West Basin s Ocean Water Desalination Intake Biofouling and Corrosion Study

Transcription

1 West Basin s Ocean Water Desalination Intake Biofouling and Corrosion Study Metropolitan Water District Foundational Action Funding Program Diane Gatza, Desalination Project Manager February 23 rd, 2017

2 PRESENTATION OVERVIEW Desalination Program History Intake experiences Study Objectives Intake Screen Testing Conclusions Intake Piping Testing Conclusions

3 WEST BASIN MWD Division I: HAROLD C. WILLIAMS President Division II: GLORIA D. GRAY Secretary Division III: CAROL W. KWAN Division IV: SCOTT HOUSTON Vice President Division V: DONALD L. DEAR Treasurer

4 DESALINATION PROGRAM HISTORY Pilot Facility El Segundo, Calif Research Studies Completed ~$3.3M Demonstration Facility Redondo Beach, Calif Research Studies ~$25M 4 DESALINATION PROGRAM OVERVIEW

5 DESALINATION DEMONSTRATION FACILTIY West Basin Demo Intake Location ~2000 off shore ~30 deep

6 INTAKE SYSTEM Material Copper/Nickel Alloy Useful Life 20+ years Flow Specifics 0.5 ft/sec approach velocity Any capacity (higher flows = more screens/larger screens) Construction Specifics Connected to a super duplex stainless steel manifold structure HDPE pipe connects to the steel manifold and carries into the facility Chlorination System Used chlorine and chloramine for biofouling control (only on the pipes)

7 INTAKE SCREENS - CORROSION

8 INTAKE SCREENS - BIOFOULING

9 INTAKE PIPING - BIOFOULING

10 STUDY OBJECTIVES 1. Intake Screen 1. Corrosion 1. Quantify rates of corrosion 2. Identify best material selection for future screens 2. Biofouling 1. Quantify rates of biofouling 2. Identify best metals for reducing biofouling and increasing useable asset life 2. Intake Piping 1. Biofouling 1. Quantify rates of biofouling 2. Identify best means of eliminating or reducing biofouling

11 SCOPE OF WORK General Project Coordination Literature Review Intake Piping Design of Pipe Testing Skid Construction of Pipe Skid Operation of Pipe Skid Intake Pipe Biofouling Testing Intake Screen Acquire coupons from manufacturers Wedge wire and solid pieces Construct a device to hold coupons in open ocean Intake Screen Biofouling Testing Intake Screen Corrosion Testing Final Report Study initiated January 2014 Study completed March 2015 Consultants Tetra Tech Tenera Environmental V&A Consultants

12 INTAKE SCREEN TESTING 5 Materials for testing CuNi (UNS C70600) 2. Johnson Screen Z Alloy (a proprietary copper-nickel alloy) CuNi (UNS C71500) Duplex stainless steel Duplex stainless steel (coated with Sherwin Williams Foul Release System)

13 INTAKE SCREEN TESTING Five racks deployed Four protected test pieces Collection intervals Every three months for one year Final rack still out in the ocean Corrosion Testing (lab) Weigh all samples. Examine samples visually to 40X Color photograph, one of each material type 10X, one of each material type 50X, one of each material type Scanning Electron Micrograph 100X, one of each material type Energy Dispersive Spectroscopy (EDS), one of each material type Biofouling Testing (photographic) % cover of growth Taxonomy of the material Size of taxa

14 *Photos taken after 364 days INTAKE SCREEN FINDINGS

15 INTAKE SCREEN FINDINGS Cu-Ni Z-Alloy Cu-Ni Coated Duplex SS Duplex SS *All Samples Taken after 364 days

16 INTAKE SCREEN FINDINGS Cu-Ni Z-Alloy Cu-Ni Coated Duplex SS Duplex SS *All Samples Taken after 364 days

17 INTAKE SCREEN FINDINGS

18 Three - 3 test pipes INTAKE PIPE TESTING Control Run (no chemical addition) Continuous Chloramination (dosed at 5.0 ppm) Shock Chlorination (dosed at 20.0 ppm for 1 hour once per week) Flanged joints for ridges Collection intervals Every three months Timed with the off-shore collection

19 INTAKE PIPE FINDINGS Control Pipe Continuous Chloramination Weekly Shock Chlorination *All Samples Taken at the end of the test

20 INTAKE PIPE FINDINGS

21 CONCLUSIONS Best intake screen material to provide longevity (3+ years) and still control biofouling and corrosion: Cu-Ni alloy Best intake pipe biofouling corrosion strategy: Continuous chloramine dosing Can be replaced by continuous chlorine dosing if needed Evaluate site specific water quality and biology No manufacturer will guarantee their screen will work Fine balance between biofouling and corrosion for screen selection Depends on the ultimate project goal

22 Thank you Diane Gatza