Bioavailability of stabilized oily waste organics in ultrasonified soil aggregates

Abstract

Stabilization of oily waste organics (OWO) in soils of land treatment farms (LTF) can limit the availability of the OWO for biodegradation. The effect of physical dispersion on bioavailability and biodegradation of OWO in a soil from a LTF was investigated. Soil samples from the LTF were ultrasonically dispersed at increasing energy levels (EL), ranging from 0 to 30 kJ kg⁻¹ at 5 kJ kg⁻¹ increments, and incubated in glass jars for 12 weeks. The headspace CO₂ concentration in the jars was monitored weekly by gas chromatography and expressed as C mineralization rates (CMR). The CMR and the cumulative C mineralized (CCM) increased with increasing EL. The CCM from the oily waste treated soil dispersed at 30 kJ kg⁻¹ was 710% higher compared to that from the untreated soil dispersed at the same EL. Compared to the treated soil dispersed at zero EL, 48% more C mineralized from that dispersed at 30 kJ kg⁻¹. The size of the potentially mineralizable C (C₀) increased with increasing EL. The C₀ for the treated soil dispersed at 30 kJ kg⁻¹ was 66% larger compared to that at zero EL. The C₀'s for the treated soil dispersed at different EL were similar, suggesting the chemistry of the C₀ exposed by dispersion were similar. The results show that substantial amounts of potentially biodegradable OWO were physically protected in soil aggregates.