With a capacity to treat 30 million litres of industrial wastewater per day, the largest wastewater treatment facility using electron beam technology in the world was inaugurated in China this month. Built on technology transferred by the IAEA since 2010, the treatment process will save 4.5 billion litres of fresh water annually – enough to quench the thirst of 100,000 people each year.
Operating at the world’s largest combed yarn importer, Guanhua Knitting Factory, in southern China, the plant uses electron beam technology to treat water polluted with residues of industrial dyes, whose molecules are too unwieldy to be broken down using bacteria or chemicals. By using electron beam technology, these long and complex molecules in the wastewater can be decomposed and the treated water can be reused.
The textile industry in China, the world’s largest producer, has used chemicals to treat wastewater. But with strengthened policies on environmental protection, they are turning to electron beam technology, which offers a highly efficient and environmentally friendly wastewater treatment method.
“Normally such wastewater would be treated through chemical processes which generate secondary waste,” said BumSoo Han, a radiation chemist at the IAEA. “Electron beam treatment is an eco-friendly and cost-effective method of wastewater treatment as it saves the treatment time and cost for chemicals and there is no secondary waste generated.”
It all started as an IAEA technical cooperation project in 2012, through which Chinese scientists developed a programme to treat wastewater with electron beams. The IAEA support included fellowships at existing facilities in other countries, a national training course and advice from visiting experts, who provided guidance on project development.
“I attended a fellowship in Hungary in 2013 through IAEA support,” said Shijun He, Professor at the Institute of Nuclear and New Energy Technology (INET) at Tsinghua University. “Working in an international laboratory and taking part in training courses directly reflects on the current work we are doing.”
In 2017, a pilot facility in Jinhua city, 300 kilometres southwest of Shanghai, was built, with a capacity to treat 1.5 million litres of wastewater per day from a nearby textile factory. Two years after the launch of this demonstration project, construction of a commercial wastewater treatment plant at the Guanhua Knitting Factory began. Constructed by CGN Nuclear Technology Development Company (CGNNT), a subsidiary of China General Nuclear Power Corporation, the new wastewater plant treats more than 30 million litres of wastewater per day through the operation of seven electron accelerators. “Over 70% of the wastewater that runs through this operation can be reused in the factory, up from the previous reuse rate of 50%. This means less water directly from the nearby river is needed for the operation of the factory, saving 4.5 billion litres of water every year,” said Dongming Hu, general manager at CGNNT.
The success of this project has been widely shared with other industries in China to implement the technology in treating increasing amounts of wastewater due to population growth and industrial and agricultural development. “We have a high amount of wastewater discharged in China and it is difficult to treat this wastewater with conventional technologies. But with electron beams, we can greatly improve the discharge water recycling rate,” said He. Other demonstration projects are underway in Xinjiang, Hubei and Guangxi provinces. “We are working on implementing electron beam technology in a variety of different industries in China,” said He.
How it all works
The textile industry consumes huge amounts of water and chemicals, such as dyes, starches, acids, salts and detergents, which are discharged during the production process. “Radiation techniques using electron beam technology can decompose the large amount of contaminants in the wastewater and remove these complex pollutants,” Han said. In this process, an electron accelerator generates ionizing radiation in the form of accelerated particles through the electron beam. This induces the generation of active radicals from the water molecule to react with the harmful organic contaminants found in the wastewater. These contaminants then become simpler chemical forms and are easier to treat through traditional methods.
“This project is a notable example of how a small amount of seed support from the IAEA Technical Cooperation and Coordinated Research Programmes contributes to stimulating the emergence of a sustainable industry in a country,” said Gashaw Wolde, who manages the IAEA’s technical cooperation projects with China. “The result is cleaner, more efficient industrial processes that clearly have a socio-economic impact at the national scale.”