reverse osmosis (hyperfiltration) and nanofiltration. The first one is based on the basic principle of osmotic pressure, while the latter makes use of molecule size for separation. Recent advances on nanotechnology are opening a range of possibilities in membrane technologies. This chapter also reviews some of these aspects: new membrane preparation and cleaning methods, new surface and interior modification possibilities, the use of new nanostructured materials, and new characterization techniques.

7. Electrospinning Nanofibers for Water Treatment Applications

Eugene Smit

Electrospinning is a highly versatile technique that can be used to create ultrafine fibres of various polymers 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. This chapter describes the combination of these features in the application of electrospun nanofibres in a variety of water treatment applications, including filtration, solid phase extraction and reactive membranes.

8. Potential Risks of Using Nanotechnology in Water Treatment on Human Health

Michele de Kwaadsteniet and Thomas Eugene Cloete

The risk assessment of nanoparticles and nanomaterials is of key importance for the continous development in the already striving 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.