Biopile study of the effects of bioaugmentation and biostimulation on bioremediation of TPH-contaminated soil

Contamination of total petroleum hydrocarbons (TPH) has caused critical environmental and health defects. Laboratory microcosms were used to measure the change in TPH concentration and the accompanying changes in microbial diversity with time. During the experiments, soil samples were collected and analyzed periodically to determine the amount of residual TPH and evaluate the effects of amendments on microbial diversity. A recently TPH-contaminated soil site has investigated to apply different enhanced bioremediation process with lab-scale of 0.0015m³ biopiles. Conceptual design of five biopiles was conducted to provide: non-agitation biopile with the indigenous microbes as Natural Attenuation test, NA, well-mixing biopile with the indigenous microbes as control test, CT, bioaugmentation with five types of enrichment culture of TPH-degrading bacteria, BAT, biostimulation with biosurfactant (rhamnolipid) to emulsify the entrapped diesel adsorbed onto the soil pore, BS. combined bioaugmentation and biostimulation with TPH-degrading bacteria and biosurfactant as BAS test. Besides NA biopile, periodic land-farming procedure was employed to these four biopiles(CT.BAT.BS.BAS). Weekly turn over mixing and water spray could keep 0.0015m3 of loamy sand soil with enough oxygen content above 10%-15% and moisture about 20%. The original total petroleum hydrocarbon (TPH_C10-C40) was about 1,4032 mg TPH/ kg dry soil and the total indigenous microbial concentration was measured at the range of 3.0×10⁴ CFU/g soil that meaned the biodegradation would be happened. Therefore, the TPH removal efficiencies (Day 112) achieved at different levels in these five biopiles, NA=24.8%, CT=62.7%, BAT=67.2%, BS=77.2%, BAS=72.7%. Bioremediation performance was promoted by the bioaugmentation and the biosurfactant addition (BS). Before 35 days, the first order reaction rate constant K values (day^-1) was evaluated as BAS(0.0329)> BAT(0.0189) >BS(0.0151)>CT(0.0095)>NA(0.0009). However, the slowing of degradation rate during the later stage could be attributed to the properties of the remaining hydrocarbons and environmental conditions. This increase of polar fraction to the results of biomass formation associated with the biodegration of hydrocarbons.