Total and Volatile Polyaromatic Hydrocarbon Losses during Aerobic Slurry Phase Biotreatment

The suitability of an aerobic biological treatment process for the removal of polyaromatic hydrocarbon (PAH) from a creosote contaminated field soil was evaluated. Project objectives were to determine: (1) the overall loss of specific PAH; (2) losses due to volatilization; (3) the effect of possible operating temperatures and microbial acclimation; and (4) the relationship between volatile losses and solid–liquid and liquid–gas partition coefficients. The results indicated that an active aerobic biotreatment process is a suitable treatment process for these contaminated soils. Overall losses that occurred were: two-ring PAH, 99–100%; three-ring PAH, 86–100%; four-ring PAH, 41–44%; and five-ring PAH, 26–37%. There was little difference in PAH removal at 20 and 35°C. The maximum volatile PAH loss that occurred was for naphthalene and ranged from 9 to 17%. For most of the other PAH, overall volatile losses were less than 1% and commonly in the 0.1–0.9% range. There were no volatile losses for some of the four-ring PAH and for all of the five-ring PAH that were measured. Volatilization became less of a factor as microbial acclimation occurred. The study documented that, in an aerobic treatment process with an active acclimated microbial population, microbial degradation of semivolatile organic chemical will be the primary loss mechanism. Several predictive relationships were determined between PAH volatile losses and liquid–gas $\left(K_H\right)$ and solid–liquid $\left(K_{\mathrm{OW}}\text{,}{K}_{\mathrm{OC}}\right)$ PAH partition coefficients.