Long Beach Seawater Desalination

Transcription

1 Urban Water Institute Conference Seawater Desalination and Power Long Beach Seawater Desalination Presented by Kevin L. Wattier, General Manager June 23, 2005

2 LBWD s Resource Mix Conservation 14% Conservation 15% Reclaimed 6% Groundwater 38% Reclaimed 12% Groundwater 33% Imports 42% Imports 30% Desal 10%

3 LBWD s Phased Approach Pilot Testing (2001, on-going) AWWARF Prototype ( ) USBR LADWP Production Plant (~2012)

4 Long Beach Research Initiatives Pretreatment NF 2 Post treatment / Distribution Upcoming Under Ocean Floor Intake and Discharge Boron Removal AwwaRF Project -NF 2 Verification -Predictive Model Upcoming Prototype Research -Energy Recovery -Process Optimization ClO 2 / UV Ongoing Disinfectant Issues

5 Boron Removal Background Naturally occurring in seawater (~4.5 mg/l) Show reproductive health effect in animals Toxic to some common trees Typically < 1 mg/l in surface waters CDHS established Action Level at 1 mg/l WHO guideline at 0.5 mg/l

6 Boron Removal Strategy Selecting appropriate base addition location is critical. Base Injection Pt Option 1 Base Injection Pt Option 2 Alk = 122 mg/l Ca 2+ = 447 mg/l Stage 1 Stage 2 Alk = 10.4 mg/l Ca 2+ = 11.7 mg/l More base required to alter ph HIGH potential for fouling Less base required to alter ph 97% rejection of Ca 2+. Decreased potential for fouling

7 Boron Removal Results Raw Water Boron (mg/l) Stage 2 Permeate NaOH dose ~ 15 mg/l California Action Level 0.5 WHO Guideline ph

8 AwwaRF Project Objectives Peer-reviewed reviewed verification/optimization of dual-pass NF process Membrane performance Bench-scale testing Process optimization Pilot-scale testing Predictive model Blending strategies Mitigation of DBP formation and corrosivity

9 AwwaRF Project Conclusions Generated computer model to predict NF membrane performance with seawater Selected suitable membranes for prototype-scale testing based on water quality and energy considerations kwh 1,000 gal Q % Q Obtained corrosion and DBP impacts blending desalinated seawater and existing supplies P + Q = 1F 1F 2F 2F 1CP1C 2CP Q 2C 2P 75% Q P

10 Disinfection Issues Problem Definition Initially, want to evaluate SDS DBP formation Observed rapid decay of residual disinfectant Isolated bromide as the cause Total Chlorine (mg/l) :00:00 DI Water Groundwater High EC/GW Blend 3:00:00 6:00:00 9:00:00 12:00:00 MWD Water High EC/MWD Blend 15:00:00 18:00:00 21:00:00 24:00:00 Time (hrs)

11 Disinfection Issues Blending Scenarios Scenario 1 Cl 2 Scenario 2 Desalinated Water Cl 2 Distribution System Desalinated Water Existing Water Cl 2 Free Cl 2 Distribution System Scenario 3 Cl 2 NH 3 Chloramine Desalinated Water Existing Water Distribution System

12 Disinfection Issues Summary Bromide is the cause for residual instability Need to establish a low Bromide standard TTHMs should not be a problem, but need to consider blend ratios and existing system water quality Additional work is currently underway to devise a comprehensive strategy to control residual instability

13 Upcoming Studies Prototype Research Energy Recovery Process Optimization Begin in 2005 and complete in 2007

14 Upcoming Studies Under Ocean Floor Intake and Discharge Seawater Intake Pretreatment Brine Disposal Prop 50 Funded Begin in 2006 and complete in 2009

15 Upcoming Studies Under Ocean Floor Intake and Discharge

16 Upcoming Studies ClO 2 / UV Key Objectives Primary Disinfection Minimize bio-fouling/increase membrane life Oxidation of emerging contaminant (toxins) Prop 50 Funded Begin in 2006 and complete in 2009

17 Additional Information Project Staff Diem X. Vuong, P.E. Dr. Robert Cheng, P.E. Tai Tseng, P.E. Eric Leung, P.E. Website: