2. Bioremediation is a process in which microorganisms degrade
organic contaminants or immobile inorganic contaminants
Also known - enhanced bioremediation or Engineered
bioremediation
Bioremediation is commonly used for the treatment of soils
contaminated with organic compounds (petroleum hydro
carbons)
-cannot degrade heavy metal but can change valance states
(hexavalent chromium to trivalent chromium)
3. Based on microorganisum used:-
Aerobic, cometabolic, and anaerobic
Based on location :-
In-situ bioremediation & ex-situ bioremediation
Based on presents of microorganism:-
Indigenous microorganisms – Microorganisms are native to
site.
Exogenous microorganisms – Microorganisms are taken from
other locations, cultured in laboratory, then added to
contaminated soil
4. Requirements
Condition for microorganisms to grow and survive
pH - should be between 5.5-8.5
Temperature - between 15-45oc
Oxygen - >2mg/L aerobic reaction
- < 2mg/L anaerobic reaction
Nutrients -carbon, hydrogen, oxygen, nitrogen, phosphorus
The actual quantity of these nutrients depends on
the BOD of contaminated soil.
Toxicity - High conc. of contaminants can be toxic
Some contaminants even at low conc. may be toxic
5. Fundamental Process
Bioremediation processes may be directed toward
accomplishing:
1.Destruction of organic contaminants
2.Oxidation of organic chemicals thereby the organic
chemicals are broken down to smaller constituents
3.Dehalogenation of organic chemicals by cleaving chlorine
atoms or other halogens from a compound
6. Degradation is a complex oxidation - reduction reaction.
The electrons or reducing equivalents produced must be
transferred to a terminal electron acceptor (TEA)
Depending upon TEA, bacteria are grouped into three
categories:
Aerobic bacteria – Only use molecular oxygen as a TEA
Facultative Aerobes / Anaerobes – Which can utilize
oxygen or when oxygen is low or non-existent may
switch to nitrate, manganese oxides or iron oxides as TEA
Anaerobes – They utilize sulfate or carbon dioxide
7. Advantages
Complete degradation of organic compounds to non-toxic by-
products
Minimum mechanical equipment requirements
Can be implemented as in-situ or ex-situ process
Cost is low
8. Disadvantages
There is a potential for partial degradation to equally toxic,
more highly mobile by-products
The process is highly sensitive to toxins and environmental
conditions
Excessive monitoring required
Difficult to control volatile organic compounds during an ex-
situ process
A longer treatment time required
