Biodegradation of nonylphenoxy carboxylates mixtures in two microcosms

The environmental fate of nonylphenoxy carboxylates (NPECs), a representative class of aerobic biodegradation intermediates of nonylphenol ethoxylates (NPEOs), is still unclear. In this study, two NPEC mixtures with the ethoxy chain units ranging from 2 to 9 and from 5 to 18, respectively, were synthesized and applied for studying their aerobic biodegradation behaviors in a modified OECD 301 biodegradation test using two kinds of microcosms, a fresh secondary effluent from a sewage treatment plant and a NPEOs enriched consortium.The determination of NPECs and their related compounds were performed by LC/MS. Degradation of NPECs occurred 4–7 days after the start up of tests with producing a concomitant of shorter chain NPECs. The long-chain NPECs mixture demonstrated a higher degradation rate than that of shorter ones. In comparison with the fresh secondary effluent system, the NPEOs enriched one showed a much slower NPECs degradation. No nonylphenol or NPEOs was detected during our survey. The results in this study could provide some useful information for the comprehensive understanding of the environmental fate of NPEOs.