Using Biological Treatment to Remove Metals: Norman's Pilot Test

Transcription

1 Using Biological Treatment to Remove Metals: Norman's Pilot Test Southwest AWWA Oklahoma City October 16, 2017 John Rehring, P.E. Carollo Engineers Chris Mattingly, P.E. City of Norman

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3 Discussion Overview Background Hevalent chromium and arsenic Drivers for Norman Biological treatment 101 Norman s pilot test Results and conclusions 3

4 Acknowledgements Collins Balcombe Oklahoma-Texas Area Office James Allard and Staff Oklahoma City Office Saied Delegah Denver Technical Center Chris Mattingly Project Manager Geri Wellborn WTP Manager Scott Aynes WTP Supervisor Brandon Dunagan Pilot Operator Giridhar Upadhyaya Project Engineer Jess Brown Carollo Research Group Director 4

5 Background 5

6 Regulatory Background Hexavalent chromium Cr(VI) California MCL 10 ug/l Potential federal MCL Naturally present in Oklahoma s Garber-Wellington aquifer Arsenic Also naturally present in Garber-Wellington Treat or shut down? 6

7 Groundwater is Key to Norman s Water Supply Future Supply diversity Treat or blend for Cr(VI) if and when necessary 7

8 Reduction/ Coagulation/ Filtration Effectively removes Cr(VI) High chemical costs ph adjustment required RO & EDR Effectively removes Cr(VI) High energy requirement Concentrated brine generation Ion Exchange Effectively removes Cr(VI) Selectivity issue Concentrated brine generation 8

9 Multiple contaminants Contaminant destruction High water recovery Low energy/ ops costs Natural & Sustainable Process Robust

10 O 2, NO 3 - ClO 4, Cr(VI) Se(VI) EPS Nutrients (P, NH 3 ) Organic carbon NH 3 Mn(II) Fe(II) CO 2, N 2, Cl-, Cr(III) NO 3-, Mn(IV), Se 0, Fe(III) 10

11 Reactor Nutrients Chlorine GAC Conventional Fixed-bed Biofilter Filter Biofilm GAC Bacteria in biofilm 11

12 Backwash wastewater to settling process, lagoon, or sewer Nutrients Polymer Well(s) Anoxic Bioreactor H 2 O 2 Aerobic Biofilter Disinfection Backwash 12

13 Norman s Pilot Test 13

14 Pilot Testing Phases at Norman September 2016 July Biological acclimation Process optimization Sustained optimal operation Robustness testing Intermittent operation 14

15 Pilot Testing Performance Targets Effluent Cr(VI) < 7 µg/l Effluent DO > 4 mg/l Effluent turbidity < 0.3 NTU for 95% of samples (in-line) HPC < 500 CFU/mL (4 log virus inactivation) Total coliform below detection (4 log virus inactivation) gpm 15

16 Results 16

17 Biological Acclimation for Nitrate Removal Occurred within 7 days 17

18 Biological Acclimation for Cr(VI) Removal Required Approximately 4 Months 18

19 Cr(VI) was the Predominant Chromium Species in the Raw Water 19

20 Cr(VI) was Reduced to Cr(III) in the Bioreactor 20

21 Biofilter Retains Cr(III) from the Bioreactor Effluent 21

22 Sustained Cr(VI) Removal Demonstrated using Optimized Operating Parameters Data Collected using Aqua Metrology System s In-line Analyzer 22

23 Is the System Robust? 23

24 Rapid Recovery was Observed when Electron Donor Feed was Re-established 24

25 The system was Minimally Affected by a 3-day System Shutdown 25

26 Cr(VI) Spiking did not Affect System Performance 26

27 Intermittent, On-demand Operation did not Affect System Performance 7 days off followed by 7 days on 27

28 Intermittent, On-demand Operation did not Affect System Performance Weekend: 100 hours on, 68 hours off 28

29 Intermittent, On-demand Operation did not Affect System Performance 1 hour on, 1 hour off for the first 12 hours 12 hours off for the next 12 hours 29

30 Additional Treatment Considerations DO remained consistently above target through all tests TTHMs <12 ug/l vs. MCL of 80 ug/l HAA5 <2 ug/l vs. MCL of 60 ug/l Backwash wastewater characterization confirmed that Cr(III) solids are filtered in the Biofilter Combined backwash wastewater residuals will not be characterized as hazardous 30

31 FeCl 2 Addition Allowed Arsenic Removal Through Adsorption/Co-precipitation 31

32 FeCl 2 Addition did not Affect Cr(VI) Removal 32

33 Conclusions 33

34 Takeaways from the 10 Month Collaborative Partnership at Norman Cr(VI) fully converted to Cr(III) and removed in the biofilter Once acclimated, the system was extremely reliable and resilient Non-hazardous residuals similar to WTP solids Arsenic removal also possible with Fe(II) addition Simple, reliable technology is capable of removing multiple contaminants biologically 34

35 Using Biological Treatment to Remove Metals: Norman's Pilot Test John Rehring, P.E. Carollo Engineers Chris Mattingly, P.E. City of Norman