After conventional filtration, the filtered water with turbidity less than 0.5 NTU, pH =7 and T=5 C on a day when the peak hourly flow is 4.0 mgd (million gallon per day). After filtration, the water is chlorinated in a contact with hydraulic characteristics shown in Figure 11.20 b. What is the applied chlorine dose if free chlorine is used for disinfection?

Transcribed Image Text:1.0r 0.8 C. 0.6 Co 0.4 0.2 Tracer output 30 Free chlorineb 60 90 10 = 90 min Preformed chloramine Chlorine dioxide Ozone 1 J 120 150 180 210 240 Time (min) 1 2 3 4 5 6 7 Peak hourly flow rate (mgd) (b) (a) Figure 11.20 Tracer analyses of a chlorine contact tank to determine t₁0 times at peak hourly flow for calculating C-t values. (a) Normalized tracer output for a test applying a continuous tracer input. (b) A plot of the t₁0 times for four tracer tests at different flow rates to draw a curve to determine t for calculating C-t values. pH 6 7 8 9 0.5°C [(mg/1).min] 110 (min) 49 70 Surface water plants that provide filtration are required to achieve at least 99.9% removal and inactivation of Giardia lamblia and 99.99% removal and inactivation of viruses by the total treatment system, including sedimentation after coagulation, if provided, granular-media filtration, and chemical disinfection. For filtration to be con- sidered effective in removal of G. lamblia cysts, the turbidity in the filtered water must be equal to or less than 0.5 NTU in at least 95% of the measurements taken each month. The recommended removals of pathogens achievable in conventional treat- ment (coagulation, flocculation, sedimentation, and filtration) are a 2.5 log reduction of G. lamblia cysts and a 2.0 log reduction of viruses [17]. Therefore, only 0.5 log of G. lamblia and 2.0 log of viruses need to be inactivated by chemical disinfection. For direct filtration (coagulation and filtration excluding sedimentation), the recom- mended removals are a 2.0 log reduction of cysts and a 1.0 log reduction of viruses, which leaves 1.0 log of cysts and 3.0 log of viruses for inactivation. Table 11.8 lists the C-t values for 90% (1.0 log) inactivation of G. lamblia cysts by various chemical disinfectants; the C-t values for 0.5 log inactivation are equal to one-half the 1.0 log inactivation values. Recommended C-t values for achieving different levels of virus inactivation are given in Table 11.9. For free chlorine, C-t values recommended for Table 11.8 C-t Values for 90% (1.0 Log) Inactivation of Giardia Lamblia Cystsa WATER TEMPERATURE 101 146 1300 21 200 0.97 150 100 50 19:36W Bostwain S 5°C 10°C 15°C [(mg/1)-min] [(mg/1)-min] [(mg/1).min] 35 50 72 146 730 8.4 0.63 26 37 54 78 620 7.4 0.48 19 Toto 28 36 59 500 6.3 0.32 Source: Adapted from Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources (Environmental Protection Agency, 1991). "C-t values for 0.5-log inactivation are one-half those shown in table. Free chlorine values are based on a residual of 1.0 mg/1.
Transcribed Image Text:1.0r 0.8 C. 0.6 Co 0.4 0.2 Tracer output 30 Free chlorineb 60 90 10 = 90 min Preformed chloramine Chlorine dioxide Ozone 1 J 120 150 180 210 240 Time (min) 1 2 3 4 5 6 7 Peak hourly flow rate (mgd) (b) (a) Figure 11.20 Tracer analyses of a chlorine contact tank to determine t₁0 times at peak hourly flow for calculating C-t values. (a) Normalized tracer output for a test applying a continuous tracer input. (b) A plot of the t₁0 times for four tracer tests at different flow rates to draw a curve to determine t for calculating C-t values. pH 6 7 8 9 0.5°C [(mg/1).min] 110 (min) 49 70 Surface water plants that provide filtration are required to achieve at least 99.9% removal and inactivation of Giardia lamblia and 99.99% removal and inactivation of viruses by the total treatment system, including sedimentation after coagulation, if provided, granular-media filtration, and chemical disinfection. For filtration to be con- sidered effective in removal of G. lamblia cysts, the turbidity in the filtered water must be equal to or less than 0.5 NTU in at least 95% of the measurements taken each month. The recommended removals of pathogens achievable in conventional treat- ment (coagulation, flocculation, sedimentation, and filtration) are a 2.5 log reduction of G. lamblia cysts and a 2.0 log reduction of viruses [17]. Therefore, only 0.5 log of G. lamblia and 2.0 log of viruses need to be inactivated by chemical disinfection. For direct filtration (coagulation and filtration excluding sedimentation), the recom- mended removals are a 2.0 log reduction of cysts and a 1.0 log reduction of viruses, which leaves 1.0 log of cysts and 3.0 log of viruses for inactivation. Table 11.8 lists the C-t values for 90% (1.0 log) inactivation of G. lamblia cysts by various chemical disinfectants; the C-t values for 0.5 log inactivation are equal to one-half the 1.0 log inactivation values. Recommended C-t values for achieving different levels of virus inactivation are given in Table 11.9. For free chlorine, C-t values recommended for Table 11.8 C-t Values for 90% (1.0 Log) Inactivation of Giardia Lamblia Cystsa WATER TEMPERATURE 101 146 1300 21 200 0.97 150 100 50 19:36W Bostwain S 5°C 10°C 15°C [(mg/1)-min] [(mg/1)-min] [(mg/1).min] 35 50 72 146 730 8.4 0.63 26 37 54 78 620 7.4 0.48 19 Toto 28 36 59 500 6.3 0.32 Source: Adapted from Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources (Environmental Protection Agency, 1991). "C-t values for 0.5-log inactivation are one-half those shown in table. Free chlorine values are based on a residual of 1.0 mg/1.

