Spurring more biofilm growth for efficient wastewater treatment
Foaming plastic carriers creates uneven surfaces, more area for necessary microorganisms
Osaka Metropolitan University
image:
How foamed polypropylene carriers are used in moving bed biofilm reactors.
view moreCredit: Osaka Metropolitan University
For the sake of the environment and our quality of life, effective treatment of wastewater plays a vital role. A biological method to treat sewage using moving, biofilm-covered plastic items known as carriers has been gaining prominence, and an Osaka Metropolitan University-led team has found ways to make the process more efficient.
The moving bed biofilm reactor (MBBR) process purifies wastewater by putting these carriers in motion to get the biofilm’s microorganisms into greater contact with organic matter and other impurities. The more biofilm that can be attached to the plastic carriers, the more microorganisms that are available to clean the wastewater.
OMU Professor Masayuki Azuma and Associate Professor Yoshihiro Ojima of the Graduate School of Engineering worked with a team from Kansaikako Co., an Osaka-based company specializing in water treatment-related products, and found that polypropylene carriers foamed to create uneven surfaces and more surface area allowed 44 times more biofilm formation than smooth plastic carriers.
Moreover, adding waste biomass such as composted seaweed when foaming further enhanced the performance of the foamed plastic carriers, especially in terms of nitrate removal during the MBBR process.
“Since there is a wide variety of wastewater, it will be necessary to prove that these foamed carriers also have superior suitability to various wastewater,” stated Professor Azuma. “It is clear that the addition of waste biomass improves the performance of the carriers, so we expect that further performance enhancement can be achieved depending on the additive.”
The findings were published in Environmental Technology & Innovation.
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About OMU
Established in Osaka as one of the largest public universities in Japan, Osaka Metropolitan University is committed to shaping the future of society through “Convergence of Knowledge” and the promotion of world-class research. For more research news, visit https://www.omu.ac.jp/en/ and follow us on social media: X, Facebook, Instagram, LinkedIn.
Journal
Environmental Technology & Innovation
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Nitrogen conversion performance of a polypropylene carrier designed to promote biofilm formation through foaming
New filtration material could remove long-lasting chemicals from water
Membranes based on natural silk and cellulose can remove many contaminants, including “forever chemicals” and heavy metals.
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By integrating cellulose into the silk-based fibrils that could be formed into a thin membrane, and then tuning the electrical charge of the cellulose, the researchers produced a material that was highly effective at removing contaminants in lab tests. Pictured is an example of the filter.
view moreCredit: Courtesy of Yilin Zhang and Benedetto Marelli
Water contamination by the chemicals used in today’s technology is a rapidly growing problem globally. A recent studyby the U.S. Centers for Disease Control found that 98 percent of people tested had detectable levels of PFAS, a family of particularly long-lasting compounds, also known as forever chemicals, in their bloodstream.
A new filtration material developed by researchers at MIT might provide a nature-based solution to this stubborn contamination issue. The material, based on natural silk and cellulose, can remove a wide variety of these persistent chemicals as well as heavy metals. And, its antimicrobial properties can help keep the filters from fouling.
The findings are described in the journal ACS Nano, in a paper by MIT postdoc Yilin Zhang, professor of civil and environmental engineering Benedetto Marelli, and four others from MIT.
PFAS chemicals are present in a wide range of products, including cosmetics, food packaging, water-resistant clothing, firefighting foams, and antistick coating for cookware. A recent study identified 57,000 sites contaminated by these chemicals in the U.S. alone. The U.S. Environmental Protection Agency has estimated that PFAS remediation will cost $1.5 billion per year, in order to meet new regulations that call for limiting the compound to less than 7 parts per trillion in drinking water.
Contamination by PFAS and similar compounds “is actually a very big deal, and current solutions may only partially resolve this problem very efficiently or economically,” Zhang says. “That’s why we came up with this protein and cellulose-based, fully natural solution,” he says.
“We came to the project by chance,” Marelli notes. The initial technology that made the filtration material possible was developed by his group for a completely unrelated purpose — as a way to make a labelling system to counter the spread of counterfeit seeds, which are often of inferior quality. His team devised a way of processing silk proteins into uniform nanoscale crystals, or “nanofibrils,” through an environmentally benign, water-based drop-casting method at room temperature.
Zhang suggested that their new nanofibrillar material might be effective at filtering contaminants, but initial attempts with the silk nanofibrils alone didn’t work. The team decided to try adding another material: cellulose, which is abundantly available and can be obtained from agricultural wood pulp waste. The researchers used a self-assembly method in which the silk fibroin protein is suspended in water and then templated into nanofibrils by inserting “seeds” of cellulose nanocrystals. This causes the previously disordered silk molecules to line up together along the seeds, forming the basis of a hybrid material with distinct new properties.
By integrating cellulose into the silk-based fibrils that could be formed into a thin membrane, and then tuning the electrical charge of the cellulose, the researchers produced a material that was highly effective at removing contaminants in lab tests.
The electrical charge of the cellulose, they found, also gave it strong antimicrobial properties. This is a significant advantage, since one of the primary causes of failure in filtration membranes is fouling by bacteria and fungi. The antimicrobial properties of this material should greatly reduce that fouling issue, the researchers say.
“These materials can really compete with the current standard materials in water filtration when it comes to extracting metal ions and these emerging contaminants, and they can also outperform some of them currently,” Marelli says. In lab tests, the materials were able to extract orders of magnitude more of the contaminants from water than the currently used standard materials, activated carbon or granular activated carbon.
While the new work serves as a proof of principle, Marelli says, the team plans to continue working on improving the material, especially in terms of durability and availability of source materials. While the silk proteins used can be available as a byproduct of the silk textile industry, if this material were to be scaled up to address the global needs for water filtration, the supply might be insufficient. Also, alternative protein materials may turn out to perform the same function at lower cost.
Initially, the material would likely be used as a point-of-use filter, something that could be attached to a kitchen faucet, Zhang says. Eventually, it could be scaled up to provide filtration for municipal water supplies, but only after testing demonstrates that this would not pose any risk of introducing any contamination into the water supply. But one big advantage of the material, he says, is that both the silk and the cellulose constituents are considered food-grade substances, so any contamination is unlikely.
“Most of the normal materials available today are focusing on one class of contaminants or solving single problems,” Zhang says. “I think we are among the first to address all of these simultaneously.”
The research team included MIT postdocs Hui Sun and Meng Li, graduate student Maxwell Kalinowski, and recent graduate Yunteng Cao PhD ’22, now a postdoc at Yale. The work was supported by the Office of Naval Research, the National Science Foundation, and the Singapore-MIT Alliance for Research and Technology.
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Written by David L. Chandler, MIT News Office
Paper: “Directed assembly of proteinaceous-polysaccharide nanofibrils to fabricate membranes for emerging contaminant remediation”
https://pubs.acs.org/doi/full/10.1021/acsnano.4c07409
Journal
ACS Nano
Article Title
“Directed assembly of proteinaceous-polysaccharide nanofibrils to fabricate membranes for emerging contaminant remediation”
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