Biodegradation of a Gas Oil Applied to Aggregates of Different Sizes
- Stella C. Mott,
- Pieter H. Groenevelt * and
- R. Paul Voroney
Land treatment of oily wastes involves repeated application and tillage cycles to promote biodegradation of the waste. Tillage intensifies greater than current practices would result in smaller aggregates, promote oil-soil interaction, and likely improve waste biodegradation. Due to the cyclical nature of treatment, it was unclear whether the obvious effect of oil-soil mixing after application or the more subtle effect of soil surface preparation before the next application would be the primary effect of increased tillage intensity. Previously untreated soil was sieved into aggregates of the following size ranges: coarse (19–25 mm in diam.), medium (5–10 mm), and fine (1–2 mm). Oily waste, emulsified in sufficient water to bring the soil to 25% water content, was evenly applied to the surface of aggregates from each size range. Treated and untreated samples were incubated for 14 d at 25°C. Biodegradation was measured by CO2 entrapment in KOH. After 14 d, the coarse and medium aggregates were ground to approximately 2 mm. Incubation of all samples was resumed without further waste application. A one-component exponential model regression indicates that application to fine aggregates resulted in a larger available mineralizable carbon pool, with more CO2 produced from treated fine aggregates. The effects are attributed to the larger available surface area. Although grinding caused a CO2 flush lasting several days, the pregrinding pattern was soon reestablished. The laboratory results suggest that waste biodegradation is inversely proportional to aggregate size before application, and that soil surface preparation into fine aggregates may be more beneficial than tillage after application.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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