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The concentrations of total chlorine and free chlorine were similar before and after the 10 min exposure to applied chlorine. Thus there was no decay of chlorine during the exposure (Table 2).

Table 2

Log10-densities (mean ± SD, n = 3) and (Log10-reduction in parenthesis) of MS2 and the 17 isolated coliphages at different concentrations of chlorine and with 10 min contact time

StrainCl 0 mg/LCltot: 0.13 ± 0.01 mg/La; Clfree: 0.04 ± 0.03 mg/LaCltot: 0.33 ± 0.02 mg/Lb; Clfree: 0.12 ± 0.04 mg/LbCltot: 0.50 ± 0.03 mg/Lc; Clfree: 0.21 ± 0.08 mg/LcLinear regression equation: = Log10-reduction; x = Clfree (mg/L)
4.54 ± 0.30 4.19 ± 0.04 (0.35) 4.81 ± 0.07 (−0.27) 4.57 ± 0.15 (0.03) y = 0.49x (R2 = 0.003) 
5.14 ± 0.04 5.02 ± 0.10 (0.12) 5.06 ± 0.11 (0.07) 5.11 ± 0.13 (0.02) y = −0.42x (R2 = −0.21) 
4.23 ± 0.05 4.02 ± 0.01 (0.21) 4.14 ± 0.11 (0.10) 4.16 ± 0.11 (0.07) y = −0.62x (R2 = −0.64) 
5.41 ± 0.29 5.41 ± 0.07 (0) 5.03 ± 0.07 (0.38) 5.17 ± 0.25 (0.24) y = −1.20x (R2 = 0.13) 
17 4.84 ± 0.42 4.58 ± 0.19 (0.26) 4.44 ± 0.12 (0.40) 4.34 ± 0.06 (0.50) y = −2.99x (R2 = 0.51) 
14 5.62 ± 0.35 5.47 ± 0.13 (0.15) 4.84 ± 0.50 (0.77) 5.03 ± 0.26 (0.59) y = −5.21x (R2 = 0.36) 
13 2.26 ± 0.10 1.99 ± 0.02 (0.27) 0.31 ± 0.39 (1.95) LDL (2.26)* y = −9.84x (R2 = 0.79) 
MS2 5.71 ± 0.36 4.01 ± 0.04 (1.70) LDL (5.71)LDL (5.71)y = −27.55x (R2 = 0.91) 
11 5.58 ± 0.21 5.37 ± 0.07 (0.21) 1.65 ± 0.31 (3.92) 0.41 ± 0.15 (5.16)* y = −30.66x (R2 = 0.93) 
5.36 ± 0.22 3.34 ± 0.21(2.02) LDL (5.36)* LDL (5.36)* y = −31.67x (R2 = 0.97) 
5.52 ± 0.18 3.81 ± 0.30 (1.71) LDL (5.52)* LDL (5.52)* y = −32.59x (R2 = 0.99) 
10 4.69 ± 0.16 2.05 ± 0.36 (2.64) LDL (4.69)* LDL (4.69)* y = −33.03x (R2 = 0.88) 
4.62 ± 0.14 2.59 ± 0.27 (2.03) LDL (4.62)* LDL (4.62)* y = −37.03x (R2 = 0.90) 
5.74 ± 0.09 5.52 ± 0.22 (0.22) 3.28 ± 0.07 (2.46) LDL (5.74)* y = −40.98x (R2 = 0.88) 
12 3.80 ± 0.58 LDL (3.80)* LDL (3.80)* LDL (3.80)* y = −43.43x (R2 = 0.83) 
16 4.41 ± 0.31 2.38 ± 0.38 (2.02) LDL (4.41)* LDL (4.41)* y = −45.99x (R2 = 0.85) 
15 5.28 ± 0.06 3.49 ± 0.33 (1.78) 0.27 ± 0.56 (5.00)* LDL (5.28)* y = −46.08x (R2 = 0.91) 
4.95 ± 0.25 0.13 ± 0.38 (4.82)* LDL (4.95)* LDL (4.95)* y = −157.3x (R2 = 0.99) 
