Textile dyeing accounts for one fifth of all industrial wastewater pollution generated worldwide and much of it, particularly in developing countries in Asia, goes untreated. Now, China is employing electron beams to treat effluent from textile dyeing plants, ushering in a new era for radiation technology.
“Despite advances in conventional wastewater treatment technology in recent years, radiation remains the only technology that can treat the most stubborn colorants in wastewater,” said Suni Sabharwal, Radiation Processing Specialist at the International Atomic Energy Agency (IAEA). “The problem is that the technology exists in developed countries, while most of the need now is in the developing world.”
To bridge the knowledge gap, the IAEA ran a coordinated research project on the technology, including its transfer to several countries, mostly in Asia. Chinese researchers, for example, have benefitted from the advice of experts from Hungary, Korea and Poland in the adoption of the technology and the construction of the plant, said Jianlong Wang, Deputy Director of the Nuclear and Energy Technology Institute at Tsinghua University in Beijing and the principal researcher behind the project.
The new plant in Jinhua city, 300 kilometers south of Shanghai, will treat 1500 cubic meters of wastewater per day, around a sixth of the plant’s output. “If everything goes smoothly, we will be able to roll out technology to the rest of the plant and eventually to other plants across the country,” Wang said.
Before opting for radiation technology using electronic beams, Chinese researchers had run an extensive set of feasibility experiments using the effluent from the plant, comparing electron beam technology with other methods. “Electron beam technology was the clear winner as both the more ecological and more effective option,” Wang added.
Other countries with large textile manufacturing industries, such as India, Bangladesh and Sri Lanka, are also considering introducing the technology with the assistance of the IAEA. India is already using gamma irradiation to treat municipal sewage sludge.
In standard wastewater treatment, bacteria are used to digest and breakdown pollutants. However, the molecules in textile effluent cannot be treated with bacteria. To color textiles, compounds with large, long and complex chains are used. Wastewater from the industry can contain more than 70 complex chemicals that do not easily degrade.
By irradiating the effluent using electron beams, scientists can break these complex chemicals into smaller molecules, which, in turn, can be treated and removed using normal biological processes. Irradiation is done using short-lived reactive radicals than can interact with a wide range of pollutants and break them down.
Chinese researchers are also considering the use of electron beam technology to treat residues from pharmaceutical plants that produce antibiotics. These residues are currently handled as hazardous waste because they contain antibiotics and antibiotic resistance genes that cannot be destroyed using conventional technologies, such as composting or oxidation. Research has revealed that electron beam technology can effectively decompose the residual antibiotics and antibiotic resistance genes, Wang explained. The establishment of a demonstration plant at an industrial scale is planned for later this year.