Treatability Study and Reverse Osmosis Pilot Study of Industrial Wastewater at a Wood Products Mill

Transcription

1 Treatability Study and Reverse Osmosis Pilot Study of Industrial Wastewater at a Wood Products Mill NC AWWA-WEA 2017 Annual Conference Randall Foulke, PE, BCEE, LEED AP Tracey Daniels, EI November 14, 2017

2 Presentation Outline Background Treatability Studies Reverse Osmosis Pilot Study and Respirometry Study Color Study Net Present Value Analysis Current Status Conclusions 2

3 Existing Conditions & Current Effluent Process industrial wastewater primarily from stack wet scrubber blowdown Existing treatment and spray irrigation fields Spray irrigation fields nearing end of service life o Mill personnel determined new fields not viable Elevated temperature of ~120 F DAF effluent o High BOD, COD, TDS o Other parameters non-detect or insignificant Long term plan to connect to local POTW Future UV disinfection at POTW Memorandum of Understanding signed o New pretreatment facilities required Design flow of 30,000-60,000 GPD 3

4 Current Process Wastewater Flow Diagram 2-Stage Ext. Aeration Basin Spray Fields Process Waste- Water Clarifier Dissolved Air Flotation (DAF) Unit Belt Press Landfill 4

5 Proposed Process Wastewater Flow Diagram Process Waste- Water Clarifier Dissolved Air Flotation (DAF) Unit New Pretreatment Process & Flow Equalization Belt Press POTW Landfill 5

6 Scope of Work Treatability Phase I Characterization of industrial wastewater Bench-scale screening of technologies Treatability Phase II Bench-scale screening of treatment technologies Pilot Study Color Study and Net Present Value Analysis Added later when POTW proposed additional color parameter limits ovendor filtration study ovendor evaporator study 6

7 Treatability Study Phase I Discharge Limits Exact discharge limits unknown at time of study Estimated based on other permits issued by POTW Ultraviolet Transmission (UVT) Measure of the amount of light that passes through a water sample Separate variable from color or turbidity Minimum of 40% UVT to use UV disinfection 40% set as goal Parameter Estimated Discharge Limit (mg/l) BOD 250 TDS 500 TSS 250 NH 3 25 Arsenic Cadmium Chromium 0.05 Copper Cyanide Lead Mercury Nickel Oil & Grease 100 Phosphorus 8 Silver Zinc

8 Treatability Study Phase I DAF effluent characteristics: High TDS and COD concentrations oinorganic salts from wet scrubber Slight foaming when agitated Dark color due to tannins oresidual organics from hog fuel boiler Bench-Scale Screening Tests: Filtration Activated Carbon (various carbon sources) Aerobic Bio-Oxidation Chemical Oxidation Strong Chemical Oxidation Ion exchange Coagulants Parameter Quantity Metals No detect TDS 7,470 mg/l TSS 95 mg/l BOD 1420 mg/l COD 6200 mg/l UVT -0.2% ph

9 Treatability Study Phase I Noteworthy Results No bench-scale tests effectively improved UVT Ion exchange showed some promise, but fouling was an issue Activated Carbon removed tannins, but not dissolved solids Conclusions: Low UVT due to tannins and dissolved solids owastewater with no color resulted in low UVT due to high concentrations of inorganics ocolor reduction resistant to any form of oxidation Further testing of activated carbon is needed Reverse osmosis should be tested 9

10 Treatability Study Phase II Bench-Scale Test Configurations: RO No GAC No ph adjustment RO No GAC ph adjustment RO GAC pretreatment ph adjustment Conclusions: TDS effectively lowered by RO Product water had UVT >40% 50% or greater recovery expected from RO GAC and ph adjustment both improved performance 10

11 Pilot Study Reverse Osmosis Design flow rate: 10 GPM Study length: 3 weeks Brackish water membranes (rated for >5,000 mg/l TDS) ohigh inorganic salt concentrations Flow equalization added ovariable hydraulic and pollutant loadings Respirometry Study Requested by POTW Two reactors simulating POTW Granular Activated Carbon Test Design flow rate: 5 GPM 11

12 Pilot Study Reverse Osmosis S Existing DAF Unit EQ Tanks Acid Tank Cleaning System S 50 μm Bag Filter S Multi- S 5 μm S Product Media RO Feed Cartridge RO Unit S Filter Tank Filter Brine S = Sample Location Parameters Tracked: UVT, turbidity, COD, TDS, TSS, BOD, ph, pressure, flow rates, temperature 12

