Studies on contaminant biodegradation in slurry, wafer, and compacted soil tube reactors

A systematic experimental approach is presented to quantitatively evaluate biodegradation rates in intact soil systems. Knowledge of bioremediation rates in intact soil systems is important for evaluating the efficacy of in-situ biodegradation and approaches for enhancing degradation rates. The approach involves three types of soil bioreactors: slurry, wafer, and porous tube. In the soil slurry reactor, biodegradation occurs in the aqueous phase by suspended and soil-immobilized microorganisms. In the soil wafer reactor, diffusivity of contaminant in the soil matrix controls the biodegradation rate. In the porous tube reactor, oxygen limitations occur inside the tube due to diffusional resistances, and oxygen consumption occurs due to biodegradation. Measurement of cumulative oxygen uptake in soil slurry, wafer, and porous tube reactors are used to determine biokinetics and transport parameters. It is shown that biodegradation rates in intact soil systems are slower than in soil slurry reactors. Furthermore, soil tube reactors in conjunction with respirometry can be used to assess bioremediation rates in intact soil systems.