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 at Carnegie Mellon University have recently refined the water desalination process, with graphene nanopores obtained using artificial intelligence.
"The ions are so tiny, and if you want to remove them, you need to either boil, evaporate, and condense the water, or push it through membranes full of very tiny pores," explained Barati Farimani, an assistant professor of mechanical engineering at Carnegie Mellon University. The current desalination and separation process is very energy and time inefficient. To combat this, Barati Farimani and his team have used artificial intelligence (AI) agents to design an improved method in a week that would likely take decades. "Ideally," he explained, "the best membrane should be one atom thick, such as graphene, a single-layer sheet."
Researchers from Korea's University of Seoul, Russia's RUDN University and several India-based institutes have created a nano-filter for water purification from synthetic dyes. The graphene-based composite can reportedly remove up to 100% of harmful compounds from water, and it can be used up to seven times without losing efficiency. In addition, the synthesis of the nanofilter itself is economical and environmentally friendly.
Synthetic dyes are used in industrial chemistry and pharmaceuticals. They reach the wastewater together with other industrial waste and pollute the environment. Existing methods of water purification are not quite practical, as the proposed adsorbents are usually disposable and work slowly. Therefore, scientists continue to look for effective and eco-friendly solutions to this problem. The team in this recent work has proposed a reusable graphene-based nanocomposite that can quickly absorb dyes from water.
MIT-led research team uses graphene oxide foam in a device that can extract uranium and other heavy metals from tap water.
Some kinds of water pollution, such as algal blooms and plastics that foul various bodies of water, are found in plain sight. However, other contaminants are not quite as visible, which potentially makes them more dangerous. Among these invisible substances is uranium. Leaching into water resources from mining operations, nuclear waste sites, or from natural subterranean deposits, the element can reach taps worldwide.
UK's G2O Water Technologies has reported securing its first commercial contract for the enhancement of water filtration membranes with graphene oxide.
The Company explains that the advantages of using graphene oxide lie in the enhancement of membrane performance, as it mitigates the effects of fouling – one of the biggest challenges operators of membrane-based water filtration systems face. With a coating of graphene oxide, successfully developed and piloted by the company in the northwest of England in collaboration with Hydrasyst Limited, operators can improve operational efficiency, reduce energy consumption and decrease chemical usage. It is anticipated that this will extend the lifetime of the membranes, as well as significantly reduce the cost and environmental impact of water treatment.
Sunrise Energy Metals to take full ownership of graphene oxide membrane development joint venture company, NematiQ
In 2018, Sunrise Energy Metals (SRL) and Ionic Industries partnered up and established a JV called NematiQ to develop graphene oxide (GO) membranes for water treatment applications. SRL initially had a 75% stake in the joint venture, before increasing its interest to 83.2% in 2020. Now, SRL announced its plan to take full ownership of NematiQ.
NematiQ has developed a process for manufacturing GO, which can be applied to a membrane support to create a graphene oxide-based nanofiltration membrane (GO-Membrane). The GO-Membrane manufacturing process has reportedly already been demonstrated on commercial-scale industrial equipment.