Virginia Administrative Code › Title 12 - HEALTH › Agency 5 - DEPARTMENT OF HEALTH › Chapter 590 - WATERWORKS REGULATIONS › Section 12VAC5-590-1005 - Ultraviolet light (UV) disinfection

Current through Register Vol. 40, No. 24, July 15, 2024
A. All UV reactors shall conform to
				NSF/ANSI/CAN standards.
B. Each
				reactor train shall be equipped with an individual flow meter or a single flow
				meter in conjunction with differential pressure sensors in each treatment
				train. Reactors shall be sized to treat the design flow.
C. Hydraulic design shall ensure that lamps
				are submerged and that the entrance of air, negative pressure, or pressure
				surges in the reactors is prevented. Open channel flow reactors are
				prohibited.
D. A pressure gauge
				shall be provided upstream of each reactor. The design shall ensure that the
				reactor's maximum rated pressure cannot be exceeded.
E. Water quality parameters that may affect
				UV disinfection system performance shall be evaluated, including calcium, iron,
				manganese, hardness, and alkalinity. Pretreatment shall be considered for water
				quality parameters that may result in lamp sleeve fouling.
F. A building to enclose and protect all UV
				equipment shall be provided. Adequate space between control panels, power
				supply, and the reactor equipment shall be provided to allow for routine
				operation and maintenance, including removing lamp and wiper assemblies and for
				off-line chemical cleaning of reactor lamps.
G. An operation and maintenance manual shall
				be provided for all UV reactors.
H.
				UV systems may be used for primary disinfection and shall be granted log
				inactivation credit for Giardia lamblia, Cryptosporidium, and viruses in
				accordance with Table 401.7, provided that they meet the requirements of
				12VAC5-590-401 E 7 c and this subsection.
1.
				Only UV reactors that have undergone independent, third-party oversight of the
				validation testing on a fully assembled system to determine the operating
				conditions under which the reactors deliver the required UV dose shall be
				considered for log inactivation credit.
2. The dose-monitoring strategy shall be
				either the UV intensity set point approach or the calculated dose approach as
				described in the "Ultraviolet Disinfection Guidance Manual For The Final Long
				Term 2 Enhanced Surface Water Treatment Rule," Office of Water (4601), EPA
				815-R-06-007, November 2006. The dose-monitoring strategy shall be demonstrated
				through the UV reactor validation testing.
3. At least two reactors shall be provided.
				Reactors shall be sized to treat the design flow with the largest reactor out
				of service.
4. Continuous
				monitoring sensors shall be provided to measure UV intensity. A continuous
				sensor shall also be provided to measure ultraviolet transmittance (UVT) if the
				calculated dose approach is utilized.
a. The
				number of sensors provided shall be the same as that used in validation testing
				of the reactor.
b. Output from a
				continuous UVT analyzer shall be capable of being input directly into a control
				loop for each UV reactor, a SCADA system, or both. A bench-top
				spectrophotometer may be provided instead of a continuous UVT
				analyzer.
c. All signals from the
				sensors shall be displayed for operator response and for recordation.
d. At least one reference sensor for
				calibration of online UV intensity sensors shall be provided. Reference sensors
				shall be capable of calibration against a traceable standard.
e. Continuous recording equipment shall be
				provided with the monitoring sensors to store in memory or print one data point
				at least every four hours.
5. A means of flow distribution and control
				among multiple reactors shall be provided. The hydraulic flow profiles and
				piping configuration shall be identical to or more protective than that tested
				during equipment validation.
a. For onsite
				validation, the inlet and outlet piping configuration for the UV facility shall
				be designed according to manufacturer recommendations and to accommodate any
				site-specific constraints.
b. To
				avoid jetting flow and swirling flow, consideration shall be given to exclude
				expansions for at least 10 pipe diameters upstream of the reactor and to
				exclude out-of-plane 90-degree bends in series.
c. Each UV reactor shall be capable of being
				isolated and removed from service. Isolation valves upstream and downstream of
				each reactor, a drain, and sample taps for each reactor treatment train shall
				be provided. If the isolation valves are also used for flow control, then the
				flow control valve shall be located downstream of the UV reactor to limit the
				disturbance of the flow entering the UV reactor. Bypass piping shall not be
				allowed.
d. The lateral piping for
				each UV reactor train shall be sized and configured to provide approximately
				equal head loss through each UV reactor train over the validated range of flow
				rates.
6. The control
				system shall be capable of meeting the monitoring and reporting requirements in
				12VAC5-590-401 and
				12VAC5-590-570.
7. Automatic shutdown capability under
				critical alarm conditions shall be provided, including lamp or ballast failure,
				low liquid level, and high temperature. Alarms shall be provided for low UV
				validated dose, low UV intensity, low UV transmittance, high flow rate, and
				mechanical wiper failure.
8.
				Ground-fault circuit interrupters shall be provided for all lamps. Backup power
				shall be considered.
9. The owner
				shall develop a start-up plan and submit the plan to the department for
				approval. The plan shall include functional testing, determination of validated
				operating conditions and control settings, performance testing, development of
				an operation and maintenance manual, and inspection schedules.