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Page 11: Guidelines for Canadian Drinking Water Quality: Guideline Technical Document - Enteric Protozoa: Giardia and Cryptosporidium

Appendix A: CT tables for the inactivation of Giardia lamblia cysts by chlorine, chlorine dioxide, chloramine and ozone at various temperatures

1a) Chlorine: 99.9% (3 log) inactivation

Table A.1. CT values (in mg•min/L) for 99.9% (3 log) inactivation of Giardia lamblia cysts by free chlorine at 0.5°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 137 163 195 237 277 329 390
0.6 141 169 200 239 286 342 407
0.8 145 172 205 246 295 354 422
1.0 148 176 210 253 304 365 437
1.2 152 180 215 259 313 376 451
1.4 155 184 221 266 321 387 464
1.6 157 189 226 273 329 397 477
1.8 162 193 231 279 338 407 489
2.0 165 197 236 286 346 417 500
2.2 169 201 242 297 353 426 511
2.4 172 205 247 298 361 435 522
2.6 175 209 252 304 368 444 533
2.8 178 213 257 310 375 452 543
3.0 181 217 261 316 382 460 552
Table A.2. CT values (in mg•min/L) for 99.9% (3 log) inactivation of Giardia lamblia cysts by free chlorine at 5°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 97 117 139 166 198 236 279
0.6 100 120 143 171 204 244 291
0.8 103 122 146 175 210 252 301
1.0 105 125 149 179 216 260 312
1.2 107 127 152 183 221 267 320
1.4 109 130 155 187 227 274 329
1.6 111 132 158 192 232 281 337
1.8 114 135 162 196 238 287 345
2.0 116 138 165 200 243 294 353
2.2 118 140 169 204 248 300 361
2.4 120 143 172 209 253 306 368
2.6 122 146 175 213 258 312 375
2.8 124 148 178 217 263 318 382
3.0 126 151 182 221 268 324 389
Table A.3. CT values (in mg•min/L) for 99.9% (3 log) inactivation of Giardia lamblia cysts by free chlorine at 10°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 73 88 104 125 149 177 209
0.6 75 90 107 128 153 183 218
0.8 78 92 110 131 158 189 226
1.0 79 94 112 134 162 195 234
1.2 80 95 114 137 166 200 240
1.4 82 98 116 140 170 206 247
1.6 83 99 119 144 174 211 253
1.8 86 101 122 147 179 215 259
2.0 87 104 124 150 182 221 265
2.2 89 105 127 153 186 225 271
2.4 90 107 129 157 190 230 276
2.6 92 110 131 160 194 234 281
2.8 93 111 134 163 197 239 287
3.0 95 113 137 166 201 243 292
Table A.4. CT values (in mg•min/L) for 99.9% (3 log) inactivation of Giardia lamblia cysts by free chlorine at 15°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 49 59 70 83 99 118 140
0.6 50 60 72 86 102 122 146
0.8 52 61 73 88 105 126 151
1.0 53 63 75 90 108 130 156
1.2 54 64 76 92 111 134 160
1.4 55 65 78 94 114 137 165
1.6 56 66 79 96 116 141 169
1.8 57 68 81 98 119 144 173
2.0 58 69 83 100 122 147 177
2.2 59 70 85 102 124 150 181
2.4 60 72 86 105 127 153 184
2.6 61 73 88 107 129 156 188
2.8 62 74 89 109 132 159 191
3.0 63 76 91 111 134 162 195
Table A.5. CT values (in mg•min/L) for 99.9% (3 log) inactivation of Giardia lamblia cysts by free chlorine at 20°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 36 44 52 62 74 89 105
0.6 38 45 54 64 77 92 109
0.8 39 46 55 66 79 95 113
1.0 39 47 56 67 81 98 117
1.2 40 48 57 69 83 100 120
1.4 41 49 58 70 85 103 123
1.6 42 50 59 72 87 105 126
1.8 43 51 61 74 89 108 129
2.0 44 52 62 75 91 110 132
2.2 44 53 63 77 93 113 135
2.4 45 54 65 78 95 115 139
2.6 46 55 66 80 97 117 141
2.8 47 56 67 81 99 119 143
3.0 47 57 68 83 101 122 146
Table A.6. CT values (in mg•min/L) for 99.9% (3 log) inactivation of Giardia lamblia cysts by free chlorine at 25°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 24 29 35 42 50 59 70
0.6 25 30 36 43 51 61 73
0.8 26 31 37 44 53 63 75
1.0 26 31 37 45 54 65 78
1.2 27 32 38 46 55 67 80
1.4 27 33 39 47 57 69 82
1.6 28 33 40 48 58 70 84
1.8 29 34 41 49 60 72 86
2.0 29 35 41 50 61 74 89
2.2 30 35 42 51 62 75 90
2.4 30 36 43 52 63 77 92
2.6 31 37 44 53 65 78 94
2.8 31 37 45 54 66 80 96
3.0 32 38 46 55 67 81 97

