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

Directa Plus and GSP collaborate to evaluate oil & gas applications for Grafysorber

Directa Plus logoDirecta Plus, a producer and supplier of graphene-based products for use in consumer and industrial markets, recently announced that it has entered into a collaboration with GSP SA. Headquartered in Romania and part of the GSP Holding group. GSP will be working with Directa Plus to evaluate the use of Grafysorber, Directa's graphene-based product for environmental applications, in the removal of hydrocarbons from contaminated water emanating from oil & gas activities.

The companies have signed a binding letter of intent to conduct field trials with a view to entering into a commercial agreement during the first half of 2018. Under the terms of the LOI, GSP will commence on-field trials in early 2018 to explore multiple applications for Grafysorber across its range of activities in the oil & gas industry, which include offshore drilling and construction, shipping, engineering, aviation, onshore facilities, logistics and catering. This will involve testing the absorbent capabilities of Grafysorber in decontaminating hydrocarbons from seawater and in the treatment of industrial water.

CealTech's marketing and sales manager explains the company's technology and business

Michel Eid (CealTeach)Norway-based CealTech was established in 2012 to commercialize a patented 3D graphene production method. The company recently received its first prototype proprietary industrial-scale Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) graphene production reactor.

We discussed CealTech's technology and business with the company's marketing and sales manager, Michel Eid. Michael holds a Ph.D. in Solid Mechanics from the Ecole Polytechnique in France, and held various roles in engineeing, manufacturing, sustaining, sales, marketing and business development. Michel joined CealTech in January 2017.

Q: Hello Michael. CealTech is commercializing a patented 3D graphene production method. Can you give us some details on the process and the material you are producing?

Our production process is based on David Boyd’s technique as per Nature communications (DOI: 10.1038/ncomms7620), ‘Single-step deposition of high-mobility graphene at reduced temperatures’. In summary, the substrate is directly exposed to a low-pressure, microwave hydrogen plasma containing small amounts of methane as carbon source. During this process, vertical grown graphene flakes nucleate and arrange perpendicularly to the surface of the substrate forming a so-called 3D network of non-agglomerated graphene flakes.

The Graphene Handbook

Manchester team creates graphene oxide membranes that can filter organic solvents

Researchers at the National Graphene Institute and School of Chemical Engineering and Analytical Science at The University of Manchester have developed an ultra-thin membrane using graphene-oxide sheets, that were assembled in a way that they were able to completely remove various organic dyes, dissolved in methanol, which were as small as a nanometre. This is exciting as GO membranes were once thought to be permeable only to aqueous solutions, but the researchers developed a new form of graphene oxide membrane that can filter organic solvents.

Manchetser and NGI team created unique GO membranes image

In the newly developed ultrathin membranes, graphene-oxide sheets are assembled in such a way that pinholes formed during the assembly are interconnected by graphene nanochannels, which produces an atomic-scale sieve allowing the large flow of solvents through the membrane. When used to filter Cognac and whisky, the membrane permitted alcohol to pass through but trapped the larger molecules that gives the whisky its color. Professor Nair, which led the group, said that "the clear whisky smells similar to the original whisky but we are not allowed to drink it in the lab, however it was a funny Friday night experiment!”

New graphene-based sensor provides real-time detection of contaminants in water

Researchers at the University of Wisconsin-Milwaukee will be presenting a graphene-based sensing platform for real-time, low-cost detection of various water contaminants at the AVS's 64th International Symposium & Exhibition, being held Oct. 29-Nov. 3, 2017, in Tampa, Florida. The new sensor detects heavy metals, bacteria, nitrates and phosphates.

The sensor works by placing graphene-based nanosheets that are semiconducting between an electrode gap. The electrical conductivity of the graphene material changes with the binding of substances, called analytes, to its surface and their chemical constituents are identified and measured. "The magnitude of the conductivity change can be correlated to the concentration of analyte, and the technology also involves the functionalization of the graphene material surface with specific probes that can target a specific analyte," said the researchers.

ERDC team develops a GO-based water treatment system

Researchers at the U.S. Army Engineer Research and Development Center (ERDC) are developing a water treatment system based on a mix of graphene oxide and a byproduct made from shrimp shells.

ERDC develops GO membranes for water treatment image

The ERDC team’s breakthrough was the ability to scale the membranes from the inch and a half diameter membranes other labs throughout the world are working on, to sheets stretching up to two feet long with the potential of making them as big as needed.

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