Sarina Ergas and David Reckhow of the Civil and Environmental Engineering Department have developed a set of customized methods for treating some of the most polluted water in the country – spent dyebath from textile mills. The processes are seen as environmentally friendly practices that can pay big dividends for companies that use them.
The researchers collaborated with 15 textile facilities in Massachusetts and developed individualized zero-discharge processes that promise to cut down dramatically on wastewater treatment costs, energy bills, water usage and the discharge of residual dye and pollutants into the environment. The concept of zero discharge is to decontaminate wastewater and recycle it back into the manufacturing process.
The recently completed three-year project was initiated and funded by the National Environmental Technology Institute, with some private sponsorship. There are approximately 217 textile factories in Massachusetts, with 136 in Bristol, Middlesex and Worcester counties, and about 30 in the four western counties. The textile industry provides almost 15,000 jobs in Massachusetts and $2 billion in annual sales.
Dyebath wastewater generated by textile mills is often rated as the most polluting among all industrial sectors. The pollution load is characterized by high color content, suspended solids, salts, nutrients and toxic substances such as heavy metals and chlorinated organic compounds. Many textile mills in the state currently discharge their wastewater to local wastewater treatment plants with minimum treatment such as pH neutralization. Other mills treat their effluent on-site and discharge it to nearby bodies of water through National Pollutant Discharge Elimination Systems permits. Neither process removes much of the residual dye color. Larger mills can discharge more than 2 million gallons of wastewater of this kind per day.
The aim of the project was to find treatment processes that were efficient at cleaning up the water, making at least 75 percent of it reusable in the mill process and minimizing operating costs. “We were looking for something that was quite bullet-proof,” says Ergas. Of the eight treatment methods tested, two were found to meet these criteria: electrochemical oxidation, which passes the spent dyebath through an electrolytic cell, in this case supplied by Zappi Water Purification Systems of Amherst, New York; and ozonation, in which an industrial-strength ozonator is applied to the used dye water.
Both methods successfully treated the wastewater, leaving some three-quarters of it suitable for mill reuse that could slash energy costs by as much as $146,000 annually. The results of the tailor-made technologies varied with each mill, depending on the overall production system it was using. Currently, treatment of dyebath water is largely unregulated, but that could change soon. “If there are going to be regulations coming down the pike,” says Ergas, “then our methods may be the only way it will be economically feasible for textile mills to stay in business.”