New legislation combined with advanced remediation must be the path towards compelling industrial producers to eliminate synthetic dyes before they reach public wastewater systems, says a group of international researchers.
The authors of a new study from the University of Bath highlight the issues of inadequate infrastructure, investment and regulatory effort around synthetic dyes. While there are several potential ways to remove dyes from water, including chemical, biological and membrane-based techniques, the study notes that different dyes require different energy-intensive treatment approaches.
The synthetic dyes widely used in the textile, food and pharmaceutical industries pose a pressing threat to plant, animal and human health, as well as natural environments around the world, the study warns.
“A worldwide regulatory effort is needed to stop dyes reaching wastewater or other water systems such as irrigation,” states the study by researchers from the U.K., China, Korea and Belgium. “Given the complexity of treating dye-containing wastewater, one solution would be to shift from the concept of centralized or regional treatment methods, to decentralized and site-specific treatment at the source, by compelling industries to remove dyes from the wastewater they create before it reaches public water systems.”
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Once dyes reach wastewater systems, treatment processes can be highly energy intensive, the study states. This leads to a lack of treatment, and means that up to 80% of dye-containing industrial wastewaters created in low- and middle-income countries are released untreated into waterways or used directly for irrigation. China, India and Bangladesh are estimated to discharge a combined 3.5 billion tons of textile wastewater each year.
The study also estimates that more than 10,000 different types of dyes have been synthesized, with annual global production estimated to be approximately one million tons.
Study co-author and lecturer in the University of Bath’s Department of Chemical Engineering, Dr. Ming Xie, says that a multi-pronged approach is needed to combat the synthetic dye issue.
“Dyes create several problems when they reach water systems, from stopping light reaching the microorganisms that are the bedrock of our food chains, preventing their reproduction and growth, to more direct consequences like the toxic effects on plants, soils, animals and humans,” Xie announced in a media statement for the study.
While the study acknowledges that regulating the textile industry is a challenging feat, the researchers hope that regulators could at least affect textile processing methods to minimize the use of the most toxic dyes. Advanced remediation technologies must be implemented in combination with proper regulation, the study states.
Some of the treatment processes examined in the new study include chemical coagulation and electro-coagulation; advanced oxidation processes; biological degradation; emerging membrane-based physical separation techniques, including tight ultrafiltration, loose nanofiltration and electro-driven nanofiltration.
Co-author Dr. Dong Han Seo of the Korea Institute of Energy Technology’s (KENTECH) Energy Materials and Devices/Environmental and Climate Technology Track, states that the new study also presents options for industries to create new revenue streams from the processing, separation and reuse of wastewater materials.
“Our review provides the latest insight on how we can effectively manage the challenge from the perspective of circular economy, effectively recycling dyes from wastewaters using treatment strategies such as advanced membrane-based separation to recover both useful dyes as well as clean water,” states Seo.