Metabolic Response of Activated
Sludge to Sodium Pentachlorophenol
J. A. HEIDMAN, Graduate Assistant
D. F. KINCANNON, Assistant Professor
A. F. GAUDY, JR., Professor
School of Civil Engineering
Oklahoma State University
Stillwater, Oklahoma
INTRODUCTION
The many industrial uses for chlorinated hydrocarbons have resulted in an increasing demand for utilization of these materials, and as a result, the possibility
of their occurrence in waste streams has increased. Sodium pentachlorophenol is
a compound of particular interest, since it has such a wide range of industrial
application. It has been successfully employed as an additive for the prevention
of the swelling of wood, cork powder, and organic fiber, as a slime-preventing
agent in paper making processes, as a biocide in cooling water systems, as a
fungicide for textile, wood products, leather and asbestos fiber boards, and as a
hide preservative, among other industrial applications. However, there is very
little information available pertaining to its effect on the activated sludge process.
The work of several investigators has established that low concentrations of
sodium pentachlorophenol are non-toxic to animals (1,2), Roche, et al (1) have
concluded that extremely high concentrations would be necessary for this compound to be toxic to man. However, its effect on aquatic life may be drastically
different. Goodnight (3) found that sodium pentachlorophenol was toxic to the
more sensitive species of fish in concentrations above 0.2 mg/1, although hardier
species were able to survive at concentrations of 0.4 to 0.6 mg/1.
Buffa, et al (4), subjected mitochondria from rat liver to varying concentrations of pentachlorophenol and observed that the compound inhibited oxidative
phosphorylation. These investigators also found that the P/O ratio decreased proportionally as the adenosine triphosphatase activity of the mitochondria rose 30,
250, and 320 per cent after 15, 30, and 60 sec, respectively. Lyr (5), and Wein-
bach, et al (6) have also established that sodium pentachlorophenol functions to
inhibit oxidative phosphorylation. Since oxidative phosphorylation is necessary for
cell growth in an aerobic system, the uncoupling of oxidative phosphorylation has
important ramifications to the activated sludge process.
The presence of varying concentrations of sodium pentachlorophenol in waste
waters can also have a pronounced effect on species predomination in biological
treatment processes, since various species exhibit different tolerances to the compound. For examples, the growth of Bacillus mycoides is inhibited at a sodium
pentachlorophenol concentration of four mg/1, whereas the growth of Aspergillus
niger and Penicillium expansum is inhibited at concentrations of 25 and 30 mg/1,
respectively. However, Aerobacter aerogenes is not inhibited until the sodium
pentachlorophenol concentration reaches 200 mg/l (7). Pitter and Tucek (8) have
reported that chlorophenols in concentrations as low as one mg/1 cause population
changes in activated sludge.
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