Alabama Administrative Code › Title 335 - ALABAMA DEPARTMENT OF ENVIRONMENTAL MANAGEMENT › WATER DIVISION - WATER SUPPLY PROGRAM › Chapter 335-7-2 - PRIMARY DRINKING WATER STANDARDS › Section 335-7-2-.09 - Maximum Residual Disinfectant Levels And Monitoring Requirements (MRDLs)

Current through Register Vol. 42, No. 9, June 28, 2024
(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.