Article last updated on: Jan 25, 2019

What is water treatment?

Water treatment is the collective name for a group of mainly industrial processes that make water more suitable for its application, which may be drinking, medical use, industrial use and more. A water treatment process is designed to remove or reduce existing water contaminants to the point where water reaches a level that is fit for use. Specific processes are tailored according to intended use - for example, treatment of greywater (from bath, dishwasher etc.) will require different measures than black water (from toilets) treatment.

Water treatment photo

Main types of water treatments

All water treatments involve the removal of solids (usually by filtration and sedimentation), bacteria, algae and inorganic compounds. Used water can be converted into environmentally acceptable water, or even drinking water through various treatments.

Water treatments roughly divide into industrial and domestic/municipal. Industrial water treatments include boiler water treatment (removal or chemical modification of substances that are damaging to boilers), cooling water treatment (minimization of damage to industrial cooling towers) and wastewater treatment (both from industrial use and sewage). Wastewater treatment is the process that removes most of the contaminants from wastewater or sewage, producing a liquid that can be disposed to the natural environment and a sludge (semi-solid waste).

Wastewater treatments usually consist of three levels: a primary (mechanical) level, in which about 50-60% of the solids are removed from raw sewage by screening and sedimentation, a secondary (biological) treatment level in which dissolved organic matter that escaped primary treatment is removed by microbes that consume it as food and convert it into carbon dioxide, water and energy. The tertiary treatment removes any impurities that are left, producing an effluent of almost drinking-water quality. Disinfection, typically with chlorine, can sometimes be an additional step before discharge of the effluent. It is not always done due to the high price of chlorine, as well as concern over health effects of chlorine residuals.

Seawater desalination are processes that extract salt from saline water, to produce fresh water suitable for drinking or irrigation. While this technology is in use and also holds much promise for growing in the future, it is still expensive, with reverse osmosis technology consuming a vast amount of energy (the desalination core process is based on reverse osmosis membrane technology).

What is graphene?

Graphene is a two dimensional mesh of carbon atoms arranged in the form of a honeycomb lattice. It has earned the title “miracle material” thanks to a startlingly large collection of incredible attributes - this thin, one atom thick substance (it is so thin in fact, that you’ll need to stack around three million layers of it to make a 1mm thick sheet!) is the lightest, strongest, thinnest, best heat-and-electricity conducting material ever discovered, and the list does not end there. Graphene is the subject of relentless research and is thought to be able to revolutionize whole industries, as researchers work on many different kinds of graphene-based materials, each one with unique qualities and designation.

Graphene and water treatment

Water is an invaluable resource and the intelligent use and maintenance of water supplies is one of the most important and crucial challenges that stand before mankind. New technologies are constantly being sought to lower the cost and footprint of processes that make use of water resources, as potable water (as well as water for agriculture and industry) are always in desperate demand. Much research is focused on graphene for different water treatment uses, and nanotechnology also has great potential for elimination of bacteria and other contaminants.

GO water permeability image

Among graphene’s host of remarkable traits, its hydrophobia is probably one of the traits most useful for water treatment. Graphene naturally repels water, but when narrow pores are made in it, rapid water permeation is allowed. This sparked ideas regarding the use of graphene for water filtration and desalination, especially once the technology for making these micro-pores has been achieved. Graphene sheets (perforated with miniature holes) are studied as a method of water filtration, because they are able to let water molecules pass but block the passage of contaminants and substances. Graphene’s small weight and size can contribute to making a lightweight, energy-efficient and environmentally friendly generation of water filters and desalinators.

It has been discovered that thin membranes made from graphene oxide are impermeable to all gases and vapors, besides water, and further research revealed that an accurate mesh can be made to allow ultrafast separation of atomic species that are very similar in size - enabling super-efficient filtering. This opens the door to the possibility of using seawater as a drinking water resource, in a fast and relatively simple way.

Further reading

The latest graphene water treatment news:

Levidian and United Utilities secure BEIS funding for biogas to hydrogen project

Levidian and United Utilities recently secured funding for the first phase of a biogas to hydrogen project.

The UK Government’s department for Business, Energy, and Industrial Strategy (BEIS) has awarded £212,000 (over USD$256,000) funding through the Net Zero Innovation Portfolio (NZIP) for the first phase of a project which will utilize biogas from wastewater treatment as a fully sustainable feedstock to produce hydrogen and graphene through the Levidian LOOP. United Utilities will lead the project.

Ultrathin covalent organic framework on graphene could be the key to better removal of pollutants

Researchers from the University of Vienna, South Korea's Institute for Basic Science (IBS) and the Chinese Academy of Sciences (CAS) have reported an ultrathin covalent organic framework (COF) that was constructed homogeneously on the surface of a graphene template via a facile hydrothermal method.

The composite material of COF and graphene reportedly shows high and rapid adsorption capacity for organic pollutants.

Versarien launches graphene-based superparamagnetic material

Versarien has announced the launch of a new hybrid nanomaterial that has superparamagnetic properties, which can be used across a range of applications, like defense and healthcare. The new material combines graphene with both iron oxide and manganese oxide nanoparticles and its development was led by Versarien's 62% owned subsidiary, Gnanomat.

The superparamagnetic material combines graphene with both iron oxide and manganese oxide nanoparticles that provide the material with magnetic properties. In return, graphene provides electrical conductivity to these electrically insulating metal oxides. Magnetic nanocomposites can readily respond to external magnetic fields which allow them to be manipulated. Potential applications of the material include the treatment of wastewater whereby pollutants are adsorbed onto the graphene surface. The material could also lends be used in biomedical and biotechnology applications, or defense applications requiring the shielding of electromagnetic fields. Magnetic manipulation could allow the recovery and recycling of the graphene, something that could not be done with normal graphene compounds.

UAE launches a global graphene funding initiative

Khalifa University in Abu Dhabi, United Arab Emirates, have launched a new global graphene funding opportunity, aiming to support the development and applications of graphene (and other 2D materials) in the areas of composites (lightweighting), water and energy.

Khlaifa University established a new fund, called the RIC-2D Research and Innovation Fund, which will offer funding of up to $2 million per year for each project, for a maximum project duration of 3 years.

Researchers develop graphene-based foam composite for efficient water filtration

While graphene-based materials have potential as adsorbent materials, their performance can be hindered due to aggregation and a lack of control over their porosities and dimensions. The researchers in a recent study, from the University of Exeter, Kyushu University and the University of Oxford, have addressed this issue by developing a unique graphene material combined with a high porosity composite foam to combat aggregation.

Pharmaceuticals are among the most prominent emerging contaminants (ECs) in water systems. They may cause severe environmental consequences along with potential health problems. To successfully eradicate ECs from processed wastewater streams, effluent and drinking water purification facilities must adopt adequate tertiary treatment methods. Adsorption is regarded as a technology with great potential in water treatment as it is dependable and less expensive compared to reverse osmosis, oxidizing, microfiltration, ultrafiltration, ion exchange, etc.