Suk-Hyun Na

Biodegradation of perfluorooctanesulfonate (PFOS) as an emerging contaminant.

Perfluorooctanesulfonate (PFOS) is a compound of global concern because of its persistence and bioaccumulation in the environment. Nevertheless, little is known of the potential for PFOS biodegradation, even though the importance of characterizing the function and activity of microbial populations detected in the environment has been discussed. This study focused on the biodegradation of PFOS by a specific microorganism. Through this study, we have identified the aerobic microorganism for the specific decomposition of PFOS from wastewater treatment sludge, as a well-known sink for environmental PFOS. This species was Pseudomonas aeruginosa strain HJ4 with a 99% similarity, a mesophilic rod type bacteria (30-37°C). A pH range of 7-9 was determined to be optimal for the growth of strain HJ4. In this study approximately 67% over a range of concentrations (1400-1800μgL(-)(1)) for PFOS was biologically decomposed by P. aeruginosa after 48h incubation. This result is reported here for the first time, which strongly pertains to the efficient biodegradation of PFOS. Therefore, our study is considered a major advancement in sustainable PFOS treatment.

Slurry Phase Decomposition of Food Waste by Using Various Microorganisms

This study investigated the reduction of food waste through the slurry phase decomposition in a source of food waste by microorganisms. The reactor used in the experiment was composed of both woodchip with wood material and sponges with polyurethane material as media of attached microorganisms, and food waste was mixed with a constant cycle consisted of a stirring device. During the experimental period of 100 days, the change in weight over the cumulative total amount of food waste added was reduced by 99%. Approximately, 1% of the residual food waste could be inherently recalcitrant materials (cellulose, hemicellulose, lignin, etc.) and thus was thought to be the result of the accumulation. The initial pH in wastewater generated from food waste was low with 3.3 and after 24 hours treatment this pH was increased to 5.8. The concentrations of COD, BOD, SS, salinity, TN and TP were gradually decreased. Food waste decay was proceeded by the seven species microorganisms identified and confirmed in this study, making a slurry phase and thus reducing residual food wastes. In the initial phase, the microbial population was approximately 3.3 × 10 cell/mL, and after 15 days this population was a constant with 5.1 × 10 cell/mL which means a certain stabilization for the reduction of food wastes. From these results, it can be considered that organic matter decomposition as well as the weight loss of food wastes by microorganisms is done at the same time.

Monitoring of Perfluorinated Compounds (PFCs) in the Yeongsan River Water System

To determine the concentrations of selected 10 perfluorinated compounds (PFCs), a field study was conducted in the water body of Yeongsan River Water System. Raw water samples were collected in the spring and the fall, respectively, which included 18 sampling sites. Collected samples were equally mixed and then served as an analytical sample. The concentration of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) were in range of 20.80-92.0 ng/L and ND-28.40 ng/L respectively. Perfluorononanoate (PFNA) and perfluorohexanesulfonate (PFHxS) were ranged from ND to 42.20 ng/L and from ND to 11.47 ng/L. The detection frequencies of other PFCs selected in this study were very sparse at very low concentrations, except for PFOS, PFOA, PFNA and PFHxS. PFOS was higher detection frequency and concentration in both spring and fall, PFOA and PFNA were in spring, and PFHxS was in fall. As a result, the observed concentrations of PFCs in the downtown water area of Gwangju, located in the wastewater treatment plants, were relatively higher than other sampling points.

Study on the biodegradation of alternatives (four species including C8H8F9KO3S) for perfluorooctane sulfonate.

Objectives The objective of this study was to evaluate the biodegradation potential of four perfluorooctane sulfonic acid (PFOS) alternatives that were developed at Changwon National University. While PFOS has been used widely in industrial and consumer products, it is known to be a persistent organic pollutant. Therefore, greener alternatives are highly desirable. Methods Biodegradation tests were run for 28 days using standard test protocols. The biochemical oxygen demand was measured daily throughout the experimental period, and the data were used to calculate the biodegradation rates. Microorganisms were isolated from the some of the tests that showed evidence of biodegradation. Results C8H8F9KO3S, which has the same number of carbons as the parent compound PFOS but a reduced number of fluorines, showed the highest biodegradation rate followed by C10H8F13KO3S. Chemical alternatives with lower number of carbons did not biodegrade readily in the experiments. Conclusions Together, these results suggest that it may be advantageous to develop PFOS alternatives with 8 carbons, the same as PFOS, but a reduced number of fluorines; as such, chemicals are more susceptible to biodegradation than the parent compound.

