Water Quality
Ambient Water Quality Criteria for Fluoride
Table 5.13 Calculated and Measured Fluoride Levels, Hardness
and Fish Survival
(18
rainbow trout @ 59 mm long and 1.8 g weight per 96 hour test
@ 12°C)
Fluor.
|
pH
7.2
|
pH
8.3
|
pH
8.3
|
pH
8.7
|
calc.
|
hardness
17
|
hardness
49
|
hardness
182
|
hardness
385
|
level
|
calcium
6.8
|
calcium
19.6
|
calcium
72.8
|
calcium
154
|
in
|
F-measure
|
dead
|
F-measure
|
dead
|
F-measure
|
dead
|
F-measure
|
dead
|
mg/L
|
start
|
end
|
fish
|
start
|
end
|
fish
|
start
|
end
|
fish
|
start
|
end
|
fish
|
0
|
2.02
|
0.02
|
0
|
0.51
|
0.20
|
0
|
0.08
|
0.03
|
1
|
0.12
|
0.15
|
0
|
10
|
9.90
|
9.1
0
|
1
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
18
|
17.9
|
17.0
|
4
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
32
|
31.4
|
30.0
|
5
|
34.0
|
35.2
|
0
|
36.3
|
33.8
|
0
|
_
|
_
|
_
|
56
|
56.1
|
53.4
|
7
|
62.3
|
67.1
|
0
|
54.1
|
63.2
|
0
|
43.0
|
39.3
|
0
|
100
|
97.4
|
96.4
|
17
|
114
|
122
|
8
|
96.5
|
99.1
|
3
|
90.8
|
63.6
|
0
|
180
|
_
|
_
|
_
|
172
|
194
|
16
|
172
|
171
|
13
|
172
|
121
|
5
|
320
|
_
|
_
|
_
|
336
|
346
|
18
|
316
|
296
|
18
|
320
|
257
|
18
|
560
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
_
|
577
|
473
|
13
|
96-h
LC50
|
51
(38-68)
|
128
(108-150)
|
140
(117-167)
|
193
(167-223)
|
At high fluoride and
high hardness the final fluoride levels were only 70 to 90
% of the initial levels. At 577 mg/L initial fluoride and 385
mg/L initial hardness (154 mg/L Ca), the fluoride loss was
104 mg/L. To precipitate this much fluoride as CaF2 would
take 109 mg of calcium leaving only 45 mg/L calcium for a hardness
of 113 and not the nominal 385. The initial 320 mg/L fluoride
@ 385 mg/L hardness becomes 257 mg/L fluoride @ 219 mg/L hardness
and the 316 mg/L fluoride @ 182 mg/L hardness becomes 296 mg/L
fluoride @ 130 mg/L hardness. This illustrates how erroneous
many literature values for fluoride, hardness and LC50's
really are, when only nominal, calculated or beginning values
are used. Data taken from Pimental and Bulkley, (1983a).
