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February 27, 2018
UV Lamp Breakage: Investigation and Response
International UV Association Americas Conference
Rodundo Beach, California
Jennifer Osgood
Chris Schulz
Outline
� Types of lamp breakage
� UV lamp breakage incidents
� Calculating/assessing mercury dilution
� Contingency Plans/Standard Operating
Procedures
UV Lamp Breakage
� Off Line
� Outside of reactor
� Mercury is in a liquid phase
� Risk is to workers
� On Line
� Occurs while water is flowing through the reactor
� Mercury is in a vapor state due to the high temperatures
� Risk is to water customers; Mercury limits are currently set at a
concentration of 2 ug/L in the USA and 1 ug/L in Canada.
� Mercury Dilution Calculations
Literature Review and Survey
� Date of Incident
� Incident Description
� Cause of Incident
� Impact of Incident
� Standard Operating Procedure
On Line Incident Causes
� Incorrectly manufactured sleeves or faulty design
� Wiper mechanism issues
� Software error leading to overheating; power surge
� Debris
� Burst main downstream of the plant that resulted in a significant increase
in flow rate through the system
� Control logic fault caused the flow control valve to open unexpectedly very
quickly. Excessive rate of flow increase resulted in an exceedance of the
maximum flow rating through a single UV disinfection train.
Mercury Dilution Calculation
Methods
Mercury release calculations should be based
on Hg mass in vapor phase
� Mercury mass in liquid and
vapor phase in operating
UV lamps depends on:
� Lamp type (MP vs. LPHO)
� Operating pressure and
temperature
� Mercury mass in vapor
phase may be treated as
proprietary information by
UV vendors
� May need to rely on ideal
gas law values based on
pressure and temperatureSource: UV
Knowledge Base
Mercury Release Calculation Methods and Lamp
Breakage Scenarios
� Pipeline Release Scenario: UV systems
discharge directly into the distribution
system, i.e., no finished water storage
buffer between the UV system and first
customer
� Clearwell Release Scenario: UV systems
followed by a finished water clearwell or
storage reservoir prior to first customer
� Lamp Breakage Scenarios:
� One lamp, one reactor
� All lamps, one reactor
� All lamps, all in-service reactors
Use Advective-Dispersive Equation (ADE) to
predict Hg concentrations in pipeline systems
Where:
C(x,t) = concentration at location x and time t
M = mass of Hg released at location x = 0
A = wetted area of pipe
KT = advective-dispersive coefficient
u = mean pipe flow velocity
Source: UV Knowledge Base
(developed by Taylor, 1954)
Pipeline Release Scenario Example – Calculate Hg
levels at different flows for fixed distance to first
customer
0
50
100
150
200
250
300
0 20 40 60 80 100 120
PLA
NT
FLO
W (
MG
D)
Sample Percentile
Max Design
Flow 250 MGD
Min Design
Flow 50 MGD
Mercury MCL
Mercury Detection Limit
1 Lamp in 1 Reactor Fails
All Lamps in 1 Reactor Fails
All Lamps in 3 Reactors Fail
0.01
0.10
1.00
10.00
100.00
Hg
co
nce
ntr
ati
on
(u
g/L
)
Max, plume displacement 2 |� 940.3 feet �| |� 916.4 feet �|
Flow Scenario Min Design Flow Max Design Flow
Flow (MQD) 50 250
Plume Travel Time (MIN) 40.4 8.10
Concentration (µg/L) 14.4 15.2
No. of UV Trains in Service 3 3
1. First residence located 4100 feet South of UV Facility
2. All lamps, one reactor
ADE results for MP reactor with 8 lamps (700
mg Hg/lamp in vapor phase)
ADE results for LPHO reactor with 72 lamps
(0.15 mg Hg/lamp in vapor phase*)
0.000
0.001
0.010