StrainCl 0 mg/LCltot: 0.13 ± 0.01 mg/La; Clfree: 0.04 ± 0.03 mg/LaCltot: 0.33 ± 0.02 mg/Lb; Clfree: 0.12 ± 0.04 mg/LbCltot: 0.50 ± 0.03 mg/Lc; Clfree: 0.21 ± 0.08 mg/LcLinear regression equation: = Log10-reduction; x = Clfree (mg/L)
4.54 ± 0.30 4.19 ± 0.04 (0.35) 4.81 ± 0.07 (−0.27) 4.57 ± 0.15 (0.03) y = 0.49x (R2 = 0.003) 
5.14 ± 0.04 5.02 ± 0.10 (0.12) 5.06 ± 0.11 (0.07) 5.11 ± 0.13 (0.02) y = −0.42x (R2 = −0.21) 
4.23 ± 0.05 4.02 ± 0.01 (0.21) 4.14 ± 0.11 (0.10) 4.16 ± 0.11 (0.07) y = −0.62x (R2 = −0.64) 
5.41 ± 0.29 5.41 ± 0.07 (0) 5.03 ± 0.07 (0.38) 5.17 ± 0.25 (0.24) y = −1.20x (R2 = 0.13) 
17 4.84 ± 0.42 4.58 ± 0.19 (0.26) 4.44 ± 0.12 (0.40) 4.34 ± 0.06 (0.50) y = −2.99x (R2 = 0.51) 
14 5.62 ± 0.35 5.47 ± 0.13 (0.15) 4.84 ± 0.50 (0.77) 5.03 ± 0.26 (0.59) y = −5.21x (R2 = 0.36) 
13 2.26 ± 0.10 1.99 ± 0.02 (0.27) 0.31 ± 0.39 (1.95) LDL (2.26)* y = −9.84x (R2 = 0.79) 
MS2 5.71 ± 0.36 4.01 ± 0.04 (1.70) LDL (5.71)LDL (5.71)y = −27.55x (R2 = 0.91) 
11 5.58 ± 0.21 5.37 ± 0.07 (0.21) 1.65 ± 0.31 (3.92) 0.41 ± 0.15 (5.16)* y = −30.66x (R2 = 0.93) 
5.36 ± 0.22 3.34 ± 0.21(2.02) LDL (5.36)* LDL (5.36)* y = −31.67x (R2 = 0.97) 
5.52 ± 0.18 3.81 ± 0.30 (1.71) LDL (5.52)* LDL (5.52)* y = −32.59x (R2 = 0.99) 
10 4.69 ± 0.16 2.05 ± 0.36 (2.64) LDL (4.69)* LDL (4.69)* y = −33.03x (R2 = 0.88) 
4.62 ± 0.14 2.59 ± 0.27 (2.03) LDL (4.62)* LDL (4.62)* y = −37.03x (R2 = 0.90) 
5.74 ± 0.09 5.52 ± 0.22 (0.22) 3.28 ± 0.07 (2.46) LDL (5.74)* y = −40.98x (R2 = 0.88) 
12 3.80 ± 0.58 LDL (3.80)* LDL (3.80)* LDL (3.80)* y = −43.43x (R2 = 0.83) 
16 4.41 ± 0.31 2.38 ± 0.38 (2.02) LDL (4.41)* LDL (4.41)* y = −45.99x (R2 = 0.85) 
15 5.28 ± 0.06 3.49 ± 0.33 (1.78) 0.27 ± 0.56 (5.00)* LDL (5.28)* y = −46.08x (R2 = 0.91) 
4.95 ± 0.25 0.13 ± 0.38 (4.82)* LDL (4.95)* LDL (4.95)* y = −157.3x (R2 = 0.99) 

Statistically significant differences from the control (Cl 0 mg/L), assessed by Related sample Friedman's two-way analysis of variance, are indicated with asterisks *p < 0.05. LDL = less than the detection limit <1 PFU/mL.

aConcentrations of total and free chlorine after 10 min contact time were 0.13 ± 0.01 mg/L and 0.04 ± 0.02 mg/L, respectively.

bConcentrations of total and free chlorine after 10 min contact time were 0.31 ± 0.01 mg/L and 0.10 ± 0.03 mg/L, respectively.

cConcentrations of total and free chlorine after 10 min contact time were 0.47 ± 0.04 mg/L and 0.19 ± 0.07 mg/L, respectively.

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