La. Admin. Code tit. 51 § XII-1119

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

Section XII-1119 - Disinfection Performance Standards

A. All surface water or GWUDISW utilized by a supplier shall be provided with continuous disinfection treatment sufficient to ensure that the total treatment process provides inactivation of Giardia cysts and viruses, in conjunction with the removals obtained through filtration, to meet the reduction requirements specified in §1113 of this Chapter.

B. Except as otherwise specified by this Section and Chapter, disinfection treatment shall comply with the minimum standards and requirements set forth in §355. A and §357 of this Part.

C. Determination of Inactivation by Disinfection. Minimum disinfection requirements shall be determined by DHH on a case-by-case basis but shall not be less than those required in Table 2 of §1115. B.1 of this Chapter. The desired level of inactivation shall be determined by the calculation of CT values; residual disinfectant concentration ("C") times the contact times ("T") when the pipe or vessel is in operation. Disinfectant contact time shall be determined by tracer studies.

1. The T₁₀ value will be used as the detention time for calculating CTs. T₁₀ is the detention time at which 90 percent of the flow passing through a vessel is retained within the vessel. Systems conducting tracer studies shall submit a plan to DHH for review and approval prior to the study being conducted. The plan shall identify how the study will be conducted, the tracer to be used, flow rates, etc. The plan shall also identify who will actually conduct the study. Tracer studies are to be conducted according to protocol found in standard engineering texts (such as Levenspiel), or the methodology in EPA's Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems using Surface Water Sources, March 1991 Edition (SWTR Guidance Manual).

2. On a case-by-case basis, alternate empirical methods of calculating T₁₀ as outlined in the SWTR Guidance Manual may be accepted for vessels with geometry and baffling conditions analogous to basins on which tracer studies have been conducted and results have been published in the SWTR Guidance Manual or the literature.

3. Additional tracer studies shall be conducted by the supplier whenever modifications are made which may impact flow distribution, contact time, or disinfectant distribution.

4. CT values utilized in this evaluation shall be those reported in the SWTR Guidance Manual.

La. Admin. Code tit. 51, § XII-1119

Promulgated by the Department of Health and Hospitals, Office of Public Health, LR 28:1341 (June 2002), amended LR 28:2522 (December 2002), LR 35:1242 (July 2009)/, Amended LR 42412 (3/1/2016).

AUTHORITY NOTE: Promulgated in accordance with R.S. 40:4(A)(8)(13) and 40:5(2)(3)(5)(6)(17)(20).