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Cycle 9 (2020 Deadline)
Nanoassisted bioremediation of diffused dioxins in soil and sediment
PI: Nguyen Thi Kim Oanh (kimoanh@ait.asia), Asian Institute of Technology Center in Vietnam (AITVN) and AIT Thailand, with co-PIs Tran Thi My Dieu, Van Lang University (VLU), and Bui Xuan Thanh, Ho Chi Minh City University of Technology (HCMUT)
U.S. Partner: Dana Barr, Emory University
Project Dates: April 2021 - April 2024
Project Overview
This PEER project studied reducing residual dioxin contamination in soils and sediments from the past use of Agent Orange during the Vietnam War. Contaminated soil with high dioxin concentrations (>1,000 ppt) has been or will be treated to destroy residual dioxins. However, large volumes of soils and sediments containing dioxins below 1,000 ppt remain. Current attempts to address these soils and sediments focus on landfill/containment to prevent direct human and ecological contact. This project aimed to develop technologies to eventually destroy dioxins using enriched indigenous microbes, which have a high potential for application to convert the passive landfills in Phu Cat, Da Nang, and Bien Hoa Air Bases into active landfills. It will also consider the effects of any additives, including nanomaterials, used in the treatment on the microbes and the quality of the soils and sediments.
Dioxins can be removed from contaminated soils and sediments via anaerobic and aerobic metabolism by microorganisms using a novel stepwise procedure of sequential anaerobic-aerobic biodegradation. This process can ultimately destroy dioxins in soils and sediments, eliminating the need for any additional steps to handle the pre-concentrated dioxins in plants or other media. Building on past experience, this project conducted lab-scale experiments to find optimal conditions for dioxin removal. The aim was to include a range of diffused dioxin levels, from below 1000 ppt to a few ppb. A design for the full-scale treatment is still under preparation to be proposed for future application for the bioremediation, taking into account the actual pollution situation and local climate.
The project also built capacity of the local partners in Vietnam by involving research teams from local universities to develop this new treatment approach, hence sustaining the local human resources to deal with the dioxin contamination in soils and sediments in Vietnam in the long term.
Final Summary of Project Activities
The co-PI and his team at Ho Chi Minh University of Technology (HCMUT) synthesized and tested nanomaterials, investigating several key factors and testing their capabilities to facilitate breakdown of a common pollutant, Congo Red, in various types of soil samples. Meanwhile, the co-PI and colleagues at Van Lang University focused on the enrichment of microbes collected from sediment near Gate 3 outside Bien Hoa Airbase and other sites near the adjacent town. The sediment materials (before and after enrichment) were analyzed using 16S rRNA Metagenomics at the K-TEST Lab, which identified several species reportedly capable of destroying dioxins.
The team then began the lab-scale experiments testing various mixtures of microbes, nanomaterials, and molasses to treat dioxin-spiked soil and dioxin-spiked sediment. These experiments used 64 vials at four conditions with 20 weeks in the anaerobic stage, followed by 6 weeks in the aerobic stage. The next phase involved experiments on actual contaminated soil from inside Bien Hoa Airbase with dioxin levels ~1.2 ppb, and the results were promising, showing that for some treatment regimes the removal of dioxins under anaerobic conditions reached more than 70%.
The researchers had visited Bien Hoa Airbase to identify potential locations to conduct the planned pilot scale experiments onsite, but the necessary permission from Vietnam’s Ministry of Defense was granted only late in August 2023, leaving not enough time to prepare for the on-site field experiments. The team instead conducted further experiments off-site in an isolated corner outside the Van Lang University dioxin lab. They collected contaminated sediment materials from outside the airbase near Gate 3, with additional sediments from the pond located in front of Gate 2. Six plastic 200-liter tanks were used in four treatments, and researchers collected samples under a preplanned schedule. The team completed these experiments in early June 2024 and the analytical results are forthcoming.
Students and early career researchers from across the three Vietnamese partner institutions were heavily involved in this PEER project, and the team developed two patent applications as part of their work: one on the indigenous microbial community enrichment procedure and one on the innovative stepwise anaerobic-aerobic treatment of dioxin-contaminated soil. The project received media attention from online newspapers and local broadcasters, and the team published several of their own findings and social media posts about their project. The PEER team delivered two dozen technical presentations across conferences and workshops and published one academic article, with additional manuscripts forthcoming. The PI also received a $80,000 grant for new research from the AFD Group.
Publication
Ngoc-Minh-Thu Vuong, Phuong-Thao Nguyen, Thi Kim Oanh Nguyen, Duy Binh Nguyen, Thi-My-Dieu Tran, Le Thi Kim Oanh, Thanh-Binh Nguyen, Tan-Thi Pham, Kun-Yi Andrew Lin, Xuan-Thanh Bui. 2023. Application of nano zero-valent iron particles coated by carboxymethyl cellulose for removal of Congo red dye in aqueous solution. Case Studies in Chemical and Environmental Engineering 8: 100469. https://doi.org/10.1016/j.cscee.2023.100469
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