Chromium-6 Drinking Water Regulation Workshop. Presented by: Steve Bigley & Mark Johnson

Transcription

1 Chromium-6 Drinking Water Regulation Workshop Presented by: Steve Bigley & Mark Johnson

2 AGENDA Introductions Chromium-6 New Regulation Compliance Options/Costs Customer Input

3 CHROMIUM (Cr) 21 st most abundant element Chromic oxide - 9 th most abundant compound in earth s crust Occurs primarily as chromium-3 (Cr3) or chromium-6 (Cr6) in water Cr6 is more soluble in water People need Cr3 to live Sources in Water Statewide - primarily natural, some isolated industrial sources Coachella Valley natural occurrence

4 LOCAL Cr6 OCCURRENCE Found naturally in Coachella Valley groundwater Levels from <1 to 21 parts per billion (ppb) 1 ppb = 1 drop in a swimming pool Cr6 levels below detection in Colorado River water used for aquifer replenishment 4

5 NEW Cr6 REGULATION In April of 2014, CDPH released a Maximum Contaminant Level (MCL) for Cr6 of milligrams per liter (mg/l) effective July 1, mg/l = 10 ppb

6 WHY IS Cr6 BEING REGULATED Required by CA Senate Bill 351 (Ortiz) 2008 rodent study Precautionary assumption Predicted to reduce potential long-term health impact

7 TIMELINE OF REGULATION Initial compliance monitoring on or before January 1, 2015 Monitoring is for each well Initial results determine next steps Compliance with Cr6 limit based on annual average

8 COMPLIANCE SCHEDULE Federal drinking water standards receive fiveyear compliance period Time is needed to build facilities to comply Being out of compliance may increase ratepayer costs

9 CVWD DRINKING WATER SUPPLY 96 active wells provide a distributed supply throughout the Coachella Valley 37 wells expected to have Cr6 levels above 10 ppb 19 wells have Cr6 levels between 8-10 ppb Mid-Valley Pipeline

10 OPTIONS FOR ACHIEVING COMPLIANCE Groundwater treatment - Individual well treatment - Clustered well treatment Surface water (Colorado River water) - Treatment and blending with groundwater - Groundwater replenishment Combination of groundwater and surface water Point-of-use or point-of-entry

11 CHROMIUM REMOVAL BEST AVAILABLE TECHNOLOGIES Weak-Base Anion Exchange (WBA) Strong-Base Anion Exchange with Residuals Treatment (SBA) Reduction Coagulation Filtration (RCF or RCMF) Reverse Osmosis (RO)

12 POINT-OF-USE Reverse Osmosis (RO) highly effective Regulatory complications Only limited use currently allowed Challenging oversight High cost Driven by Operation & Maintenance demands

13 ION EXCHANGE TREATMENT Ion Exchange Ions of Cr6 attach to specially coated resin beads Cr6 in water Chloride on resin Resin bead

14 WEAK BASE ANION EXCHANGE (WBA) Raw Water Treated Water Carbon dioxide for ph reduction Bag filters Resin vessels Aeration or Caustic Operations Bag filter replacement Carbon dioxide refills Resin replacement

15 STRONG BASE ANION EXCHANGE (SBA) Raw Water Resin Vessels Bag Filters Operations Regeneration Residuals treatment and disposal Treated Water OFF-SITE REGENERATION Brine Tanks Waste Brine Tanks TREATMENT OF SPENT BRINE AND DISPOSAL OF BRINE AND SOLIDS

16 COMPLIANCE ELEMENTS Pilot testing/source of supply study Develop compliance plan Develop funding plan Complete design, environmental & right-ofway Complete construction Get state approval

17 EVALUATION CRITERIA Water quality benefit (regulatory compliance -current and future, taste) Cost (capital, O&M and annualized cost) Operational complexity (number of staff, level of treatment certification) Operational flexibility (multiple sources of supply, ability to adapt to changing conditions) Diversification (supply, treatment, meets future demand, reliability) Public acceptance / environmental (location, chemicals, truck traffic, noise, confidence with solution) Implementation complexity (Right of way, encroachment permits, Division of Drinking Water permitting, timeline)

18 TYPICAL SITE PLAN CLUSTERED GROUNDWATER TREATMENT - WBA

19 WELL SITE RENDERING WBA TREATMENT

20 TYPICAL SITE PLAN INDIVIDUAL WELL TREATMENT (SBA)

21 WELL SITE RENDERING SBA TREATMENT

22 CENTRALIZED SBA RESIN REGENERATION PLANT Used for SBA groundwater treatment option Consolidates regeneration for: Brine Evaporation Ponds Ion Exchange Resign Regeneration Facility - Cost savings - Redundancy - Increased reliability - Recycled/reduced waste production compared to CVWD s existing SBA with on-site regeneration

23 IMPORTED WATER Essential for managing groundwater Meeting replenishment goals Direct replenishment Source substitution Coachella Canal (1949) State Water Project (1973)

24 SURFACE WATER TREATMENT

25 PRELIMINARY PLANT LOCATIONS

26 SURFACE WATER TREATMENT Example Treatment Train Coachella Canal Rapid Mix Flocculation DAF or Plate Settlers Pre-oxidant: Cl 2 Coagulant: Alum, or PACl, Polymer ph Adjustment: H 2 SO 4 or CO 2 Supernatant Recycle Cl 2 Granular Media or Membrane Filtration GAC Cl 2 Waste backwash water Clearwell BW Settler Groundwater for blending TDS NaOH Finished water to system Ground water Reductant: Ferrous To sewer or evaporation ponds Dewatering

27 SURFACE WATER TREATMENT WITH GROUNDWATER BLENDING 8 MGD surface water TDS = 880 ppm Cr6 = 0 ppb 4 MGD groundwater TDS = 171 ppm Cr6 = 14 ppb 8 MGD groundwater TDS = 171 ppm Cr6 = 14 ppb 12 MGD surface water treatment plant TDS = 672 ppm Cr6 = 0.6 ppb Surface water could make up some supply deficit All impacted wells can be used, making up the remainder of the deficit Cr6 is well below the limit in Colorado River water 20 MGD supply sent to customers TDS = 460 ppm Cr6 = 6 ppb

28 COST-SAVING CONSIDERATIONS Split stream groundwater treatment/blending Surface water blending with groundwater Centralized regeneration

29 MID-VALLEY REPLENISHMENT Imported water used to replenish groundwater Long-term benefits Relieves groundwater overdraft Reduces groundwater Cr6 Proven Long local history Simple to implement

30 COST COMPARISON OF SCENARIOS CAPITAL ($ M) Clustered Well Treatment Individual Well Treatment Mid-Valley SWTP and Individual Well Treatment East Valley SWTP and Individual Well Treatment Point-of-use Mid-Valley and East Valley SWTP and Individual Well Treatment Bars provide a cost range that reflects project cost uncertainties at this conceptual phase

31 COST COMPARISON OF SCENARIOS ANNUALIZED ($ M) Bars provide a cost range that reflects project cost uncertainties at this conceptual phase

32 PHASED IMPLEMENTATION 37 wells now expected to be out of compliance Common elements including 19 wells 18 wells treated Mid-valley surface water treatment + 14 wells East valley surface water treatment + 4 wells Mid-valley & east valley surface water treatment, no well treatment Recharge & one of the other options above

33 TIMELINE Pilot Testing Compliance Plan Financing Design Land Acquisition & Permitting Construction Acceptance

34 NEXT STEPS Provide study results and public feedback to Board Board determines compliance plan Develop funding plan & rate impacts Public outreach Initiate design, environmental & right-of-way Construction begins

35 Questions & Comments