A3.10.6.1 Biological Options


Bioremediation is the use of micro-organisms to convert harmful chemical compounds to less harmful chemical compounds. The microorganisms are generally bacteria, but fungi have also been used.


Pump and Treat Systems

Groundwater is pumped to the surface, treated, and either used directly or returned to the ground. Surface treatment often involves aeration, the addition of nutrients, and in some cases seeding with microbial cultures capable of degrading contaminants known to be in the ground.



Windrows are long triangular piles of soil, formed out of the excavated material that is destined for treatment. The process involves aeration and mixing of contaminated soil by mechanical processing, addition of nutrients (and in some cases microorganisms), and control of moisture content by periodic addition of water / covering with special fleeces. In most cases contaminated soils are excavated and treated at a site where leachate can be controlled by constructing barriers.



Landfarming is very similar to windrowing. It is carried out in cases the contaminated soils are near enough to the surface to make the excavation step unnecessary or contaminated soils are spread in a thin layer across a treatment area.



Biopiles piles are a form of soil treatment where bulking agents, nutrients, and water are added. However, static piles are not mixed and temperatures are usually near ambient.  Aeration can be passive or forced by applying a vacuum or blowing air through the pile. Bulking agents used are usually made up of manure or compost, which supports a larger microbial population than soil and provides inorganic nutrients, and relatively inert materials such as sawdust, wood chips, or compost. Water is added periodically, as needed to sustain the microbial population.



In composting, the contaminated material is mixed with organic bulking agents (such as manure) and formed into piles or windrows. An accelerated bioremediation effect then takes place. The bulking agents help increase soil porosity to facilitate airflow. The energy released during organic degradation results in temperature elevation of the pile. Water can be added periodically and the piles or windrows are mechanically mixed at regular intervals.