Current through August 31, 2023
01.
General. (3-24-22)
a. Ultraviolet
(UV) light technology is a primary disinfectant typically used for
Cryptosporidium, Giardia lamblia, and virus inactivation of both surface water
and ground water supplies. Reactor performance in terms of inactivation of any
particular organism is a function of the delivered dose which is determined by
validation testing. (3-24-22)
b. UV
disinfection credit will be awarded for filtered systems and unfiltered systems
if the system meets the requirements for unfiltered systems in
40 CFR
141.71. Systems will receive Cryptosporidium,
Giardia lamblia, and virus treatment credits by achieving the corresponding UV
dose values for the appropriate target pathogen and log reduction shown in
Subsection 529.03, calculated to take into
account the validation factor and reduction equivalent dose. The target
pathogen and the target log inactivation shall be used to identify the
corresponding required UV dose. (3-24-22)
c. For water systems using UV light to meet
microbial treatment requirements, at least ninety-five percent (95%) of the
water delivered to the public every month must be treated by UV reactors
operating within validated conditions for the required UV dose.
(3-24-22)
d. When reviewing
proposed UV disinfection projects, the Department will use the USEPA UV
Disinfection Guidance Manual for the Final Long Term 2 Enhanced Surface Water
Treatment Rule referenced in Subsection
002.02 (UV Disinfection Guidance
Manual) for guidance. (3-24-22)
02.
Pilot Studies and
Validation. (3-24-22)
a. The Department
may allow on-site pilot studies on a case by case basis. Pilot studies are
usually used to determine how much fouling occurs on site, to evaluate UV
system reliability (e.g. UV sensors, UV transmittance (UVT) monitors, ballast
reliability) and to provide operators experience running a UV system. They may
also be used to assess lamp aging or impacts of power quality. See Subsection
501.19 for general information
on conducting pilot studies. (3-24-22)
b. Validation testing determines the
operating conditions and monitoring algorithms that the UV system will use to
define how much UV dose is being delivered by the reactor during operation. The
validated dose as determined through validation testing is compared to the
required dose in the UV Dose Table (Subsection
529.03) to determine
inactivation credit. The validated dose is calculated by dividing the
determined reduction equivalent dose by a validation factor to account for
biases and experimental uncertainty. UV light treatment reactors shall be
validated by a third party entity approved by the Department. At a minimum,
validation testing must account for the following: UV absorbance of the water;
lamp fouling and aging; measurement uncertainty of on-line UV sensors; UV dose
distributions arising from the velocity profiles through the reactor; failure
of UV lamps and other critical system components; inlet and outlet piping
configuration of the UV reactor; lamp and UV sensor locations; and other
parameters required by the Department. The Department may allow alternative
test microbes such as MS2 phage where the UV dose response better matches that
of Cryptosporidium and Giardia lamblia to provide more accurate and efficient
UV dose monitoring. Additional guidance is available in the UV Disinfection
Guidance Manual, referenced in Subsection
002.02, or another validation
standard as approved by the Department. (3-24-22)
c. Validation testing shall be conducted on
full scale testing of a reactor that conforms uniformly to the UV reactors used
by the system and inactivation of a test microorganism whose dose response
characteristics have been quantified with a low pressure mercury vapor lamp.
(3-24-22)
d. Validation testing
must determine and establish validated operating conditions under which the
reactor delivers the required UV dose in Subsection
529.03. Validated operating
conditions include: (3-24-22)
i. Flow rate;
(3-24-22)
ii. UV Intensity as
measured by a UV sensor; (3-24-22)
iii. UV lamp operating status.
(3-24-22)
e. The
department may approve an alternative approach to validation testing.
(3-24-22)
03.
