Canadian Water Quality Spring Member Meetings Ion Exchange and Contaminant Removal Presented in Kamloops, BC and Truro, NS

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1 Canadian Water Quality Spring Member Meetings Ion Exchange and Contaminant Removal Presented in Kamloops, BC and Truro, NS By Jim Sabzali of Aldex Chemical Co. Ltd Agenda Treatment Options How are Ion Exchange resins made? Contaminants: Inorganic - extensive Contaminants: Organic - brief Oxidants: Chlorine (Cl 2 ), chloramine (NH 2 Cl), Ozone (O 3 ), Hydrogen peroxide (H 2 O 2 ) AND cross-linking Fe, Mn, H 2 S, As and F Summary 1

2 Treatment options to purify water Chemical Precipitation / Coagulation Hardness and alkalinity removal by lime process (hot or cold) Iron removal Ion Exchange Membranes Cellulose acetate, hollow fiber, NF, UF Reverse Osmosis Evaporation / Distillation Carbon Filtration UV light + sub-micron filtration The Basic Chemical Process Stirrer Suspension Polymerization Process (Monomer Phase) Styrene DVB Water Suspension system ChemicaI Initiator DVB / Styrene / Water & suspension system charged to reactor. Monomer is stirred, large globules break into smaller droplets. Initiator starts styrene/dvb exothermic reaction forming small plastic beads 2 nd reactor: polymer + sulfuric acid sulfonic acid attaches to S-DVB backbone and IS the functional group 2

3 Cross-linking (DVB content) Gives the beads strength Prevents resin from being water soluble DVB is the cross-linking chemical 2% to 20% is the DVB range of most resins Higher DVB beads resistant to shrinking and swelling Physical Structure Requirements of ion exchange beads: Insoluble In the form of spheres vs. irregular shape in order to guarantee a void volume within the resin bed to facilitate flow Bead size typically 16 to 50 US mesh Resistant to fracture controlled by the swelling during exhaustion and regeneration Active sites must be permanently attached 3

4 Physical Structure: Gel Resin Gel structure Most common resin available Exchange sites distributed evenly thru bead 10% of the resins exchange capacity is found on the surface; 90% within the bead 8% most common DVB content 8% proven to be the most economical Resin price Expected operating life Physical Structure: Macroporous Resin A sponge like structure allows: High level DVB without affecting kinetics Increases bead toughness Large pores allow capture of large molecules Bead contains less exchange sites contributing to lower capacity Pores take up to 10% to 30% of the capacity 4

5 Gel vs. Macroporous Gel Higher operating efficiencies Less costly Macroporous Better physical stability Eliminates breakage from osmotic stress More resistant to organic fouling Better oxidation resistance specifically from chlorine Why use higher cross-linked resins? Higher cross-linked (XL) resins have greater resistance to oxidative attack (any oxidant chlorine, chloramine, ozone, peroxide, bleach) Higher XL resins will last longer in water with elevated levels (i.e. > 1 ppm) oxidant Are Higher XL resins more economical? Higher XL resins are more efficient at removing tannins = color = organics = TOC 5

6 Ion Exchange Basics Accelerated Oxidation Test: 6% H2O2 1,000 ppm Fe Na form for 4 hrs. of vigorous agitation Affect of Oxidants on resin life? Rule of Thumb: Influent oxidant level < 1 ppm for normal life (6-8 years for an 8% XL resin like C800) Every 1 ppm increase, resin life cut in ½ < 1ppm = 6-8 years 2 ppm = 3-4 years 3 ppm = years 4 ppm = 9 12 months 5 ppm = ~5-6 months 6

7 Case Study: Oxidant level vs resin life? Manager for SE OEM water treatment company did study using 1 softener in his home Influent oxidant level: 5 ppm 8% SAC gel, 10% and SAC MP resins tested Rule of Thumb: expect ~6 5 ppm Resin replaced when flow (& pressure drop) problems persisted Resin Choice vs. Relative Cost Relative Performance: 8% SAC gel lasted 8 months 10% SAC gel lasted 3 years SAC MP lasted 5 years Relative Cost: 8% SAC gel = $x per cubic foot 10% SAC gel = $1.2x per cubic foot SAC MP = 2.0x per cubic foot 7

8 Case Study: Oxidant level vs resin life? Economics: 8% SAC gel costs x and lasts 8 mo. means home-owner replaces resin 15x in 10 years (cost 15x). 10% SAC gel lasted 3 years means home-owner replaces resin 3.3x in 10 years (cost 4x) SAC MP lasted 5 years means home-owner replaces resin 2x in 10 years (cost 4x) Why use a higher cross-linked resin? Using any higher cross-linked resin is more economical for home-owner in long run Much lower frequency of resin change-out 25% of the resin cost over 10 years 8

9 Inorganic Contaminants Cationic: Ca, Mg, Mn, Fe, B, Pb, Al, Cu, Zn, Rd Anionic: SO 4 2-, NO 3-, HCO 3-, Cr 6+, As III, As V, U, Polyphosphates, F Non-specific: Oxidants, H 2 S Up and Coming Contaminants Organics next presentation Perfluorinated compounds or PFC s (non-stick coatings, firefighting foams) highly water soluble No regulations (yet) but 0.07 mg/l proposed (EPA) for life-time exposure to PFOA and PFOS PFOA (perfluorooctanoic acid) PFOS (perfluoroctane sulfonate) Pharmaceuticals (non-recreational) VOC s (MTBE, ETBE, TAME, aromatics, BTX s) Treatment via GAC, Anion IX, RO, UV, oxidants 9

