Date: August 6, 1997

To: Karl Spilhaus

From: David Trumbull

RE: Summary of EPA/Industry Study of Metals in Textile Effluent

The textile industry has concluded a year-long research project to develop and validate the ultrafiltration method for the measurement of bioavailable metals in textile effluents. The research was sponsored by the research arm of the American Textile Manufacturers Institute (ATMI) was funded in part by a grant from the United States Environmental Protection Agency (USEPA). Several textile and dyestuff organizations, including NTA, contributed funds to the project.

BACKGROUND

USEPA has developed numerical standards for metals such as copper and chromium found in dyes and other chemicals used in textile dyeing and finishing. The standards are based on the concentration of these metals in their ionic form. Application of these numeric standards to National Pollution Discharge Elimination System (NDPES) permits have resulted in unnecessarily stringent effluent limitation for metals. USEPA criteria often are exceeded in textile effluent with no measurable aquatic toxicity.

MEASURING BIOAVAILABLE METAL

The term bioavailability is used to describe the physical and chemical characteristics which determine how substances interact with living organism. It is the bioavailable fraction of the metal that induces toxicity in aquatic life. Metals found in textile discharges are highly complexed, and a relatively small fraction of the total metal present may be in ionic or bioavailable form.

In a cooperative effort to demonstrate the inappropriateness of the USEPA Water Quality Criteria, as they are being applied to textile dyeing and finishing effluents, ATMI submitted a report to USEPA presenting toxicity and metals data for numerous metal-containing dyes and textile effluents. These data clearly showed that toxicities of these dyes and effluents could not be correlated with metal concentrations. Further, the data showed total recoverable metal concentrations significantly higher than the water quality criteria were present without toxicity.

Recognizing the need to evaluate current regulations for metal parameters, USEPA held a workshop in Annapolis, Maryland on January 25-29, 1993. During this meeting the need for methods of quantifying and regulating their bioavailable forms of metals was discussed. Although the conclusions reached at the Annapolis meeting clearly recognized the position of the textile industry, guidance for consideration of metal-organic complexes has not been provided to permit writers. Follow-up meetings with USEPA officials revealed that concerns regarding the fate of these compounds had prevented the issuance of such guidance and that information on the fate of metal-containing dyes should be presented.

ATMI contacted dye manufacturers. In addition, an extensive literature review was performed. Based on the available data, a report was prepared by ATMI which showed that the fate of metal-containing dyes should not be an issue.

While data show that the metals found in textile effluents are not readily bioavailable and should be considered separately from other metal forms, a simple method for the speciation of metals in effluents was not available. USEPA has not approved a method of analysis to determine the portion of the total recoverable metal present in an ionic or bioavailable form.

USEPA has acknowledged the significance of the problem by recently revising its guidance document concerning the interpretation and implementation of aquatic life criteria for metals. In that document USEPA states “...the principal issue is the correlation between metals that are measured and metals that are biologically available.” This revised guidance document ends with a discussion of future research including the statement “USEPA might also consider other biological or chemical techniques for ascertaining the effective concentration of bioavailable metals.”

Ultrafiltration of textile effluents has been suggested as a speciation technique for textile effluents and preliminary results have been reported.

THE METHOD

The research presented in this report developed a modification of the existing method for measuring total recoverable metal, consisting of ultrafiltration of effluents at pH=1 using a 500 MWCO membrane. It is proposed that the metals species measured in the ultrafiltrate permeate be designated “labile metal.” Compared with concentrations obtained from the total recoverable method, labile metal concentrations were found to more closely approximate numeric water quality criteria for chronic toxicity.

The ultrafiltration modification of the method for total recoverable metal would be applicable to textile effluent containing metal as an integral part of the dye molecule, and offers a more reasonable monitoring alternative for determining compliance with numeric quality standards for both direct dischargers and POTWs with significant textile effluents. The key to the method is that the labile metals, including metal salts, that should be regulated must be separated from the metal dye coordination complexes.

The field samples used in this study were chosen to provide a wide range of sites that had textile, industrial, and sanitary inputs. The sites included direct dischargers and POTWs. Textile contributions include sites that do and do not conduct dyeing operations with metal dyestuffs. Thirty-three sites were selected.

RESULTS

The study concludes that the pH=1 ultrafiltration measurement of USEPA’s method for total recoverable metals offers an improved technique for the measurement of labile metals in textile effluents where metal dyestuffs are present.

MORE INFORMATION

The report was prepared by the American Textile Foundation. The coordination of the work presented in this study was conducted by Earth Tech of Charlottesville, Virginia. A related study was conducted by George Baughman of the Dept. of Textiles, Merchandising, and Interiors at the University of Georgia; results from the Univ. of Georgia have been included in this report to provide the most comprehensive set of ultrafiltration data. Nearly fifty publications are cited in the report. There are 35 pages of tables and diagrams supporting the methodology and conclusions of the report.