Biorremediacion

Chemosphere 59 (2005) 845–852 www.elsevier.com/locate/chemosphere

Evaluation of bioremediation effectiveness on crude oil-contaminated sand
Sang-Jin Kim *, Dong Hyuk Choi, Doo Suep Sim, Young-Sook Oh
Received 19 March 2004; received in revised form 6 October 2004; accepted 25 October 2004

1

Microbiology Lab., Korea Ocean Research and Development Institute, P.O. Box 29, Ansan 425-600,Republic of Korea

Abstract A treatability study was conducted using sea sand spiked with 3% or 6% (w/w) of Arabian light crude oil to determine the most effective bioremediation strategies for different levels of contamination. The sea sand used in the study was composed of gravel (0.1%), sand (89.0%), and silt and clay (10.9%). The water content of the sea sand was adjusted to 12.6% (w/w) for thestudy. Different combinations of the following treatments were applied to the sand in biometer flasks: the concentration of oil (3% or 6%), the concentration of a mixture of three oil-degrading microorganisms (Corynebacterium sp. IC-10, Sphingomonas sp. KH3-2 and Yarrowia sp. 180, 1 · 106 or 1 · 108 cells gÀ1 sand), the concentration of the surfactant Tween 80 (1 or 10 times the critical micelleconcentration), and the addition of SRIF in a C:N:P ratio of 100:10:3. Three biometer flasks per combination of experimental conditions were incubated, and the performance of each treatment was examined by monitoring CO2 evolution, microbial activity, and oil degradation rate. The results suggest that the addition of inorganic nutrients accelerated the rate of CO2 evolution by a factor of 10. Theapplication of oil-degrading microorganisms in a concentration greater than that of the indigenous population clearly increased biodegradation efficiency. The application of surfactant slightly enhanced the oil degradation rate in the contaminated sand treated with the higher concentration of oil-degrading microorganisms. The initial CO2 evolution rate was shown to efficiently evaluate the treatabilitytest by providing significant data within a short period, which is critical for the rapid determination of the appropriate bioremediation approach. The measurements of microbial activity and crude oil degradation also confirmed the validity of the CO2 evolution rate as an appropriate criterion. Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Bioremediation; Nutrients; Surfactant; Oil-degradingmicroorganisms; CO2 evolution rate; Oil degradation rate; ETS activity; Norhopane ratio

1. Introduction
Abbreviations: SRIF, slow release inorganic fertilizer; CMC, critical micelle concentration; ETS, electron transport system. * Corresponding author. Tel.: +82 31 400 6240; fax: +82 31 406 2495. E-mail address: s-jkim@kordi.re.kr (S.-J. Kim). 1 Present address: Department of EnvironmentalEngineering and Biotechnology, Myongji University, Yongin 449-728, Republic of Korea.

A major aspect of engineered in situ bioremediation is the supply of nutrients such as nitrogen and phosphorus, electron acceptors such as oxygen, and/or microorganisms to the contaminated area (Kim et al., 1998). Natural soils often contain the microorganisms necessary for degrading compounds formed in nature0045-6535/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2004.10.058

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S.-J. Kim et al. / Chemosphere 59 (2005) 845–852

(Alexander, 1994), but bioaugmentation of the populations may enhance the rate of bioremediation. Furthermore, inorganic nutrient supplementation may speed up the process, because the addition of large quantities of oil resultsin a high C:N ratio that is unfavorable to microbial activity (Neralla et al., 1995; Choi et al., 2002). Careful consideration is necessary, however, when undertaking a bioremediation project, in order that the best approach for a given contaminant and set of site characteristics may be determined. A proper site evaluation and a bioassessment or treatability investigation should be conducted...