A New Process for Removal of Organic Pollutants from Textile Dyeing Wastewaters



Problem:

The textile industry uses more than 100 billion gallons of water each year. The majority of this water, which is used in preparation and dyeing processes, is discharged with contaminants that require extensive wastewater treatment. The textile dyeing wastewater pollutants are generally characterized by high concentrations of color, COD, BOD, total organic carbon (TOC) and dissolved solids. More seriously, dyeing effluents are often contaminated by high contents of toxic metal chemicals, including chromium, copper, cobalt, lead, zinc, etc. Since the metal contaminants in textile dyeing effluent are present in the complexed form, conventional precipitation and/or reduction methods cannot effectively remove them from the effluent. The dyes in the wastewater are poorly removed by existing technologies.

Solution:

A new treatment process has been developed for simultaneous removal of colors and heavy-metal pollutants. The innovative treatment process consists of three components: hydrophobic precipitation of dyes using proprietary chemicals; self-association of the colloid particles to form polymer-like networking aggregates; and separation of the aggregates from water.

Bench-scale tests with dyeing wastewaters from a textile dyeing plant in Kentucky demonstrate that this new treatment process and system can efficiently remove 90-99 percent of the colors/dyes from the wastewater. For all the cases studied, the untreated effluent had a color content of l200-8000 c.u. (ADMI). Using this new treatment process, the color content was effectively reduced to below 100 c.u. (ADMI) at a cost of less than 50 cents per 1000 gallons. This corresponds to above 90 percent color reduction. Interestingly, the results show that there is a linear relationship between the reduction of color content and the removal of toxic metals. Treated effluents having a low color content also have a low copper concentration. For example, the copper concentration was reduced from 0.5-1 ppm for the untreated effluent to 10--50 ppb for the treated waters, compared with conventional chlorination methods which can only reduce the color content to 300 c.u. (ADMI), while no reduction in copper content could be achieved. Pilot-scale studies demonstrate that the new treatment process is cost-effective, even for the treatment of dyebath discharges having color contents of 3000-10,000 c.u. relatively low costs.

Benefits:

The new process has many advantages over conventional treatment methods, including:

Time and Costs:

The basic study will require an expenditure of $200,000 over a 12-month period. This is being proposed for support by at least ten companies for an investment of $20,000 each. The follow-on program to conduct pilot-scale study at the individual company site will require a further investment of about $50,000 per company.

If you are interested in participating in this project or would like further information on this process, contact:

Dr. B.K. Parekh Associate Director
Center for Applied Energy Research
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