I have been working in these areas now and I have a several ideas on the use of nanotechnology in water treatment and in particular for disinfection

Yes Sir, It can be. Please go through the attached links. Regards

https://icl.googleusercontent.com/?lite_url=http%3A%2F%2Fwww.horizonpress.com%2Fnanotechnology&lc=en-IN

Yes. 

Securing and managing access to clean water is a challenge both for developing

and for more economically developed countries. This document reports on the key

issues of water access; some important technologies for water purification and

resource management; nanotechnology, water and industry; and key challenges -

findings from discussions with stakeholders. It is intended to address policy issues

faced by both developed and developing countries. The document also identifies

policy recommendations for consideration and adoption.

http://www.oecd.org/sti/nano/47601818.pdf

Yes. Even we can have filter made up of nano material and the material characteristic is controlled through bias to filter out the impurity

Of course. Here you can find a good example and a description of one of the methods that could work. 

https://www.indiegogo.com/projects/drinkpure-a-novel-water-filtration-device

Yes,

It is being used to treat water for drinking but also attempt are made to decontaminate and desalinate groundwater.

Yes, for example using nanoparticles made of polymer functionalized by chelating agents to purify from metals or using polymers with antibacterials properties.

‘Nano’ materials have potentials application in many areas because of their high surface-to-volume ratio. At this nano-scale, these materials gain interesting optical, electronic and catalytic properties. Hence, these materials are  finding applications in various fields, Viz :  as biological detection agents, for controlled drug delivery, low-threshold laser type treatments, as an optical filters, and also in sensors... so the same concepts can be used in Water Industry.

U can find the detailed relevant information from the attachments and from this link...

Hope this will give u an Idea to explore the concept in water treatment. 

http://link.springer.com/article/10.1007/s11051-005-7523-5

One way of removing harmful nitrate from drinking water is to catalyse its conversion to nitrogen. This process suffers from the drawback that it often produces ammonia. By using palladium nanoparticles as a catalyst, and by carefully controlling their size, this drawback can be eliminated. It was research conducted by Yingnan Zhao of the University of Twente’s MESA+ Institute for Nanotechnology that led to this discovery.

http://www.utwente.nl/mesaplus/archive/!/2015/1/357005/nanoparticles-for-clean-drinking-water

Nanotechnology holds the potential for the treatment of surface water, groundwater and wastewater contaminated by toxic metal ions, organic and inorganic solutes and microorganisms. Nanomaterials can strip water of toxic metals and dangerous organic molecules, or turn salt water into fresh water. There are also plenty of other nanotech solutions in development. Nanotechnologies that have the best chance are ones that can be integrated with existing systems; membranes improved with nanoparticles that can slot seamlessly into water treatment plants; Nanoparticles of Biomagentite, an iron mineral to get rid of chlorinated organic molecules and some toxic metals, Silver to kill bacteria, Titanium dioxide to break down common organic contaminants such as hormones, pharmaceuticals, or manure. Nanotech desalination and treatment devices could go straight to point of use, or be used in small-scale or emergency situations. Nanotechnology may potentially provide a variety of options to “tailor–make” solutions to filter out contaminants such as heavy metals (e.g. mercury, arsenic) and biological toxins, including waterborne disease causing pathogens, as well as organic and inorganic solutes. Each existing technology for water treatment has inherent limitations, and nanotechnology provides a platform for offering affordable and safe drinking water by providing relatively inexpensive water purification systems and the rapid and low cost detection of impurities.

Dear Sir,

Of Course Nanotechnology can be definitely used for the water treatment purpose. Presently Ag nanoparticles are widely used for this purpose. Of course they are costly and other alternatives have to be implemented. But the advantage of Ag nanoparticles is their processing is very easy.

Treating drinking water is a broad subject and includes removal of a large no. of contaminants, such as heavy metal ions, pesticides, oil spillage, chemical and biological warfare agents to name a few. As some of friends pointed it out above, that use of nanoparticles can be associated with other environmental hazards.

I would like to introduce an emerging concept of utilizing micromotor assisted degradation of biological and chemical threats, removal of oil spillage and cleaning water by Fenton-like reaction. You may find very interesting papers by searching keywords like, micromotors for cleaning polluted water, micromotors for removing oil, micromotors for degradation of chemical threats, etc. Our group has also demonstrated that alkanethiol modified chemically-powered micromotors can capture and transport oil driplets from one location to the other, DOI: 10.1039/C4RA16589F.

Significant contributions by groups of Joseph Wang, Oliver G. Schmidt and Samuel Sanchez have been reported in recent years.

Yes, nanotechnology is used for for water purification and  technology is  commercially available. 

nanifibre made filter with suitable catalyst can be used for water filtration

Yes. There are studies in various fields that employ nanoscale materials and systems for treating drinking water or for reuse. See the article: QU, Xiaolei; ALVAREZ, Peter JJ; LI, Qilin. Applications of nanotechnology in water and wastewater treatment. water research, v. 47, no. 12, p. 3931-3946, 2013.

Nanotechnology promises to dramatically enhance many water purification technologies However, one of the key issues related to nanotechnology is the question of how to apply it. Specifically, it is not clear how to interface nanoparticles with contaminants. At present, many expensive nanoparticles cannot be added to water like commodity chemicals and some nanoparticles could present new hazards to human health and the environment..

