Environmental Engineering Reference
In-Depth Information
The independent factors affecting the processes of biological breakdown are
listed in Table 15.10. Favorable factors for the application of biological breakdown
in cleaning operation are listed in Table 15.11; the adverse conditions are also
included for comparison.
Factor
Notes
Micro-organisms
Natural micro-organisms are satisfactory
Acclimatization could be necessary
Appropriate environmental conditions must be provided
Toxicity
Non-toxic conditions required
Oxygen
Aerobic conditions desired
O
2
(aerobic conditions); NO
3
-
, Fe
3+
, Mn
2+
and SO
4
2-
Electron acceptance
pH
5.5-8.5 (optimal degradation)
Nutrients
Nitrogen, phosphorus and other nutrients required for microbial
growth
Temperature
Affects the degradation rate
Table 15.10.
Factors affecting the degradation processes [SHA 00]
Favorable factors
Unfavorable factors
Chemical characteristics:
- small number of organic contaminants
- varied microbial populations
- other factors already mentioned in Table
15.10
Chemical characteristics:
- many contaminants
- complex mixture of organic and non-
organic compounds
- toxic concentrations
- spaced microbial activity
-lack of appropriate accepting electrons
- pH < 5.5 or >8.5
Hydrogeological characteristics:
- granulaous porous media
- high permeability (>10
-6
m/s)
- uniform mineralogy
- homogenous media
- saturated media
Hydrogeological characteristics:
- fractured rocks
- low permeability (<10
-6
m/s)
- complex mineralogy
- heterogenous media
- unsaturated and saturated conditions
Table 15.11.
Favorable and unfavorable factors for biological breakdown in situ [WAG 86]
