2.7. Data collection and statistical analysis
Chlorine and monochloramine disinfectant suspension tests
were performed against six identified bacterial isolates and mean
cfu mL1 ± SD were calculated for each contact time and concen-
tration. Cell counts were log10 transformed before plotting. Statis-
tical analysis was performed using Minitab version 17. MIC data
were compared against zones of inhibition of hypochlorite assays
using the non-parametric Spearman correlation test.
3. Results
3.1. Water conditions
Minimum free chlorine and total chlorine concentrations were
found to be 0.01 mg L1 and 0.1 mg L1
, respectively at the time of
collection of samples. Thirty-eight samples were collected from
buildings having a cold-water storage tank, or cistern, within the
building, while 14 samples were collected from the buildings with
completely closed supply lines (Table 1). Water storage tanks are
inspected once in six months and disinfected generally on an
annual basis in these buildings. All reported drinking-water quality
values were within permissible concentrations at time of sampling;
however, disinfection conditions declined at point of use.
3.2. Bacterial communities in drinking water
Approximately 80% of water samples tested positively for at
least one bacterium (per 100 mL water). The frequency of positive
detections was similar between building types; however, cistern-
related samples had greater abundances of bacteria: averaging 3.4
colony forming units (CFU) from cistern-systems, versus 1.4 CFU in
buildings without cisterns.
2.7. Data collection and statistical analysisChlorine and monochloramine disinfectant suspension testswere performed against six identified bacterial isolates and meancfu mL1 ± SD were calculated for each contact time and concen-tration. Cell counts were log10 transformed before plotting. Statis-tical analysis was performed using Minitab version 17. MIC datawere compared against zones of inhibition of hypochlorite assaysusing the non-parametric Spearman correlation test.3. Results3.1. Water conditionsMinimum free chlorine and total chlorine concentrations werefound to be 0.01 mg L1 and 0.1 mg L1, respectively at the time ofcollection of samples. Thirty-eight samples were collected frombuildings having a cold-water storage tank, or cistern, within thebuilding, while 14 samples were collected from the buildings withcompletely closed supply lines (Table 1). Water storage tanks areinspected once in six months and disinfected generally on anannual basis in these buildings. All reported drinking-water qualityvalues were within permissible concentrations at time of sampling;however, disinfection conditions declined at point of use.3.2. Bacterial communities in drinking waterApproximately 80% of water samples tested positively for atleast one bacterium (per 100 mL water). The frequency of positivedetections was similar between building types; however, cistern-related samples had greater abundances of bacteria: averaging 3.4colony forming units (CFU) from cistern-systems, versus 1.4 CFU inbuildings without cisterns.
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