APPENDIX CC Contd.
(11) Chemical Treatment
Principal Chemicals used in treatment:
1974-75 1975-76 Long tons Average dose (parts per million) Long tons Average dose (parts per million) Fresh Water Alum 4 051 11.8 3 802 10.3 Hydrated lime 4 050 11.8 3 926 10.7 Liquid Chlorine 469 1.4 548 1.5 Sodium silicofluoride (as fluoride) 368 0.7 475 0.8 Salt Water Liquid Chlorine 107 1.7 101 1.6(12) Quality of Supply
(a) Chemical quality (values expressed in parts per million)
1974-75 1975-76 Range Average Range Average Total hardness (as CaCO3) 10-55 31 10-36 24 Salinity (as NaCl) 8-97 39 10-74 26 Total dissolved solids 23-148 73 27-107 53 Fluoride (as F) (Target level 1.0 p.p.m.) 0.8 0.8(b) Bacteriological quality
1974-75 1975-76 Free from Coliform No. taken orgs/100 ml Free from Coliform No. taken orgs/100 ml Samples from treatment works and service reservoirs 99.88% 3 324 100% 3 654 Samples from consumers' taps 99.24% 4 088 99.67% 5 113234
APPENDIX CC Contd.
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(11) Chemical Treatment
Principal Chemicals used in treatment:
1974-75
Long tons
Average dose (parts per million)
Long tons
1975-76
Average do se (parts per million)
Fresh Water
Alum
4 051
11.8
3 802
10.3
Hydrated lime
4 050
11.8
3 926
10.7
Liquid Chlorine
469
1.4
548
1.5
Sodium silicofluoride
368
0.7
475
0.8
(as fluoride)
(as fluoride)
Salt Water
Liquid Chlorine
107
1.7
101
1.6
(12) Quality of Supply
(a) Chemical quality (values expressed in parts per million)
1974-75
1975-76
Range
Average Range
Average
Total hardness (as CaCO3)
10 55
31
10- 36
24
Salinity (as NaCl)
8- 97
39
10- 74
26
Total dissolved solids
23-148
73
27-107
53
0.8
0.8
Fluoride (as F)
(Target level 1.0 p.p.m.)
(b) Bacteriological quality
Samples from treatment works
and service reservoirs
Samples from consumers' taps
1974-75
Free from Coliform No. taken orgs/100 ml
1975-76
Free from Coliform
No. taken orgs/100 ml
3 324
99.88%
3 654
100%
4 088.
99.24
5 113
99.67%
234
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