Effect of bioaugmentation and diesel fuel type on soil bioremediation
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1998-08
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Water Resources Research Center, University of Hawaii at Manoa
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Abstract
The enhancement of bioremediation by bioaugmentation in soil contaminated with diesel fuel No. 2 and No. 6 (Bunker C) is uncertain. A clayey soil was contaminated with 6,000 mg of either diesel fuel per kg of soil and seeded (5 x 10-7 cells/g of soil) with a Hawaii soil bacterium (UH138) known to utilize several hydrocarbons. The soil was limed, fertilized, and incubated in jars at 30°C for several months. The concentrations of total petroleum hydrocarbons (TPH) and of polycyclic aromatic hydrocarbons (PAH) in soil were measured by gravimetry and immunoassay, respectively. Poisoned controls (0.6% HgCl2) were used to determine the extent of hydrocarbon degradation due to microbial activity. A rapid first order biodegradation of TPH (84% in 23 days) occurred in soil contaminated with diesel fuel No. 2, regardless of bacterial seeding. Biodegradation of PAH was linear and reached 84% by day 98 in both seeded and unseeded treatments. Bioaugmentation had no effect on bioremediation of diesel fuel No.2. The decrease in TPH and PAH was paralleled by an increase in populations of total bacteria, phenanthrene-degrading bacteria and microorganisms capable of utilizing hexadecane and diesel fuel No. 2 as well as by an enhancement in CO2 evolution by the soil. Indigenous Zygomycetes grew profusely in diesel fuel No. 2 contaminated soil. Cunninghamella echinulata var. echinulata was isolated from the soil and was shown to be able to utilize several hydrocarbons. Thus, Zygomycetes may have contributed to the rapid decrease in contaminant. In soil contaminated with diesel fuel No. 6, the measurements of TPH and PAH were more variable due to the uneven distribution of the product. No biodegradation of the contaminant occurred over a period of 138 days. The growth of Zygomycetes was scant. The counts of total bacteria remained unchanged after the addition of diesel fuel No. 6. However, counts of the indigenous phenanthrene-degrading bacteria increases dramatically ( 4 log units) during the first 54 days whereas the level of the seeded bacteria remained stable. The counts of mineral oil degraders decrease by 2 log units after day 2. Co2 evolution from the soil confirmed that diesel fuel No. 6 was not degraded by either the indigenous microflora or the seeded bacterium. Thus, diesel fuel No. 2 was highly degradable by the indigenous population, however, diesel fuel No. 6 was recalcitrant.
Description
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Bioremediation--Technological innovations, Soil remediation—Technological innovations., Bioremediation--Technological innovations.
Citation
Chua-Chiaco BW. 1998. Effect of bioaugmentation and diesel fuel type on soil bioremediation. Honolulu (HI): Water Resources Research Center, University of Hawaii at Manoa. WRRC unedited report, 1998-05.
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Xv, 117 pages
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Microbiology; no. 3376
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