TABLE 3.
E. coli detected in outflow from two flow chamber biofilm experiments by using Colilert Quanti-Tray MPNa
| Biofilm designation | Outflow sample day | Time (days) after final bacterial inoculation | Biofilm conditions | No. of E. coli or coliform cells/100 ml of outflow |
|---|---|---|---|---|
| 3 | 6 | 1 | Control (no E. coli added) | <1 |
| 3 | 7 | 2 | Control | <1 |
| 3 | 8 | 3 | Control | 3 |
| 3 | 9 | 4 | Control | 1 |
| 3 | 10 | 5 | Control | <1 |
| 8 | 11 | 6 | 1 CT ClOH (on day 14) | >201b |
| 11 | 2 ppm NH2Cl residual | <1 | ||
| 12 | 4 ppm NH2Cl residual | <1 | ||
| 7 | 12 | 7 | Control | 254 |
| 8 | 1 CT ClOH (on day 14) | 4,425 | ||
| 7 | 14 | 9c | Control | 750 |
| 8 | 1 CT ClOH (on day 14) | 504 | ||
| 10 | 4 ppm NH2Cl for 155 min (on day 14) | 4,725 |
a
Bacteria were inoculated once a day during the first 5 days of the 2-week incubation period.
b
The E. coli concentrations in the sample exceeded the upper detection limit of the Quanti-Tray. Subsequent samples were diluted before incubation with the Colilert medium.
c
Samples collected after chlorine and monochloramine exposures.