Biodegradation test of the alternatives of perfluorooctanesulfonate (PFOS) and PFOS salts

Objectives: In this study, we investigated the biodegradation rates of 8 perfluorooctanesulfonate (PFOS) alternatives synthesized at the at Changwon National University in comparison to those of PFOS potassium salt and PFOS sodium salt. Methods: A biodegradability test was performed for 28 days with microorganisms cultured in the good laboratory practice laboratory at the Korea Environment Corporation following the OECD Guidelines for the testing of chemicals, Test No. 301 C Results: While , and were not degraded after 28 days, the 3 alternatives were biodegraded at the rates of 31.4% for , 25.6% for , 23.6% for , 20.9% for , 15.5% for , 8.5% for and 4.8% for . When the concentration was the same(500 mg/L), had the lowest tension with 20.94 mN/m, which was followed by (23.36 mN/m), (27.31 mN/m), (28.17 mN/m), (29.77 mN/m) and (33.89 mN/m). Having higher surface tension of 57.64 mN/m and 67.57 mN/m, respectively, than those of the two types of PFOS salts, and were found valueless as substitute for PFOS. Conclusion: The biodegradation test suggest that 6 compounds could be used as substitutes for PFOS. and were found to be the best substitutes based on biodegradation rate and surface tension, followed by , and . was found to have relatively low value as an alternative but it still had a potential to substitute the conventional PFOS.

Study on Environmental Hazards of Alternatives for PFOS

While PFOS sodium salt (C8F17SO3Na) was not degraded by microorganisms for 28 days, the 4 alternatives were biodegraded at the rates of 21.6% for C25F17H32S3O13Na3, 20.5% for C15F9H21S2O8Na2, 15.8% for C23F18H28S2O8Na2 and 6.4% for C17F9H25S2O8Na2, respectively. The acute toxicity test using Daphnia magna was conducted for 48 hours, the half effective concentration (EC50) of PFOS sodium salt (C8F17SO3Na) was evaluated in 54.5 mg/L. While the 4 alternatives did not show any effect at 500.0 mg/L. The surface tension of the PFOS salt (C8F17SO3Na) is 46.2 mN/m at a concentration of 500.0 mg/L. While the surface tension of the 4 alternatives was found to be superior to PFOS sodium salt (C8F17SO3Na). The surface tension of C23F18H28S2O8Na2 (20.9 mN/m) has the lowest, followed by C15F9H21S2O8Na2 (23.4 mN/m), C17F9H25S2O8Na2 (27.3 mN/m), C25F17H32S3O13Na3 (28.2 mN/m). The four kinds of alternatives (C15F9H21S2O8Na2, C17F9H25S2O8Na2, C23F18H28S2O8Na2, C25F17H32S3O13Na3) were found to be superior to PFOS sodium salt (C8F17SO3Na) in terms of biodegradation, Daphnia sp. acute toxicity and surface tension, and thus they were considered applicable as PFOS alternatives. Especially biodegradation rate of C15F9H21S2O8Na2, C23F18H28S2O8Na2 and C25F17H32S3O13Na3 was relatively high as 15.8~21.6%, and Daphnia sp. acute toxicity and surface tension were considerably superior (surface tension 39~55%) to PFOS sodium salt. Therefore, these alternatives are considered to be available as an alternative of PFOS.

Existing test data for the Act on Registration & Evaluation, etc. of Chemical Substances

Objectives In this study, the possibility of using existing test data provided in Korea and elsewhere for the registration of chemical substances was examined. Data on 510 chemical substances that are among the first subject to registration under the “Act on the Registration and Evaluation, etc. of Chemical Substances (K-REACH)” were analyzed. Methods The possibility of using existing data from 16 reference databases was examined for 510 chemical substances notified in July 2015 as being subject to registration. Results Test data with the reliability required for the registration of chemical substances under the K-REACH constituted 48.4% of the required physicochemical characteristics, 6.5% of the required health hazards, and 9.4% of the required environmental hazards. Conclusions Some existing test data were not within the scope of this research, including data used for registration in the European Union (EU). Thus, considering that 350 of these 510 species are registered in EU Registration, Evaluation, Authorisation & Restriction of Chemicals, more test data may exist that can be utilized in addition to the data identified in this study. Furthermore, the K-REACH states that non-testing data (test results predicted through Read Across, Quantitative Structure- Activity Relationships) and the weight of evidence (test results predicted based on test data with low reliability) can also be utilized for registration data. Therefore, if methods for using such data were actively reviewed, it would be possible to reduce the cost of securing test data required for the registration of chemical substances.