10 Easy Cation Contaminants Hardenss: Ca and Mg Other metals: Fe, Mn, Pb, Al, Cu, Zn Alpha and Beta emitters: Rd and U Standard softening resin will removal all except uranium (U) Operate softener to hardness break (1 grain) Uranium removed via SBA I or SBA II, salt regenerated Selectivity co-efficient for U higher than all other anions Easy Anion Contaminants Sulfate (SO 4 ), Nitrate (NO 3 ), Alkalinity (HCO 3 ) Hexavalent Chrome (Cr 6+) Polyphosphates Uranium Standard SBA I or SBA II resin, salt regenerated will remove SO42-, NO3-, HCO3-, Cr6+ SBA I acrylic gel resin removes polyphosates Possible to non-selectively remove arsenate (As V) using SBA I or II resin Other options for As including arsenic selective media 10

11 Hard to remove Contaminants Fe and Mn Arsenic III and V Fluoride Hydrogen Sulfide Combination of contaminants (Fe, Mn, H 2 S, As III, As V) Others depends on competing ions and concentration of target ion(s) Forms of Iron (Fe) in Water Ferrous, Fe 2+ Clear water iron Dissolved iron Soluble iron Ferric, Fe 3+ Oxidized iron iron oxide Insoluble iron Precipitated iron Red water iron - rust Organic Iron Bacterial iron Chelated iron Heme iron Colloidal Iron Dispersed iron 11

12 Iron Removal Iron > 0.3 ppm will cause staining Resin will remove 50+ ppm iron (Fe 2+ ) in the Maritimes due to low ph raw water Rest of Canada: SAC resin may handle up to 5 ppm Fe 2+ Use Fe filter media for Fe levels > 2 ppm Regenerate softener more frequently using lbs. NaCl / cu.ft. (prevents Fe build-up) To oxidize: 1 ppm of Fe will consume 1 ppm chlorine Manganese (Mn) Removal 1987 Aesthetic Objective (AO) established 0.05 mg/l (50 ppb) 2017 HPB proposes new AO 0.02 mg/l (20 ppb) AO primary objective to regulate / lower Mn to levels so discolored water (brown or black MnO precipitate) will not be an issue Max. Allowable Concentration (MAC) not altered from 0.1 mg/l (100 ppb) Standard SAC Na resin - regenerate softener more frequently using lbs. NaCl / cu.ft. Periodic cleaning with mild acid (phosphoric citric) 12

13 Removing a combination of Contaminants Fe, Mn, As III, As V, H 2 S New media able to remove all in 1-step 1 natural zeolite + 1 modified ion exchange resin Both operate using same chemistry Media oxidizes Fe, H 2 S and Mn in solution backwash particulate H2S oxidized AND metal oxides bind with As III and V Influent: 10 ppm Fe, Mn, H 2 S and As III, As V N/D for all except 29 ppb Influent: 0.5 ppm Fe, Mn, H2S and 100 ppb As III & V N/D for all Regenerant: oxygen!! Why are As & F so pernicious? Both bio-accumulate i.e. hang around for a long time We re exposed to both from air, food and water AsO 4 3- acts like PO 4 3- can from tri-calcium arsenate and replace tri-calcium phosphate (bone) Fluoride can react with bone structure forming calcium fluoride which can Weakens bone and tooth structure (fluorosis) NaF (toothpaste) Cryolite (Na3AlF) insecticide approved for organically grown Pharmaceuticals nearly 20% of all pharmaceutical contain F Prevacid (antacid), Prozac (antidepressant), Livostin (antihistamine), Fen-Phen (appetite surpressant), Cipro (antibiotic) 13

14 Arsenic III and V Arsenic has been known to be toxic for 2,000+ years Arsenic is a known carcinogen ingestion may lead to skin, bladder, liver and lung cancers Trace amount in almost all soil, water, food and air Oxy-compounds (As or arsenate) and AsO 3 3- (arsenite) are far more toxic than are organic species MAC for As is 10 ppb however as little as 0.17 µg/l (170 ppt) can cause poisoning effects An adult would have to ingest 70 milligrams of arsenic to be poisoned in a single dose Arsenic III and V Proven methods for As removal Co-precipitation with iron or aluminium Activated alumina Non-selective Ion Exchange resins Reverse Osmosis Adsorbents (> 12 metal oxides based media) 14

15 Fluoride Fluoride is naturally occurring and can be found in the earth s crust, water and air Fluoride, typically applied to teeth has cavity prevention benefits Fluoride is bio-accumulative and has been found to be an endocrine disruptor and neurotoxin Lethal dose for most adults estimated at 5-10 grams Enough fluoride in a tube of toothpaste to kill a child Drinking water not only source of F - most comes from food. MAC for F 4 ppm Proven methods for Fluoride Removal Chemical precipitation (CaO ~ 50%) Reverse Osmosis (90%+) Distillation (95%+) Adsorption (95%+) Bone Char Activated Alumina Ion Exchange (SBA salt regenerated 95%+) Include all anions in solution including Using 8-10 lbs NaCl/CF assume SBA I (10.5 Kgr/CVF) or SBA II (13.5 Kgr/CF) de-rated capacity Determine throughput and multiply by 0.80 (20% reduction) Employ a redudancy (POU RO for drinking water; whole house use AA polisher after anion) 15

16 Ion Exchange Basics Summary: Ion Exchange proven technology able to remove a variety of contaminants Treat oxidants as a contaminant as they will affect resin performance Standard resins (softening & anion) able to remove a number of contaminants Many ways to skin a cat wide variety of selective and non-selective IXR s + other treatment options to consider (RO, AA, zeolites) By Jim Sabzali of Aldex Chemical Co. Ltd. jsabzali@aldexchemical.com