If land-farming is selected (soil is excavated and placed on a liner for treatment), the contaminated soil should be spread to a depth of 18 to 20 inches. The outside edge of the land-farm tract should be bermed to prevent runoff caused by a large rainfall. A tractor, dragging an offset disc harrow, should till the soil at least once a week, preferably more often. If frequent tilling is impractical, diluted hydrogen peroxide (500 ppm final dose) can be added to the soil to aerate it, instead. A moisture content of 30 to 40% of the soil's holding capacity should be maintained (this equals around 9% for Texas sands, up to 23% for loams). The soil should be kept moist by adding water (fresh water or seawater is acceptable, although the salt content should be monitored) and a dose of approximately 0.5 gallons of Alken Clear-Flo® 5100 for each cubic yard to be treated, to spread the bacteria and assist with breaking the oil-water surface tension, in addition to augmenting with our new gram-positive petroleum degrading strains. After inoculating with activated Alken Clear-Flo® 7036, 7037 or 7038 together with its nutrients, cover the area with chopped alfalfa hay to help maintain moisture.
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The ideal nutrient balance recommended for hydrocarbon remediation by Alken-Murray Corporation is Carbon: Nitrogen: Phosphorus equals 100:10:2 Although Kenneth Kerri, in his 1997 EPA publication, Industrial Waste Treatment, advises on p. 379, that a ratio of 100:5:1 is effective for petroleum remediation, Alken-Murray has found his suggested balance more suitable for remediation of other types of industrial and municipal wastewater applications. [1] In general, at least 1 ppm of ammonium nitrogen and 0.4 ppm of ortho-phosphate needs to be present. It is critical to control the inorganic nutrients in order to accelerate bacterial metabolism. Nitrogen, which makes up nearly 15% of the molecular composition of a bacterial cell, is utilized by the bacteria to manufacture its cell walls, nucleic acids and proteins. Phosphorus, in the form of inorganic phosphates, is used by the microogranisms to synthesize phospholipids and nucleic acids and for the energy transfer reactions of ATP. Enzymes that hydrolyze phosphate ester are present in nearly all organisms. Without adequate phosphorus, the ability of the bacteria to utilize hydrocarbons in the soil is sharply decreased. Alken-Murray now offers Alken® Bio-Nutrient 4, a soluble, rapid acting formula with a nutrient balance of Nitrogen to Phosphorus of 3:1 and a small amount of dicyandiamide added to prevent nitrification from occurring. By keeping the nitrogen in the positively charged ammonium form, it sticks to the negatively charged soil, unlike the negatively charged nitrate, which can wash out. Nitrate, in this application, would add to the pollution, while this product contributes to remediation. Bio-Nutrient 4, in the exact dosage prescribed by Alken-Murray, is added once a month. Although Alken-Murray formulas have been known to remediate petroleum products even in the presence of up to 1,000 ppm of mixed heavy metals, any level above 20 ppm requires a bench scale analysis to assure that the inhibition will not prevent proper remediation. Bacterial formulas, from competing companies, are often inhibited when heavy metals exceed 5 ppm, so Alken-Murray's formulas can withstand up to 4 times higher metals contamination than competitors. [1] Kerri, Kenneth D. Industrial Waste Treatment, Volume II, Environmental Protection Agency 1997, page 379 |