1b) Chlorine: 90% (1 log) inactivation

Table A.7. CT values (in mg•min/L) for 90% (1 log) inactivation of Giardia lamblia cysts by free chlorine at 0.5°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 46 54 65 79 92 110 130
0.6 47 56 67 80 95 114 136
0.8 48 57 68 82 98 113 141
1.0 49 59 70 84 101 122 146
1.2 51 60 72 86 104 125 150
1.4 52 61 74 89 107 129 155
1.6 52 63 75 91 110 132 159
1.8 54 64 77 93 113 136 163
2.0 55 66 79 95 115 139 167
2.2 56 67 81 99 118 142 170
2.4 57 68 82 99 120 145 174
2.6 58 70 84 101 123 148 178
2.8 59 71 86 103 125 151 181
3.0 60 72 87 105 127 153 184
Table A.8. CT values (in mg•min/L) for 90% (1 log) inactivation of Giardia lamblia cysts by free chlorine at 5°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 32 39 46 55 66 79 93
0.6 33 40 49 57 68 81 97
0.8 34 41 49 58 70 84 100
1.0 35 42 50 60 72 87 104
1.2 36 42 51 61 74 89 107
1.4 36 43 52 62 76 91 110
1.6 37 44 53 64 77 94 112
1.8 38 45 54 65 79 96 115
2.0 39 46 55 67 81 98 118
2.2 39 47 56 68 83 100 120
2.4 40 48 57 70 84 102 123
2.6 41 49 58 71 86 104 125
2.8 41 49 59 72 88 106 127
3.0 42 50 61 74 89 108 130
Table A.9. CT values (in mg·min/L) for 90% (1 log) inactivation of Giardia lamblia cysts by free chlorine at 10°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 24 29 35 42 50 59 70
0.6 25 30 36 43 51 61 73
0.8 26 31 37 44 53 63 75
1.0 26 31 37 45 54 65 78
1.2 27 32 38 46 55 67 80
1.4 27 33 39 47 57 69 82
1.6 28 33 40 48 58 70 84
1.8 29 34 41 49 60 72 86
2.0 29 35 41 50 61 74 88
2.2 30 35 42 51 62 75 90
2.4 30 36 43 52 63 77 92
2.6 31 37 44 53 65 78 94
2.8 31 37 45 54 66 80 96
3.0 32 38 46 55 67 81 97
Table A.10. CT values (in mg·min/L) for 90% (1 log) inactivation of Giardia lamblia cysts by free chlorine at 15°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 16 20 23 28 33 39 47
0.6 17 20 24 29 34 41 49
0.8 17 20 24 29 35 42 50
1.0 18 21 25 30 36 43 52
1.2 18 21 25 31 37 45 53
1.4 18 22 26 31 38 46 55
1.6 19 22 26 32 39 47 56
1.8 19 23 27 33 40 48 59
2.0 19 23 28 33 41 49 59
2.2 20 23 28 34 41 50 60
2.4 20 24 29 35 42 51 61
2.6 20 24 29 36 43 52 63
2.8 21 25 30 36 44 53 64
3.0 21 25 30 37 45 54 65
Table A.11. CT values (in mg·min/L) for 90% (1 log) inactivation of Giardia lamblia cysts by free chlorine at 20°C
Residual (mg/L) pH
6 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 12 15 17 21 25 30 35
0.6 13 15 18 21 26 31 36
0.8 13 15 18 22 26 32 38
1.0 13 16 19 22 27 33 39
1.2 13 16 19 23 28 33 40
1.4 14 16 19 23 28 34 41
1.6 14 17 20 24 29 35 42
1.8 14 17 20 25 30 36 43
2.0 15 17 21 25 30 37 44
2.2 15 18 21 26 31 38 45
2.4 15 18 22 26 32 38 46
2.6 15 18 22 27 32 39 47
2.8 16 19 22 27 33 40 48
3.0 16 19 23 28 34 41 49
Table A.12. CT values (in mg·min/L) for 90% (1 log) inactivation of Giardia lamblia cysts by free chlorine at 25°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 8 10 12 14 17 20 23
0.6 8 10 12 14 17 20 24
0.8 9 10 12 15 18 21 25
1.0 9 10 12 15 19 22 26
1.2 9 11 13 15 18 22 27
1.4 9 11 13 16 19 22 27
1.6 9 11 13 16 19 23 28
1.8 10 11 14 16 20 23 29
2.0 10 12 14 17 20 24 29
2.2 10 12 14 17 21 25 30
2.4 10 12 14 17 21 25 31
2.6 10 12 15 18 22 26 31
2.8 10 12 15 18 22 26 32
3.0 11 13 15 18 22 27 32

