This powerpoint presentation begins by providing a brief overview of transient pressures from unsteady flow, the source of external contamination, and AwwaRF Project #4152, "Managing Distribution System Pressures to Protect Water Quality." Topics presented include: intrusion algorithm; identify intrusion locations; development of QMRA; virus transport without a disinfectant residual; risk model iterations; risk management options; impact of external virus concentration; norovirus infectivity; negative pressure duration; sensitivity analysis; and, the importance of axial dispersion - research needed. A case study of an Illinois water system is presented, along with types of surge mitigation including hydropneumatic tanks, and comparison of norovirus and rotavirus risk. Conclusions indicate the following: sufficient information is available to model risks from intrusion,
this study examined just one set of scenarios; the coincidence of virus consumption and the duration of the negative pressure event are the most critical parameters driving risk; maintenance of a free chlorine residual (>0.2 mg/L) provides
a protective barrier against low-level intrusions; a monochloramine residual (0.5 mg/L) does not have a big impact on
Norovirus risk reduction due to the highly infectious nature of the
viruses; external virus concentrations, mixing, or orifice size had little impact
of risk; pressure management to reduce the extent of negative pressure
events is particularly important in chloraminated systems; axial dispersion of microbes (through interactions with biofilms) will
likely have an important impact on risk and should be studied. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.4 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 30 |
| Published : | 11/01/2009 |