13 Pilot Study Reverse Osmosis Results: Removal of constituents Parameter EQ Tank Average RO Product Average Average Percent Removal Expected Discharge Limit COD (mg/l) 11, % Unknown BOD (mg/l) 6, % 250 TDS (mg/l) 19, % 500 TSS (mg/l) % 250 Turbidity (NTU) % N/A Note: BOD, COD, TDS and TSS concentrations higher from DAF effluent (EQ tank average) than experienced during Treatability Phase I or Phase II work. 13

14 Pilot Study Reverse Osmosis Results: UVT All locations before RO: UVT = -0.2% UVT in product (recovery rate): Average: 67% UVT Goal: >40% UVT omet goal in all samples except one UVT (%) 100.0% 90.0% 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% Product Water UVT Test Day 14

15 Pilot Study Reverse Osmosis Results: Recovery Rate RRRRRRRRRRRRRRRR = QQ PPPPPPPPPPPPPP 100% Feed RO Unit QQ FFFFFFFF Product Brine Recovery (%) 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Recovery Rate Test Day Average: 22% 15

16 Pilot Study Reverse Osmosis Results: Color, Membrane Cleaning, and Recovery Rate Color Removal Observed Color measurements not taken at this time Membrane Cleaning Acid and alkaline cleanings performed Saw good recovery of pressure Recovery Rate Lower than predicted by bench scale test 16

17 Pilot Study Respirometry Study Two identical biological oxidation reactors, 4-gallon capacity Reactor 1 mill influent: RO Product Water Reactor 2 mill influent: Filtered DAF Effluent Mill influent and POTW influent blended at expected ratios + a shock test (doubled mill percentage) POTW Influent [Mill Influent] Aeration Chamber Settling Chambers Effluent Air Sludge Wasting 17

18 Pilot Study Respirometry Study Reactor 1 (Product Water) Effluent UVT average 75.8% Reduction in MLSS and MLVSS during study, likely due to low BOD of influent (dilution by product water) Reactor 2 (Filtered DAF Effluent) Effluent UVT consistently -0.2% Better MLSS and MLVSS performance than Reactor 1 Color removal not observed Both reactors performed well in relation to: ph Sludge Volume Index Dissolved Oxygen Removal of BOD, COD, TSS, TDS Whole Effluent Toxicity 18

19 Pilot Study Granular Activated Carbon 4 columns in series Column Size: 12.5 H x 1.5 D Flow Rate: 5 GPM Contact time: 30 minutes per column GAC Type: virgin bituminous carbon 19

20 Pilot Study Granular Activated Carbon Results Color removal No measureable improvement in UVT Carbon experienced breakthrough within 3-7 hours of contact time Conclusions Approximately 0.6 lb of GAC needed per gallon of wastewater Cost-prohibitive 20

21 Color Study and Net Present Value Analysis Background: MOU signed with POTW 3 discharge phases each will have a new pretreatment permit effluent limits Color became additional parameter Decreasing Limits: o250 Pt-Co units before UV o50 Pt-Co units when UV is installed These limits are expected, but not yet binding Photos suggest that RO product water will be under 250 Pt-Co, unknown if it will be under 50 Pt-Co Approximate Pt-Co standards

22 Color Study and Net Present Value Analysis Color Study Dilution Filtration Oxidation Manufacturer Analyses Samples of DAF effluent sent to filter and evaporator vendors Net Present Value Analysis 22

23 Color Study Results: Dilution is not the solution 0.4% DAF effluent to DI water was required to reach 250 Pt-Co units Filtration Testing (0.45 μm) No measureable effect Oxidation Testing: Hydrogen Peroxide and Fenton s Reagent ono measureable effect for either 23

24 Analysis by Filter Manufacturer Existing DAF Unit 50 μm Bag Filter Multi- Media Filter RO Feed Tank 5 μm Cartridge Filter RO Unit Product Brine During RO pilot study: The 50 μm bag filter did not require replacement during pilot study MMF required moderate backwashing The 5 μm filter required changing every 2-4 hours A sample of DAF effluent sent to filter manufacturer to optimize filter selection 24

25 Analysis by Filter Manufacturer Filter manufacturer performed two tests: Total solids analysis oresults ranged from 46.2 PPM w to PPM w Particle size distribution (by particle analyzer sensor) opeak in number of particles around 10 μm diameter o90% of particles below 32 μm o99% below 75 μm Recommendations: 15-micron mechanically-cleaned filter 5 micron bag filter with extended-life media Existing DAF Unit 15 μm Filter RO Feed Tank 5 μm Bag Filter RO Unit Product Brine 25

