Alkylphenol ethoxylate degradation products in land-applied sewage sludge (biosolids)

Alkylphenol ethoxylates, widely used in commercial and household detergents in the United States, can degrade during the wastewater treatment process to more toxic, estrogenic, and lipophilic compounds. These include octylphenol (OP), nonylphenols (NPs), nonylphenol monoethoxylates (NP1EOs), and nonylphenol diethoxylates (NP2EOs). These compounds have received considerable attention due to their acute toxicity and ability to disrupt the endocrine system. In Europe, regulations have been established to control their impact on the environment. In this study, biosolids derived from all 11 U.S. wastewater treatment plants examined contained detectable levels of OP, NPs, NP1EOs, and NP2EOs. Nine exceeded the current Danish land application limit (30 mg/kg; sum of NPs, NP1EOs, and NP2EOs) by 6-33x. NPs were the major component, and their concentrations therein ranged from 5.4 to 887 mg/kg (dry weight). OP, reportedly 10-20x more estrogenic than NP, was detected in these same nine biosolids at levels up to 12.6 mg/kg. Three biosolids were also subjected to the U.S. Environmental Protection Agency Toxicity Characteristic Leaching Procedure Method 1311. NPs and NP1EOs were both detected in the leachate; the former at concentrations from 9.4 to 309 microg/L. On the basis of effect levels published in the literature, alkylphenol ethoxylate degradates in U.S. biosolids may cause adverse environmental impacts.