UV
Dose Table. The treatment credits listed in the dose table are based on
UV light at a wavelength of two hundred fifty-four (254) nm as produced by a
low pressure mercury vapor lamp. To receive treatment credit for other lamp
types, the system shall demonstrate an equivalent germicidal dose through
validation testing.
|
UV Dose Table (millijoules per
square centimeter) |
|
Log |
Cryptosporidium |
Giardia
lamblia |
Virus |
|
0.5 |
1.6 |
1.5 |
39 |
|
1.0 |
2.5 |
2.1 |
58 |
|
1.5 |
3.9 |
3.0 |
79 |
|
2.0 |
5.8 |
5.2 |
100 |
|
2.5 |
8.5 |
7.7 |
121 |
|
3.0 |
12 |
11 |
143 |
|
3.5 |
15 |
15 |
163 |
|
4.0 |
22 |
22 |
186 |
(3-24-22)
04.
Reactor Design. Inlet and
outlet conditions shall ensure that UV dose delivery at the plant is equal to
or exceeds that utilized during validation. At a minimum, design criteria shall
address target pathogen(s), required log inactivation and UV dose, flow rate,
UVT, and lamp aging and fouling factors. UVT and flow rate shall be selected to
account for seasonal changes in UVT. Lamp aging and fouling factors shall be
supported by documentation or pilot study data. Recommended approaches of the
UV Disinfection Guidance Manual, referenced in Subsection
002.02, shall be used in meeting
this requirement. (3-24-22)
a. The reactor
systems must be designed to monitor and record parameters to verify the
operation within the validated operating conditions approved by the Department.
The system must be equipped with facilities to monitor and record UV intensity
as measured by a UV sensor, flow rate, lamp status, UVT, and other parameters
designated by the Department. (3-24-22)
b. The ultraviolet treatment device shall be
designed to provide a UV light dose equal to or greater than that specified in
the UV Dose Table for the required log reduction. The UV Disinfection Guidance
Manual, referenced in Subsection
002.02, shall be utilized in
evaluating the appropriate dose required for the target microbe. The reactor
shall also deliver the target dose while operating within the validated
operating conditions for that particular unit. (3-24-22)
c. The ultraviolet treatment assemblies shall
be designed to allow for cleaning and replacement of the lamp, lamp sleeves,
and sensor window or lens. (3-24-22)
d. All ultraviolet treatment device designs
shall evaluate lamp fouling and aging issues and manufacturer's recommendations
regarding fouling, aging, and replacement shall be discussed in the Operation
and Maintenance Manual. (3-24-22)
e. For in-situ cleaning of the lamp sleeve,
the design shall protect the potable water from cleaning solutions.
(3-24-22)
f. 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. (3-24-22)
g. On-line systems that use wipers or brushes
may use chemical solutions provided they are NSF/ ANSI Standard 60 certified.
(3-24-22)
h. An automatic shutdown
valve shall be installed in the water supply line from the ultraviolet
treatment device such that if power is not provided to the reactor or valve,
the valve shall be in the closed position. (3-24-22)
i. The design of the inlet and outlet piping
configuration and the locations of expansions, bends, tees and valves shall
assure that the UV dose delivery is equal to or greater than the required UV
dose. Approach length prior to each reactor included in the credited dose
calculations, downstream length following each reactor, and locations of any
cleaning device/mechanism shall be based on validation testing.
(3-24-22)
j. For parallel trains,
the flow to each reactor shall be equally distributed and metered or otherwise
account for uneven flows in the design to ensure that the required UV dose is
delivered to each train under varying flow conditions. (3-24-22)
k. Valves shall be provided to allow
isolating and removing from service each UV reactor. (3-24-22)
l. Reactors shall be provided with air relief
and pressure control valves per manufacturer requirements. (3-24-22)
m. UVT analyzers shall be provided if UVT is
part of the dose monitoring strategy. It is recommended that UVT be monitored
on a regular basis for all systems to assess UVT variability.
(3-24-22)
n. A single train with a
standby reactor or a sufficient number of parallel ultraviolet treatment
devices shall be installed to ensure that adequate disinfection is provided
when one unit is out of service. The Department may approve an alternate method
that provides adequate disinfection such as standby chlorination. Any system
that produces water on an irregular schedule may provide documentation for the
Department's review and approval that a single reactor would be an acceptable
design by demonstrating there would be adequate for time for maintenance and
cleaning during operation shutdowns. (3-24-22)
o. No bypass of the ultraviolet treatment
process may be installed unless an alternate method of providing adequate
disinfection is provided. (3-24-22)
05.
