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Solid Phase Techniques

Water Contamination
Soil Contamination
How Bioremediation Works
Types of Bioremediation
Alternatives to Bioremediation
Exxon Valdez

     Landfarming - Landfarming is the most
          simple of the three types of solid phase
          bioremediation.  It involves the
          excavation and spreading of the
          contaminated soils onto a lined bed
          (pad).  The soil is usually spread so that
          it is about 18 inches thick all around. 
          The bed typically has a collection
          system of some sort, designed to collect
          any leachate that may seep through the
          contaminated soil. Leachate is a solution
          containing contaminants that are picked
          up through the leaching of soil.  The soil
          is then tilled and turned over repeatedly
          to allow aeration to occur.  Gennerally,
          a high molecular weight, heavily
          nitrated compounds, and heavily
          chlorinated compounds tend to slow
          down the rate of contaminant
               Controlling the frequency of
          aeration enables the cleanup crews to
          control the amount of oxygen that is
          involved in the degradation process. 
          They also control the moisture content
          of the soil by irrigation and spraying. 
          They are able to control the pH of the
          soil on the bed by adding crushed
          limestone.  This crushed limestone
          helps to form a buffer around neutral. 
          Usually, these beds are in an enclosure. 
          This prevents any inclement weather
          from affecting the degradation of the
          contaminants.  It also helps to contain
          any evapourated contaminants. 

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     Biopiling - This is exactly what you would
          expect from its name.  The
          contaminated soil is excavated and put
          into piles.  These piles are usually 2-3
          metres in height.  These piles are placed
          over an aeration system.  This system
          pulls air through pile of contaminated
          soil by means of a vacuum pump.  This
          movement of air not only provides
          oxygen to the microorganisms, by it
          also pulls some of the contaminants out
          of the soil as it passes through soil. A
          collection system similar to the one
          used in landfarming is also
          used with soil biopiles. 
               Optimal bioremediation
          conditions are maintained by the control
          of the moisture and nutrient levels. 
          Another form of control is the placement
          of the piles into enclosures.  This
          prevents and unwanted weather 
          changes and helps to control any
          temperature changes.  Volitatile
          contaminants (evapourated
          contaminants) are minimal beacuse the
          vacuum pump pulls any evapourated
          contaminants through the pile, keeping
          them from escaping into
          the atmosphere. 
               These piles do require quite a bit of
          space, but they do not need as much
          space as landfarming does.  It is a
          short term technology that usually only
          operates for a few weeks or a few

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     Composting - Composting involves first the
          excavation of the contaminated soil.  A
          bulking agent of some sort is added to
          the contaminated soil, which is then
          known as compost material. Bulking
          agents include things like: hay, straw,
          and corn cobs.  These things make it
          much easier for the cleanup crews to
          maintain the maximum rate of
          degradation of the contaminants.  The
          bulking agents allow the cleanup crews
          to easily control the amounts of water
          and air that are available to the
          microorganisms involved in
          the degradation reaction. 
               There are three methods of
          composting that are used.  The first is
          called static pile composting.  This
          involves the formation of piles and
          aerating them by means of a blower or a
          vacuum pump.  The second is called
          mechanically agitated  in-vessel
          composting, which involves the
          compost material being placed in a
          treatment vessel.  Here, it undergoes
          mixing and aeration.  The third is called
          windrow composting.  This method
          involves placing the compost material
          into windrows (long piles as in a
          farmer's field).  This windrows are then
          mixed up thoroughly by tractors and
          other such equipment.  
               Windrow composting is the most
          common method, mainly because it is
          the most cost-effective method.  
               One interesting thing about
          composting is that it not only works in
          soil but it also can be applied to
          contaminated lagoons and swampy
          areas.  Another good thing about
          composting is that all of the necessary
          equipment can be commercially