The finding does not weaken the case for wastewater treatment; it warns mills that lower energy cost and faster dye degradation can carry hidden occupational and environmental risks.
A new University of Massachusetts Amherst study has found that some electrochemical textile wastewater treatment practices can unintentionally generate high levels of toxic byproducts, including chloroform and bromoform. The research, published in the Journal of Hazardous Materials, examined how dye wastewater behaves when treated through electro-oxidation, a process increasingly studied for breaking down persistent colourants in textile effluent.
Salt improves performance—but changes the chemistry
Electrochemical treatment works by using electrodes to break down organic pollutants such as textile dyes. To reduce energy use and improve treatment speed, many systems add sodium chloride, or common salt, to increase water conductivity. The problem, according to the UMass team, is that chloride can form reactive chlorine species during electrochemical reactions. These can then generate disinfection byproducts familiar from drinking-water chemistry, but less scrutinized in industrial textile effluent.
For wet-processing mills, the issue is commercially important because sodium chloride is widely used in dyeing and effluent streams. A process that appears efficient on colour removal or chemical oxygen demand may still create a new risk if byproducts are not monitored.
Azo dyes and brominated dyes raise concern
The researchers tested azo dyes, which they said represent about 50% of the dye market, and found chloride-based toxic byproducts at concentrations in the hundreds of parts per billion. When bromine-containing textile dyes were tested, the treatment generated bromoform at 526 ppb.
The United States does not set specific limits for these compounds in textile wastewater treatment, but the EPA’s drinking-water limit for total trihalomethanes is 80 ppb. The researchers described the detected levels as alarming because some results were several times above that reference point.
The compliance lesson for mills
The study identifies three mitigation routes: replacing sodium chloride with alternatives such as sodium sulfate, using catalysts that reduce byproduct formation, or improving worker protection through measures such as ventilation. Each option carries a trade-off between cost, treatment speed, energy use and safety.
The next step for industry is not to abandon electrochemical treatment, but to specify it more carefully. Buyers, regulators and wet-processing facilities should watch for byproduct testing, worker-exposure controls and pretreatment designs that reduce dependence on chloride-driven oxidation.
