TABLE 1.
Sample names and descriptions of water quality for each system
| System and sample | Sample description | pH | Turbidity (NTU)a | DOC (mg/liter)b | NH2Cl (mg/liter)c | Nitrite as N (mg/liter) | Nitrate as N (mg/liter) | AOB presenced | AOA presenced | % viable cellse | Total no. of cells/ml |
|---|---|---|---|---|---|---|---|---|---|---|---|
| WA system | |||||||||||
| Source water | Raw, untreated inlet | 7.6 | 0.49 | 1.70 | <0.1 | <0.003 | 0.049 | − | +++ | 58.8 | 1.66E+06 |
| Postdisinfection | Posttreatment | 8.2 | 0.83 | 2.10 | 3.53 | 0.004 | 0.036 | − | + | 3.4 | 2.72E+06 |
| WA-1 inlet | Storage tank inlet | 8.3 | 0.85 | 2.20 | 3.59 | 0.007 | 0.036 | + | ++ | 3.9 | 2.64E+06 |
| WA-1 outlet | Storage tank outlet | 8.2 | 0.74 | 2.20 | 3.34 | 0.004 | 0.045 | + | +++ | 3.9 | 2.76E+06 |
| WA-2 tank | Storage tank | 8.2 | 1.01 | 2.50 | 3.11 | 0.004 | 0.042 | + | ++ | 4.5 | 2.78E+06 |
| WA-3 inlet | Storage tank inlet | 8.4 | 0.35 | 2.20 | 2.84 | 0.005 | 0.047 | + | ++ | 2.7 | 2.89E+06 |
| WA-3 outlet | Storage tank outlet | 8.4 | 0.33 | 2.30 | 2.52 | 0.006 | 0.053 | ++ | ++ | 3.8 | 2.00E+06 |
| WA-4 CT | Customer tap | 8.3 | 0.24 | 2.10 | 2.46 | 0.413 | 0.303 | +++ | + | 3.3 | 2.52E+06 |
| SA system | |||||||||||
| Source water | Raw, untreated inlet | 7.4 | 77.0 | 12.6 | <0.1 | 0.012 | 0.184 | +++ | +++ | 58.1 | 1.98E+07 |
| Postdisinfection | Posttreatment | 8.4 | 0.40 | 5.40 | 4.7 | 0.013 | 0.253 | + | +++ | 13.6 | 4.83E+05 |
| 1.5 km postdisinfection | 1.5-km point postdisinfection | 8.2 | 0.20 | 5.20 | 3.6 | 0.009 | 0.269 | + | ++ | 4.9 | 3.08E+05 |
| SA-1 CT | Customer tap | 8.9 | 0.10 | 5.00 | 1.0 | 0.059 | 0.600 | + | +++ | 11.5 | 1.24E+05 |
| SA-2 tank | Storage tank | 8.3 | 0.20 | 5.50 | 1.4 | 0.054 | 0.488 | + | ++ | 5.1 | 2.14E+05 |
| SA-2 CT | Customer tap | 7.9 | 0.20 | 4.90 | <0.1 | 0.009 | 1.150 | ++ | ++ | 50.0 | 6.90E+05 |
| SA-3 tank | Storage tank | 8.5 | 0.60 | 5.80 | 2.4 | 0.021 | 0.338 | + | − | 2.3 | 3.59E+05 |
| SA-4 tank | Storage tank | 8.5 | 8.00 | 5.50 | 2.4 | 0.026 | 0.396 | + | +++ | 5.3 | 3.23E+05 |
| SA-5 CT | Customer tap | 9.0 | 0.30 | 4.10 | 2.1 | 0.022 | 0.464 | ++ | +++ | 51.6 | 3.80E+04 |
a
NTU, nephelometric turbidity unit.
b
DOC, dissolved organic carbon.
c
Monochloramine.
d
The presence of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (A) was semiquantified using the height of the DNA melting peaks. The standard was nominally scored as high (+++), with weak peaks scored as +, peaks between the weak and control levels as ++, and negative PCR results as −.
e
See Materials and Methods for the method of calculation.