OPG WTP Performance / Trends in High Purity Water Treatment

Presented at IAPWS WorkshopMay 11, 2009

By

Gabriel Nicolaides

Outline

• Darlington WTP - Background• Pickering WTP - Background• Demin Water Quality: DND vs. PND• Demin Water Quality Survey• Trends in High Purity Water Treatment• New WTP Design Considerations• RO for Primary Demineralization• UF for Pretreatment• Different Options for Polishing Deionization

Darlington WTP - Background

WTP design finalized in 1985, WTP in service 1986 Fourth in a series of WTPs designed by “old” Ontario

Hydro: 1. PNGS, 2. BNGS-A, 3. BNGS-B, 4. DNGS “conventional” WTP design consisting of clarification /

sand filtration / activated carbon / ion exchange Key features incorporated into the design of the WTP:

• Deep water intake 1 km off-shore, 10 m below the water surface• Dual clarifiers • External regeneration of mixed beds

Darlington WTP Process

Pickering WTP - Background

• OPG’s 1st outsourced WTP

• 10 year operating contract awarded to Nalco in Feb. 2001; a local company, Eco-Tec, supplied the equipment and assists with WTP operation and key maintenance activities

• WTP in-service since Oct. 2001

Site Selection/Raw Water Source

• WTP located outside of protected area; allows vendor ready access and permits equipment retrofits as commercial modifications

• CCWR outfall structure used for raw water supply pumps, warm raw water for improved RO efficiency and reduced foot-print

Pickering WTP – External View

OPG owns the building housing the WTP; Nalco owns and operates the equipment

PND WTP Process

Pickering WTP – Internal View

Demin Water Quality: DND vs. PND

WTP Demineralized Water Quality at PND and DND vs. OPG Specifications and WANO Guidelines

Parameters Units Pickering WTP Darlington WTP1 Darlington WTP2 WANO Achievable PWR

(Mean: 2004 - 2006) (2003 Quality Data) (Mean: 2006 - 2007) Pickering OPG / Darlington3 Make-up Water Guidelines4

Temperature ( ºC) 20.6 NA NA NA NA NAResistivity at 25 ºC Mohm-cm 18.28 17.2 16.9 > 16.7 > 12.5 > 12.5Calculated Conductivity at 25 ºC mS/m 0.0055 0.0058 0.0059 < 0.006 ≤ 0.008 < 0.008Sodium µg/kg 0.074 0.14 0.08 < 0.2 ≤ 1.0 < 1.0Reactive Silica µg/kg 0.33 2.33 5.38 < 2.0 ≤ 10 < 10Total Organic Carbon (TOC) µg/kg 6.1 125 NA < 10.0 NS < 20

"NA" - Not Available; "NS" - Not Specified1 Darlington WTP Plant Performance Review, Report No. N-REP-74000-10000 R00, 20032 Darlington WTP Plant Performance & Operating Cost Review, Report No. N-REP-74000-10003 R00, July 20083 OPG Chemistry Specifications, N-STH-01807-10000, Section B16, Rev. 00, June 19, 20034 Guidelines for Chemistry at Nuclear Power Stations, WANO GL 2001-08, August 2002

Demin Water Chemistry Control Limits

Demin Water Quality Survey

• DND WTP was ranked against 24 other Nuclear Stations. DND WTP ranked 10th out of 25 stations, placing it in the 2nd quartile

• PND WTP ranked 6th out of the 25 stations, placing it in the 1st quartile

Trends in High Purity Water Treatment

• Outsourcing of WTP Operation• Extensive Use of Membrane-Based

Technologies (e.g. UF, RO)• Improved demin water quality especially

lower Na & TOC levels• Reduction / elimination of hazardous

chemicals (acid, caustic)• Automatic operation / remote monitoring

reduces labour cost

New WTP Design Considerations

• What are you starting with? - Feed water Quality & Characteristics– Source – surface water, well water, other– Seasonal Variations & Effects– Dissolved & Suspended Solids

• What quality do you need? - Finished water Quality & Characteristics– Benchmark Chemistry– Dissolved Solids (TDS, specific ions, etc.)– TOC

“Heart” of the Water Treatment System is RO

ROUF EDI or IX polishing

RO Membrane Feed Specs

• RO feedwater requirements are:

SDI: < 3.0 Chlorine (free): < 0.01 ppm Iron: < 0.1 ppm Turbidity: < 0.2 NTU

Filtration Spectrum

Hollow-fibre Ultrafiltration

Inlet Water

1 mm Screen

Membrane TankZW1000V3

Reject NeutralizedWaste to Drain/Sewer

Drain/Recirculation

Pump

Air ScourBlower

NaOH SodiumBisulphite

Optional for Neutralization

Permeate to TreatedWater Storage

Permeate/Bakcpulse

Pump

StorageTank

BackpulseTank

NaOCl Citric Acid

Screen

Reject / neutralized waste to drain

Comparison of UF vs. MMF

Pretreatment UF Conventional

Description • ZW 1000 IHF UF, Out/In• 0.02 m nominal pore size

• MMF• 5 m cartridge filter

Treated Water Quality

• Consistent, reliable quality• SDI < 2.5, 100% of the time, usually < 1.5• Turbidity: < 0.1 NTU• Positive barrier to particles and pathogens - no breakthrough• Bacteria: > 5 log removal• GiardiaCyst: > 4 log removal• Virus: > 4 log removal

• Fluctuating quality• SDI < 4 ~90% of the time

• Turbidity: < 1.0 NTU• MMF not a positive barrier to colloidal and suspended particles. Quality of water produced fluctuates significantly with respect to particulates.

RO Membrane Systems: < 2 MegOhm

• RO rejection range of 96 – 99+% on dissolved solids

Deionization: 2 – 18 MegOhm

– Electrodeionization (EDI) – regenerated continuously with electricity

– Traditional DI – resin is regenerated with acid and caustic on-site

– Traditional DI – resin regenerated off-site

Acknowledgements

• GE Water & Process Technologies: Sandy Schexnailder