Electrochemical wastewater treatment: applications and scale-up

Transcription

1 Electrochemical wastewater treatment: applications and scale-up D. Woisetschläger 1,2), M. Siebenhofer 1) 1) Institute of Chemical Engineering and Environmental Technology Graz University of Technology Inffeldgasse 25c/II 8010 Graz, Austria 2) VTU Engineering GmbH Parkring Grambach/Graz, Austria 1

2 Renate, Charlotta & Dieter 2

3 Outline Introduction Task Experimental Setup Results & Scale up Conclusion 3

4 Advanced Oxidation Processes Photolysis UV-Peroxide PEROXON Fenton-Reaction Photo-Fenton process Photo catalysis Ozonisation EAOP Boron-doped diamond electrodes Non-active electrode Inert surface, low absorption property High oxygen evolution overvoltage M H2O M( HO ) High redox potential H E (OH /H 2 O = 2.80 vs NHE) e Non-selective reaction with organic pollutants 4

5 Task Compare anode materials for the oxidation of organics Degradation of organic model substances Effect of side reactions Formation of halogenated organic compounds (AOX) Fouling, solid deposit Foam formation Treatment of industrial wastewater Chemical industry Dye industry Pharmaceutical industry Pulp and Paper industry Landfill leachate Scale-up 5

6 COD [mg/l] Current density Electrochemical wastewater treatment: applications and scale-up Electrochemical Oxidation of organics Q n z F 6000 Theoretical charge [Ah/g] 5000 charge transfer control 100% 80% Main parameters 60% Electrode material COD Exchange current density Fluid dynamic conditions Applied current density % 20% 0% Operation boundaries 2000 Charge transfer controlled region Mass transfer controlled region 1000 mass tranfer control Evaluation of charge-, mass- and heat transfer

7 Laboratory Setup power supply + - U ~ _ I heat exchanger electrochemical cell sampling σ QI 03 reservoir anode cathode O2 QI 01 ph T QI 02 pump 7

8 Laboratory Setup Electrolysis I BDD anode area [m²] Batch volume [l] Current density [A/m²] ~ _ Inter-electrode gap 4.5 [mm] Membrane assembly possible yes Cell Self construction Electrolysis cell II BDD anode area 0.02 [m²] Batch volume 1 3 [l] QI Current density [A/m²] Inter-electrode gap 3 5 [mm] reservoir Membrane assembly possible cell heat exchanger σ 03 electrochemical anode cathode power supply yes Electro MP Cell + - U I sampling O2 QI 01 Elektrolysis III BDD anode area QI [m²] Batch volume 5-10 [l] Current density [A/m²] Inter-electrode gap 2 [mm] Membrane assembly possible cell ph T 02 pump no DiaCCon Bärbel 8

9 Pilot plant setup Elektrolysis Pilot Scale BDD anode area 2 x 1.05 [m²] Batch volume [l] Current density [A/m²] Inter-electrode gap 2 [mm] cell Self construction Technical Data COD Performance max. 0.5 [kg COD 1000 [A/m²] Specific energy min. 20 [kwh/kg COD ] consumption Min. conductivitiy > 1 [ms/cm] Total suspended < 1000 [mg/l] solids TSS 9

10 c/c0 COD [%] Electrochemical wastewater treatment: applications and scale-up Anode material: active/non-active electrodes 100% 80% BDD 60% 40% PbO2 Pt/Ti IrO2 20% 0% time [h] Oxidation trends of glucose with different electrode materials: COD 0, BDD = [mg/l], COD 0, PbO2 = [mg/l], COD 0, Pt/Ti = [mg/l], COD 0, IrO2 = [mg/l]; T = 298 [K] 10

11 c/c0 [%] Electrochemical wastewater treatment: applications and scale-up Oxidation of organics on BDD-electrodes 100% 80% 60% 40% COD Glucose Phenolindex 1,4-Dioxane COD Humic acid 20% 0% Degradation trends of water constituents with BDD-electrodes: c 0,COD = [mg/l], c 0,Phenolindex = 70 [mg/l], c 0 1,4-Dioxane = [mg/l]; T = 298 [K] 11

