Protocol for Improved Ultraviolet Disinfection Design and System

Optimization

PNCWA 2010Bend, OR

26 October 2010

Jeff Bandy, Ph.D.Carollo Engineers

WRF06/2-019

Quick Outline

1. NWRI bioassay testing: requirements, nuances, and challenges

2. Case study: Trojan UV3000 at City of Escondido’s Hale Avenue Resource Recovery Facility

3. A few take-home messages

WRF06/3-019

NWRI Checkpoint Bioassay Requirements

o Minimum of 8 biological tests, varying flow and UVT

o MS2 bacteriophageo Demonstrate doses of

o 100 mJ/cm2 (media filtered effluent)

o 80 mJ/cm2 (MF effluent)o 50 mJ/cm2 (RO effluent)

o Capacity is defined by the 75th percentile confidence interval of UV dose

o Non-infectious viruso (+)ssRNAo 30 nm φ

WRF06/4-019

System sizing must be based upon sound science…

1. Characterize system performance based on the following variables:

• Head loss/Water level• UVT• Flow• Power• Lamp aging• Sleeve fouling

2. Testing is performed according to the 2003 NWRI/AWWARF Ultraviolet Disinfection Guidelines

3. Be sure to only use third party- validated reactors!

WRF06/5-019

…which results in complex dose algorithms/sizing formulas…

2

10

UVAEUVADC

oUVABA

QS

SUVADose

⋅+⋅+

⋅

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛⋅⋅=

UVTCQBADose ⋅+⋅−=

( )

( )

( )

( ) ⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

⎟⎟⎠

⎞⎜⎜⎝

⎛

−⋅+

⋅

⋅⋅=⋅+⋅+

⋅+⋅+

⋅+⋅+

UVTCQBA

UVTFQED

UVTCQBA

n

zFFEOLLDose

loglog

loglog

loglog

1010

10

WRF06/6-019

…which are based upon data with significant variability.

WRF06/7-019

1) Examine the variability of the original data set

Predicted UV Dose = UVTA QB BanksC10D

WRF06/8-019

2) Determine confidence interval around the average data set

WRF06/9-019

3) Test system, demonstrate performance

WRF06/10-019

Example WWTP in CA (~5 mgd)

Wedeco Lancaster

WRF06/11-019

William Duke

System downrated by 5% and just barely makes capacity.

WRF06/12-019

Quartz Sleeve Fouling and Lamp Aging Factors1. UV system capacity is directly

dependent on FF (fouling factor) and EOLL (end of lamp life factor)

2. Unless otherwise demonstrated, NWRI assumes extremely conservative combined aging and fouling (CAF) factorso EOLL: 0.5o FF: 0.8

3. However, actual CAF factors are highly variable and site-specific

( )UVTCQBAFFEOLLDose loglog ⋅+⋅+⋅⋅=

WRF06/13-019

Site-Specific Sleeve Fouling

Type of Wastewater Rate of Sleeve Fouling (% change in UVT per day)

Ballasted Flocculation / Filter Effluent 13-20

Secondary Effluent 7.1

Filtered Secondary Effluent 1.5

Filtered Secondary Effluent 2.5

Filtered Secondary Effluent 4

Filtered Secondary Effluent No fouling witnessed over 30 days

WRF06/14-019

Assumed EOLL is Very Conservative

Compare this to example assumed NWRI EOLL of 0.5 and a replacement period of

6,000 hours

WRF06/15-019

Multiple Causes of Lamp Failure

Excessive lamp hours

Excessive lamp starts

Ballast failure

Dead spots in open-channel UV banks allow easy pathways for treatment targets and are opportunities for avoidable permit violations.

WRF06/16-019

Regrowth Permit Violations

WRF06/17-019

Where Should A UV System Be Sampled for Compliance?

S

S

S

S

S

Rigorous channel maintenance and sampling after the last UV bank prevents effluent sample contamination.

WRF06/18-019

Benefits of Online UV Sensors

o Real-time dose monitoring, facilitating maintenance

o Full control of maintenance schedule

o True measurement of dose

o Similar to DW UVo Optimizes energy useo Not all systems use them,

but they are strongly recommended

WRF06/19-019

Case Study: City of Escondido Hale Avenue Resource Recovery Facility (HARRF) Trojan UV3000

Carollo was hired to benchmark Trojan UV3000 system, diagnose problems, and increase capacity for Title 22 reuse.