My answer is YES. Nanotechnology hold promises for drinking water treatment. Although some nanoparticles have demonstrated toxicity to organisms, there are ways to ensure recovery of the particles when used for water treatment (e.g. using CNT sponges instead of CNT fibers or using nanomaterials deposited on magnetic particles so that the nanocomposite can be easily recovered using a magnetic field). The other hindrance is cost relative to existing technologies. But based on economies of scale, the cost of nanomaterials will continue to reduce as production increases. Existing technologies are insufficient for removal of pharmaceuticals and a few other emerging pollutants but nanomaterials have shown promising adsorption capacities for this important class of materials.

Dear,

Yes, due to a high reactivity, the use of nanoparticles leads, for example, to increase the efficiency of sorptive and catalytic processes. Especially oxyhydroxides of polyvalent metals have been widely used for the synthesis of nanomaterials (Zr, Ti, V, Fe, etc), because of their thermal and mechanical stability, resistance to oxidants, organic solvents and radioactive emissions, as well as enhanced sorption properties. Actually, I investigate nanasryctured adsorbents based on oxyhydroxide of zirconium and oxides of aluminium, manganese and ferric. They have a significant absorption capacity toward polyvalent anions, such as phosphates, borates, carbonates, chromates, arsenates and arsenites, molybdates, as well as heavy metal cations, as lead, copper, nickel and strontium. To prevent secondary pollutions all my adsorbents based on non-toxic oxyhydroxide of zirconium with adding of other metal oxides and also to improve hydrodinamic conditions during adsorption process I obtaine non powder, but spherical product from nanosized particles.

One way of removing harmful nitrate from drinking water is to catalyse its conversion to nitrogen. This process suffers from the drawback that it often produces ammonia. By using palladium nanoparticles as a catalyst, and by carefully controlling their size, this drawback can be partially eliminated. It was research conducted by Yingnan Zhao of the University of Twente's MESA+ Institute for Nanotechnology that led to this discovery.

Read more at: http://phys.org/news/2015-01-nanoparticles.html#jCp

Growth in the development and production of engineered nanoparticles (ENPs) in recent years has increased the potential for interactions of these nanomaterials with aquatic and terrestrial environments. Carefully designed studies are therefore required in order to understand the fate, transport, stability, and toxicity of nanoparticles. Natural organic matter (NOM), such as the humic substances found in water, sediment, and soil, is one of the substances capable of interacting with ENPs. This review presents the findings of studies of the interaction of ENPs and NOM, and the possible effects on nanoparticle stability and the toxicity of these materials in the environment. In addition, ENPs and NOM are utilized for many different purposes, including the removal of metals and organic compounds from effluents, and the development of new electronic sensors and other devices for the detection of active substances. Discussion is therefore provided of some of the ways in which NOM can be used in the production of nanoparticles. Although there has been an increase in the number of studies in this area, further progress is needed to improve understanding of the dynamic interactions between ENPs and NOM.

http://www.sciencedirect.com/science/article/pii/S0045653514009126

Affordable water purification using silver nanoparticles

http://www.thehindu.com/sci-tech/technology/affordable-water-purification-using-silver-nanoparticles/article4690096.ece

Nanofiltration is used for long time ago as pre-treatment for desalination processes. It is mainly applied in drinking water for softening (hardness removal), de-coloring and micro pollutant removal.

The nanostructured catalytic membranes may work brilliantly removing toxic metal ions,microorganisms but it also produces the fear of removing essential trace minerals necessary in water.It may turn to distilled water which cannot be used for drinking.

http://iwapublishing.com/books/9781780401089/detection-pathogens-water-using-micro-and-nano-technology

http://iwapublishing.com/books/9781780406879/nanotechnology-industrial-wastewater-treatment

http://iwapublishing.com/books/9781780404585/nanotechnology-water-and-wastewater-treatment

The necessity of benefiting a breakthrough in filtration technology has led to increasing attention in advanced functional nanosized materials such as nanofibers for filtering devices as a solution for providing water at lower energy costs.

Article Electrospun Nanofibrous Membranes of Polyacrylonitrile/Hallo...

By using as Nano Zero-Valent iron particles play a significant role as an effective tool for cleaning –up contaminated site & ground water containing toxic metal (chromium) which is less costly & environment friendly.

Dear all,

Our group just published a review paper in which we compared nanotechnology-based water treatments with conventional treatment methods in terms of performance, cost, and effects. Some real-life case studies of both techniques were also compared. Here is a link to the paper, and I can send you a private copy if you cannot access the link.

Cheers,

Yemi

http://www.sciencedirect.com/science/article/pii/S1385894715015181

yes, these days nanofibers of different inorganic and organic polymers are being used for water purification. like nanofibers can be functionalized and can be used as selective removal like arsenic, copper and other heavy metals from drinking water.

hope you got.

We have obtained several modified anthracite and some other materials by a nanosised layer of oxides in terms to purify water from iron, manganese etc. The method we have used is simple, allow to produce kg's of material at very short period of time. It lead to reduce size of filters and to make them self-regenerating

Yes it is possible to use nano materials for water treatment. But the way how to apply is quit issue since nano materials have potential risk in health.