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.
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.
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.
The latest graphene water treatment news:
Researchers led by Northwestern University engineers and Argonne National Laboratory scientists have reached new findings regarding the role of ionic interaction within graphene and water. Their insights could open the door to the design of new energy-efficient electrodes for batteries or provide the backbone ionic materials for neuromorphic computing applications.
"Every time you have interactions with ions in matter, the medium is very important. Water plays a vital role in mediating interactions between ions, molecules, and interfaces, which lead to a variety of natural and technological processes," said Monica Olvera de La Cruz, Lawyer Taylor Professor of Materials Science and Engineering, who led the research. "Yet, there is much we don't understand about how water-mediated interactions are influenced by nanoconfinement at the nanoscale."
G2O Water Technologies (G2O) has announced an expansion into a new laboratory at Liverpool City Region’s Sci-Tech Daresbury following a £600,000 investment, including £320,000 of funding from NPIF – Maven Equity Finance, managed by Maven and part of the Northern Powerhouse Investment Fund.
Headquartered in Manchester, the G2O uses graphene-based coatings technology to provide high quality and cost-effective solutions to a broad range of filtration applications. G2O’s technology is used for the treatment of water waste across multiple markets, including oil, gas and industrial.
Vanderbilt engineers recently designed a simple defect-sealing technique to correct variations in pore size in graphene membranes. The researchers reported a breakthrough in scalable fabrication of graphene membranes with a sealing technology that corrects variations in the pore size so they remain small enough to trap salt ions and small molecules but allow water to pass.
One of the most complex engineering challenges when making membranes so thin is to maintain integrity in the uniformity of the pores, which requires drilling atomically precise holes in a one-atom thick sheet of carbon atoms. “A single large hole can cause high leakage and compromise membrane performance,” said Piran Kidambi, assistant professor of chemical and biomolecular engineering.
Versarien has announced the launch of its first graphene-enhanced protective face mask, which utilizes Polygrene, Versarien’s graphene-enhanced polymer.
The launch of the new protective face mask is said to coincide with the first two orders Versarien has received following recent prelaunch sales activity, which resulted in 100,000 masks being delivered to a leading British university and 20,000 ordered by a UK electrical and mechanical servicing and repairs business.
New rGO-based nanocomposite photocatalysts can generate hydrogen while while removing pollutants from water
Indian Institute of Technology Mandi research team, in collaboration with researchers from Yogi Vemana University, has designed a novel graphene-based photocatalyst that can remove pollutants from water while simultaneously generating hydrogen using sunlight.
In their work, the researchers have designed a series of novel and multifunctional nanocomposite photocatalysts by coupling mesocrystals of calcium titanate with edge sulfur atoms enriched molybdenum disulfide and reduced graphene oxide.