Ala. Admin. Code r. 335-7-2-.09

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

Section 335-7-2-.09 - Maximum Residual Disinfectant Levels And Monitoring Requirements (MRDLs)

(1) The following are the MRDLs:

Disinfectant	MRDL in mg/L
Chlorine	4.0 (as Cl2)
Chloramines	4.0 (as Cl2)
Chlorine Dioxide	0.8 (as ClO2)

(2) Community and NTNC water systems measure for disinfectant residuals.

(a) Systems that use either chlorine or chloramines as a primary or secondary disinfectant must measure the disinfectant levels at the time and location of monthly distribution microbiological samples that are collected to determine compliance with the total coliform rule.

(b) Community, NTNC, and transient noncommunity water systems using chlorine dioxide must measure the chlorine dioxide level daily at the entrance to the distribution system. On each day following a daily sample monitoring result that exceeds the MRDL, the system is required to take three chlorine dioxide distribution system samples. If chlorine dioxide or chloramines are used to maintain a disinfectant residual in the distribution system, or if chlorine is used to maintain a disinfectant residual in the distribution system and there are no disinfection addition points after the entrance to the distribution system, the system must collect three samples as close to the first customer as possible, at intervals of at least six hours. If chlorine is used to maintain a disinfectant residual in the distribution system and there are one or more disinfection addition points after the entrance to the distribution system, the system must collect one sample as close to the first customer as possible, one sample at a location representative of average residence time, and one sample representative of the maximum residence time in the distribution system.

(c) Non-compliance with the chlorine or chloramine MRDL will occur when the running annual average of monthly samples, computed quarterly, exceeds the MCL. When a water system switches between chlorine and chloramines, the average of all results must be used and the disinfectant utilized recorded on all monitoring reports. If a system fails to complete 12 consecutive months' monitoring, compliance with the MCL for the last four-quarter compliance period must be based on an average of the available data.

(d) Acute non-compliance with the chlorine dioxide MRDL will occur when any daily sample taken at the entrance to the distribution system exceeds the MRDL and on the following day one or more of the three samples taken in the distribution system exceed the MRDL or the system fails to collect samples in the distribution system the day following an exceedance of the chlorine dioxide MRDL at the entrance to the distribution system. The system must also take immediate corrective action to lower the level of chlorine dioxide below the MRDL. Nonacute non-compliance with the chlorine dioxide MRDL will occur when any two consecutive daily samples collected at the entrance to the distribution system exceed the MRDL and all distribution system samples collected are below the MRDL or the system fails to collect samples at the entrance to the distribution system the day following an exceedance of the chlorine dioxide MRDL. The system must also take corrective action to lower the level of chlorine dioxide below the MRDL at the point of sampling.

Ala. Admin. Code r. 335-7-2-.09

New Rule: Filed May 2, 2000; effective June 6, 2000. Amended: Filed December 24, 2003; effective January 28, 2004. Amended: Filed November 7, 2005; effective December 12, 2005. Amended: Filed December 18, 2007; effective January 22, 2008. Amended: Filed April 21, 2009; effective May 26, 2009. Amended: Filed August 21, 2012; effective September 25, 2012.

Previous Rule .08 was renumber to .09 per certification filed December 18, 2007; effective January 22, 2008.

Authors: Thomas S. DeLoach, Edgar K. Hughes, Dennis D. Harrison

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