Date: April 3, 1997

To: Karl Spilhaus

From: David Trumbull

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

The U.S. environmental Protection Agency (USEPA) has established guidelines and criteria for water quality standards. Of specific concern to the textile industry are numerical standards for metals such as copper and chromium found in dyes and other chemicals used in textile dyeing and finishing. As a consequence of being based on metals in their ionic form, the application of water quality standards have resulted in unnecessarily stringent effluent limitation for metals. USEPA criteria often are exceeded in textile effluents with no measurable aquatic toxicity.

The discrepancy is attributable to the differences in the physical and chemical forms of metals. Bioavailability describes characteristics which determine how metals interact with living organisms. It is the bioavailable fraction of the metal that induces toxicity in aquatic life. Metal that is not in a bioavailable form will not cause toxicity. 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.

ATMI submitted a report to USEPA presenting toxicity and metals data for numerous metal-containing dyes and textile effluents. The study demonstrated that metals present in dyes and textile effluents were not readily bioavailable and exhibited far less toxicity than would be predicted by the USEPA Water Quality Criteria.

Recognizing the need to evaluate current regulations for metal parameters, USEPA held a workshop in Annapolis, Maryland on January 25-29, 1993. 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. While the short-term toxicity of metal-organic complexes appeared to be significantly lower than indicated by the concentration present as total recoverable metals, the long-term fate of the metal complexes in the environment was of concern to USEPA.

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 shows 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.

Recently, USEPA has recommended and some states have adopted water quality standards based on the dissolved metal parameter. However, the highly complexed metals found in textile effluents are generally soluble but are often not bioavailable. Thus, water quality standards based on the dissolved metal parameter will not provide the needed relief for the textile industry.

EPA 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. This technique used 500 Dalton molecular weight cutoff (MWCO) membranes to separate textile effluents. This study did not establish a complete method protocol and only dealt with a limited number of samples.

USEPA has recently proposed Interim Guidance that specifically deals with discharges from these sources. This study was begun as a cooperative venture between ATMI and USEPA to look further at the ultrafiltration technique as a possible analytical method to establish speciation in textile effluents.

The research presented in this report present ultrafiltration of effluents at pH=1 using a 500 MWCO membrane and the resulting Labile Metals measurement as an alternative to the Total Recoverable Metals measurement currently used for evaluating numerical criteria compliance. This method is applicable to textile direct dischargers and POTWs with textile influents containing dyestuffs which have copper, chromium, nickel and cobalt as an integral part of the dye molecule.

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 tested in this study show the applicability of the method to real world samples. These samples show that when dyestuffs are present, the labile metal concentrations are less than the metals measured by the Total Recoverable Method. When dyestuffs are not present, the pH=1 Ultrafiltration Method gives equivalent results to the Total Recoverable Method.

In conclusion, the pH=1 ultrafiltration measurement of Labile Metal is a better method for evaluating metal concentrations when textile dyestuffs are present. Because the method is equivalent to the Total Recoverable Method, it will not be applicable to samples that do not contain dyestuffs and it will not be applicable to low metal levels.