Page 54 - Environmental Control in Petroleum Engineering

42 Environmental Control in Petroleum Engineering

for the best available technology (BAT) are 29 mg/L on a monthly
average and 42 mg/L for a daily maximum. Like all regulatory targets,
these numbers are subject to change.
The concentrations of dissolved hydrocarbons in produced water
depends on the solubility of the hydrocarbon. For discharges in the
Gulf of Mexico, dissolved hydrocarbon concentrations for phenols,
benzene, and toluene were found to be between 1,000 and 6,000
micrograms/L, while the concentrations of high molecular weight
hydrocarbons was considerably lower (Stephenson, 1992). These data
are summarized in Table 2-7.

Oxygen Depletion

Produced water is invariably oxygen depleted. If discharged, oxygen
depleted water can impact fauna requiring dissolved oxygen for
respiration. Oxygen depletion can be a problem for discharge in
shallow estuaries and canals, particularly if the produced water forms
a layer along the bottom because of its higher density. This dense layer
would be isolated from the atmosphere, limiting its contact with

Table 2-7
Dissolved Hydrocarbon Concentrations in Produced Water

Average Concentration Standard Deviation
Hydrocarbon (rnicrograms/L) (micrograms/L)

Gas Production
Phenols 4,743 5,986
Benzene 5,771 4,694
Toluene 5,190 4,850
C 2 Benzene 700 1,133
Oil Production
Phenols 1,049 889
Benzene 1,318 1,468
Toluene 1,065 896
C' 2 Benzene 221 754
Naphthalene 132 161
Other PAHs 7 18
Source: from Stephenson, 1992,
Copyright SPE. with permission.