WRF06/20-019

Trojan UV3000 at HARRF

2 Channels5 Banks/Channel320 Lamps/Bank3,200 lampsDesigned for 9 mgd Title 22 water

N

WRF06/21-019

Trojan UV3000 at HARRF

WRF06/22-019

N

Poor flow split: Eastern channel: 10-15% higher flow

2003 Comissioning report ID’ed uneven flow split

WRF06/23-019

Bank # UV Dose (mJ/cm2)

1 32

2 59

3 64

4 66

5 61

At NWRI/CDPH conditions:o 100 mJ/cm2

o UVT: 55%o EOLL: 0.5o FF: 0.8Capacity waslimited to 4 mgd

Poor approach hydraulics crippled bank #1 dose delivery

5 MGD in lost capacity = $3~4M in lost revenue

WRF06/24-019

Computational fluid dynamics suggested ¼ hp mixers

o Simple solution

o Low cost

o Low energy

o No construction

o Homogenized flow could boost capacity

Unfortunately, testing showed no significant benefit.

WRF06/25-019

Test Flow Rate UVT Banks Tested Lower 75% C.I. RED

(mgd) (%) # (mJ/cm2)1 4.4 63.2 1 19.872 1.1 63.8 1 46.813 3.1 63.4 1 30.584 1.8 64.4 1 48.915 4.0 57.1 1 26.276 3.0 55.4 1 22.787 2.1 54.9 1 23.438 1.0 55.0 1 34.899 4.2 56.4 1, 2 54.0010 3.1 56.3 1, 2 62.1911 2.0 57.1 1, 2 79.8812 1.0 56.3 1, 2 122.6313 4.0 64.8 1, 2 95.5214 3.0 64.8 1, 2 105.3515 2.0 65.1 1, 2 115.4416 1.0 66.2 1, 2 151.86

Restructure and repeat bioassay testing to isolate Bank 1 from Banks 2-5

Isolate Bank 1

Test Additive Banks

WRF06/26-019

Calculating the fouling factor

Tested both sides (180o rotation) of 4 sleeves after 60 days in operation. Average of 40% drop in intensity.

Sleeve fouling after 59 days

0.0

0.2

0.4

0.6

0.8

1.0

Rel

ativ

e Se

nsor

Rea

d

FouledClean

Rel

ativ

e U

V S

enso

r Int

ensi

ty

WRF06/27-019

Calculating the fouling factor

WRF06/28-019

Calculating the aging factor

At least 4 lamps per age, multiple sensor readings. Lamps should be tested far past 6,000 hrs to determine EOLL and replacement rate.

LSI UV6414 Low-Pressure UV Lamp Aging at HARRF

0.000.100.200.300.400.500.600.700.800.901.00

0 1000 2000 3000 4000 5000 6000

Lamp Hours (hrs)

Rel

ativ

e O

utpu

t,

EOLL6000 hrs = 0.927

WRF06/29-019

How we calculated UV dose

REDcalc = Reduction Equivalent Dose (UV dose), calculated with the UV dose-monitoring equation above (mJ/cm2).

EOLL = End of lamp life factor (0.927)

FF = Fouling factor (0.746)

UVT = UV transmittance (%).

Q = Flow rate (million gallons per day [mgd]).

n = Number of banks in operation

( )

( )

( )

( ) ⎥⎥⎥

⎦

⎤

⎢⎢⎢

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UVTCQBA

UVTFQED

UVTCQBA

calc nFFEOLLRED

loglog

loglog

loglog

1010

)1(

10

WRF06/30-019

Capacity at 55% UVT, 4 banks

0

20

40

60

80

100

120

140

160

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Flow (mgd)

RED

75 (c

alc Bank 1

Bank 2Total Channel

EOLL = 0.927FF = 0.749

RE

D75

, cal

cula

ted

(mJ/

cm2 )

WRF06/31-019

0

50

100

150

200

250

300

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Flow (mgd)

RED

75 (c

alc Bank 1

Bank 2Total Channel

Capacity at 65% UVT, 4 banks

o >8 mgd capacity through both channelso Recovered capacity at about $20k/mgd

EOLL = 0.927FF = 0.749

RE

D75

, cal

cula

ted

(mJ/

cm2 )

WRF06/32-019

A few take-home messages…

1. Reuse UV designs require conservatism2. Equipment sizing is no longer simple3. When designing UV systems, especially in retrofitted

chlorine contact basins, hydraulic concerns are paramount

4. Appropriate and flexible data analysis and dose monitoring equations may be a silver bullet

5. If possible, find out your site-specific EOLL and FF 6. A successful UV system needs a dedicated and

proactive operations staff

WRF06/33-019

WRF06/34-019

Separating Fact From Fiction

1. UV is a robust disinfectant.2. No DBPs or toxic residuals.3. Costs less than hypo for many

applications (but not all)4. Regulatory review depends on

“truth in advertising”: make sure that installation = approved design

5. Review delays – poor scheduling compounded by lack of staff time

6. Review information – lacking detail & completeness

Fact Fiction1. Easy to design.2. Low maintenance.3. Simple to operate.4. Simple field verification and

regulatory approval.5. Review not meant as

impediment to project6. Regulators have access to all

necessary information, incl:1. Design & installation

procedures2. Manufacturer information3. Regulators = the “experts”