Ingeniero

BIODEGRADATION TREATMENT OF A CONTAMINATED RIVER SHORE LINE
Claudio H. Fridman, P.E., M.S.
(A.R.S. Asociación para el Estudio de los Residuos Sólidos, Argentina)

ABSTRACT:
This survey focused the remediation of crude oil contamination over the shore line of the De La Plata River (Argentina) spilt from a tanker.
It was tried different systemsand technologies. One of them, very fast and with the ability of hydrocarbons recovering is ‘soil washing’. After processing, the remaining pollutant is still over the regulated guideline. It was evaluated to lower that concentration through some biological method, checking the feasibility for the kind of microorganisms to be used and considering actions to manage the physicochemical and kineticfactors.

CASE STUDY:
During January of 1999, sailing by the Access Canal to Buenos Aires port, crushed a tanker full of light crude oil; for several time, a lot of oil spilt out of the ship over the waters. Due to meteorology conditions the oil layer reach the shore line, rise over the land and vegetation and ascend through little streams and creeks. So, it was found contamination as far as1 kilometer from the beach.

Data and values of the impact on the beach (sand) and land (silt and clay) are shown in the following table:

SAMPLE # DESCRIPTION / LOCATION TPH [ppm]
1 Site Playa Nueva (South) - Surface Layer 84,900
2 Site Playa Nueva (South) - Lower Horizon (-70 mm) 2,550
3 Site Playa Nueva (North) - Surface Layer 52,300
4 Site Playa Nueva (North) – Middle Horizon (-50mm) 4,860
5 Site Playa Nueva (North) – Lower Horizon (-100 mm) 612
6 Shore Line – Low tide 1,770
7 Shore Line – High tide 36,400
8 Gully Medium Coast Line [sandy soil area] 7,750
9 Gully Medium Coast Line [silty soil area] 7,930
10 Gully Medium Coast Line [grass and greed area] 137,200
11 Manual clean-up in mid and low Beach - Sector 1 98,700
12 Manual clean-up in mid and low Beach -Sector 2 61,900

The owner of the oil and the Authorities, after the first rough clean up, evaluate to face some ‘controlled natural biodegradation’ or otherwise to perform some type of fast in-situ treatment due to political and social issues.

In regard to the second possibility it was evaluate (pilot plant scale) a soil washing system for in-situ processing, based in contacting the hydrocarboncontaminated soils with the washing solution. The patented technology is named SWAT (Soil Washing Active Treatment), and operate near 90ºC with a modified sodium silicate based chemical.
Clean up results are shown in the following table:
Actually, results are hardly dependent of each soil matrix. It is pretty clear that this treatment is enough for sandy soils, where the quality fitsguidelines for a public beach (below 100 ppm). Nevertheless, humic-silty soils keep top much remaining hydrocarbons as to allow a direct deliver to the site, without risk for the natural environment.
It was evaluate that a complementary treatment, able to remediate the remaining content, should be performed on-site and be of biological nature.
Due to make the minimization of the level of contaminants ina reasonable period (it was estimated 3-4 months), it might be chosen between indigenous microorganisms, to do some kind of biostimulation (nutrients and surfactants addition), or to perform bioaugmentation (inoculation of acclimatized colonies for easy development with the same carbon source), or if to use commercial mixed strains, supposed fully specific as recommended by their breeders.SUMMARY OF THE PAPER:
1) Introduction: it is discussed the basis for biological treatments in regard to what do they bring in terms of reduction of pollutants, minimizing of toxicity, mobility, etc.
Also is exposed a comparison between theoretical benefits with reality (bench versus field).
a) It is overviewed the interaction of several issues on the ability and rate of biodegradation of...