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Contrary to sector A, coliform bacteria was detected in sector B after 18 hours of stagnation (Table 9). However, coliform bacteria was measured only in the steel pipe segment and the amount was 7.6 times lower to the one obtained in the same pipe material in sector C (scenario 1) and 4 times lower than the amount measured in sector B (scenario 1). The decline of bacteria levels may be attributed to the perfect mixing at cross junction. Since the initial level of disinfectant (0.88 mg/L) was higher in this sector than those measured in sectors B and C in scenario 1 (0.37 and 0.53 mg/L), the sector could maintain free chlorine concentration above 0.2 mg/L in PVC and HDPE pipe segment and had less coliform occurrence. However, since chlorine decay is faster in steel pipe, chlorine reached its minimum value (0 mg/L) only in this segment. However, only 10 CFU/mL was recorded. E. coli bacteria analysis was negative in samples collected in all the system. Water quality parameters are presented in Table 10.

Table 9

Total coliforms level in sector B

Sampling pointTotal coliform Sample 1 (CFU)Total coliform Sample 2 (CFU)Total coliform Sample 3 (CFU)MeanStandard deviationTotal coliforms (CFU)E. coli (CFU)
PVC pipe 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
HDP pipe 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
Steel pipe 12 10 10 2.0 10 0.0 
Sampling pointTotal coliform Sample 1 (CFU)Total coliform Sample 2 (CFU)Total coliform Sample 3 (CFU)MeanStandard deviationTotal coliforms (CFU)E. coli (CFU)
PVC pipe 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
HDP pipe 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
Steel pipe 12 10 10 2.0 10 0.0 
Table 10

Water quality parameters for samples from different pipe material in sector B for scenario 2

Sampling pointChlorine (mg/L)pHTemperature (°C)Turbidity (NTU)TOC (mg/L)
Initial water quality characteristics 
 0.88 17.5 1.2 0.52 
Final water quality characteristics 
PVC pipe 0.25 18.8 1.2 1.04 
HDP pipe 0.35 19.0 1.3 2.40 
Steel pipe 0.00 18.9 1.5 1.35 
Sampling pointChlorine (mg/L)pHTemperature (°C)Turbidity (NTU)TOC (mg/L)
Initial water quality characteristics 
 0.88 17.5 1.2 0.52 
Final water quality characteristics 
PVC pipe 0.25 18.8 1.2 1.04 
HDP pipe 0.35 19.0 1.3 2.40 
Steel pipe 0.00 18.9 1.5 1.35 

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