Ultrapure Hexavalent Chromium Treatment for Residential Supply

Transcription

1 Mojave Water Agency Technical Advisory Committee Meeting April 7, 2016 Apple Valley, CA Ultrapure Hexavalent Chromium Treatment for Residential Supply David Eberle, PE Arcadis Phoenix, AZ Kevin Sullivan, PE PG&E San Francisco, CA

2 Focus of Today s Presentation Presentation Objectives 1. Provide a brief overview of the Remediation Program, including successes and ongoing progress. 2. Discuss the Whole-House Replacement Water Program for residential Cr(VI) treatment. 3. Elaborate on the significant complications of achieving ultrapure water quality standards in residential / municipal treatment applications. 2

3 Remediation Program Overview 3

4 The Hinkley Gas Compressor Station used hexavalent chromium in cooling water to prevent corrosion; spent water stored in unlined ponds. 4

5 Plume Monitored, Contained, & Treated Cr(VI) < 10 g/l in all active Hinkley domestic wells Plume exceeding 10 g/l is localized Network of monitoring wells tracks plume Strategic pumping and fresh water injection contains plume Treatment has shown proven results 5

6 Remediation is well underway Significant Remediation Progress Final remedy includes in-situ, agricultural treatment and fresh water injection wells Highest concentrations treated in near-term Lower concentrations require ~ 40 years to fully treat 6

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9 Residential Treatment 9

10 Residential Treatment Background Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 10

11 CAO R6V A2 ( The Order ) Issued by Lahontan Regional Water Quality Control Board Replacement water service required for affected area wells: Laterally within one mile down- / cross-gradient of plume boundary 3.2 g/l total chromium 3.1 g/l Cr(VI) No state or federal MCL for Cr(VI) at the time of the Order Mandated PHG as the Cr(VI) treatment standard: 0.02 g/l Allowed 0.06 g/l, acknowledging analytical reliability limits Required CA drinking water standards at home interior sinks Includes treatment of contaminants unrelated to Cr(VI) plume Nitrate, arsenic, and uranium known to occur in Hinkley groundwater 11

12 Residential Treatment Background Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 12

13 Residential Treatment Background Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 October 5, 2012 Deadline for installation of first two treatment systems 13

14 Residential Treatment Background Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 October 5, 2012 Deadline for installation of first two treatment systems 120 Days Design Procurement Fabrication Installation Testing Commissioning 14

15 Residential Treatment Background Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 October 5, 2012 Deadline for installation of first two treatment systems August 31, 2013 Deadline for installation of all treatment systems 15

16 Residential Treatment Background Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 October 5, 2012 Deadline for installation of first two treatment systems August 31, 2013 Deadline for installation of all treatment systems 15 Months 30+ Locations 16

17 Challenges Compliance standards: Whole-house water Cr(VI) < 0.06 g/l CA primary / secondary MCLs at interior sinks Schedule Treatment flexibility Climate: Extreme summer heat (>105 o F) Freezing winter nights (<20 o F) High winds Airborne dust Vandalism Sustainability 17

18 Whole-House Water POE Treatment Treatment Process ResinTech SBG1 strong base anion exchange resin 2 x 6 ft 3 (~45 gal) resin vessels in lead-lag configuration Process Design & Operation Model individual well water quality Determine # of bed volumes to lead vessel breakthrough Enter 80% and 100% BVs into system PLC SCADA alert issued at 80% BVs Remove lead vessel, move lag to lead, install new lag 18

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23 Reverse Osmosis POU Treatment Kinetico K5 Drinking Water Station Performance validated in prior pilot testing Certified for Cr(VI) removal by the California Division of Drinking Water & Environmental Management No certification for removal to PHG levels Carbon / sediment prefilter cartridge Taste & odor post-filter cartridge 98 percent Cr(VI) rejection expected (under standard test conditions) 23

24 Sustainability Features Not required, but important! No emissions Resins is regenerated offsite & recycled to other applications IX systems operates at 100% recovery (no wasted water) RO concentrate blends with household drain flows: Percolates back into groundwater table Exhibits fewer contaminants (removed by IX) WHW treatment units are painted to match desert landscape: Reflects heat Visually less obtrusive 24

25 System Performance Cr(VI) Removal Sample Location # of Cr(VI) Samples Total > 0.06 g/l % of Samples with Cr(VI) Range of Cr(VI) Detections ( g/l) IX Effluent % RO Permeate 41 up to 0.48 RO permeate detections occurred more frequently and at higher concentrations Most RO detections occurred when IX effluent samples were < 0.06 g/l (i.e., non-detect) Confirmation samples were almost always < 0.06 g/l 25

