A. All
public water systems using surface water or GWUDISW as its source of water
supply and serving at least 10,000 individuals shall perform a disinfection
profile of its disinfection practice on a continuous, daily basis. All public
water systems using surface water or GWUDISW as its source of water supply and
serving less than 10,000 individuals shall perform a disinfection profile of
its disinfection practice on a continuous, weekly basis.
1. Any system that meets the criteria of
Subsection A of this Section shall perform monitoring on each day [or, in the
case of systems serving less than 10,000 individuals, once each week (on the
same calendar day)] of operation to determine the total logs of inactivation of
Giardia lamblia cysts, based upon the
CT99.9 (3-Log) values in Appendix E of the SWTR Guidance
Manual, as appropriate, through the entire treatment plant. Any system that
uses chloramines, ozone, or chlorine dioxide for primary disinfection shall
additionally calculate the total logs of inactivation of viruses for each day
of operation, based upon the CT99.99 (4-Log) values in
Appendix E of the SWTR Guidance Manual. Systems with more than one point of
disinfectant application shall conduct monitoring for each disinfection
segment. The following parameters shall be monitored:
a. the temperature of the disinfected water
at each disinfectant residual concentration sampling point during peak hourly
flow;
b. if the system uses free
chlorine, the pH of the disinfected water at each free chlorine residual
disinfectant concentration sampling point during peak hourly flow;
c. the disinfectant contact time(s) ("T") at
peak hourly flow at each residual disinfectant concentration sampling point
using approved mathematical computations as outlined in Appendix C of the SWTR
Guidance Manual or using the system's specific curve which is graphed as
"Detention Time (T10 in minutes) vs. Flow (in MGD)" (as
per the example shown in Figure C-4 of Appendix C of the SWTR Guidance Manual)
to determine the contact time based upon flow, subject to the following
additional requirements:
i. for systems
serving 3,300 persons or more, the disinfectant contact time(s) is to be
determined through the use of data developed from actual tracer studies
conducted on the system (see Paragraph 1119.C.1). [Theoretical contact time(s)
using baffling factors are not to be used for systems serving 3,300 persons or
more.];
ii. for systems serving
less than 3,300 persons, the disinfectant contact time(s) may be estimated
through the use of data developed in a theoretical manner by determining
pipeline capacities, treatment basin capacities, clearwell storage capacity,
storage tank capacities, etc., and applying the appropriate geometry and
baffling factor(s) (see Paragraph 1119.C.2)
;d. the residual disinfectant
concentration(s) ("C") of the water before or at the first customer during peak
hourly flow;
(NOTE: If the treatment plant uses its own finished water
for potable purposes, the first customer may be the treatment plant itself.);
and
e. if the system uses
more than one point of disinfectant application before the first customer, the
system must determine the parameters identified in Subparagraphs a-d of this
Paragraph for each individual disinfection segment immediately prior to the
next point of disinfectant application during peak hourly flow so that a
cumulative CT value can be determined before the treated water reaches the
first customer.
(NOTE: If the treatment plant uses its own finished water
for potable purposes, the first customer may be the treatment plant
itself.)
