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)

Thank You!

osgoodjl@cdmsmith.com

schulzcr@cdmsmith.com