On-site Experiments of Bioremediation on Crude Oil in Coastal Areas of Japan
Conducted by the National Institute for Environmental Studies
By Hideaki Maki

Coastal Environment Research Team, Watershed Environments and Management
Research Project, the National Institute for Environmental Studies (an Independent
Administrative Institution)
In recent years, bioremediation (a method of direct remediation of polluted sites using
microorganisms), which had been used mostly as a partial method of cleaning up soilpollution, has been the focus of attention because of its usage also as a method forcleaning up coastal areas that have been polluted by drifting oil that originated mainly
from oil tanker accidents. Bioremediation not only has the character of making u se oforganisms that exist in the natural field and decompose polluting substances, but also
has only a slight influence on the ecological system. Moreover, bioremediation’s further
advantage of being low-cost also gives rise to high expectations, so that its application
for cleaning up crude oil that has drifted to the coast can be considered for areas wheremethods of physical collection would be difficult, or for residual oil left behind in cases
when complete removal was unable to be carried out.

In bioremediation for oil that has drifted to the shore, the kind of method that has sofar

been

used

overseas

mostlyinvolved

promotingdecomposition

throughbiostimulation by adding f r o m the outside nutritive salts such as nitrogen andphosphorous, which act as rate-determining factor in the decomposition of crude oil,for indigenous crude oil decomposing microbes. However, in reports of actual examples
in the past, since all the conditions prevalent at the sites where such applications were
made, such as geog raphic features, the marine environment, climate, and ecologicalsystems, varied greatly, the crude oil decomposition promotion effect achieved throughadding nutritive salts was by no means uniform, and there were cases where hardly
anyimprovement

at all could

beseen.

There

were very few

instancesofimplementation of bioremediation at polluted sites on the coasts of Japan, and we werein the state of having almost no knowledge that had been obtained either o n ascientific basis or from neutral evaluation by a public organization.

In the light of these circumstances, our institute conducted developmental studies of1

methods to evaluate the effects and safety of bioremediation of oil that has drifted tocoastal areas, mainly through on -site experiments in coastal areas of Japan. Throughthe understanding and cooperation of various organizations located near the sites, wewere able to carry out on -site experiments in areas facing the Japan Sea, the PacificOcean, and the Sea of Okhotsk. At this symposium, I will introduce the outlines andresults of several of these experiments.

The experimental method involved aerating Arabian Light crude oil produced in theMiddle East, and forcibly mixing it in advance with sea water, thus creating amousse-like substance , which was mixed with pebbles of sand from the local area. This
mixture was then combined with multi-purpose synthetic fertilizer granules w i t hcontrolled release ( a s l o w -acting effect) for agricultural u s e , f o r the purpose of
supplying nutritive salts, and the resulting substance laid under the sea in a coastalarea. At specified interval, samples were collected and the process of decomposition of
the crude oil evaluated.
The following results were obtained:

For typical saturated or aromatic hydrocarbon compounds that are contained in crudeoil, such as alkanes, naphthalene, and phenanthrene, a significant promotion effect inthe microbial decomposition, through the addition of fertilizer, could be seen.

Also, regarding the total amount of crude oil removed from the matrix polluted by
crude oil (that is, the pebbles of sand), including physical exfoliation, when comparedwith the areas where fertilizer had not been added, in the areas where fertilizer hadbeen added, the amount removed had increased considerably.

When the figures related to the crude oil removal were calculated, it appeared that thesubstantial rate of contribution of decomposition through microorganisms was about
20% in areas where fertilizer had been added while, physical removal due toexfoliation was from about 40 to 60%.
When we compared the effects of adding fertilizer that featured different forms ofnitrogen such as nitrate, ammonia and urea, organic nitrogen (urea, cross-linked urea)
indicated greater crude oil decomposition and a greater physical exfoliation enhancing
effect than inorganic nitrogen (nitrate, ammonia) did.
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Compared to coastal areas by the Sea of Japan, where there is a small tidal difference,areas on the Pacific Ocean coast, where there is a large tidal range, showed a higher
active decomposition of crude oil, and this difference was especially dramatic in
relation to alkanes.

The activation of crude oil decomposition through the addition of fertilizer wasaccompanied by a reduction in the diversity of microorg anism consociation (in otherwords, the growing dominance of specific bacteria). However, although during thefertilizer addition experiments, diversity decreased, it gradually recovered over aperiod of time. As a result, the respective compositions of th e microorganism groups in
the areas where the nutritive salts had been added and those where they hadn ’t cameto resemble each other.

No negative effect from the addition of fertilizer on marine crustaceans (amphipods) oron diatoms was seen.
As shown ab ove, even for the experiments we have so far carried out in two separate
locations, the Japan Sea side and the Pacific Ocean side, quite different results wereobtained, and it is felt that we need to accumulate deeper knowledge through on-siteexperiments in a wide variety of coastal areas.

In the future, in order to develop methodology to evaluate the degree of recovery ofareas that are habitats of living beings that is brought about through bioremediation,and to evaluate the state of diffusion of nutritive salts into surrounding ocean areas,through conducting further large-scale on-site experiments in conditions that are closeto actual ones, we believe that bioremediation of oil that has drifted to coastal areas inJapan can approach readiness for practical implementation.

We were able to carry out this research and development only through theunderstanding

andcooperationof

Hyogo

Prefecture,

Kasumicho,

Kagoshima

Prefecture, Nishinoomote City, and the Ministry of the Environment, as well as that ofthose associated with fishery cooperative associations in areas near the experimentalsites. I would like to take this opportunity to sincerely thank them all.

I would also like to express my profound gratitude to Mitsubishi Chemical Corporation3

and Chisso Asahi Fertilizer Co., Ltd. for so kindly supplying u s w i t h synthetic
fertilizer sample products for use in our experiments.

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