Document DM7EZBn54gOLRv8JkgdKYzeEQ

BACK TO MAIN BIODEGRADATION (Acclimated Activated Sludge and Sediment Cultures) TEST SUBSTANCE Identity: Perfluorooctanesulfonate; may also be referred to as PFOS or FC-95. (1-Octanesulfonic acid, 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8heptadecafluoro-, potassium salt, CAS # 2795-39-3) Remarks: The test substance is a white powder. The 3M production lot number was 217 (TN-A-2130). Purity determined to be 86.9% by LC/MS, 1H-HMR, 19F-NMR and elemental analyses techniques subsequent to analyses cited in the attached report. METHOD Method: Designed by Springborn Laboratories, Inc. Includes 3 elements: Toxicity evaluation, Acclimation phase with biodegradability evaluation, Acclimated inoculum, closed vial biodegradation studies. Test Type: Aerobic GLP: No Year completed: 2000 Toxicity Evaluation Study: Contact time: 48-hours Inoculum source: Activated sludge from the Wareham Wastewater Treatment Plant aeration basin, Wareham, Massachusetts. Inoculum loading in test vessels: 30 mg/L (dry weight) Test medium: Appropriately diluted OECD 301A media plus 5.0 mg/L [14C]sodium benzoate. Test concentrations: 20.8 mg/L (nominal) Study design: Inoculum control: media, inoculum, [14C] sodium benzoate, water Test: media, inoculum, [14C] sodium benzoate, PFOS stock soln Incubation conditions Temperature: 22C Agitation: Shaker table at 150 rpm Test vessels: Single stoppered 250 mL Erlenmeyer flask containing 100 mL OECD mineral salts media and a small headspace trap containing 2.0 mL 1M KOH for each test and control system. Dosing procedure: Each test flask received all components at test initiation. Sampling frequency: 6, 24, and 48-hours Analytical method: Liquid scintillation counting of KOH trap samples BACK TO MAIN Acclimation phase with biodegradability evaluation: Contact time: 16 weeks Inoculum source: Activated sludge from the Wareham Wastewater Treatment Plant aeration basin, Wareham, Massachusetts, secondary return activated sludge from New Bedford, Massachusetts Wastewater Treatment Plant, o ne disk from a rotating biological contacter plant at Bridgewater, Massachusetts, sediment from below the Wareham activated sludge plant's outfall, and a sandy soil from Wilson County, North Carolina. Initial inoculum loading in test vessels: sludge at 1000 mg/L (dry weight) on Day 0, soil at 10,000 mg/L and sediment at 1000 mg/L (dry weight) added on Day 7. Test medium: Primary influent from the Wareham wastewater treatment plant, OECD 301A media, trace minerals, yeast extract, and activated sludge extract. The bioreactors were acclimated to this media for approximately 27 days prior to dosing. Test concentrations: Initial nominal dose 20.8 mg/L PFOS, gradual additions to system over 112 days resulted in final measured concentration in system of 28.4 mg/L PFOS. Study design: Inoculum control: media, inoculum Abiotic control: media, PFOS Test: media, PFOS, inoculum Incubation conditions Temperature: 22 + 2C Agitation: Shaker table, in environmental chamber, at 150 rpm Test vessels: One 300 mL baffled Erlenmeyer flask containing 100 mL media for the test system. More than one (number not specified) 2 liter Erlenmeyer flasks containing 1000 mL each for the inoculum and abiotic controls. The inoculum and abiotic controls set up after 21-days into the study. Dosing procedure: Weekly removal and replacement of 70% of flask contents. Removal accomplished by first pulling out 10 mL of total flask contents (biomass and media) and then taking 60 mL of supernatant resulting from centrifugation of remaining volume (90 mL) of flask contents. This was replaced with an equal volume (70 mL) of fresh medium, including freshly collected sewage influent, and inoculum, and adding 1.4 mL of the 1060 mg/L PFOS stock solution. The inoculum control flasks did not receive the PFOS stock solution. Sampling frequency: Weekly; samples analyzed only on days 7, 14, 21, 28, 35, and 112. Analytical method: LC/MS analyses