ZeroPM removal workshop: ZeroPM approaches for water treatment: AC, IEX, electrosorption and electrochemical degradation

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036756. ZeroPM approaches for water treatment: advanced adsorption and electrochemical degradation Marcel Riegel and Heico Schell German Water Centre (DVGW-TZW) Treatment Options for Water Process engineering grouping: 1. Adsorption 2. Flocculation 3. Liquid-liquid separation / pre-concentration 4. Destruction •Activated Carbon (AC) •Ion Exchange (IEX) (single use) •PFAS specific flocculants •Reverse Osmosis / Nanofiltration •Foam Fractionation •IEX (including regeneration) •AC (including controlled desorption) •Electrochemical degradation •Plasma destruction 1 2 3 4 E x a m p l e s 2 Treatment Options for Water Process engineering grouping: 1. Adsorption 2. Flocculation 3. Liquid-liquid separation / pre-concentration 4. Destruction •Activated Carbon (AC) •Ion Exchange (IEX) (single use) •PFAS specific flocculants •Reverse Osmosis / Nanofiltration •Foam Fractionation •IEX (including regeneration) •AC (including controlled desorption) •Electrochemical degradation •Plasma destruction 1 2 3 4 E x a m p l e s 3 Introduction: Activated Carbon (AC) •State of the art for (drinking) water treatment •Limitations: •Short chain carboxylic acids (PFBA & PFPeA) are poorly adsorbable •High DOC (dissolved organic carbon) competes for adsorption sites Short operating times frequent material changes high treatment costs 4 Introduction: Ion Exchange (IEX) •Higher product price (5 to 10 times higher than AC) •Faster adsorption kinetics smaller filter columns lower investment cost •Higher capacity for PFAS longer operation times than AC •PFOS: 10 x longer than AC •PFOA: 5 x longer than AC •PFHxA: 4 x longer than AC •PFPeA: 2 x longer than AC •PFBA: 1.5 x longer than AC Less advantages for removing short chain PFAS 5 Introduction: Ion Exchange (IEX) / 2 •IEX can be regenerated and used multiple times (dishwasher) •Strongly basic anion exchangers (SBA): higher affinity to PFAS regeneration only possible using an organic phase (EtOH) •Weakly basic anion exchangers (WBA): lower affinity to PFAS regeneration possible with NaOH •Short chain PFAS are easear to eluate from IEX than long chain PFAS 6 Technical Aproach in ZeroPM AC Feed Removal of long chain PFAS WBA Drinking water Removal of short chain PFAS PFAS loaded regenerate Regeneration Using NaOH (no organic phase, no Chlorid) Electrochemical degradation of PFAS Ground water PFAS contamination: PFBA 30 ng/L PFPeA 100 ng/L PFHxA 100 ng/L PFHpA 40 ng/L PFOA 200 ng/L PFAS-20 450 ng/L Drinking water limit: 100 ng/L 7 Pilot plant AC V = 130 L Q = 660 L/h = 5 BV/h EBCT = 12 min vF= 10 m/h IEX V = 2 L Q = 20 L/h = 10 BV/h EBCT = 6 min vF= 10 m/h 8 Performance AC + IEX R1R2R3 R4 R5 R6 R7 R8 R9R10R11 R12 R13 R14 0 100 200 300 400 500 0 20000 40000 60000 Concentration / (ng/L) Throughput / BV ΣPFAS influent ΣPFAS effluent Regeneration period: 1 week to 2.5 month Throughput [Bed Volumes] Concentration [ng/L] 9 Electrosorption/-desorption Effluent concentrations 16 0 50 100 150 200 250 300 350 0 200 400 600 800 1000 1200 1400 TFA [µg/L] Throughput [bed volumes] control column polarised column +1,0 V electrosorption -2,5 V desorption 0 50 100 150 200 250 0 200 400 600 800 1000 1200 1400 PFPrA [µg/L] +1,0 V electrosorption -2,5 V desorption 17 Pathway 1: Oxidation by hydroxyl radical Pathway 2: Direct destruction at BDD anode Electrochemical PFAS destruction H2OPFAS substances transformed PFAS CO2↑ F– H + OH● cathode DIACHEM®anode (BDD) PFAS substances e– e– Literature: Oxidative Destruction of Perfluorooctane Sulfonate Using Boron-Doped Diamond Film Electrodes von K. E. Carter, J. Farrel in Environmental Science and Technology 42(16):6111-5 · 2008 https://doi.org/10.1021/es703273s Electrochemical degradation of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in groundwater. Trautmann, A. M.; Schell, H.; Schmidt, K. R.; Mangold, K-M; Tiehm, A. in Water science and technology 71 (10), S. 1569–1575. 2015 https://doi.org/10.2166/wst.2015.143. PFAS destruction – Equipment – System electrolysis plant: 20 L scale •ECWP with 8 electrode packages 18 0 100 200 300 400 500 0 2 4 6 8 10 12 PFPBA PFPeA AOF Electrochemical elimination of short-chain PFAS in IEX regenerates cond. κ ≈ 150 S/cm Scale: 10 L I = 2 A cond. κ ≈ 470 µS/cm Scale: 10 L I = 1.5 A Regenerate IEX 0,8 - 1 M NaOH Synthetic regenerate 2 mM NaOH 19 0 5 10 15 20 0 2 4 6 Concentration [µg/L] Time [h] PFPBA PFPeA PFHxA Electrochemical elimination of short-chain PFAS in drinking water Scale: 10 L Soft drinking water κ ≈ 600 µS/cm I = 1.5 A Initial PFAS conc.: 100 µg/L each Hard drinking water κ ≈ 1800 µS/cm 20 0 20 40 60 80 100 120 0 50 100 150 Concentration PFAS [µg/L] Time [min] 0 50 100 150 TFA PFPrA PFBA PFPeA PFHxA PFHpA PFOA TFMS PFBS Elimination of short-chain PFAS in drinking water Stoichiometric fluorine (from PFAS) and measured fluoride (free ions) relative to the total volume 0 1000 2000 3000 4000 5000 6000 start 150 min start 150 min 70% pump rate 70% pump rate Fluorine mass [µg] soft drinking water 600 µS/cm TFA PFPrA PFBA PFPeA PFHxA PFHpA PFOA TFMS PFBS Fhard drinking water 1800 µS/cm 21 Formation of transformation products Scale: 10 L Soft drinking water κ ≈ 600 µS/cm I = 1,5 A Initial PFAS conc.: 100 µg/L PFOA PFOA as single substance 22 0.0 0.1 0.1 0.2 0.2 0.3 0.3 0 30 60 90 120 150 Concentration [µM] Time [min] TFA PFPrA PFBA PFPeA PFHxA PFHpA PFOA Summary electrochemical polarisation and oxidation Better electrosorption is shown mainly with the ultra-short PFAS As the ultra-short PFAS can only be insufficiently retained with GAC, electrosorption offers a possibility to achieve better sorption capacities PFAS are electrochemically oxidised and mineralized Long PFCA molecules are transformed into shorter ones The shorter the molecule, the more energy is required The higher the conductivity of the matrix, the more energy is required National project started to modify GAC for better electrosorption properties and the biological degradation of harmful by-products from electrolysis will be investigated. 23 This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036756.