Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 811 - Requirements For The Operation And Design Of Community Water Systems
Subchapter VII - Treatment
Section NR 811.60 - Ultraviolet (UV) Light

Universal Citation: WI Admin Code ยง NR 811.60

Current through August 26, 2024

Ultraviolet light technology is a primary disinfectant typically used for Cryptosporidium and Giardia lamblia inactivation of both surface water and groundwater supplies. The U.S. Environmental Protection Agency Ultraviolet Disinfection Guidance Manual, EPA 815-D-03-007 dated June 2003, which is incorporated by reference, shall be used as the basis for the validation, design, and operation of all ultraviolet light systems. Ultraviolet light disinfection systems shall meet the requirements of ANSI/NSF standard 55 Class A dated August 13, 2021, which is incorporated by reference. Water systems designed to provide ultraviolet light disinfection shall comply with all of the following:

Note: A copy of the U.S. Environmental Protection Agency Ultraviolet Disinfection Guidance Manual, EPA 815-D-03-007 dated June 2003 is available for inspection at the Legislative Reference Bureau and may be obtained for personal use from the U.S. Environmental Protection Agency, epa.gov. A copy of ANSI/NSF standard 55 Class A dated August 13, 2021 is available for inspection at the Legislative Reference Bureau and may be obtained for personal use from NSF International, nsf.org.

(1) TREATMENT OBJECTIVES. The target pathogen and the target log inactivation shall be used to identify the corresponding required UV dose.

(2) WATER QUALITY CONSIDERATIONS AND PRETREATMENT. In order to provide adequate disinfection treatment, some water sources may need treatment prior to ultraviolet light disinfection. UV disinfection of surface water sources shall follow filtration. Department approval for specific pretreatment requirements is required if any of the parameters in Table No. 3 are exceeded in the water to be treated by ultraviolet light.

Table No. 3

Inlet Water Quality Parameters
Parameter Maximum or Range
UV 254 mm Absorption 0.155 cm-1
Dissolved Iron 0.3 mg/l
Dissolved Manganese 0.05 mg/l
Hardness 120 mg/l
Hydrogen Sulfide Non-detectable odor
Fouling Microorganisms None
pH 6.5 to 9.5
Suspended Solids 10 mg/l
Turbidity 1.0 NTU
Total Coliform 1,000/100 ML

(3) VALIDATION. Ultraviolet light treatment devices shall be validated by a third party entity in accordance with the U.S. Environmental Protection Agency Ultraviolet Disinfection Guidance Manual EPA 815-D-03-007 dated June 2003 or another validation standard as approved by the department. The final installation shall be equivalent or more protective than the validation testing installation.

Note: A copy of the U.S. Environmental Protection Agency Ultraviolet Disinfection Guidance Manual, EPA 815-D-03-007 dated June 2003 is available for inspection at the Legislative Reference Bureau and may be obtained for personal use from the U.S. Environmental Protection Agency, www.epa.gov.

(4) MATERIALS. The ultraviolet light housing shall be type 304 or type 316L stainless steel.

(5) DESIGN.

(a) The ultraviolet treatment device shall be designed to provide a UV light dose of a minimum of 40 millijoules per square centimeter (mJ/cm 2) and shall also deliver the target dose as prescribed by s. NR 810.62 by operating within the validated operating conditions for that particular unit.

(b) The ultraviolet treatment assemblies shall be designed to allow visual observation, cleaning, and replacement of the lamp, lamp sleeves, and sensor window or lens.

(c) All ultraviolet lamps shall be housed in type 214 quartz sleeves.

(d) Where in-situ cleaning of the lamp sleeves is proposed, the design shall protect the potable water from cleaning solutions.
1. When off-line chemical cleaning systems are used, the UV enclosure shall be removed from service, drained, flushed with an NSF/ANSI Standard 60 certified solution, drained, and rinsed before being placed back in service.

2. On-line systems that use wipers or brushes may use chemical solutions provided they are NSF/ANSI Standard 60 certified.

(e) An automatic shutdown valve shall be installed in the water supply line prior to the ultraviolet treatment device. When power is not provided the valve shall be in the closed position.

(f) The inlet and outlet piping to the reactors shall assure that the UV dose delivery is equal to or greater than the UV dose delivered during validation.

(g) The flow to each reactor shall be equally distributed and metered.

(h) Valves shall be provided to allow isolating and removing from service each UV reactor.

(i) Reactors shall be provided with air relief and pressure control valves per manufacturer requirements.

(j) UV transmittance (UVT) analyzers shall be provided if UVT is part of the dose monitoring strategy.

(k) Sample taps shall be provided downstream of each reactor.

(6) CONTROLS.

(a) A delay mechanism shall be installed to provide sufficient lamp warm-up prior to allowing water to flow from the ultraviolet treatment unit.

(b) An automatic shutdown shall be designed to activate the shutdown valve in cases where the ultraviolet light dose falls below the approved design dose or outside of the validated specifications.

(c) Where the UV is necessary to provide adequate disinfection, 99.9 percent of the volume of water passing through the reactors shall receive UV light treatment within the validated specifications. This may require the use of a bleed line from the reactors during lamp warm up and cool down periods.

(7) BACK-UP. A sufficient number of parallel ultraviolet treatment devices shall be installed to insure that adequate disinfection is provided when one unit is out of service. The department may approve an alternate method that provides adequate disinfection.

(8) TREATMENT BYPASS. No bypass of the ultraviolet treatment process may be installed unless an alternate method of providing adequate disinfection is provided.

(9) MONITORING. Continuous monitoring of UV intensity as measured by a UV sensor, flow rate, and lamp status shall be provided for each ultraviolet treatment device to demonstrate that the device is operating within the range of conditions for which it was validated for the required UV dose. Each monitoring device shall be connected to the control system for the shutdown valve for the respective ultraviolet treatment device. The department may require additional monitoring devices and control systems if any of the water quality characteristics listed in Table No. 3 are representative of the water to be treated and may impair the effectiveness of the ultraviolet light treatment.

(10) CHLORINE ADDITION. Unless waived by the department, chlorine shall be added after UV for virus inactivation and to provide a residual in the distribution system.

(11) PILOT TESTING. Pilot testing is generally not required unless factors such as fouling or aging cannot be predicted by bench-scale testing.

Disclaimer: These regulations may not be the most recent version. Wisconsin may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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