DEVELOPMENT OF BIOAVAILABILITY AND BIOKINETICS DETERMINATION METHODS FOR ORGANIC POLLUTANTS IN SOIL TO ENHANCE IN-SITU AND ON-SITE BIOREMEDIATION

Determination of biodegradation rates of organics in soil slurry and c ompacted soil systems is essential for evaluating the efficacy of bior emediation for treatment of contaminated soils. In this paper, a syste matic protocol has been developed for evaluating biokinetic and transp ort parameters in soil slurry and compacted soil bioreactors. The prot ocol involves abiotic evaluation of adsorption/desorption rates, and e quilibria followed by the use of respirometry to determine biodegradat ion rates using soil slurry, wafer, and porous tube reactors. In the s oil slurry reactor, mimicking ex-situ soil biotreatment, degradation o ccurs in the aqueous phase by suspended microorganisms and by immobili zed microbiota present in the soil phase. In a soil wafer reactor, whi ch consists of a thin layer of soil, biodegradation occurs primarily i n the soil phase, as compared to the aqueous phase, which consists of free and bound water in and around the soil particles. The wafer react or represents biotreatment using bioventing or land farming methods. I n the porous tube reactor, rate of oxygen diffusion through the compac ted soil affects the overall rate of biodegradation. The porous tube r eactor represents in-situ biotreatment. Experiments were conducted to determine the cumulative oxygen uptake using an uncontaminated low org anic carbon soil with phenol as the spiked contaminant. Detailed mathe matical models were developed for each type of soil reactor (slurry, w afer, and porous tube), and these models were fitted to the cumulative oxygen uptake data to derive the best-fit transport and biokinetic pa rameters. Application of the transport and biokinetic parameters to de termine the attainable treatment end points is discussed in this paper .