La. Admin. Code tit. 51 § XII-1127

Current through Register Vol. 50, No. 11, November 20, 2024

Section XII-1127 - Disinfection Profiling

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 CT_99.9 (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 CT_99.99 (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.)

B. In addition, systems subject to the requirements of Subsection A of this Section shall compute their daily or weekly (dependent upon system size, see Subsection A of this Section) total logs of inactivation utilizing a computer spread sheet format/formulas approved by DHH. The system shall retain printed disinfection profile data as daily or weekly (dependent upon system size, see Subsection A of this Section) individual spreadsheets (containing the monitoring data, CT computation, and total log inactivation data) and in monthly/yearly graphical profile form for review as part of sanitary surveys conducted by DHH.

La. Admin. Code tit. 51, § XII-1127

Promulgated by the Department of Health and Hospitals, Office of Public Health, LR 28:2524 (December 2002), amended LR 35:1243 (July 2009).

AUTHORITY NOTE: Promulgated in accordance with R.S. 40:4 (A)(8) and R.S. 40: 5 (2)(3)(5)(6)(17)(20).