Study on the Biodegradability of Dispersants and Dispersant/Bunker-C Oil Mixtures and the Dissolved Oxygen Consumption in the Seawater(I) - The Biodegradability of Dispersants and the Dissolved Oxygen Consumption in the Seawater -

해수중에서 유처리제 및 유처리제/Bunker-C유 혼합물의 생분해도와 용존산소소비에 관한 연구(I) - 유처리제의 생분해도와 용존산소소비 -

As the dispersants and the dispersant/oil mixtures are degraded naturally by the microorganisms in the seawater, the consumption of dissolved oxygen may cause marine organisms to be damaged especially in the waters where the dissolved oxygen level is low due to the pollution and the restriction of seawater flow. The biodegradation experiment, the TOD analysis and the element analysis for three dispersants(SG, GL and WC) and a nonionic surfactant(OA-5) were conducted for the purposes of evaluating the biodegradability of dispersants and studying the effect of dispersants on dissolved oxygen in the seawater. The results of biodegradation experiment showed 1mg of dispersants to be equivalent to $0.403{\sim}0.595mg$ of $BOD_5$ and to $0.703{\sim}0.855mg$ of $BOD_{20}$, and 1mg of nonionic surfactant to be equivalent to 0.50mg of $BOD_5$ and to 0.97mg of $BOD_{20}$ in the natural seawater. The results of TOD analysis showed 1mg of dispersants to be $2.37{\sim}2.80mg$ of TOD and 1mg of nonionic surfactant to be 2.45mg of TOD. The results of element analysis showed carbon content and hydrogen content to be $67.6{\sim}76.5\%$ and $10.2{\sim}12.2\%$ for dispersants, and $65.3\%$ and $10.3\%$ for nonionic surfactant, respectively. No nitrogen element was detected in dispersants and a nonionic surfactant. The biodegradability of dispersants shown as the ratio of $BOD_5/TOD$ was found to be in the range of $17{\sim}21\%$, and that of nonionic surfactant was found to be about $20\%$. This means that dispersants and nonionic surfactant belong in the organic matter group of middle-biodegradabilily. The deoxygenation rates($K_1$) and ultimate oxygen demands($L_o$) obtained through the biodegration experiment and Thomas slope method were found to be $0.121{\sim}0.171/day$ and $3.155{\sim}3.810mg/l$ for 4mg/l of dispersants and to be 0.181/day and 1.911mg/l for 2mg/l of nonionic surfactant in the seawater, respectively.

유처리제의 생분해도와 유처리제가 해수중의 용존산소에 미치는 영향을 구명하기 위해서 세 제품의 유처리제(SG, GL, WC)와 비이온 계면활성제(OA-5)에 대한 TOD분석, 원소분석 및 해수중에서의 생분해 실험을 행한 결과를 요약하면 다음과 같다. 1. 1mg의 유처리제는 $2.37{\sim}2.80mg$의 TOD, 1mg의 비이온 계면활성제는 2.45mg의 TOD를 나타내었다. 2. 유처리제는 탄소가 $67.6{\sim}76.5\%$, 수소가 $10.2{\sim}12.3\%$였고, 비이온 계면활성제는 탄소가 $65.3\%$, 수소가 $10.3\%$였으며 어느 것에서도 질소는 검출되지 않았다. 3. 유처리제는 생분해시 제품에 따라 다소 차이가 있었으나 1mg의 유처리제가 $0.403{\sim}0.595mg$의 $BOD_5$ 및 $0.703{\sim}0.855mg$의 $BOD_{20}$를 유발하였다. 또한 1mg의 비이온 계면활성제는 0.50mg의 $BOD_5$ 및 0.97mg의 $BOD_{20}$를 나타내었다. 4. 해수중에서 탈산소계수($K_1$)는 유처리제(4.0mg/l)의 경우 $0.121{\sim}0.171/day$, 비이온 계면활성제(2.0mg/l)의 경우 0.181/day로 나타났다. 또한 유처리제 1mg의 최종산소요구량($L_o$)은 $0.789{\sim}0.953mg$로서 계면활성제 1mg의 최종산소요구량 0.956mg과 비슷하였으며, Glucose 1mg의 TOD값 1.07mg에 접근하는 값이었다. 5. 해수 중의 생분해도($BOD_5/TOD$)에 있어서, 유처리제는 $17{\sim}21\%$, 비이온 계면활성제는 약 $20\%$로서 모두 중간 분해군에 속하였다.