Editorial Feature

Nanotechnology and Water Purification

The worldwide population is growing at an exponential rate of 83 million people each year, and is expected to reach 7.9 billion by 2020. The challenge of a rapidly growing population combined with an unpredictable climate has further pushed researchers towards developing innovative technologies that can ensure human beings and animals have access to safe drinking water. In an effort to ensure that the human population is not deprived of clean water, various nanotechnology methods have been developed to remove potentially toxic contaminants from drinking water supplies.

Photo credit | CK Foto

Contaminants in Water

           The United States Environmental Protection Agency (EPA) broadly defines a water contaminant as anything that is not a water molecule. These contaminants can be organic and/or inorganic chemicals, or biological, radiological or physical substances that can potentially cause adverse effects upon consumption.

The following table provides some examples of these types of contaminants that can be present in any water supply:

Table 1: Description and examples of commonly found water contaminants.

Class of Contaminant

Description

Examples

Physical

  • Affects the physical appearance or related properties of water
  • Sediment
  • Organic material
  • Soil erosion products

Chemical

  • Can be natural or man-made
  • Nitrogen
  • Bleach
  • Salts
  • Pesticides
  • Metals
  • Toxins produced by bacteria, human or animal drugs

Biological

  • Organisms in water
  • Also known as ‘microbes’ or ‘microbiological’ contaminants
  • Responsible for several waterborne diseases (e.g., cholera)
  • Bacteria
  • Viruses
  • Protozoa
  • Parasites

Radiological

  • Chemical elements with an unbalanced number of neutrons and protons
  • Resulting atoms can emit ionizing radiation
  • Cesium
  • Plutonium
  • Uranium1

Heavy Metals

  • Released into the environment through natural and industrial processes
  • Arsenic
  • Cadmium
  • Chromium
  • Lead
  • Zinc
  • Nickel
  • Copper2

Limitations of Conventional Water Purification Methods

           Some of the most commonly used water purification methods include screening, filtration, sedimentation, gravity separation, reverse osmosis, ion exchange, neutralization, remineralization, micro- and ultrafiltration and several others3. Despite the usefulness of these techniques, they are often costly methods that require high amounts of energy and water to complete and/or the use of excess reagents.

The Advantage of Nanotechnology for Water Filtration

           Nanotechnology-derived water filtration processes are much more efficient as compared to traditional techniques, as these solutions can be fabricated with features that can enhance the adsorption of materials from water. For example, properties such as reactivity and pore volume, as well as both hydrophilic and hydrophobic interactions, can be manipulated at nanolevel in water treatment solutions to exhibit high performance at an affordable cost.

           Table 2 provides an overview of the types of nanomaterials that have already been successful in water treatment systems.

Table 2: Nanomaterials used for water filtration and their applications.

Nanomaterial

Pros

Cons

Contaminants Removed

Nanoadsorbents

  • High specific surface
  • High adsorption rate
  • High production costs
  • Heavy metals
  • Organic materials
  • Bacteria

Nanometals and Nanometal Oxides (e.g., nanosilver, nano titaniumdioxide (TiO2), magnetic nanoparticles, etc)

  • Abrasion-resistant
  • Supramagnetic – facilitates separation
  • Short intraparticle diffusion distance compressible
  • Photocatalytic
  • Low cost
  • Not as reusable as compared to other nanomaterials

  • Heavy metals
  • Radionuclides
  • Media filters
  • Powders
  • Pellets

Membranes and Membrane Processes (e.g., nanofiltration, nanocomposite, self-assembling, aquaporin-based and nanofiber membranes)

  • Provide a physical barrier for substances depending on their pore and molecule size
  • Reliable
  • Automated
  • Requires a high amount of energy
  • Can be incorporated into any type of water and/or wastewater treatment systems4

Limitations

           Nanotechnology is a highly effective alternative method to removing a wide range of contaminants from any type of water supply. Despite their high specificity in eliminating certain contaminants, nanomaterials exhibit certain limitations, especially when considering the potential uptake of these materials into wildlife. For example TiO2 and silver nanoparticles, some of the most commonly used nanoparticle species, can have particularly harmful effects on aquatic organisms including bacteria, algae, invertebrates, fish and plants4. To combat the potential adverse effects associated with the use of certain nano-water filtration systems, it is imperative that both national and international efforts are made to develop highly efficient systems capable of monitoring the levels of nanoengineered materials within our water supplies.

         

References

  1. “Types of Drinking Water Contaminants” – United States Environmental Protection Agency
  2. Chowdhury. S., Jafar Mazumder, M. A., Al-Attas, O., & Husain, T. (2016). Heavy metals in drinking water: Occurrences, implications, and future needs in developing countries. Science of The Total Environment. DOI: 10.1016/j.scitotenv.2016.06.166.
  3. Kunduru, K. R., Nazarkovsky, M., Farah, S., Pawar, R. P., Basu, A., & Domb, A. J. (2017). Nanotechnology for water purification: applications of nanotechnology methods in wastewater treatment. Water Purification. DOI: 10.1016/B978-0-12-804300-4.00002-2.
  4. Gehrke, I., Geiser, A., & Somborn-Schulz (2015). Innovations in nanotechnology for water treatment. Nanotechnology Science and Applications. DOI: 10.2147/NSA.S43773.

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Benedette Cuffari

Written by

Benedette Cuffari

After completing her Bachelor of Science in Toxicology with two minors in Spanish and Chemistry in 2016, Benedette continued her studies to complete her Master of Science in Toxicology in May of 2018. During graduate school, Benedette investigated the dermatotoxicity of mechlorethamine and bendamustine, which are two nitrogen mustard alkylating agents that are currently used in anticancer therapy.

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