Polluted rivers treated with successful new material developed in Shanghai
The Jiantoucun River in Baoshan District was one of the two rivers that were named and shamed in October last year after its water remained stinky and black for three months.
But now, passers-by smell no unpleasant odors when near the river thanks to a graphene composite developed by a team from Shanghai University and led by Wu Minghong, vice president of the university.
Graphene is regarded as a material of great application prospects with many uncommon properties. For example, it is the strongest material ever tested and conducts heat and electricity efficiently.
Wu’s team has developed a solution to precisely control inter-layer spacing of graphene oxide flakes inside graphene oxide membranes. The achievement was published in famous international science journal “Nature” in October 2017, and won the team the second prize in China’s State Natural Science Awards in January this year.
With this solution, they adjusted the inter-layer spacing to a size that is suitable for micro-organisms, and mixed the material with selected micro-organisms to get a kind of microbial agent, according to Tang Liang, a team member and a professor at the School of Environmental and Chemical Engineering of Shanghai University.
The combination of graphene and engineering bacteria enhanced the bacteria’s depollution effect.
According to Tang, the graphene material can spread widely in the water and has a large surface area, absorbing pollutants in the water and decomposing some organic molecules. The engineering bacteria living in the graphene material can also decompose organic pollutants and take them as food so as to survive and multiply.
“The micro-organisms in the river can actually decompose some pollutants to clean the water themselves, but when the pollution was too serious, they would lie dormant to protect themselves and stop working,” said Tang.
“Our work is to restore the water quality and eco-system in the river to a level where the micro-organisms would wake up and resume work so that the river can regain the ability to clean itself. As the restoration happens at the very bottom of the biological food chain, it will not harm the water or other aquatic life, leaving no secondary pollution.”
They applied the method in a river inside the university campus in May last year and saw successful water purification results within a month.
When seeking an intermediate trail of the product, they received support from the Shanghai Industrial Technology Center of Graphene, a platform jointly launched by the city government and the district authority to facilitate industrialization of lab achievements related to graphene.
Meng Yan, director of the center, said part of their work was to read publications about graphene in world-famous journals — they noticed the team in 2016 and have kept in touch with them since then, serving as a bridge to get their invention into industrial application.
At that time, Baoshan was also looking for solutions to treat the Xiaomengjiazhai River — the most polluted river in the Shanghai Baoshan City Industrial Park.
The university team received the task at the end of June, with a one-year contract, and applied the graphene microbial agents into the river. After a month, the odor and blue-green algae disappeared, the ammonia nitrogen content in the water dropped from 13.6 milligrams per liter to 1.5, and water transparency grew from 20 centimeters to 90.
“We’ve also seen the return of plankton and dragonfly larvae in the river, a symbol of water environment improvement,” said Tang.
Some villagers said it returned to the state it was 30 years ago, while maintenance workers nearby are willing to wash their hands in it now.
After the first success, the team received new “orders” to gradually treat another five rivers in the district, including the Jiantoucun River.
The water quality of all the six rivers has reached tier-V, the basic standard for surface water, while some even reached tier-IV or III.
Tang said they are still working on those rivers to further improve the aquatic environment, while some other places in Jiangsu, Fujian and Hunan provinces have noticed the achievements they have made and come to them for help.
A company has been established by Shanghai University, the Shanghai Industrial Technology Center of Graphene and Baoshan District — the university has authorized the company to use five related patents.
The team has also won a contract with the State Grid, Tang said.
Meng said graphene is one of the key areas for Shanghai’s industrial development, and the center is also incubating other technologies using graphene, such as materials for aerospace and green coating.