Protocol for evaluating biokinetics and attainable end‐points of polycyclic aromatic hydrocarbons (PAHs) in soil treatment

Abstract

This paper describes quantitation of biodegradation kinetics in soil slurry and compacted soil systems using polycyclic aromatic hydrocarbons (PAHs) as the test contaminants. The experimental protocol, elaborated in this paper, results in the measurement of biokinetic parameters which can be used to quantitate both ex‐situ and in‐situ bioremediation rates and assess the attainable end‐points. Biodegradation studies were conducted for naphthalene using soil slurry, soil wafer and soil column reactors. Microcosm reactors were set‐up to acclimate soil microbiota, and carbon dioxide evolution was used as a measure of acclimation. It was found that reasonable degree of PAH acclimation was achieved after 250 days of microcosm operation. Abiotic adsorption/desorption studies showed that equilibrium was achieved in about 20 hours and approximately 45% of the initial amount of naphthalene is adsorbed by the time equilibrium is attained. Further, desorption was much slower than adsorption with equilibrium being attained in 40 hours. Soil slurry studies conducted in the respirometer showed that oxygen uptake occurred after an acclimation time of about 42 hours and that the PAHs were completely biodegraded.