Enhanced Research Using RCF For Cr(VI) Removal. MWD FAF Technical Conference February 23, 2017

Transcription

1 Enhanced Research Using RCF For Cr(VI) Removal MWD FAF Technical Conference February 23, 2017

2 City of Glendale & Water Incorporated 1906 Approx. 200,000 Residents Approx. 33,000 water services One of Founding MWD Member Agencies in 1928 Pumper in San Fernando Basin and Verdugo Basin 30% to 40% local supply Co-owner of LA Glendale Water Reclamation Plant First recycled water use in 1978 Three Superfund Operable Units Cr6 Removal Research Project Starting in 2001 Two demonstration scale facilities, WBA and RCF MWD FAF at the RCF

3 RCF Facility Reduction of Cr(VI) compound to Cr(III) by adding ferrous sulfate Oxidize excess ferrous with either oxygen or chlorine Coagulation of Cr(III) compounds into larger particles using polymers Filtration of Cr(III) particles

4 MWD FAF Cr(VI) Removal Study Project Stakeholders Project Research Team Hazen and Sawyer Project Operation Team CDM Smith Inc. Project Management Team City of Glendale Project Sponsors MWD and DWR (Proposition 50)

5 MWD FAF Cr(VI) Removal Study Objectives (Tasks): 1) Optimize reduction time and iron dose in the RCF treatment process 2) Testing of RCF alternative pumping 3) Cost evaluation of Enhanced RCF vs. SBA & WBA 4) Develop site layouts and treatment process drawings 5) Blending analysis

6 Original RCF vs Enhanced RCF Original RCF Enhanced RCF Cr(VI) Reduction Time (mins) Facility Footprint Large Small Ferrous Iron Dosage (mg/l) Oxidation Approach Filter Pump Aeration tank/chlorine contact tank Progressive cavity pump Inline chlorine injection w/ static mixer Centrifugal pump

7 Enhanced RCF Process Schematic

8 Task 1 Optimize reduction time and iron dose Criteria: 1) Tested three reduction time 15, 5 and 1 minute. 2) Using two ferrous iron dose 2 and 3 mg/l 3) Chlorine residual target: mg/l 4) Total of six (6) runs in six weeks

9 Task 1 Optimize reduction time and iron dose Results: 1) Reduction time of 1 min. was not sufficient. 2) Reduction time of 5 and 15 mins was effective for Cr(VI) reduction (below or close to 1 µg/l). 3) Ferrous iron dose of 2 mg/l was effective for low Cr(VI); 3 mg/l was needed for high Cr(VI) sources. 4) Only minor Cr(III) re-oxidation from chlorination

10 RCF Pumping Approach Progressive Cavity Pump Specified for the Original RCF To minimize floc breakup before the filters Costly (6x the centrifugal pump cost)

11 RCF Pumping Approach Centrifugal Pump Tested in the Enhanced RCF Study Significant cost savings Easy to obtain

12 Task 2 Testing of RCF Alternative Pumping Operating the RCF with Centrifugal Pump Tested two ferrous iron dose: 2 and 3 mg/l With two reduction tims: 5 and 15 mins. Other operational conditions same as progressive cavity pumping Total of four runs with 1 week each run

13 Task 2 Testing of RCF Alternative Pumping Results: Cr(III) particles were effectively removed by granular media filtration with centrifugal pumping (particles did not break apart) Chromium concentrations in filter effluent were similar to progressive cavity pump Results suggest that centrifugal pump can replace progressive cavity pump for cost savings.

14 Task 3 Cost Analysis Three leading technologies for Cr(VI) removal: RCF (with and without recycle backwash water) WBA SBA Treatment Costs includes: Capital cost Annual O&M cost 20-year net present value (NPV) Comparing four system flow rates (gpm): 100, 500, 1,000, and 2,000

15 Task 3 Cost Analysis Results

16 Task 3 Cost Analysis Results SBA lowest treatment cost for 500 gpm WBA lowest treatment cost for 100 gpm RCF with recycle higher cost due to additional infrastructure and the recycling wastewater process Overall SBA, WBA, and RCF (without recycle) cost differences are not large for system 500 gpm Other factors: site space, sewer access, and operational preference

17 Task 3 Cost Analysis Results Treatment 100 gpm 500 gpm 1000 gpm 2000 gpm RCF with recycle $2,795 $925 $627 $509 RCF no recycle $1,939 $575 $386 $319 SBA (110 mg/l Sulfate) $1,932 $557 $384 $309 WBA $1,384 $549 $394 $350

18 Task 4 Treatment Process and Equipment Layouts Site layout and treatment process were developed based on a 1,000 gpm system. Treatment site space requirement: WBA (smallest) RCF without recycle SBA RCF with recycle (largest)

19 Task 4 WBA Equipment Layout

20 Task 4 RCF without Recycle Equipment Layout

21 Task 4 SBA Equipment Layout

22 Task 4 RCF with Recycle Equipment Layout

23 Task 4 WBA PFD

24 Task 4 RCF without Recycle PFD

25 Task 4 RCF with Recycle PFD

26 Task 4 SBA PFD

27 Task 5 Blending Analysis Three approaches for Cr(VI) MCL compliance 1. Treatment approach (i.e. removal) 2. Non-treatment approach (i.e. blending) 3. Combination of treatment and nontreatment approaches (i.e. treat only a portion of the flow and achieve Cr(VI) treatment goal through blending with lower Cr(VI) water)

28 Task 5 Blending Analysis Treatment combined with non-treatment Pros: require smaller treatment footprint lower capital cost Cons: require an alternative water source with lower Cr(VI) for blending may result in higher O&M cost

29 Task 5 Blending Analysis Study Scenarios No. Scenario Purpose 1 Baseline Evaluates the treatment costs of blending versus non-blending for RCF, WBA, and SBA using Glendale s water quality. 2 Effects of Water Quality Evaluates the impacts of key water quality on the comparison of blending versus non-blending for WBA and SBA. 3 Effects of Treatment Goal Evaluates the impacts of Cr(VI) treatment goal on the comparison of blending versus non-blending for RCF, WBA and SBA.

30 Task 5 Blending Analysis - Results Scenario 1 Treatment Costs The blending option showed significant savings in terms of unit treatment costs for all three technologies Scenario 2 Water Quality Impacting Factors Alkalinity the key limiting factor (ph) for WBA process WBA pocess require low ph Sulfate controls the resin regen frequency in SBA process higher sulfate concentration increase regen frequency Blending option showed an advantage over the nonblending option

31 Task 5 Blending Analysis - Results Scenario 3 Impacts of different Cr(VI) treatment goals With Cr(VI) treatment goals at 6 and 8 µg/l, blending option continued to show an overall cost savings over non-blending option

32 Conclusion The RCF process can be optimized to reduce footprint and cost by: Eliminating multiple process equipment with reduction time of 5 minutes, in lieu of 45 mins. Use of inline chlorine injection, in lieu of chlorine contact tank or aeration tank Use of centrifugal filtration pump, in lieu of progressive cavity pump Integrating blending more cost effective than treating the entire flow

33 Link to Cr(VI) Research Reports

34 Q & A