Federal legislation states that "At least 99.9% (3-logs removal and/or inactivation of Giardia lamblia and 99.99% (4-logs) removal and/or inactivation of viruses" is achieved for all surface water treatment. A facility inject chlorine just before the water enter the distribution system. There is no clear well storage and disinfection is done through the distribution system. The first house served by the water treatment facility is located 1 mile from the plant. The pipe of the distribution system is 6 inches in diameter and the maximum flow rate is 2000 gallons per minute. The pH of the water is 7.5, and the temperature is 15 degree C. What will be the total chlorine dose needed to ensure that water reaching the first house has been disinfected to the required level stated above, if the water chlorine demand from organics is 1.5 mg/L, the ammonia content is 1 mg/L NH_3/L.| Tahle 2 C-T Values for of Viruses 4-log 3-log Inactivation InactivationInactivation
Disinfectant 2-log Inactivation 3-log Inactivation 4-log Inactivation
90.0% 99.9% 99.9%
Chlorine 3 4 6
Chloramine 643 1067 1491
Chlorine dioxide 4.2 12.8 25.1
ozone 0.5 0.8 1.0
Giardia inactivation
Log inactivation Ct mg-min/L
0.5 20
1.0 40
1.5 60
2.0 79
2.5 99
3.0 119