Biogeochemical Cycles - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 168

Within aquatic ecosystems, microbial decomposition of organic matter plays a
prominent role in the energy and mass transformation processes. Organic wastewater
discharge in a water body results in dissolved oxygen uptake, either directly by chemical
oxidation of the reducing pollutants or by their metabolism by microorganisms, i.e.,
their biodegradation. The increase in water temperature accelerates the kinetics of
chemical and microbiological oxygen use and pollution load reduction.
Growth kinetics of the bacterial population degrading toxic chemicals is not
well understood. 78 The presence of competing substrates and other bacteria, the
toxicity of the chemical to the degrading bacteria, and the possibilities of adaptation
to the chemical or co-metabolism make quantification of population changes dif-
ficult. As a result, toxic chemical fate models assume a constant biological activity
rather than modeling the bacteria directly. Often, measured first-order biodegrada-
tion rate constants from other aquatic systems are used directly. Table 4.43 is a

TABLE 4.43
Selected Biotransformation Rate Constants

Pseudo-First-Order Rate
Constant Range, day − 1

Estimated Second-Order Rate
Constants, ml cell − 1 h − 1 Chemical

Pesticides
Carbofuran
DDT
Parathion
Dioxin TCDD
Atrazine
Alachlor

0.03
0.0-0.10
0.0-0.12
<0.01
0.02-0.03
0.05-0.06

1 × 10 −8
3 × 10 −12
—
1 × 10 −10
1 × 10 −8
3 × 10 −8

PCBs
Aroclor 1248

0.0-0.007 10 −9 -10 −12

Halogenated aliphatic hydrocarbons
Chloroform

0.09-0.10 1 × 10 −10

Halogenated ethers
2-Choloroethyl vinyl ether 0.0-0.20 1 × 10 −10

Monocyclic aromatics
2,4-Dimethylphenol
Pentachlorophenol
Benzene 14
Toluene 14
Phenol

0.24-0.66
0.00-33.6
0.006-0.01
0.01-0.019
—

1 × 10 −7
3 × 10 −8
1 × 10 −7
1 × 10 −7
3 × 10 −6

Phthalate esters
bis(2-ethylhexyl)phtalate

0.00-0.14 1 × 10 −7

Polycyclic aromatic hydrocarbons
Anthracene
Benzo[a]pyrene

0.007-15.0
0.0-0.075

3 × 10 −9

3 × 10 −12

Source: Schnoor, C.J.L., Environmental Modeling: Fate and Transport of Pollutants in Water, Air, and
Soil , John Wiley & Sons, New York, 1996. With permission.