0.100
1.000
10.000
Hg
co
nce
ntr
ati
on
(u
g/L
) Mercury MCL
Mercury Detection Limit
1 Lamp in 1 Reactor Fails
All Lamps in 1 Reactor Fails
All Lamps in 3 Reactors Fail
Max, plume displacement 2 |� 752.7 feet �| |� 709.5 feet �|
Flow Scenario Min Hour Design Flow Max Design Flow
Flow (MQD) 50 250
Plume Travel Time (MIN) 40.4 8.10
Concentration (µg/L) 0.0277 0.0293
1. First residence located 4100 feet South of UV Facility
2. All lamps, one reactor
No. of UV Trains in Service 3 3
*Hg/lamp in vapor phase varies – amount listed came from case study in UV Knowledge Base
Comparison of MP and LPHO Hg release results
72 LPHO Lamps per Reactor (0.15 mg/lamp)
No. of Lamps Break 1 72 216
Concentration C (ug/L) C (ug/L) C (ug/L)
Flow 250 0.000406 0.0293 0.0878
Flow 50 0.000385 0.0277 0.0831
8 MP Lamps per Reactor (700 mg/lamp)
No. of Lamps Break 1 8 24
Concentration C (ug/L) C (ug/L) C (ug/L)
Flow 250 1.90 15.17 45.51
Flow 50 1.80 14.36 43.09
Clearwell Hg Release Scenario Example – Impacts
of well-baffled vs. poorly baffled clearwells
� Englewood, CO Clearwell
(984,000 gallons, 25 mgd,
CFD BF=0.71, Tracer Study
BF=0.66)
� Poorly Baffled Clearwell
(3.1 million gallons, 35 mgd,
CFD BF=0.01)
CFD modeling results for well-baffled clearwell
� MP reactor with 8 lamps (700
mg Hg/lamp in vapor phase)
CFD modeling results for well-
baffled clearwell
� LPHO reactor with 72 lamps
(0.15 mg Hg/lamp in vapor
phase)
CFD modeling results for poorly baffled
clearwell
� MP reactor with 8 lamps
(700 mg Hg/lamp in vapor
phase)
CFD modeling results for poorly baffled
clearwell
� LPHO reactor with 72 lamps
(0.15 mg Hg/lamp in vapor
phase)
Conclusions
� MP reactor with larger Hg concentration in vapor phase has significantly higher risk for exceeding Hg regulatory limits than LPHO reactor
� Pipeline Hg release scenario:
� Flow has minimal impact on Hg dilution concentrations
� Plume displacement increases at lower flows (i.e., longer detention time)
� Clearwell Hg release scenario:
� Peak Hg concentrations are similar in baffled and unbaffled clearwells, but plume displacement profile is extended in unbaffled clearwells
� Clearwell volume dilution calculations, adjusted by baffle factor, may underestimate the peak mercury concentrations and length of the plume displacement.
� CFD or tracer test results provide a more accurate prediction of downstream mercury dilution impacts.
UV Knowledge Base: Response Plan for Lamp
Breakage
1. Close valve sufficiently downstream of reactor to contain initial mercury release. (LPHO -
Containment of the initial releases likely not needed because mercury concentrations are
orders of magnitude below the MCL)
2. Close upstream and downstream reactor isolation valves.
3. Divert water contained in the conduit to waste, MERSORB® treatment or storage.
4. Sample conduit water before and after treatment as needed.
5. Flush conduit and bring back on line.
6. Pump contaminated water in reactor to a MERSORB® column for treatment.
7. Sample reactor water before and after treatment.
8. Cleanup reactor - remove quartz shards, liquid mercury, and lamp parts. Inspect other
sleeves.
9. Inspect other sleeves. Replace broken and damaged sleeves and lamps.
10. Flush reactor with dilute acid solution HCl followed by water
11. Verify mercury concentrations in standing water are acceptable.
12. Bring reactor back on line.
Red font indicates MP activities only; Black font indicates MP and LPHO activities
Contingency Plan/Standard Operating Procedure
(CLCJAWA SOP Flow Chart)