SECTION 252:656-21-3. Ultraviolet radiation disinfection systems (UV systems)

(a)   Use of UV for disinfection. Ultraviolet radiation disinfection systems ("UV systems") shall only be used to disinfect high quality effluent having:

(1)   at least 65% ultraviolet radiation transmittance at 254 nanometers wave length; and

(2)   BOD and suspended solids concentrations no greater than 30 mg/l at any time.

(b)   Sizing and UV dosage. The following are the sizing and dosage requirements for UV systems:

(1)   A wastewater treatment system utilizing a UV system to comply with disinfection requirements in an OPDES permit and/or to disinfect Category 3 reclaimed water shall be:

(A)   sized using the:

(i)   design peak hourly flow for OPDES permits; or

(ii)   sized using the anticipated design flow for Category 3 reclaimed water; and

(B)   designed to deliver a UV dosage of no less than 30 mJ/cm (30,000 µW • sec/cm) based on MS-2 phage inactivation after adjustments for maximum tube fouling, lamp output reduction after 8,760 hours of operation, and other energy absorption losses.

(2)   A wastewater treatment system utilizing a UV system to disinfect Category 2 reclaimed water shall be:

(A)   sized using the anticipated design flow; and

(B)   designed to deliver a UV dosage of no less than 210 mJ/cm (210,000 µW • sec/cm) after adjustments for maximum tube fouling, lamp output reduction after 8,760 hours of operation, and other energy absorption losses. This dosage is to be delivered assuming a UV transmittance of 55%. [See 252:656-27-3(a)(6) (relating to log removal requirements).]

(3)   A wastewater treatment system utilizing both chlorination and UV disinfection to obtain required log removal for Category 2 reclaimed water shall be:

(A)   sized using the anticipated design flow; and

(B)   designed to deliver a UV dosage of no less than 40 mJ/cm (40,000 µW • sec/cm) after adjustments for maximum tube fouling, lamp output reduction after 8,760 hours of operation, and other energy absorption losses. This dosage is to be delivered assuming a UV transmittance of 55%. [See 252:656-27-3(a)(6) (relating to log removal requirements).]

(c)   Control system. All UV systems shall have:

(1)   controls capable of maintaining the UV dosage proportional to the wastewater flow through the system,

(2)   the capacity to determine the actual wastewater flow going through the UV system,

(3)   the capability to measure UV transmittance manually or automatically, and

(4)   indicators for:

(A)   UV intensity,

(B)   lamp and ballast panel temperatures,

(C)   power (on/off),

(D)   lamp output,

(E)   elapsed time of lamp usage,

(F)   all alarms, and

(G)   metering power.

(d)   Maintenance. UV systems shall:

(1)   be equipped with a drain; and

(2)   be designed so that equipment can be isolated for maintenance.

(e)   Safety equipment. Proper safety equipment (i.e., goggles, clothing, etc.) shall be provided to protect persons from UV radiation.

(f)   Lamps and ballasts. The UV system shall be constructed so that its lamps and ballasts are accessible.

(g)   Availability of spare parts. The minimum number of spare parts necessary to ensure continuous disinfection during maintenance and repair shall be available at the facility. The spare parts required shall include lamps, ballasts, quartz sleeves, sleeve wiper rings, cleaning chemicals, and any other items required by the manufacturer, owner, and engineer.

(h)   Monitoring and alarms. The design engineer shall be responsible for specifying what the monitoring and alarm requirements need to be in order to assure continuous disinfection in compliance with the limits in the permit.

(i)   Cleaning and maintenance. UV systems shall be routinely and properly maintained to assure disinfection requirements are continuously met.

(j)   Additional requirements when using UV disinfection for reclaimed water. For systems supplying Category 2 reclaimed water, filtration is required as part of the disinfection process. The particle removal system shall meet the redundancy requirements in 252:656-21-1(e) and be designed to handle the anticipated design flow.

(1)   The hydraulic capacity of the inactivation step shall be sized to convey the anticipated design flow.

(2)   An independent, third party bioassay based on MS-2 phage shall be used to verify the design UV requirements. Only bioassay methods described in this Section will be approved by DEQ. The UV system shall deliver the target dosage based on the equipment's derating factors described below. Before design approval, the bioassay reports for the specific equipment being considered shall be approved and on file with the DEQ, with specific sections marked confidential, if applicable. If needed, the UV equipment manufacturer shall verify that the scale up or scale down factor utilized in the design is appropriate for the specific application under consideration. Without exception, the basis for verifying the design delivered UV dose meets the requirements of this Section shall be an independent third party bioassay, signed and sealed by a professional engineer licensed by the State of Oklahoma.

(A)   The bioassay procedure shall conform to an applicableprotocol in the:

(i)   National Water Research Institute's Ultraviolet Disinfection Guidelines for Drinking Water and Water Reuse (August 2012);

(ii)   NSF International, The Public Health and Safety Company, 40 CFR 35.6450 Environmental Technology Verification Protocol (October 2002);

(iii)   USEPA Design Manual: Municipal Wastewater Disinfection, EPA/625/1-86/021 (1986); or

(iv)   USEPA Ultraviolet Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule, 815-R-06-007 (November 2006).

(B)   The design equations provided by the validation report shall be developed in accordance with a standardized bioassay protocol approved by DEQ.

[Source: Added at 17 Ok Reg 1140, eff 6-1-00; Amended at 23 Ok Reg 937, eff 6-15-06; Added at 28 Ok Reg 1282, eff 7-1-11; Amended at 31 Ok Reg 1315, eff 9-12-14]