Dyed without waste
A factory in Belgium specialises in dyeing fabrics. Every year around 12,000 kilometres of textile materials are dyed. And for that, millions of litres of water are needed. After use, the water is full of colorants, chemicals and salts.
How to recycle this polluted water in an efficient and affordable way, so it can be re-used in the whole dyeing process? European researchers think they’ve found an answer to this question.
Fabrics are weaved, tested, rolled, shaved, whitened, dyed, dried and stabilised in the factory and water is present in many of these different processes.
The factory says it consumes an average of some 350 million litres of water every year.
“We use some 80 litres of water per kilo of fabric. This water is used to whiten the fabric, then to colour it and then to fix the colours onto the textile materials, so they don’t wipe out.
‘At the end, we get a water full of colorants of course, and it is very acidic. So we first neutralize this acidity and then we discharge our waste water to the municipal waste water treatment plant,” explained Jan Morel, Maintenance Manager, Utexbel.
Treatment of this coloured water at municipal facilities is extremely costly.
Aware of these economical and environmental challenges, the factory has teamed up with scientists from a European research project.
Their aim is to find solutions to recycle water from textile dyeing in efficient, affordable ways.
Scientists have designed a test recycling unit. Two different processes are used to clean up the water.
A first process, called electro-coagulation, eliminates colorants.
A second, called reverse osmosis, contributes to the elimination of salts.
“First we go to the auto-filtration membranes, where we take out all the small particles and all the other things. Then we go to the second process, called reverse osmosis, that will take even salts and all the rest of the stuff.
‘At the end of the day you get this nice colour-free water, totally clean, nothing in it not even salts. And if you look at the beginning, we started with the dirty water with all the colorants in it. So our end product is where we started,” said Eric van Sonsbeek, Chemical Engineer, EColoRO.
Strict control analysis at each step is used to confirm the efficiency of the different processes.
“We can say that all chemical pollutants and colorants are removed, let’s say that around 93-96% percent of them are removed. Colour is nearly 100% percent removed in this process,” enthused Mert Can, Process Engineer, EColoRO.
Researchers now plan to upscale the existing test unit to a bigger one to be used at the factory, with an eye to creating a closed loop where water is constantly recycled and reused.
“If you have a technology in place that enables you to reduce water intake by 75% or more, already there is a very big cost reductions. Also, you will not discharge to the municipal waste water plant any more, so you will not have any issues with balancing your waste water with that coming from other streams into the municipal waste water treatment plants. So you are freeing up capacity there in the municipal setting,” Andreas Tenn Cate, Chemical Engineer, ISPT/ECWRITI Project Coordinator said.
Scientists say they hope this technology could also improve the competitiveness of the textile and clothes manufacturing sector in the European Union, that employs some 1.6 million people.