Question

After conventional filtration, the filtered water with turbidity less than 0.5 NTU, pH =7 and T=5 C on a day when the peak hourly flow is 4.0 mgd (million gallon per day). After filtration, the water is chlorinated in a contact with hydraulic characteristics shown in Figure 11.20 b. What is the applied chlorine dose if free chlorine is used for disinfection?

1.0r
0.8
C. 0.6
Co
0.4
0.2
Tracer output
30
Free chlorineb
60 90
10 = 90 min
Preformed chloramine
Chlorine dioxide
Ozone
1
J
120 150 180 210 240
Time (min)
1 2 3 4 5 6 7
Peak hourly flow rate (mgd)
(b)
(a)
Figure 11.20 Tracer analyses of a chlorine contact tank to determine t₁0 times at
peak hourly flow for calculating C-t values. (a) Normalized tracer output for a test
applying a continuous tracer input. (b) A plot of the t₁0 times for four tracer tests at
different flow rates to draw a curve to determine t for calculating C-t values.
pH
6
7
8
9
0.5°C
[(mg/1).min]
110
(min)
49
70
Surface water plants that provide filtration are required to achieve at least 99.9%
removal and inactivation of Giardia lamblia and 99.99% removal and inactivation of
viruses by the total treatment system, including sedimentation after coagulation, if
provided, granular-media filtration, and chemical disinfection. For filtration to be con-
sidered effective in removal of G. lamblia cysts, the turbidity in the filtered water
must be equal to or less than 0.5 NTU in at least 95% of the measurements taken each
month. The recommended removals of pathogens achievable in conventional treat-
ment (coagulation, flocculation, sedimentation, and filtration) are a 2.5 log reduction
of G. lamblia cysts and a 2.0 log reduction of viruses [17]. Therefore, only 0.5 log
of G. lamblia and 2.0 log of viruses need to be inactivated by chemical disinfection.
For direct filtration (coagulation and filtration excluding sedimentation), the recom-
mended removals are a 2.0 log reduction of cysts and a 1.0 log reduction of viruses,
which leaves 1.0 log of cysts and 3.0 log of viruses for inactivation. Table 11.8 lists
the C-t values for 90% (1.0 log) inactivation of G. lamblia cysts by various chemical
disinfectants; the C-t values for 0.5 log inactivation are equal to one-half the 1.0 log
inactivation values. Recommended C-t values for achieving different levels of virus
inactivation are given in Table 11.9. For free chlorine, C-t values recommended for
Table 11.8 C-t Values for 90% (1.0 Log) Inactivation of Giardia Lamblia Cystsa
WATER TEMPERATURE
101
146
1300
21
200
0.97
150
100
50
19:36W Bostwain S
5°C
10°C
15°C
[(mg/1)-min] [(mg/1)-min] [(mg/1).min]
35
50
72
146
730
8.4
0.63
26
37
54
78
620
7.4
0.48
19
Toto 28
36
59
500
6.3
0.32
Source: Adapted from Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public
Water Systems Using Surface Water Sources (Environmental Protection Agency, 1991).
"C-t values for 0.5-log inactivation are one-half those shown in table.
Free chlorine values are based on a residual of 1.0 mg/1.

Accepted Answer

Answer 
We need to find log reductionCCo from figure(11.20 a) using 4 Mgd and figure (11.20 b)
Let…