1c) Chlorine: 68.4% (0.5 log) inactivation

Table A.13. CT values (in mg·min/L) for 68.4%  (0.5 log) inactivation of Giardia lamblia cysts by free chlorine at 0.5°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 23 27 33 40 46 55 65
0.6 24 28 33 40 48 57 68
0.8 24 29 34 41 49 59 70
1.0 25 29 35 42 51 61 73
1.2 25 30 36 43 52 63 75
1.4 26 31 37 44 54 65 77
1.6 26 32 38 46 55 66 80
1.8 27 32 39 47 56 68 82
2.0 28 33 39 48 55 70 83
2.2 28 34 40 50 59 71 85
2.4 29 34 41 50 60 73 87
2.6 29 35 42 51 61 74 89
2.8 30 36 43 52 63 75 91
3.0 30 36 44 53 64 77 92
Table A.14. CT values (in mg·min/L) for 68.4% (0.5 log) inactivation of Giardia lamblia cysts by free chlorine at 5°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 16 20 23 28 33 39 47
0.6 17 20 24 29 34 41 49
0.8 17 20 24 29 35 42 50
1.0 18 21 25 30 36 43 52
1.2 18 21 25 31 37 45 53
1.4 18 22 26 31 38 46 55
1.6 19 22 26 32 39 47 56
1.8 19 23 27 33 40 48 58
2.0 19 23 28 33 41 49 59
2.2 20 23 28 34 41 50 60
2.4 20 24 29 35 42 51 61
2.6 20 24 29 36 43 52 63
2.8 21 25 30 36 44 53 64
3.0 21 25 30 37 45 54 65
Table A.15. CT values (in mg·min/L) for 68.4% (0.5 log) inactivation of Giardia lamblia cysts by free chlorine at 10°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 12 15 17 21 25 30 35
0.6 13 15 18 21 26 31 36
0.8 13 15 18 22 26 32 38
1.0 13 16 19 22 27 33 39
1.2 13 16 19 23 28 33 40
1.4 14 16 19 23 28 34 41
1.6 14 17 20 24 29 35 42
1.8 14 17 20 25 30 36 43
2.0 15 17 21 25 30 37 44
2.2 15 18 21 26 31 38 45
2.4 15 18 22 26 32 38 46
2.6 15 18 22 27 32 39 47
2.8 16 19 22 27 33 40 48
3.0 16 19 23 28 34 41 49
Table A.16. CT values (in mg·min/L) for 68.4% (0.5 log) inactivation of Giardia lamblia cysts by free chlorine at 15°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 8 10 12 14 17 20 23
0.6 8 10 12 14 17 20 24
0.8 9 10 12 15 18 21 25
1.0 9 11 13 15 18 22 26
1.2 9 11 13 15 19 22 27
1.4 9 11 13 16 19 23 28
1.6 9 11 13 16 19 24 28
1.8 10 11 14 16 20 24 29
2.0 10 12 14 17 20 25 30
2.2 10 12 14 17 21 25 30
2.4 10 12 14 18 21 26 31
2.6 10 12 15 18 22 26 31
2.8 10 12 15 18 22 27 32
3.0 11 13 15 19 22 27 33
Table A.17. CT values (in mg·min/L) for 68.4% (0.5 log) inactivation of Giardia lamblia cysts by free chlorine at 20°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 6 7 9 10 12 15 19
0.6 6 8 9 11 13 15 18
0.8 7 8 9 11 13 16 19
1.0 7 8 9 11 14 16 20
1.2 7 8 10 12 14 17 20
1.4 7 8 10 12 14 17 21
1.6 7 8 10 12 15 18 21
1.8 7 9 10 12 15 18 22
2.0 7 9 10 13 15 18 22
2.2 7 9 11 13 16 19 23
2.4 8 9 11 13 16 19 23
2.6 8 9 11 13 16 20 24
2.8 8 9 11 14 17 20 24
3.0 9 10 11 14 17 20 24
Table A.18. CT values (in mg·min/L) for 68.4% (0.5 log) inactivation of Giardia lamblia cysts by free chlorine at 25°C
Residual (mg/L) pH
6.0 6.5 7.0 7.5 8.0 8.5 9.0
< 0.4 4 5 6 7 8 10 12
0.6 4 5 6 7 9 10 12
0.8 4 5 6 7 9 11 13
1.0 4 5 6 8 9 11 13
1.2 5 5 6 8 9 11 13
1.4 5 6 7 8 10 12 14
1.6 5 6 7 8 10 12 14
1.8 5 6 7 8 10 12 14
2.0 5 6 7 8 10 12 15
2.2 5 6 7 9 10 13 15
2.4 5 6 7 9 11 13 15
2.6 5 6 7 9 11 13 16
2.8 5 6 8 9 11 13 16
3.0 5 6 8 9 11 14 16

