BIOREACTORS
PRESENTED BY: SUMBAL

DEFINITION:
The term "bioreactor" in the context of
soil and water bioremediation refers to
any vessel or container where biological
degradation of contaminants is isolated
and controlled.

BIOREACTOR:
Range from: crude devices such as lined
depressions in the ground to advanced metal
containers where environmental conditions
can be monitored and controlled.
Treatment mechanism: in a bioreactor is
natural degradation by existing and/or added
populations of microorganisms
Effective in: remediating soil, and in some
cases water, polluted with fuel hydrocarbons
(oil, gasoline, diesel) and organics.

BIOREACTOR DESIGN:
DEPENDS ON:
Contaminant type: soil, sludge, water
Cost.
Oxygen transfer.
Mixing.
TWO MAJOR SOIL BIOREACTORS:
Dry bioreactors.
Slurry bioreactors.

DRY BIOREACTOR:
 Treat soil with no other amendments other than
microbes and nutrients.
 Adequate moisture is maintained for microbial
growth by sprinkler system or by rainfall.
 Physical mixing of the soil keeps it aerated.
After the remediation process is complete the
soil can be transported to a desired location.

Negative point:
Frequently results in soil/microbe pellet formation

SLURRY BIOREACTORS
 Proven more effective and efficient against a wider
range of pollutants.
 In a slurry reactor the soil is mixed with equal or
greater amounts of water and mixed with microbes
and nutrients to form a soil slurry.
 Conditions in a slurry reactor are easier to maintain
than dry reactors and result in faster treatment
rates.(Nyer, 1993).

ADVANTAGES AND DISADVANTAGES
 ADVANTAGES:
 Relatively rapid treatment.
 Reduced pellet formation.
 Increased slurry homogenization.
 Increased bioavailability.
 DISADVANTAGES:
 Soil-water separation can become a problem (Nyer, 1993).
 Also, there is a need for wastewater treatment after the soil
is dewatered.

BIOREACTORS FOR GROUNDWATER:
 Usually fixed film or some form of activated
sludge reactors.
 Fixed film reactors contain high surface area
media that support microbial growth.
 Activated sludge reactors are aerated basins
where microbes are mixed with the wastewater
and nutrients.

AEROBIC AND ANAEROBIC PROCESSES
 Bioreactors can also be designed to operate aerobic and anaerobic
processes.
 Anaerobic degadation reduce highly halogenated compounds such as
trichloroethylene to less halogenated compounds.
 Aerobic degradation pathways:
 effective against a wider range of pollutants
 most widely implemented processes.
 Use of anaerobic and aerobic steps in series offers a method to
treat substances that do not respond to conventional treatment.
 (An example is highly chlorinated organic pollutants. Anaerobic
organisms can dechlorinate the substance to a point where aerobic
organisms can completely degrade it.)

Microorganisms
Workhorses of the bioremediation process.
 The microorganisms responsible for pollutant
degradation are usually bacteria but can also be
fungi.
 Microbes usually need not be added to the soil in a
bioreactor since they are usually present in
adequate amounts.
 The exception being when a toxic substance has
removed all endemic microorganisms

Electron acceptor:
 Require a supply of nutrients and an electron acceptor.
 Aerobic organisms use oxygen as the final electron
acceptor and organic carbon as a carbon source.
 Anaerobic organisms use sulfate or carbon dioxide as
the electron acceptor.
 Facultative organisms: utilize nitrates, iron, and
manganese as electron acceptors.

NUTRIENTS:
 Main nutrients: Nitrogen and phosphorous
 A general rule of thumb for N and P loading is five
parts nitrogen and one part phosphorus.
 Micronutrients such as Ca, Fe, Mg, Mb, and S are
usually present in sufficient amounts in the soil to
adequately supply microbe metabolism.

THANKS!