The goals of this powerpoint presentation were to:
assess the impact of dynamic water quality
conditions on microorganism inactivation;
identify the factors that affect the
maintenance of a secondary disinfectant
residual, including the benefits of maintaining
various target levels;
determine the ability of a disinfectant residual
entering the distribution system to inactivate
microorganisms that may be encountered; and,
assess the ability of a disinfectant residual to
serve as an indicator for distribution system
microbial integrity. "Impact of Distribution System Water
Quality on Disinfection Efficacy" (AwwaRF / USEPA Project 2771) includes the following
four phases:
revisit existing information in the form of a literature review,
a modeling effort,
utility survey and
historical water quality data analysis;
determine inactivation potential (bench scale);
evaluate the impact of acute and chronic
water quality changes on disinfection efficacy; and,
examine analytical limitations of secondary
disinfectants (organochloramines). The goal of annular reactor testing is to
assess efficacy of free chlorine and
monochloramine to inactivate suspended
and attached microorganisms.
The objectives of annular reactor testing are to:
determine target disinfectant residual to
preserve water quality during simulated
microbial contamination;
evaluate the impact of pipe material and
water age on water quality, disinfection
efficacy and biofilm production; and,
examine the usefulness of flushing and
increased disinfection to remediate
microbial contaminations. The experimental plan is presented, along with the results of the disinfection phases and pulse of E. coli. Presentation summary includes the following:
Acclimation phase -- the upstream reactor
of each train had the highest biofilm
HPCs, followed by the middle reactor,
and then the downstream reactor;
Low-level disinfection phase -- biofilm HPCs
did not increase in the upstream reactors
(disinfectant residual), but increased in
the downstream reactors;
High-level disinfection phase -- suspended
HPCs at train effluent were lower;
little effect on biofilm HPCs (increase
when compared with acclimation phase); log reduction of suspended and biofilm
HPCs was higher in the chlorinated trains
than in the chloraminated trains with
comparable Ct values;
monochloramine was more efficient than
free chlorine against biofilm coliforms, but
less efficient than free chlorine against
suspended coliforms in the CI reactors;
and, biochemical assays indicated that
coliforms isolated from the bulk liquid
differed from those isolated from the
biofilm of the same reactor. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.2 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 26 |
| Published : | 11/01/2008 |