26 System Performance Cr(VI) Removal Sample Location # of Cr(VI) Samples Total > 0.06 g/l % of Samples with Cr(VI) Range of Cr(VI) Detections ( g/l) IX Effluent % RO Permeate 41 up to 0.48 Bottled Water %

27 Potential Sources of Cr(VI) 1. Analytical contamination and error 2. Whole-house treatment system components 3. Household plumbing 4. RO unit components 27

28 Analytical Contamination and Error Method Variation with respect to: Holding times Buffering agents Method Use of field filtration (218.6) ** Discontinued ** Potential error due to either field filtration or nano-oxidation could influence the detection of Cr(VI) at 0.06 g/l levels even when the method is precisely executed. 28

29 Whole-House Treatment System Components Primary Component Materials / Chemicals PVC plastic Stainless steel Other metals Erodible chlorine tablets Cr(VI) leaching? 29

30 Household Plumbing Paired Faucet and RO Tap Sampling Results Cr(VI) Concentration ( g/l) Sample Date IX Effluent Sink 1 Sink 2 Sink 3 Faucet RO Faucet RO Faucet RO 11/12/12 ND ND 0.07 ND 0.5 ND 12/10/12 ND 0.13 ND ND ND 0.15 ND 30

31 Household Plumbing Paired Faucet and RO Tap Sampling Results Cr(VI) Concentration ( g/l) Sample Date IX Effluent Sink 1 Sink 2 Sink 3 Faucet RO Faucet RO Faucet RO 11/12/12 ND ND 0.07 ND 0.5 ND > 0.6 g/l needed for 0.06 g/l RO permeate 90% rejection 12/10/12 ND 0.13 ND ND ND 0.15 ND Household plumbing can leach detectable Cr(VI) Plumbing materials could contribute to RO permeate detections 31

32 RO Unit Components Components Downstream of Membrane Barrier Component Post-filter cartridge Stainless steel shaft in metering valve Bladder tank 32

33 RO Unit Components Components Downstream of Membrane Barrier Component Post-filter cartridge Stainless steel shaft in metering valve Bladder tank Both exhibited total chromium [Cr(III) + Cr(VI)] detections two orders of magnitude higher than the 0.06 g/l Cr(VI) PHG 33

34 Denouement Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 October 5, 2012 Deadline for installation of first two treatment systems August 31, 2013 Deadline for installation of all (30+) treatment systems 34

35 Denouement Date(s) Event June 7, 2012 October 5, 2012 August 31, 2013 Cleanup and Abatement Order No. R6V A2 Cr(VI) concentrations are below 10 gl in all Deadline for installation of first two treatment systems domestic and community wells. Deadline for installation of all (30+) treatment systems July 1, 2014 California Cr(VI) MCL of 10 g/l becomes effective 35

36 Denouement Date(s) Event June 7, 2012 Cleanup and Abatement Order No. R6V A2 October 5, 2012 Deadline for installation of first two treatment systems August 31, 2013 Deadline for installation of all (30+) treatment systems July 1, 2014 California Cr(VI) MCL of 10 g/l becomes effective October 31, 2014 Whole-House Replacement Water Program concludes 36

37 Summary & Conclusions Key Messages 1. Ultrapure domestic water treatment is achievable 2. Ultrapure domestic water treatment has substantial challenges 3. Parts-per-trillion contamination may be virtually ubiquitous 4. All materials (even certified ) can exhibit leaching in water: Concentration Kinetics 37

38 Summary & Conclusions Key Messages 1. Ultrapure domestic water treatment is achievable 2. Ultrapure domestic water treatment has substantial challenges 3. Parts-per-trillion contamination may be virtually ubiquitous 4. All materials (even certified ) can exhibit leaching in water: Concentration Kinetics Driven by advancements in analytical methods and treatment technologies? 38

39 Summary & Conclusions Key Messages 1. Ultrapure domestic water treatment is achievable 2. Ultrapure domestic water treatment has substantial challenges 3. Parts-per-trillion contamination may be virtually ubiquitous 4. All materials (even certified ) can exhibit leaching in water: Concentration Kinetics Is it appropriate? Driven by advancements in analytical methods and treatment technologies? 39

40 Summary & Conclusions Key Messages 1. Ultrapure domestic water treatment is achievable 2. Ultrapure domestic water treatment has substantial challenges 3. Parts-per-trillion contamination may be virtually ubiquitous 4. All materials (even certified ) can exhibit leaching in water: Concentration Kinetics Are we prepared for the implications? Driven by advancements in analytical methods and treatment technologies? 40

41 Questions? David Eberle Arcadis (602) Kevin Sullivan PG&E (925)