2. Chlorine dioxide

Table A.19. CT values (in mg·min/L) for inactivation of Giardia, pH 6.0-9.0
Log inactivation Water temperature (°C)
1 5 10 15 20 25
0.5 10 4.3 4 3.2 2.5 2
1 21 8.7 7.7 6.3 5 3.7
1.5 32 13 12 10 7.5 5.5
2 42 17 15 13 10 7.3
2.5 52 22 19 16 13 9
3 63 26 23 19 15 11

3. Chloramine

Table A.20. CT values Table 1 Footnote a (in mg·min/L) for inactivation of Giardia, pH 6.0-9.0
Log inactivation Water temperature (°C)
1 5 10 15 20 25

Table 1 Footnotes

Table 1 Footnote 1

Values estimated from monochloramine data.

Return to Table 1 footnote a referrer
0.5 635 365 310 250 185 125
1 1270 735 615 500 370 250
1.5 1900 1100 930 750 550 375
2 2535 1470 1230 1000 735 500
2.5 3170 1830 1540 1250 915 625
3 3800 2200 1850 1500 1100 750

4. Ozone

Table A.21. CT values (in mg·min/L) for inactivation of Giardia
Log inactivation Water temperature (°C)
≤ 1 5 10 15 20 25
0.5 0.48 0.32 0.23 0.16 0.12 0.08
1 0.97 0.63 0.48 0.32 0.24 0.16
1.5 1.5 0.95 0.72 0.48 0.36 0.24
2 1.9 1.3 0.95 0.63 0.48 0.32
2.5 2.4 1.6 1.2 0.79 0.60 0.4
3 2.9 1.9 1.43 0.95 0.72 0.48

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2017-01-04