The status of biodegradability testing of nonionic surfactants

A wide range of nonionic surfactants was studied in an extensive inter‐laboratory biodegradability testing program carried out by member companies of The Soap and Detergent Association over a three year period. The objectives were to determine the biodegradability of a variety of nonionic surfactants, and to develop a reliable laboratory scale test method which could be used to evaluate the biodegradability of new candidate materials. The results of this research and testing confirm that the primary and secondary alcohol ethoxylates, the alkyl alkanolamides, and the alkyl amine oxides are all highly biodegradable. These materials represent the important classes of nonionics used in household and institutional synthetic detergents. The removal of these materials under conditions of normal secondary wastewater treatment can be anticipated. The diversity of structures represented in the complete nonionic surfactant spectrum, and the problems of residue analysis imposed serious obstacles in the development of a single standard laboratory procedure which will correlate well with the limited field data presently available. The objective of establishing a standard test for all nonionics was not achieved. Residues of nonionic surfactants from household and institutional synthetic detergents do not appear to contribute to esthetic water pollution or to interfere with waste treatment processes. A variety of biodegradability assessment procedures, applicable to specific nonionics or nonionic groups are currently available and should assure that their residues will not adversely affect the quality of receiving waters. The Subcommittee plans to maintain a program for continued research in nonionic biodegradability testing.