an operators’ perspective: how new uv system designs

An Operators’ perspective: How new UV system designs simplify maintenance efforts

IUVA Conference, February 28th , 2018

Redondo Beach, California

Jeff Lamson, Superintendent, Fremont Water Reclamation CenterKirsten Meyer, UV Product Manager, Xylem

Outline

• The site

• Reasons for converting to UV

• The UV system selected

• Typical maintenance works

• Conclusions

2

The site

3

The site – Identified issues

• Original plant was built in 1949, with several upgrades conducted between 1964-1988

• Plant discharges into the Sandusky River

• Plant improvements required by the Federal Clean Water Act

• Reduce Combined Sewer Overflows from 70 events to 4 (by 2028)

• Plant capacity increase from 10 mgd to 24 mgd

• Refurbishment of existing Sodium Hypochlorite disinfection/ Sodium Bisulfite de-chlorination system

4

The new treatment process

5

Screens

Grit removal

A2O(Anaerobic, Anoxic, Oxic)

Secondary clarification

Cloth disc filtration

UV disinfection

• Total investment of $71.5 million

Reasons for converting to UV disinfection

• Safety issues

• Problems with air locking of dosing pumps

• Eliminate permit for residual chlorine (0.038 mg/l)

• Reduce labor time associated to the disinfection system

• Significant effort for sampling and dosing adjustment

6

UV system design parameters

Peak flow: 24 mgd

Average flow: 7.6 mgd

UVT: 65%

SS: max. 30 mg/l

Disinfection Target:

126 E. coli cfu/100 ml @ monthly geometric mean

UV dose: 25 mJ/cm² MS-2 RED

7

The UV system selected

8

Wedeco Duron UV system

2 channels3 banks each12 lamps/ bank

Performance data

9

Typical maintenance activities associated to chlorination/ de-chlorination system

• Unloading Sodium hypochlorite and Sodium bisulfite

• Adjusting pump speeds

• Collecting and analyzing samples in order to adjust dosage of both hypo and bisulfite

• Repairing diaphragms in pumps

• Fixing air lock issues in pumps

• Fixing air lock issues in feed lines

• Fixing issues in winter with lines freezing

• Repairing/ replacing bisulfite pumps

10

Routine maintenance associated to any UV system

11

Typical maintenance activities

acc. to “UV Disinfection for Wastewater: Low-Dose Application Guidance for Secondary and Tertiary Discharges”

Weekly Routine Maintenance Activities

Check & calibrate online UV transmittance analyzer

12

Accessory to most UV systems

• Relevant to assure reliable and most economic disinfection

• Self cleaning component (ultrasonic)

• Easy access from top of channel• Manual cleaning / compressed air

• ~30 minutes for cleaning 1/week• ~45 minutes for calibration (if

required; approx. 1/ month)

Monthly Routine Maintenance Activities

13

Check sleeves and wiper for leaks & cleaning efficiency

Traditional/ horizontal UV systems

• Use crane to remove bank from channel

• Visual inspection• Check of leakage to either

chemical cleaning agent, hydraulic-oil, or pneumatic air losses

• >10 minutes / bank (leakage detection may sometimes be challenging and time consuming)

Monthly Routine Maintenance Activities

14

Check sleeves and wiper for leaks & cleaning efficiency

Duron inclined UV systems

• Lift module via integral lifting• Visual inspection• No risk of leakage due to

electrically driven purely mechanical wiper

• ~5-10 minutes / bank

Maintenance Activities – When Required

15

Replace lamps

Traditional, horizontal UV systems

• Use crane to remove bank/ module from channel

• Disconnect bank/ module from junction box

• Disconnect lamps from lamp cables

• Replace lamps as required• Return UV bank/ module into

channel

• Min 15 minutes / module


16

Replace lamps


• Open module cover; module can remain in channel

• Alternatively lift module out of channel

• Disconnect lamps to be replaced• Replace lamps as required

• ~5-10 minutes / lamp

17

Replace wiper rings/ cleaning solution

Horizontal UV systems

• Use crane to remove entire bank from channel

• Remove all quartz sleeves (min. 2x today’s lamp count!)

• Replace wiper rings

• Return quartz sleeves

Additional work (depending on type of system):

• In case of chemical-mechanical wipers: check and replenish cleaning solution; replace if discolored

• In case of hydraulic driven wipers: check for leakage points

• In case of pneumatic driven wipers: check for leakage points


18

Replace wiper rings/ cleaning solution


• Fast & simple to conduct within ~15 min for a complete module

• 1 pre-assembled component to be replaced

• Conducted by 1 person without the need for any tools

• No cleaning solution required, no handling of chemicals

• No risk for leakage of any fluent


Conclusion

19

“We now spend only about 1/3 of the time with

maintenance activities on the UV system than we did on

the Sodium hypochlorite/ Sodium bisulfite system.”

Jeff Lamson

an operators’ perspective: how new uv system designs

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