Section 811.60. Ultraviolet (UV) Light.

  Ultraviolet (UV) light technology is a primary disinfectant typically used for Cryptosporidium and Giardia lamblia inactivation of both surface water and groundwater supplies. The USEPA Ultraviolet Light Disinfection Guidance Manual (USEPA UVDGM) shall be used as the basis for the validation, design and operation of all UV systems. Water systems which are designed to provide ultraviolet light disinfection shall comply with the following:

(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. - See PDF for table

(3)   Validation. Ultraviolet light treatment devices shall be validated by a third party entity in accordance with the USEPA Ultraviolet Light Disinfection Guidance Manual (USEPA UVDGM) or another validation standard as approved by the department.

(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 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.

History: CR 09-073 : cr. Register November 2010 No. 659 , eff. 12-1-10.