The first generation of mechanistic models of bacterial regrowth in distribution systems (DS)
provides insight into cause and effect relationships. However, the state of knowledge about the
processes included in these models is insufficient to warrant deterministic predictions. Even if
the process descriptions are reasonable, the uncertainty in values of key system constants limits
predictions of bacterial growth. A new mechanistic model was developed to incorporate the
accepted knowledge of physical, chemical and biological processes with the hydraulic features in order to capture the unsteady state behavior of the DS. Sensitivity testing showed that
rate constants for chlorine decay reactions in bulk water and on the pipe wall as well as the
maximum growth rate constant of attached bacteria are the most important parameters. A simple
hypothetical network was used to test evaluate the effects of uncertainty in these three system
constants by running 100 Monte Carlo simulations. Cumulative probability plots (CPP) showed
that a wide range of predictions for concentrations of bacteria and chlorine in bulk water at
various nodes in the DS. The magnitude of these concentrations and the range of values were
greatly affected by water residence time to each node. Once the chlorine residual is depleted,
bacterial growth is mainly influenced by the amount of substrate available. However, high
values of maximum growth rate coefficient of attached bacteria and bulk and wall decay
coefficients did not necessarily lead to the maximum bacterial growth at a given sampling site. Includes 18 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 300 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 9 |
| Published : | 06/17/2004 |
