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In addition to microbial indicators, physical and chemical parameters of water quality are essential to the comprehensive performance quantification of the DWDS. Table 1 lists the physical and chemical parameters of the distributed water quality under various environmental conditions. Specifically, at low flow velocity of 0.1 m/s, the turbidity level of the distributed water was estimated as 0.25 NTU, which gradually increased to 0.52 NTU as the flow velocity was elevated from 0.1 to 1.5 m/s. Further increase in flow velocity to 2.0 m/s caused only a slight reduction of the turbidity level to 0.44 NTU. The turbidity level slightly decreased from 0.37 to 0.25 NTU with the initial increase of chlorine concentration from 0 to 2.0 mg/L. In contrast, the addition of 3.00 mg C/L carbon and 100.0 μg P/L phosphorus significantly elevated the turbidity levels from 0.31 to 0.86 and 0.78 NTU (P < 0.05), respectively. An increase in flow velocity from 0.1 to 2.0 m/s and an increase in the initial chlorine concentration from 0 to 2.0 mg/L, gradually decreased the TOC values from 1.77 to 1.19 mg/L and from 2.04 to 1.41 mg/L, respectively. Addition of phosphorus from 0 to 100.0 μg P/L yielded a similar TOC variation from 1.73 to 1.18 mg/L when compared to the values obtained for the flow velocity scenarios. Not surprisingly, a significant increase in the TOC value from 1.73 to 3.67 mg/L was observed upon addition of carbon from 0 to 3.00 mg C/L (P < 0.05). The and soluble phosphorus concentrations fluctuated between 0.33 and 0.45 mg/L and between 16.4 and 32.8 μg/L, respectively when the flow velocity varied from 0.1 to 2.0 m/s. Relatively high levels of oscillations were observed for the (between 0.27 and 0.47 mg/L) and soluble phosphorus (between 16.3 and 41.2 μg/L) concentrations in response to increasing initial chlorine concentration from 0 to 2.0 mg/L. Interestingly, an increase in the addition of carbon from 0 to 3.00 mg C/L resulted in clear reductions of concentration from 0.45 to 0.26 mg/L and soluble phosphorus from 26.1 to 4.7 μg/L, respectively. An increase in the addition of phosphorus from 0 to 100.0 μg P/L yielded a continuous increase of soluble phosphorus from 26.1 to 81.4 μg/L and a clear decrease in the estimated concentration from 0.45 to 0.23 mg/L. No detectable residual chlorine nor any minor changes in the conductivity values were found for all scenarios, except for the ones in which the initial chlorine concentrations was 1.5 and 2.0 mg/L and the residual chlorine was estimated as 0.50 and 1.00 mg/L, respectively. The environmental fluctuations had little influence on the TDS and pH, as seen with small variations in TDS value ranging from 111.3 to 115.3 mg/L and pH value ranging from 7.25 to 7.73, as observed for all scenarios.

Table 1

Estimated physical and chemical parameters (mean ± s.d., n = 3) of the bulk water at 24 h after incubation under various environmental conditions

