Презентация на тему Bioremediation

contaminants into relatively harmless byproducts, such as ethene and

water
Biodegrade
Mineralize
Biotransform
Techniques or types of bioremediation:
A component of Natural Attenuation
Enhanced Bioremediation
Bioaugmentation

complete enough, Not frequently occurring enough to be broadly

used for some compounds, especially chlorinated solvents
The current trend is to stimulate/enhance a site’s indigenous subsurface microorganisms by the addition of nutrients and electron donor
In some cases, bioaugmentation is necessary when metabolic capabilities are not naturally present.

organics derived from human or animal wastes (and the

sludges produced)
~1950 Approaches to extend wastewater treatment to industrial wastes
~1960 Investigations into the bioremediation of synthetic chemicals in wastewaters
~1970 Application in hydrocarbon contamination such as oil spills and petroleum in groundwater
~1980 Investigations of bioremediation applications for substituted organics
~1990 Natural Attenuation of ’70 and ’90, and the development of barrier approaches
~2000 High-rate in situ bioremediation; source zone reduction; bioaugmentation

(BTEX)
Pyrene and other polynuclear aromatics
Chlorinated aromatics and solvents
Herbicides and

pesticides
Nitroaromatic explosives and plasticizers

and pipes
Landfills
Burial areas and dumps
Injection wells

treat to drinking water resources
Components of fuels are known

carcinogens
Current fuel oxygenate, MTBE, very mobile and not very degradable
Ethanol is due to replace MTBE, but its behavior in the subsurface is not yet understood

due to their extensive use at industrial, DOD, and

dry cleaner sites.
Chlorinated compounds commonly exist as dense nonaqueous-phase liquids (DNAPLs) that act as long-term, continuing sources that slowly solubilize into groundwater.
Known carcinogenic and toxic effects
Not a primary substrate for any known bacteria

lenses
Pools in low areas
Creates soluble plumes for years
Extremely hard

to remediate

barriers
Air and Hydrogen Sparging
Biological (microbes)
Chemical (surfactants)

create an eyesore
Capable of impacting source zones and thus,

decreasing site clean-up time

requires specific conditions
There is no Superbug
Contaminants must be

bioavailable
Biodegradation rate and extent is controlled by a “limiting factor”

anaerobic biodegradation
Reduces aqueous concentrations of contaminant
Reduction of contaminant mass
Most

significant process resulting in reduction of contaminant mass in a system

H2O, and salts) end-products via biological mechanisms
Biotransformation refers to

a biological process where the end-products are not minerals (e.g., transforming TCE to DCE)
Biodegradation involves the process of extracting energy from organic chemicals via oxidation of the organic chemicals

substrate
enough available to be the sole energy source
Secondary

substrate
provides energy, not available in high enough concentration
Cometabolic substrate
fortuitous transformation of a compound by a microbe relying on some other primary substrate

acceptor, the process is called aerobic biodegradation
All other biological

degradation processes are classified as anaerobic biodegradation
In most cases, bacteria can only use one terminal electron acceptor
Facultative aerobes use oxygen, but can switch to nitrate in the absence of oxygen

reduction
Sulfate reduction
Methanogenesis
Bacterial Metabolism

NO3–
Continue down the list in this order
O2 ––>

NO3– ––> Fe3+ ––> SO42– ––> CO2

contaminants of interest
Understand the possible catabolic pathways of metabolism

and the organisms that possess that capability
Understand the environmental conditions required to:
Promote growth of desirable organisms
Provide for the expression of needed organisms
Engineer the environmental conditions needed to establish favorable conditions and contact organisms and contaminants

time oxygen is the primary factor limiting in situ

biodegradation
In most cases if adequate oxygen can be supplied then biodegradation rates are adequate for remediation
Other limiting factors exist, but are usually secondary to oxygen

Degradation for Benzene: C6H6 + 7.5O2 ––> 6CO2 + 3H2O

in water :
Actively pumped: H2 O2 , aerated

water
Passively: ORC ® , membrane, aeration
In gaseous form, usually air
Bioventing above the water table
Air sparging below the water table

Oxygen Supply is the Key to Aerobic
In Situ Bioremediation

an anaerobic process, and is often referred to as

reductive dechlorination
R–Cl + 2e– + H+ ––> R–H + Cl–
Can occur via
Dehalorespiration (anaerobic)
Cometabolism (aerobic)

terminal electron acceptor, rather than as a donor
Confirmed only

for chlorinated ethenes
Rapid, compared to cometabolism
High percentage of electron donor goes toward dechlorination
Dehalorespiring bacteria depend on hydrogen-producing bacteria to produce H2, which is the preferred primary substrate

an electron acceptor is needed to transfer from one

product to the next

encouraged, but monitored closely
The dechlorination products of PCE are

more hazardous than the parent compound
DCE is 50 times more hazardous than TCE
Vinyl Chloride is a known carcinogen

relying on some other primary substrate
Generally a slow process

- Chlorinated solvents don’t provide much energy to the microbe
Most oxidation is of primary substrate, with only a few percent of the electron donor consumption going toward dechlorination of the contaminant
Not all chlorinated solvents susceptible to cometabolism (e.g., PCE and carbon tetrachloride)

in subsurface
Dechlorinators can utilize H2 at lower concentrations than

methanogens or sulfate-reducers
Addition of more complex substrates that can only be fermented at low H2 partial pressures may provide competitive advantage to dechlorinators

apparently universal electron donor, but no universal substrate
Laboratory or

small-scale field studies required to determine if particular substrate will support dechlorination at particular site

Propionate
Butyrate gas sparge Propionic acid
Cheese whey Humic acids

- Sucrose
Chicken manure naturally occurring Surfactants -
Corn steep liquor Isopropanol Terigitol5-S-12
Ethanol Lactate Witconol 2722
Glucose Lactic acid Tetraalkoxsilanes
Hydrocarbon Methanol Wastewater
contaminants Molasses Yeast extract
Mulch

Lactate
Sulfate Molasses
Carbohydrates

Biosparge Air (oxygen) Ammonia
Hydrogen
Propane

Slow-release Oxygen Hydrogen
(ORC) (HRC)

COD=Lactate + Acetate + Propionate