Quartz Sleeve Fouling Prevention

While Maintaining Maximum Electrical Efficiency

IUVA Conference by Ludwig Dinkloh, Global Product Manager

Introduction / Motivation

Note: Wiping System not operational!

Outline

1. Definition of Fouling

2. Types of Fouling

3. Monitoring of Fouling

4. Overview of Fouling Factors used by the Industry

5. Impact of Fouling

6. Recommendations/Conclusions

Definitions

Fouling Factor:

The reduction in available UV output due to changes

in transmittance of the (lamp) enclosure (e.g. quartz

sleeve) separating the UV lamp from the liquid. The

reduction in available UV output is determined by

comparison to a new enclosure.

(Lamp) Enclosure Fouling:

The formation of material on the enclosure, which

causes a reduction in the UV intensity emitted

through the enclosure.

Slight Adaptations from NWRI 2012 Guideline:

Types of Fouling

Mainly Organic Fouling Mainly Inorganic Scaling

Effluents @ high organic

load (mainly prim & sec)

All types of effluents @ high

inorganic loads

When lamps are off

=> no disinfection

When lamps are on

=> temperature difference

No wiping, wiping off With or without wiping

(*)

* from Brooks T. et al (Carollo) “Lessons Learned from UV System Performance Audits for Reuse Applications”, IUVA 2016

Monitoring of Fouling

• Direct monitoring of fouling?

• Indirect monitoring of fouling via UV intensity sensors

(sensor value influenced by lamp output, lamp age, fouling and

UVT of effluent)

• Measured UV intensity then used in UV systems‘ control

philiosphy (RED equation), e.g.:

Consequence for Monitoring

Irrespective of UV system configuration

at least one (1) UV intensity sensor is needed per “switchable unit”.

Advantage of many “switchable units”: flexibility => lower OPEX

Disadvantage of many “switchable units”: more monitoring

BUT: “no monitoring – no credit” (or safety/reliability)

Real Measurement of Quartz Sleeve Fouling

Design Basis 1/2

Design Basis 2/2

Examples of Fouling Factors*

Manufacturer Calgon

Carbon

Enaqua Suez

Ozonia

Trojan Xylem

Wedeco

Model C³500D C10i.10123 AquaRay 3X UVSigna Duron

Description Horizontal,

lamps inside

quartz sleeves

Horizontal,

lamps outside

of AFP tubes

Vertical,

lamps inside

quartz sleeves

Inclined, lamps

inside quartz

sleeves

Inclined, lamps

inside quartz

sleeves

Lamp type LPHO

Amalgam

LPHO non-

Amalgam

LPHO

Amalgam

LPHO

Amalgam

LPHO

Amalgam

Lamp power 500 W 138 W 406 W 1,000 W 600 W

Cleaning/

wiping system

Mechanical None Mechanical Mechanical/

chemical

Mechanical

3rd Party

Fouling factor

0.90 0.89 0.95 0.94 0.958

*Public Domain Information from Bid Openings

Important: differences in kWh/MGD per UV system

Carollo Experience (IUVA 2016)

What happens without Wiping?

UV Pilot Study Documentation for St. Joseph, MO by Black & Veatch (2009)

Application of the Fouling Factor in Designs

As per Dose Validation Equation (equation is system-specific)

where:

RED = The RED calculated with dose monitoring equation, also

referred to as the “calculated dose” in the UVDGM

UVA = UV absorbance at 254 nm

S = Measured UV sensor value

S0 = UV intensity at 100% lamp power

Q = Flow rate

DL = UV sensitivity of challenge/target organism

A,B,O = Model coefficients obtained by fitting the equation

Fouling Factor Impact on Design

Very system-specific;

f(flexibility in design and dose equation)

Fouling Factor Impact on Operation

System-specific;

f(dose equation coefficients,

system and lamp flexibility)

Cleaning Performanceunder challenging Conditions

Channel 2 Bank B

Module 1

(conventional wiper)

Channel 2 Bank B

Module 2

(wiper design for tough effluents)

Secondary effluent with dissolved iron of ~ 2 mg/l!

Visual inspection of wiping tests after 4 months of tests

UVT Measurements of Quartz Sleeves

Recommendations / Conclusions

1. Subject to the effluent quality, fouling does occur in varying degree irrespective of UV system

2. Minimization (or occurrence) of scaling is UV system specific

3. A project-specific and system-specific (!) fouling factor is used to allow for a certain loss of UV transmittance of the “enclosure”=> careful selection incl. O&M aspects and kWh/MGD comparison

4. Impact on design: the higher the fouling factor, the more lamps are needed (CAPEX)=> to be weighed against overall in-built redundancy/safety

5. Impact on operation: the more fouling, the higher the power draw (OPEX)=> to be monitored (with S/S0) plus indication via power

6. Consequence for monitoring: min. one (1) UV intensity sensor per switchable unit

Thank you!

ludwig.dinkloh@xyleminc.com