26 Analysis by Evaporator Manufacturer Tests performed on DAF effluent and a concentrated DAF effluent meant to simulate RO Brine Mechanical Vapor Compression (MVC) Evaporator Produces distillate stream Potential for heat recovery from other mill operations could reduce O&M costs Conclusion: Viable for use on DAF Effluent or RO Brine Distillate sample averaged 237 Pt-Co units 26

27 Net Present Value Analysis Compared 11 Treatment Alternatives Option R1 Option R2 Option R3 Option R4 Option R5 Option R6 Option R7 Option R8 Option E1 Option E2 Option E3 60,000 GPD from DAF RO Recycle Product Evaporate Brine 60,000 GPD from DAF RO Recycle Product Pump and Haul Brine 60,000 GPD from DAF RO Discharge and Recycle Product Evaporate Brine 60,000 GPD from DAF RO Discharge and Recycle Product Pump and Haul Brine 30,000 GPD from DAF RO Recycle Product Evaporate Brine 30,000 GPD from DAF RO Recycle Product Pump and Haul Brine 30,000 GPD from DAF RO Discharge and Recycle Product Evaporate Brine 30,000 GPD from DAF RO Discharge and Recycle Product Pump and Haul Brine 60,000 GPD from DAF MVC Evaporator Discharge and Recycle Distillate Landfill Residual 30,000 GPD from DAF MVC Evaporator Discharge and Recycle Distillate Landfill Residual 30,000 GPD from DAF Thermal Evaporator Discharge and Recycle Distillate Landfill Residual Assumptions based on RO and Color Studies, information from vendors, current operating costs of the mill Evaluated both an MVC evaporator and a thermal evaporator Included Capital Costs, and O&M up to 7 years 27

28 Net Present Value Analysis $25 R1: 60,000 GPD - RO - Recycle Product - Evaporate Brine Net Present Value (millions) $20 $15 $10 $5 R2: 60,000 GPD - RO - Recycle Product - Pump & Haul Brine R3: 60,000 GPD - RO - Discharge/Recycle Product - Evaporate Brine R4: 60,000 GPD - RO - Discharge/Recycle Product - Pump & Haul Brine R5: 30,000 GPD - RO - Recycle Product - Evaporate Brine R6: 30,000 GPD - RO - Recycle Product - Pump & Haul Brine R7: 30,000 GPD - RO - Discharge/Recycle Product - Evaporate Brine R8: 30,000 GPD - RO - Discharge/Recycle Product - Pump & Haul Brine E1: 60,000 GPD - MVC Evaporator - Discharge/Recycle Distillate $ Years E2: 30,000 GPD - MVC Evaporator - Discharge/Recycle Distillate E3: 30,000 GPD - Thermal Evaporator - Discharge/Recycle Distillate 28

29 Net Present Value Analysis Net Present Value (millions) $5 $4 $3 $2 $1 $ Years R5: 30,000 GPD - RO - Recycle Product - Evaporate Brine R7: 30,000 GPD - RO - Discharge/Recycle Product - Evaporate Brine E2: 30,000 GPD - MVC Evaporator - Discharge/Recycle Distillate E3: 30,000 GPD - Thermal Evaporator - Discharge/Recycle Distillate Option Capital Costs O&M Costs per year R5 $2,874,000 $209,000 R7 $2,879,000 $217,000 E2 $3,959,000 $127,000 E3 $1,814,000 $499,000 Evaporator operating costs do not take into account the use of waste heat. Other RO systems might get better recovery, lowering O&M costs 29

30 Current Status Mill has installed new wastewater sewers, lift station and force main to connect to the POTW Mill is evaluating the Net Present Value Analysis POTW is arranging funding for a lift station and force main to convey wastewater to the WWTP 30

31 Conclusions Wood product mill wastewater high in BOD, COD, TDS and dark color Low UVT due to tannins and inorganic dissolved solids Treatability Studies Any form of oxidation, chemical treatment or ion exchange not effective RO, GAC, and evaporation potentially viable Pilot Study GAC cost prohibitive Low recovery rate from RO Net Present Value Analysis Evaporation by itself effective, but high installation costs Some combination of RO and/or evaporation is the most cost-effective 31

32 Questions? Randy Foulke: Tracey Daniels: 32