Controls. (3-24-22)
a. A delay mechanism shall be installed to
provide sufficient lamp warm-up prior to allowing water to flow from the
ultraviolet treatment unit. (3-24-22)
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.
(3-24-22)
06.
Reliability. The system must be capable of producing the plant
design capacity at all times. (3-24-22)
a.
Standby equipment. Unless otherwise approved by the Department based on
documentation provided by the design engineer and in accordance with Subsection
529.04.n., a minimum of two
(2) reactors is required to maintain disinfection when one unit is taken out of
service. Each reactor must be sized to deliver the required UV dose under the
operating conditions of flow and UVT that occur at the plant. The conditions
shall fall within the validated range of the reactor as determined during
validation testing. (3-24-22)
b.
Power supply. The quality and reliability of the power supply shall be analyzed
and back-up power supplies shall be discussed in the contingency plan.
(3-24-22)
c. Validated operating
conditions. If UVT is above the validated range of UVT, the UV dose monitoring
algorithm shall default to the maximum of the validated range. If UVT is below
the validated range, the UV system operation shall be recorded as outside of
the validated operating conditions. When UVT falls outside of ranges identified
in the validated operating conditions, the contingency plan shall be enacted if
UVT is part of the dose monitoring strategy. (3-24-22)
d. Contingency plan. A contingency plan for
total UV disinfection failure, loss of power, or in the event that water
quality changes produce water quality unsuitable for UV disinfection shall be
described in the preliminary engineering report. (3-24-22)
07.
Monitoring. Water systems
using UV light must monitor for the parameters necessary to demonstrate
operation within the validated conditions of the required UV dose. PWSs must
check the calibration of UV sensors and online UVT monitors and recalibrate in
accordance with a protocol approved by the Department. At a minimum, the
following parameters must be monitored: (3-24-22)
a. Flow rate. If the flow rate is below the
validated range, then the UV dose monitoring algorithm shall default to the
validated range. If the flow rate is above the validated range, then the UV
system operation shall be recorded as outside of the validated operating
conditions; (3-24-22)
b. UV
intensity as measured by UV sensors; (3-24-22)
c. UVT if UVT is part of the dose monitoring
strategy; and (3-24-22)
d. Lamp
status. (3-24-22)
08.
Alarms. The settings or predetermined set points for the alarms
shall be specified in the preliminary engineering report. The report shall also
specify the alarms that shall activate the contingency plan response. At a
minimum, the following alarms are required: (3-24-22)
a. Low UV intensity; (3-24-22)
b. High turbidity if required by the
Department; (3-24-22)
c. Low UVT;
(3-24-22)
d. Low UV dose;
(3-24-22)
e. Lamp failure;
(3-24-22)
f. UVT monitor failure;
(3-24-22)
g. UV sensor failure;
(3-24-22)
h. Low water level; and
(3-24-22)
i. High flow rate.
(3-24-22)
09.
Initial Startup. The following items shall be tested and verified
before UV disinfected water is distributed: (3-24-22)
a. Electrical components; (3-24-22)
b. Water level; (3-24-22)
c. Flow split between reactor trains if
applicable; (3-24-22)
d. Controls
and alarms; and (3-24-22)
e.
Instrument calibration. (3-24-22)
10.
Operation and Maintenance
Manual. A project specific operation and maintenance manual shall be
provided as required in Subsection
501.12. See definition of
Operation and Maintenance Manual in Section
003 for the typical contents of an
operation and maintenance manual and the included operations plan. The
operations plan in the operation and maintenance manual shall include, but is
not limited to the following information: (3-24-22)
a. Lamp aging and replacement intervals. Lamp
replacement intervals may be based on the degree of lamp aging as indicated by
the UV sensors; (3-24-22)
b. Lamp
fouling analysis and cleaning procedures; (3-24-22)
c. Lamp replacement; and (3-24-22)
d. Lamp breakage.
(3-24-22)
