The Control of Sphaerotilus Natans
by a Southern Kraft Mill
JAMES J. McKEOWN, Sanitary Engineer
Rayonier Incorporated
Jesup, Georgia
The growth of the slime, Sphaerotilus natans, during winter months has
on occasion become a nuisance to net fishermen. The American shad is
netted in quantity below the waste outfall of Rayonier's Jesup Division during
the winter. Six years of research has developed a method that is effective in
controlling the slime growth.
Slime first appeared below the mill's outfall during the winter of 1955-
56. The mill had been in operation for nearly two years at the time. The
slime, identified as sphaerotilus natans, was interfering with net fishing.
The infestation was causing a heavy buildup of slime on the fishing nets which
if allowed to dry was difficult to remove. Subsequent years showed that
Sphaerotilus only reached infestation during the winter months. Furthermore,
those winters in which the river overflowed its banks alleviated the heavy
growth. The shad season lasts from January 1 to April 15. The breakpoint
for flow (at which the river overflows its banks) is 12,000 cfe. The thermal
breakpoint is in the 20-25 C range. Since water temperature usually remains
below 20 C during the winter, flow is considered as a limiting factor according to Table I.
TABLE I
FREQUENCY OF OCCURRENCE OF AVERAGE MONTHLY FLOWS
EQUAL TO OR LESS THAN 12, 000 CFS
(1931-1960)
(Frequency of Optimum River Conditions for Slime Growth)
Month Frequency of Occurrence
January     43 per cent of the time or once every 2.3 years
February  30 per cent of the time or once every 3. 3 years
March  16 per cent of the time or once every 6.2 years
April  17 per cent of the time or once every 5.9 years
The long range solution could, therefore, take advantage of the years
when the river would remain high.
The Jesup Division of Rayonier Incorporated is located 60 miles upstream
from the Atlantic Ocean on the Altamaha River in Georgia. The plant produces chemical cellulose using the sulfate or kraft process. The mill first
began operations in 1954 and doubled capacity in 1957. A total of 45 million
gals of waste flows from the mill each day. Information on the river basin
and mill waste has been published (1).
Sphaerotilus natans. once thought to be a colorless algae, is a member
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