PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM095) Primary and ultimate biodegradation of 14C-nonylphenol ethoxylate surfactant.
Staples, C1, Naylor, C2, Carbone, J3, Klecka, G4, 1 Assessment Technologies, Inc., Fredericksburg, VA, USA2 C. G. Naylor Consulting, Austin, TX, USA3 Rohm and Haas Company, Spring House, PA, USA4 The Dow Chemical Company, Midland, MI, USA
ABSTRACT- Nonylphenol (NP) and the 9-mole ethoxylate of nonylphenol (NPE9) were synthesized with a uniform radioactive 14C label in the aromatic ring. The 14C-NP isomer distribution and 14C-NPE9 oligomer distribution closely matched that of commercial NPE9. Biodegradation of 14C-NPE9 was examined under conditions simulating a passive river water environment and activated sludge treatment. The extent of 14CO2 evolution from river water was monitored for 128 days. Over 40% of the NPE aromatic ring carbon was converted to CO2 and as much as another 18% was incorporated into the biomass. Primary degradation of NPE (conversion to metabolites other than NP and NPE carboxylates) was estimated to be 87% - 97%. NP was a minor metabolite. Wastewater treatment plant primary effluent dosed with 5 mg/L 14C-NPE9 was fed into a semi-continuous activated sludge (SCAS) system for 28 days at which time dosing ceased. The system continued to be operated for an additional 19-day die-away period. During the total 47 days of the test, levels of 14C-NPE9 were measured in clarified effluent and settled solids, and evolved CO2 was captured and quantified. During the die-away phase, radiolabeled material continued to become more incorporated into the biomass and to mineralization to carbon dioxide continued. 14C species in the river water, effluent and settled solids consisted of NPE and acidic, water-soluble metabolites, some with the phenolic ring opened. The extent of NPE removal from wastewater by the SCAS system was 95%. These studies demonstrate that the phenolic ring of NPE is degraded and mineralized by activated sludge treatment and in the aquatic environment.
Key words: biodegradation, activated sludge, 14C-nonylphenol synthesis, mineralization