12 c/c 0,COD [%] Dissolved oxygen [mg/l] Electrochemical wastewater treatment: applications and scale-up Effect of colloids/macromolecules 100% COD 100 % Glucose 16 90% 80% COD 75 % Glucose + 25 % Humic Acid COD 50 % Glucose + 50 % Humic Acid % 60% 50% 40% OH O H 2 O O 2 e 30% 20% 10% 0% Oxidation of glucose and humic acid: i = 500 [A/m²], V = 1 [l], A = 0.02 [m²], c 0,COD = 10,000 [mg/l]; Inset: Dissolved oxygen vs. Charge; T = 298 [K] 12

13 COD, Chloride [mg/l] AOX [mg/l] Electrochemical wastewater treatment: applications and scale-up Side reactions: Formation of halogenated organic compounds (AOX) AOX Glucose Chloride Formation of halogenated organic compounds: COD 0 = 10,000 [mg/l], Chloride 0 = 3,000 [mg/l], i = 500 [A/m²]; T = 298 [K] 13

14 COD, Chloride [mg/l] AOX [mg/l] NH4-N [mg/l] Electrochemical wastewater treatment: applications and scale-up Formation/Reaction of AOX with ammonium AOX 16 NH4-N Glucose Chloride Formation of AOX and reaction with ammonium, CCD 0 = [mg/l], c 0,Cl- = 3000 [mg/l], c 0,NH4-N = 3000 [mg/l], i = 500 [A/m²], A = 0,02 [m²]; T = 298 [K] 14

15 Fouling, Scaling, Foam formation 2 2 CO3 Ca CaCO 3 CIP-procedure Polarity swing & frequency Pre- treatment: Ion exchange resign device Anti-foaming agent Design and sizing of equipment 15

16 Treatment of industrial wastewaters Wastewater Target Charge input Comment Dye industry colour, COD removal 10 [Ah/l] Laboratory scale, i = 1000 [A/m²], Target achieved Pulp and Paper industry Phenol 15 [Ah/l] Laboratory scale, i = 500 [A/m²], Target achieved Pharmaceutical industry 1,4-Dioxane 21 [Ah/l] Laboratory scale, i = 500 [A/m²], Target achieved Chemical industry COD removal 30 [Ah/l] Laboratory scale, i = 1000 [A/m²], Target achieved Chemical industry AOX removal 80 [Ah/l] Laboratory scale, i = 1000 [A/m²], Target achieved, charge input too high Landfill leachate COD removal, colour 90 [Ah/l] Laboratory scale, i = 500 [A/m²], Target not achieved, charge input too high Production process Phenol, COD removal 110 [Ah/l] Laboratory scale, i = 1000 [A/m²] Target achieved, charge input too high 16

17 Scale-up pilot plant Scale-up factor: 14 Construction of two electrolysis cells with 1.05 [m²] anode area Modular arrangement up to 3.6 [m²] per cell 17

18 COD [mg/l] COD [mg/l] Electrochemical wastewater treatment: applications and scale-up Performance pilot plant [A/m²] 1000 [A/m²] 1500 [A/m²] Pilot scale Laboratory scale Comparison COD degradation laboratory (A = m²) and pilot plant (A = 1.05 m²); Inset: Variation of the current density, COD degradation pilot plant (A = 1.05 m²); T = 298 [K] 18

19 Conclusion EAOP electrochemical wastewater treatment Task: Process development in laboratory and pilot plant scale Treatment of synthetic and industrial wastewaters Optimization of electrode material; BDD-electrodes perform well Investigation of side reactions: typical problems understood and solved Formation of halogenated organic compounds Fouling, solid deposits Foam formation Scale-up (modular arrangement): validated 19

20 Thank you for your attention! Dr. Dieter Woisetschläger VTU Engineering GmbH Parkring Grambach/Graz, Austria Institute of Chemical Engineering and Environmental Technology Graz University of Technology Inffeldgasse 25c/II 8010 Graz, Austria 20