Degradation of nonylphenol ethoxylates during the composting of sludges from wool scour effluents

The aqueous scouring of raw wool produces an effluent that typically has a pollution toad of at least 10 times that of domestic sewerage. The bulk of these pollutants may be removed by the SIROLAN-CF chemical flocculation process to produce a clear effluent and a sludge rich in wool wax. This sludge also contains practically all of the wool scouring detergent initially present in the untreated effluent. As the mast commonly used detergents for this purpose, nonylphenol ethoxylates (NPE), are toxic to the environment, their fate must be carefully evaluated when disposal options for these sludges are considered. This paper examines the fate of NPE and the metabolites produced during the composting of a mixture of these sludges and municipal greenwaste. Over 14 weeks the NPE residues were decreased by >96%. The principal degradation pathway involved the oxidative hydrolytic shortening of the paly(ethylene oxide) chain of the hydrophile to produce low levels of the biorefractory metabolites nonylphenol (NP), nonylphenol monoethoxylate (NPEO1), nonylphenol diethoxylate (NPEO2), nonylphenoxy acetic acid (NPE1C), and nonylphenoxyethoxy acetic acid (NPE2C). Concomitant degradation of the nonylphenyl hydrophobe also occurred but at about half the rate of the degradation of the polyoxyethylene hydrophile. No metabolites of the breakdown of the hydrophobe were observed.