of biomass and media for PFOS. TOC via carbon analyzer obtained weekly on supernatants after 1.0 m filtration. BACK TO MAIN Acclimated inoculum, closed vial biodegradation studies Contact time: 61 and 63 days Inoculum source: Acclimated sludge from the acclimation phase above (after 12 weeks of acclimation) Initial inoculum loading in test vessels: 200 mg/L (dry weight) Test medium: OECD 301A medium plus yeast extract and resazurin Test concentrations: 0.212 and 105 mg/L (nominal), set up on two different days Study design: Blank control: media only Inoculum control: media, inoculum Abiotic control: media, PFOS Test: media, PFOS, inoculum Incubation conditions Temperature: Not noted Agitation: Not noted Test vessels: 0.212 mg/L exposure: 22 mL serum vials, containing 15 mL test solution. 12 set for blank controls, 12 for inoculum controls, 20 for abiotic controls, and 20 for the test. 105 mg/L exposure: 22 mL serum vials, containing 15 mL test solution. 16 set for inoculum control, 16 for abiotic control, 16 for the test. Dosing procedure: Each test flask received all components at test initiation. Sampling frequency: 0.20 mg/L exposure: Days 0, 16, 30, 61 105 mg/L exposure: Days 0, 15, 30, 63 Analytical method: LC/MS for PFOS, both exposure levels. Headspace analyses of CO2 via carbon analyzer on half of the samples collected for the 105 mg/L exposure. Remarks: Stock solutions used to dose the toxicity and biodegradation test systems were prepared at concentrations of 1.060 and 1.010 mg/L. These concentrations are approximately twice the water solubility of PFOS RESULTS Toxicity Evaluation Study: Evolution of 14CO2 from the control flask (46,700 DPM at 48-hours) was not substantially different from that of the flask with the presence of PFOS (47,000 DPM at 48-hours). Concludes that 20.8 mg/L will not inhibit microbes. Acclimation phase with biodegradability evaluation No clear evidence was seen of biodegradation of PFOS in this study. Two possible confounding factors, which might have affected the mass balance, were postulated: BACK TO MAIN 1. PFOS was found to be initially distributed primarily in the medium, and as time went by, was found primarily associated with the biomass (cells). 2. A white precipitate was observed in the flasks after 2 weeks; appears that PFOS concentrations were exceeding water solubility and precipitating out of solution. Acclimated inoculum, closed vial biodegradation studies No clear evidence was seen of biodegradation of PFOS in this study. Concentrations of PFOS remained relatively constant during the course of the 0.20 mg/L exposure study. Approximately a 20% decline in PFOS concentration was noted in the 105 mg/L exposure study. However, the loss mechanism could not be clearly differentiated between matrix effects and biodegradation. Analyses of CO2 in the headspace in the 105 mg/L exposure study found very little difference in CO2 production between the blank and PFOS-containing vessels. CONCLUSIONS The overall conclusion of these studies is that PFOS is very recalcitrant in the activated sludge/sediment system. DATA QUALITY Reliability: Klimisch ranking = 3. The stock solution used to dose the systems was prepared at twice the water solubility. There were no initial measured concentrations taken in the acclimation phase study. As a result, it is unclear exactly what the bioavailable and/or soluble concentration of PFOS was in this study. This also affects the concentration of PFOS that was transferred to the test flasks for the acclimated biodegradation study. Without an accurately determined starting concentration, mass balance calculations are not feasible. In addition, the acclimated inoculum closed vial biodegradation study did not include details on sample incubation conditions. REFERENCES This study was conducted at Springborn Laboratories, Inc., Wareham, Massachusetts at the request of the 3M Company. Report completed 11/3/00. Lab Project number E01-0434. OTHER Last changed: 6/12/01