Scenarios
 Physical and chemical indexes
FactorValueTurbidity (NTU)TOC (mg/L)NH4+-N (mg/L)Soluble P (μg/L)Residual Chlorine (mg/L)TDS (mg/L)Conductivity (μS/cm)pH
Velocity (m/s) 0.1 0.25 ± 0.01 1.77 ± 0.10 0.37 ± 0.11 32.8 ± 7.2 0.00 ± 0.00 114.3 ± 0.6 214.3 ± 0.6 7.25 ± 0.02 
0.5 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.04 
1.0 0.33 ± 0.01 1.69 ± 0.08 0.43 ± 0.10 20.7 ± 2.4 0.00 ± 0.00 112.7 ± 0.6 215.0 ± 0.0 7.30 ± 0.05 
1.5 0.52 ± 0.03 1.58 ± 0.05 0.45 ± 0.12 16.4 ± 2.3 0.00 ± 0.00 113.7 ± 0.6 215.7 ± 0.6 7.70 ± 0.03 
2.0 0.44 ± 0.01 1.19 ± 0.13 0.33 ± 0.05 30.1 ± 2.2 0.00 ± 0.00 114.0 ± 1.0 216.3 ± 0.6 7.66 ± 0.05 
Initial chlorine (mg/L) 0.37 ± 0.02 2.04 ± 0.07 0.27 ± 0.09 20.4 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 207.0 ± 0.0 7.32 ± 0.03 
0.5 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.09 
1.0 0.28 ± 0.01 1.58 ± 0.14 0.47 ± 0.11 41.2 ± 4.4 0.00 ± 0.00 112.0 ± 0.6 213.7 ± 0.6 7.29 ± 0.05 
1.5 0.26 ± 0.01 1.47 ± 0.03 0.40 ± 0.03 31.6 ± 3.8 0.50 ± 0.05 113.3 ± 0.6 216.0 ± 1.0 7.50 ± 0.06 
2.0 0.25 ± 0.02 1.41 ± 0.05 0.24 ± 0.13 16.3 ± 3.6 1.00 ± 0.04 114.7 ± 0.6 219.3 ± 0.6 7.73 ± 0.03 
Carbon addition (mg C/L) 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.03 
0.25 0.36 ± 0.01 1.80 ± 0.04 0.42 ± 0.01 14.8 ± 1.2 0.00 ± 0.00 112.0 ± 0.0 213.7 ± 0.6 7.15 ± 0.05 
1.00 0.77 ± 0.02 2.17 ± 0.09 0.36 ± 0.01 10.2 ± 6.1 0.00 ± 0.00 112.7 ± 0.6 212.7 ± 1.0 7.09 ± 0.05 
2.00 0.81 ± 0.02 2.81 ± 0.05 0.30 ± 0.01 5.8 ± 0.8 0.00 ± 0.00 114.3 ± 0.6 214.0 ± 1.5 7.13 ± 0.04 
3.00 0.86 ± 0.03 3.67 ± 0.09 0.26 ± 0.01 4.7 ± 3.1 0.00 ± 0.00 115.3 ± 0.6 215.0 ± 2.9 7.30 ± 0.06 
Phosphorus addition (μg P/L) 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.05 
10.0 0.36 ± 0.03 1.49 ± 0.17 0.38 ± 0.02 30.3 ± 0.8 0.00 ± 0.00 112.7 ± 0.6 212.5 ± 0.6 7.36 ± 0.04 
30.0 0.68 ± 0.03 1.26 ± 0.12 0.35 ± 0.01 40.1 ± 0.6 0.00 ± 0.00 113.0 ± 0.0 213.0 ± 0.6 7.40 ± 0.09 
60.0 0.73 ± 0.01 1.22 ± 0.02 0.29 ± 0.01 67.4 ± 2.4 0.00 ± 0.00 113.3 ± 0.6 213.0 ± 0.0 7.40 ± 0.05 
100.0 0.78 ± 0.02 1.18 ± 0.05 0.23 ± 0.03 81.4 ± 0.0 0.00 ± 0.00 113.7 ± 0.6 214.3 ± 0.6 7.20 ± 0.03 
Scenarios
 Physical and chemical indexes
FactorValueTurbidity (NTU)TOC (mg/L)NH4+-N (mg/L)Soluble P (μg/L)Residual Chlorine (mg/L)TDS (mg/L)Conductivity (μS/cm)pH
Velocity (m/s) 0.1 0.25 ± 0.01 1.77 ± 0.10 0.37 ± 0.11 32.8 ± 7.2 0.00 ± 0.00 114.3 ± 0.6 214.3 ± 0.6 7.25 ± 0.02 
0.5 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.04 
1.0 0.33 ± 0.01 1.69 ± 0.08 0.43 ± 0.10 20.7 ± 2.4 0.00 ± 0.00 112.7 ± 0.6 215.0 ± 0.0 7.30 ± 0.05 
1.5 0.52 ± 0.03 1.58 ± 0.05 0.45 ± 0.12 16.4 ± 2.3 0.00 ± 0.00 113.7 ± 0.6 215.7 ± 0.6 7.70 ± 0.03 
2.0 0.44 ± 0.01 1.19 ± 0.13 0.33 ± 0.05 30.1 ± 2.2 0.00 ± 0.00 114.0 ± 1.0 216.3 ± 0.6 7.66 ± 0.05 
Initial chlorine (mg/L) 0.37 ± 0.02 2.04 ± 0.07 0.27 ± 0.09 20.4 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 207.0 ± 0.0 7.32 ± 0.03 
0.5 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.09 
1.0 0.28 ± 0.01 1.58 ± 0.14 0.47 ± 0.11 41.2 ± 4.4 0.00 ± 0.00 112.0 ± 0.6 213.7 ± 0.6 7.29 ± 0.05 
1.5 0.26 ± 0.01 1.47 ± 0.03 0.40 ± 0.03 31.6 ± 3.8 0.50 ± 0.05 113.3 ± 0.6 216.0 ± 1.0 7.50 ± 0.06 
2.0 0.25 ± 0.02 1.41 ± 0.05 0.24 ± 0.13 16.3 ± 3.6 1.00 ± 0.04 114.7 ± 0.6 219.3 ± 0.6 7.73 ± 0.03 
Carbon addition (mg C/L) 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.03 
0.25 0.36 ± 0.01 1.80 ± 0.04 0.42 ± 0.01 14.8 ± 1.2 0.00 ± 0.00 112.0 ± 0.0 213.7 ± 0.6 7.15 ± 0.05 
1.00 0.77 ± 0.02 2.17 ± 0.09 0.36 ± 0.01 10.2 ± 6.1 0.00 ± 0.00 112.7 ± 0.6 212.7 ± 1.0 7.09 ± 0.05 
2.00 0.81 ± 0.02 2.81 ± 0.05 0.30 ± 0.01 5.8 ± 0.8 0.00 ± 0.00 114.3 ± 0.6 214.0 ± 1.5 7.13 ± 0.04 
3.00 0.86 ± 0.03 3.67 ± 0.09 0.26 ± 0.01 4.7 ± 3.1 0.00 ± 0.00 115.3 ± 0.6 215.0 ± 2.9 7.30 ± 0.06 
Phosphorus addition (μg P/L) 0.31 ± 0.03 1.73 ± 0.08 0.45 ± 0.08 26.1 ± 3.1 0.00 ± 0.00 111.3 ± 0.6 211.0 ± 0.0 7.26 ± 0.05 
10.0 0.36 ± 0.03 1.49 ± 0.17 0.38 ± 0.02 30.3 ± 0.8 0.00 ± 0.00 112.7 ± 0.6 212.5 ± 0.6 7.36 ± 0.04 
30.0 0.68 ± 0.03 1.26 ± 0.12 0.35 ± 0.01 40.1 ± 0.6 0.00 ± 0.00 113.0 ± 0.0 213.0 ± 0.6 7.40 ± 0.09 
60.0 0.73 ± 0.01 1.22 ± 0.02 0.29 ± 0.01 67.4 ± 2.4 0.00 ± 0.00 113.3 ± 0.6 213.0 ± 0.0 7.40 ± 0.05 
100.0 0.78 ± 0.02 1.18 ± 0.05 0.23 ± 0.03 81.4 ± 0.0 0.00 ± 0.00 113.7 ± 0.6 214.3 ± 0.6 7.20 ± 0.03 

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