Ala. Admin. Code r. 335-7-6-.11

Current through Register Vol. 42, No. 12, September 30, 2024

Section 335-7-6-.11 - Disinfection Profiling And Benchmarking

(1) Systems must conduct disinfection profiling for all surface water sources and sources that have been designated as ground water under the influence of surface water that does not comply with one of the following must conduct disinfection profiling for up to three years beginning not later than March 16, 2000.

(a) The water system has conducted simultaneous monitoring of water in the distribution system for HAA5 and TTHM that meets the monitoring sample number and location requirements for TTHM. The arithmetic average of all results for the last four quarters of monitoring completed by March 16, 1999 is not greater than .064 mg/L for TTHM and not greater than .048 mg/L for HAA5.

(b) The water system has conducted monitoring in accordance with the Information Collection Rule (ICR) and the arithmetic average of all results for the last four quarters of monitoring for TTHM is not greater than .064 mg/L and monitoring for HAA5 is not greater than .048 mg/L.

(c) The water system confirms a minimum CT using chlorine of no less than 70 is available between the filter effluent and the first customer and submits graphs of filtered water turbidity and probability profiles that demonstrate that the maximum turbidity of water each day from each water treatment plant filter determined every fifteen minutes for the last 12 consecutive months is no greater than 0.1 NTU in 95% of all samples analyzed and no individual turbidity determined on water from any filter exceeds 0.3 NTU.

(2) Any system required to conduct a disinfection profile must daily, during peak hourly flow, for a period of 12 consecutive calendar months:

(a) Determine the temperature, pH and residual disinfectant concentration (C) of water at a point just before each disinfectant is added and at or before the first customer,

(b) Determine the disinfectant contact time (T) in each disinfection segment before the first customer,

(c) Determine the total CT (CT_Total) of water before the first customer by adding the individual CT determined for each disinfection treatment segment before the first customer,

(d) Calculate the total Giardia lamblia and virus inactivation ratio by dividing the calculated CT (CT_calc) by the CT required for 99.9% inactivation (CT₉₉.₉) for each successive disinfection segment,

(e) Determine the total logs of Giardia lamblia and virus inactivation by multiplying the sum of the Giardia lamblia and virus inactivation ratios (CT_calc /CT₉₉.₉) for each successive disinfection segment by 3 (3 x Sum (CT_calc /CT₉₉.₉)), and

(f) Retain the disinfection profile data in graphic form for onsite review by the Department and/or for submittal to the Department for review if requested.

(3) Any system required to develop a disinfection profile that decides to make a significant change or modification to its disinfection practice must contact the Department prior to making such change. Significant changes or modifications to disinfection practice include changes to the point of disinfection; disinfectant(s) used in the treatment plant; the disinfection process; or any other modifications identified by the Department as a significant change to disinfection.

(4) Any system that is proposing to change or alter its disinfection practice must submit a description of the proposed change, the disinfection profile (graphically), disinfection benchmark and an analysis of how the proposed changes will affect the current level of disinfection.

(5) Benchmarking is the process of defining the lowest Giardia lamblia inactivation value.

(a) For systems with one year of profiling data the disinfection benchmark is the lowest of 12 monthly average Giardia lamblia inactivation values.

(b) For systems with more than one year of profiling data the disinfection benchmark is the average of the lowest monthly Giardia lamblia inactivation average value in each year divided by the number of years profile data is collected.

(6) When determining the Giardia lamblia or virus inactivation, systems must use a method approved by the Department or EPA.

Ala. Admin. Code r. 335-7-6-.11

New Rule: Filed May 2, 2000; effective June 6, 2000. Amended: Filed April 25, 2003; effective May 30, 2003. Repealed and New Rule: Filed November 7, 2005; effective December 12, 2005. Amended: Filed December 18, 2007; Effective January 22, 2008.

Authors: Edgar K. Hughes, Dennis D. Harrison

Statutory Authority:Code of Ala. 1975, §§ 22-23-33, 22-23-49, 22-22A-5, 22-22A-6.