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

Latest Graphene Water Treatment news

Graphene-based water filtration project progresses and receives funding boost

Sep 18, 2017

The Smart Filter project received new Innovate UK funding that follows a previous £700,000 project grant awarded in 2015. The previous grant enabled a two-year project by G2O and the Centre for Process Innovation (CPI), focused on transferring and scaling up the water filtration technology from laboratory to industry, ensuring the technology is usable with full quality control.

The technology has since been validated at CPI and the new grant will focus on transferring it to large-scale manufacturing. That will include the use of industrial printing technology to manufacture membranes and validate their performance using prototypes and will involve collaboration with a number of UK partner organizations including chemicals manufacturer William Blythe and CPI.

Spray-on graphene-based coating for improved desalination membranes

Sep 13, 2017

An international group of researchers, including scientists from Shinshu University in Japan and Penn State’s ATOMIC Center, created a graphene and graphene oxide-based coating for desalination membranes which are said to be more scalable and sturdier than current nanofiltration membrane technologies available.

The result of this creation would hopefully be a filter for clean water solutions, protein separation, wastewater treatment, as well as pharmaceutical and food industry applications. This membrane uses a simple spray-on technology to coat a mixture of graphene oxide and graphene in solution onto a backbone support membrane of polysulfone that is modified with polyvinyl alcohol. The team reports that even in the early stages of the development of the membrane, it can already reject 85% of salt, which is sufficient for agricultural purposes, and 96% of dye molecules.

Graphene Oxide market report

NSF grant to fund development of inkjet-printed graphene-based water quality sensors

Sep 04, 2017

The National Science Foundation recently awarded University of Wisconsin-Milwaukee scientists $1.5 million to perfect a method of mass-producing graphene-based small water sensors using inkjet printing. The goal is to determine whether the process can be customized in order to scale up production and in a more economic way than traditional manufacturing methods.

Inkjet-printed graphene-based water quality sensors image

The graphene-based sensors, developed at UWM, reportedly outperform current technologies in accuracy, sensitivity and sensing speed. Their performance and size make them useful for continuously monitoring drinking water for miniscule traces of contaminants like lead.

Connecticut team designs a unique process for exfoliating graphene

Aug 31, 2017

Researchers at the University of Connecticut, assisted by ones from the University of Akron, have patented a unique process for exfoliating graphene, as well as manufacturing innovative graphene nanocomposites that have potential uses in a variety of applications.

The new process doesn’t require any additional steps or chemicals to produce graphene in its pristine form. “The innovation and technology behind our material is our ability to use a thermodynamically driven approach to un-stack graphite into its constituent graphene sheets, and then arrange those sheets into a continuous, electrically conductive, three-dimensional structure” says the lead scientist in the study. “The simplicity of our approach is in stark contrast to current techniques used to exfoliate graphite that rely on aggressive oxidation or high-energy mixing or sonication – the application of sound energy to separate particles – for extended periods of time. As straightforward as our process is, no one else had reported it. We proved it works”.

Masdar team reports progress of graphene-based membranes for water desalination project

Aug 06, 2017

Researchers at the UAE-based Masdar Institute, part of the Khalifa University of Science and Technology, have announced significant progress in their research in the field of optimized graphene-based membranes, which aim to make water filtration and desalination more efficient and sustainable.

The team worked to develop membranes made of layered reduced graphene-oxide sheets that are able to block the passage of salt ions in a membrane-based seawater desalination process. The spacing between the sheets is what ultimately affects the membrane’s efficacy, or its ability to filter impurities like salt ions while still permitting water molecules to pass through. The spaces between sheets must be just right – if they are too large and salt ions are not filtered out, and if they too small and even water molecules are unable to penetrate the membrane.

Versarien - Think you know graphene? Think again!Versarien - Think you know graphene? Think again!