| Popis: |
A testing method for biodegradability of nonionic surfactant has recently been legislated by Japanese Industrial Standards Committee. As the method is, however, concerned only with the disappearance of surface activities, a comparison of results of several kinds of tests is preferred in oder to evaluate the complete degradability. As a part of the evaluation work the authors conducted river die-away tests of some commercial nonionic surfactants using the river water taken from the upper, the middle and the lower reaches of Tama River, in which biodegradabilities were followed by three analytical methods, i.e. (A) foam, (B) CTAS and (C) COD (Cr).It was found that nonylphenol ethoxylate was not degraded at all in clean water of the upper reaches and was degraded slowly in highly polluted water of the middle or lower reaches as compared with primary or secondary alcohol ethoxylate. In view of COD (Cr), only a part corresponding to the ethoxyl chain of nonylphenol ethoxylate was seemed to be degraded even in the water of the lower reaches, while alcohol ethoxylates were seemed to be degraded completely in all cases. |
