Method development for ionexchange brine treatment James Runge

Method development for ionexchange brine treatment James Runge PWN Technologies University of Bath European Regional Development Fund WATER. VANDAAG EN MORGEN

Introduction • PWNT uses a water treatment process called suspended ion-exchange (SIX®) in which natural organic matter (NOM) and negatively charged ions are removed from surface water using an anion exchange resin. • The waste stream produced by the SIX® process is known as ion-exchange (IEX) brine. • The IEX brine is rich in sodium chloride, sodium sulphate and natural organic matter (NOM). • If these components can be separated from the brine there is potential re-use in the SIX® process and in agriculture. • The recovery of these resources and subsequent reuse leads towards helping to make the process a zero-waste process. 2 European Regional Development Fund WATER. VANDAAG EN MORGEN

What is in the brine? • The IEX brine produced by the SIX® is rich in four main components. NOM FA Na. Cl • These are sodium chloride, sodium sulphate, bicarbonate and natural organic matter (NOM). HA HCO 3 - Na 2 SO 4 • The natural organic matter is rich in humic substances. 3 European Regional Development Fund WATER. VANDAAG EN MORGEN

What are humic substances? • HS is organic matter distributed in soil, natural waters and sediments. • Can be divided into three types: • Humic acid • Fulvic acid • Chemical properties of humic substances (Stevenson 1982) • Humin • The NOM in the IEX brine contains only FA and HA. 4 European Regional Development Fund WATER. VANDAAG EN MORGEN

Humic acid (HA) and Fulvic acid (FA) Humic acid • • Insoluble in acidic solutions (p. H < 2). Variety of functional groups Amphiphilic and can form micelle like structures. Brown-grey in colour. European Regional Development Fund Fulvic acid • Soluble at all p. H values. • Smaller, less functional groups in structure • Yellow-brown in colour. 5 WATER. VANDAAG EN MORGEN

How do we separate these components? Two Methods: • Electrodialysis (ED) - To recover chloride ions from the brine. • XAD resin fractionation - To separate HA and FA fractions from the brine. 6 European Regional Development Fund WATER. VANDAAG EN MORGEN

Sodium chloride recovery 7 European Regional Development Fund WATER. VANDAAG EN MORGEN

Electrodialysis • Works on the principle that ions will migrate when placed in an electric field. • Anions will move towards the anode and the cations will move towards the cathode. • ED stack contains alternating cation and anion exchange membranes. • Produces two streams: increased ion concentration and depleted ion concentration. • Charges on the anode and cathode can be reversed so the flow ions across the membrane occurs in the opposite direction, EDR • Helps to reduce fouling on the membranes. 8 European Regional Development Fund WATER. VANDAAG EN MORGEN

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Diluate Tank Membrane stack Concentrate Tank European Regional Development Fund 11 WATER. VANDAAG EN MORGEN

Example of feed and bleed testing Semi-continuous monoselective electrodialysis Change in conductivity with time 70 90 Conductivity / m. S/cm 70 50 60 40 50 30 40 30 20 20 10 Conductivity m. S/cm 80 60 10 0 50 100 150 200 250 300 350 Axis Title Diluate European Regional Development Fund Concentrate Reversal CIP RO Rinse WATER. VANDAAG EN MORGEN 12

Example of feed and bleed testing Semi-continuous monoselective electrodialysis Variation in current density Change in current density compared to diluate conductivity 25 60 20 50 15 40 30 10 20 5 Current Density / m. A/cm 2 Diluate Conductivity / m. S/cm 70 10 0 50 100 150 200 250 300 350 Axis Title Diluate European Regional Development Fund Current Density Reversal CIP RO Rinse WATER. VANDAAG EN MORGEN risne 2 13

Results • Variation in current density between ED and EDR modes. • Is one side of the membrane more fouled than the other? 40000 450 35000 400 30000 350 300 250 20000 200 150 10000 100 50 0 SO 42 - and TOC / mg L-1 • ED produces a concentrate stream high in Cl- and low in SO 42 - and TOC. Cl- concenttration / mg L-1 What do we observe? 0 0 20 40 60 80 100 120 140 Run Time / Hours Chloride Sulphate TOC • Does the frequency of reversals need to be increased? 14 European Regional Development Fund WATER. VANDAAG EN MORGEN

NOM recovery 15 European Regional Development Fund WATER. VANDAAG EN MORGEN

Resin Fractionation • Uses non-ionic macroporous adsorption resins. • Different to IEX resin so only NOM will bind to the resin • Separates the dissolved organic carbon into hydrophilic and hydrophobic fractions. • Selective adsorption – hydrophilic compounds will not bind to the resin and are removed as waste. • Standardised method used by IHSS (Internation Humic Substance Society) 16 European Regional Development Fund WATER. VANDAAG EN MORGEN

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Humic substances extraction for field trials simplification of IHSS protocol European Regional Development Fund WATER. VANDAAG EN MORGEN

Upscaling? Looking towards upscaling there are many challenges: • Simplification of the technique for it work on a larger scale • Is DAX-8 commercially available in large quantities? Use different resin type? • Not separating HA and FA will this effect adsorption? • Do we treat the brine first with electrodialysis? • Effect of p. H on the adsorption. 19 European Regional Development Fund WATER. VANDAAG EN MORGEN

Conclusions • Two methods for treating IEX brine • ED has proven to be a successful method for recovering Na. Cl for reuse in the SIX® • But variations in long-term performance of the pilot in recent months. • Need to develop new method for recovery of NOM • Resin fractionation currently undergoing lab-scale trials. • How can we upscale to pilot scale method? 20 European Regional Development Fund WATER. VANDAAG EN MORGEN

Thank you! Questions? 21 European Regional Development Fund WATER. VANDAAG EN MORGEN