December 11, 2000

ALKYLPHENOLS BULLETIN
FIELD STUDIES CONFIRM BIODEGRADABILITY OF NP, NPE

New research presented at the Society of Environmental Toxicology and Chemistry (SETAC) meetings in Nashville, TN, and SETAC Third World Congress in the United Kingdom demonstrated that nonylphenol (NP) and nonylphenol ethoxylates (NPEs) are inherently biodegradable and are effectively eliminated in properly functioning treatment plants and septic systems.

C.G. Naylor et al. reported that public wastewater treatment plants in the United States and Canada showed an average removal rate of at least 95 percent of NPEs, while on-site household septic systems in the US were found to remove more than 99.9 percent of the NPEs and all degradation intermediates. Further, the research showed that NP and NPEs biodegraded rapidly in sludge-amended soil.

"The results show that properly operating treatment plants, amendment of treatment plant biosolids to agricultural fields and conventional household septic systems all effectively control the entry of nonylphenol and nonylphenol ethoxylates into the environment," the researchers concluded.

The extensive biodegradation potential of NPEs in septic systems and soil, and the effectiveness of the treatment in septic systems, were confirmed in data presented at SETAC by B.E. Huntsman et al. and C.A. Staples et al., who examined the fate of NPE surfactant within two household septic systems in the Midwest region of the US. Chemical monitoring was conducted using a series of soil lysimeters and groundwater wells.

The two-year experiment showed extensive degradation of the surfactant within the first of two septic fields proximate to the initial entry into the soil, with a greater than 7,000-fold reduction in mass between the effluent, the leach lines and the top 1.25 meters of soil below the leach lines. Based on a travel time of approximately 200 days, this corresponds to a half-life of three to four weeks. Degradation was even faster in the second system, with calculated half-lives of between one and three weeks. Concentrations of NP, NPEs and their biodegradation intermediates were all non-detectable in groundwater at both sites, contrary to expectations if these materials were not degradable.

This field data confirmed the findings of a number of earlier laboratory tests (Staples, SETAC 98, Naylor, et al., SETAC 98) confirming the degradability of nonylphenol and its ethoxylates in the environment, and that they are effectively removed in on-site wastewater treatment systems.                                                                                                                              

 

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