Client: SYSCO

Category: Plantation Project (Soil Remediation)

Location: Dade County, Florida USA

Problem: An underground leaking motor oil storage tank went unnoticed and unidentified for 15 years. Two areas of soil were contaminated with motor oil.

Batch #1 208 cubic yards 18,000 ppm
Batch #2 178 cubic yards 8,530 ppm

Introduction

In the initial proposal, 208 cubic yards of the more heavily contaminated soil was to excavated and transported for inclusion in the cement manufacturing process. However, our laboratory results demonstrated that all of the fractions of the oil and grease were quickly degraded by the microorganism in PDM-7 H.C. Of special interest, was the fact that the higher concentrations supported greater growth and faster activity.

Based on these considerations, all of the soil was treated on-site using bioaugmentation remediation techniques.

The initial site assessment report concerning this soil described extremely high quantities of oil and grease that were adhered to soil particles. Grease and oil levels up to 18,000 ppm were found in preliminary samples taken at this site.

The soil was treated in two batches. Each batch was separately removed to a containment area. The soil was treated with the PHase III, Inc. product PDM-7 H.C. and Nutrients.

The oil and grease levels were monitored during the treatment period until a level less than 500 ppm was obtained. The first batch was then removed from the containment area and the second batch was treated in a similar manner.

Bacteriological

1. Pre - Treatment Analysis: Aerobic and anaerobic plate counts were made on several samples of soil. The flora was also characterised as to general type of microorganisms.
In tests designed to determine amount and type of microorganisms naturally present in the untreated soil that could digest oil, a few types were present. However, these organisms made up only a significant percentage of the total population.

2. Product Characterisation: PDM - 7 H.C. is a live, synergistic group of bacteria that effectively digest petroleum products and other toxic organic chemicals. It will even digest heavy, tarry types of oil and organic sludge converting all of these compounds to non - toxic, inert compounds such as carbon dioxide and H2O.
The bacteria in PDM - 7 H.C. are all harmless soil bacteria that normally live in the soil. They are grown in pure cultures in our laboratory and specifically blended for use as a bioremediation product.

3. Post - Treatment analysis: Aerobic and anaerobic plate counts were made on soil samples throughout the duration of the treatment process. The total count of each type remained essentially the same over the periods tested. However, the population was soon dominated by the major types in PDM - 7 H.C. This was to be expected, as they are natural soil organisms. The percentage of oil utilizing bacteria present in the soil soon increased by approximately 50%.
The nitrogen phosphate and moisture levels in the soil were also monitored and maintained in the proper range.

Treatment.

After the soil was placed in the containment area, it was mechanically treated to produce very small pieces and the product was applied. This process was designed to greatly increase the surface area exposed to the bacteria. The soil was mechanically treated to improve the distribution of organisms two to three times a week unless the schedule was interrupted by rain. The soil in the containment area was covered at night and at all times when personnel were not on site.

Samples were usually taken from three different sites in the interior of the pile after mechanical agitation. The three samples were combined in the laboratory and then analyzed for oil with a Techator SoxTec Extraction apparatus using Freon. The samples were run in quadruplicate and analyzed for petroleum hydrocarbon by E.P.A. Method 418.1.

Control Studies

The contaminated soil was evaluated for endemic bacterial activity prior to the on-site remediation. Soil was placed in the containment area and mechanically treated to produce very small pieces. This process was designed to greatly increase the surface area exposed to the natural bacteria. The soil was mechanically treated to improve distribution of the organisms two to three times a week unless the schedule was interrupted by rain. The soil in the containment area was covered at night and at all times when personnel were not at the site. Additionally, nutrients were added to the soil in an effort to stimulate the growth of the endemic bacteria, thereby prompting contamination reduction.

Samples were taken form three sites in the interior of the piles after mecanical agitation. The samples were analyzed in duplicate fro hydrocarbon via E.P.A. Method 418.1

Results

The results of the controlled studies performed on the on-site treatment are shown in Table 1. The contaminated soil showed insignificant reduction in the contamination levels when the soil was not treated or nutrient fed only. Even when aeration was utilized with nutrients, the reductions were extremely slow. This shows the rate of reduction is not economically feasible.

Tables II and III show selected results obtained during the course of treatment. These results show that, based on Batch I, approximately 2,880 pounds of oil were degraded in 61 days, or approximately 43 pounds a day. When several rain days are considered, the rate would even be faster. Aerobic and anaerobic plate counts show the normal flora once again would begin to dominate bacterial population in the Batch I soil.

Summary

The soil, which was very heavily contaminated with oil, was bioremediated to acceptable levels by using a strictly biological process within 60 days using PDM-7 H.C. Outside experts had predicted a endemic remediation time of 12 to 18 moths, if it occurred at all.

Table 1

CONTROL BIOREMEDIATION STUDIES