Bioremediation: land farming

Contaminated soils are mixed with soil amendments such as soil bulking agents and nutrients, and then they are tilled into the earth. The oily debris should be evenly spread over the scarified land surface in a layer 2-10cm thick. Contaminants are degraded, transformed, and immobilized by microbiological processes and by oxidation.

Semi-solids and solids lightly oiled.

May be very easily implemented.

Allows biodegradation of oily waste with little equipment (requires large area of land away from ground water and human settlements).

Oil with a high asphaltene and resin content degrades slowly due to the molecular recalcitrance of the hydrocarbons while oil with a high aliphatic and aromatic content is a much more nutrient-dependent process and will degrade more rapidly within the adequate environment. It is recommended to carry out a GC/ MS analysis to define the composition of the oil and evaluate its biodegradability.
Lightly oiled sediment (sand, gravel, soil, mud), less than 1 to 2% of oil.
Land farming is best suited for debris comprised of small particles such as oiled soils, and should not be attempted for waste comprised of particles larger then 15cm to avoid handling difficulties and problematic mixing of the waste.

Requires large area of land in a suitable environment: land farming is best suited to warm climates with moderate precipitation and evaporation. The degradation process may stop when temperatures fall below freezing.
Regular tilling is necessary for aeration.
Sufficient moisture is required in the oil/soil mixture to support microbial activity, which is usually naturally available except in very dry areas.
Areas should be located where water bodies and other supplies of potable water are not at risk from the possible release of contaminants.
Slope of area should be less than 4% (or else plan for run-off water management).
Soil permeability should be low to avoid percolation of leachates into the ground water. Slope should also be low to avoid running.
Additions of nitrogen (as ammonium nitrate) and soluble phosphorous (e.g. super-phosphate) are necessary for the degradation of oily wastes at optimum rates.
Environmental monitoring is necessary (soil and ground water analysis).

Main risk is the contamination of the ground water by percolation of contaminants and running surface water carrying the contaminant away from the land farming area.

Refer to limits of contaminants that can be spread on land (e.g. regulations related to land farming of mud from sewage water treatment plants).
May require EIA or legal authorisation.

Land farming degrades oil into carbon dioxide gas, water and matter within 2 years or less.
Bioremediation is a long term process (months to year(s)).
Bioremediation degrades aromatics, N-alkanes and iso-alkanes. Resins and Asphaltenes are usually resistant to bioremediation. Cyclic hydrocarbon (Saturated and Aromatics) are partially biodegraded