Marketability and Selective Recovery of Salts from Brackish Water Desalination

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1 Marketability and Selective Recovery of Salts from Brackish Water Desalination Robert A. Fowlie, P.E. Dr. Kerry Howe, Ph.D, P.E. Josh Goldman NMWRRI Conference New Water New Energy Alamogordo, NM December 2011

2 Purpose Beneficial use of reverse osmosis (RO) concentrate (salts and brine) as a possible option to offset costs of disposal Identify markets, purity requirements and potential obstacles for marketing recoverable salts and brine Present results of current research and development on selective recovery methods

3 Salts for Potential Recovery Focus on six sodium and calcium salts that represent 85 to 95% of dissolved solids in concentrate 1. Calcium carbonate 2. Calcium sulfate 3. Sodium sulfate 4. Sodium carbonate 5. Sodium chloride 6. Calcium chloride

4 Uses of Concentrate Salts Calcium Carbonate Two types GCC and PCC Main uses Pulp and paper (GCC) Rubber (PCC) Building construction Water treatment Production PCC 25% GCC 75%

5 Uses of Concentrate Salts Calcium Sulfate (Gypsum) Processed (calcined) used for wallboard & plaster Uncalcined used for cement and agriculture Synthetic gypsum obtained from removal of sulfur dioxide from power plant emissions (flue gas desulfurization) Agricultural / Industrial Processes 5% Consumption Wallboard / Plaster Products 95%

6 Uses of Concentrate Salts Sodium Sulfate Obtained from natural deposits or synthetically manufactured from recycled products Mainly used in powdered detergents Used in glass and pulp industries Carpet Freshener 4% Textiles 4% Misc. 24% Pulp & Paper 15% Consumption Glass 18% Powdered Detergents 35%

7 Uses of Concentrate Salts Sodium Carbonate (Soda Ash) Mined or made synthetically (Solvay Process) Used mainly in production of glass and chemicals Also used in water treatment and pulp and paper industry Pulp & Paper 2% Chemicals 31% Soap & Detergents 11% Consumption Glass Production 52% Water Treatment 2% Flue Gas Desulfurization 2%

8 Uses of Concentrate Salts Sodium Chloride Produced by mining, evaporation of brine and solution mining Available in dry and liquid forms (brine) Mainly used for roadway deicing Brine used as feedstock in chemical industry Agriculture & Food 3% Distributors 9% Chemical Industry 38% Consumption Water Treatment 3% Roadway Deicing 47%

9 Uses of Concentrate Salts Calcium Chloride Produced by refining naturally occurring brine By-product of Solvay Process Provided in dry form and in solution Used for deicing and dust control Image from:

10 Market Analysis Current Pricing Salt Price ($/ton) Calcium Carbonate GCC $250 PCC $300 Calcium Sulfate (Gypsum) Crude $8 Calcined $36 Sodium Sulfate $130 Sodium Carbonate $275 Sodium Chloride Dry $35 Brine $8 Calcium Chloride Dry $250 Liquid $160 Ref: USGS Mineral Commodity Statistics and Information 2009

11 Market Analysis Domestic Production of Salts Domestic Production of Selected Salts 2009 Salt Volume Produced (tons/year) Calcium Carbonate 1,223,220,000 Calcium Sulfate (Gypsum) 34,272,200 Sodium Sulfate 330,600 Sodium Carbonate 12,011,800 Sodium Chloride 50,692,000 Calcium Chloride 1,700,000 TOTAL 1,332,226,600

12 Market Analysis Volume of salt produced by 10-mgd plant treating 5000 mg/l TDS water at 100% recovery - 80,000 tons/year Less than 1/10th of 1 percent of salts produced in 2009 Minimal affect on open market Localized market Volume Salts Produced Localized Demand for Specific Salts

13 Purity Requirements Calcium Carbonate 96% as CaCO 3 Less than 0.5% by weight of sulfate, chlorides and other constituents Calcium Sulfate (Gypsum) 75 to 85% pure for use in cement Gypsum used in wallboard is negatively affected by certain salts The maximum content of Na 2 O, K 2 O, and Mg 2 O in wallboard is 0.3% by weight Maximum concentration of chloride in gypsum 100 ppm

14 Purity Requirements Sodium Sulfate 99% pure by weight for use in powdered detergent Sodium Carbonate 99% pure for use in glass industry-free of chloride and iron Sodium Chloride Brine used in chlor-alkali process must be free of sulfate, calcium and magnesium that will affect electrolytic process Rock Salt 96% pure NaCl

15 Purity Requirements Calcium Chloride ASTM Standard D98 Limitations on other chlorides (magnesium) Other limits are proprietary to the specific user Conclusions Salts extracted from concentrates would need to meet stringent purity requirements Treatment process for extraction would need to produce high-quality product

16 Synthetic Salt Production Synthetic Salt Production Summary Salt Calcium carbonate Calcium sulfate (gypsum) Sodium sulfate Sodium carbonate (soda ash) PCC made up 25% of the total U.S. market in Synthetic production by precipitation from brine and/or waste PCC is made by the milk of lime process. This involves calcining limestone (CaCO 3 ) to make lime (CaO), dissolving the lime in water to form Ca(OH) 2, and then adding CO 2 that precipitates CaCO 3. Synthetic calcium sulfate made up 57% of the total U.S. market in Synthetic calcium sulfate is made as a waste product from flue gas desulfurization. Synthetic sodium sulfate made up 50% of the U.S. market in Sodium sulfate can be produced as a by-product of battery recycling and the production of chemicals,such as hydrochloric acid, boric acid, rayon,and cellulose. Synthetic sodium carbonate (soda ash) is produced using the Solvay Process in large quantities in Europe and other countries. The Solvay Process combines sodium chloride (NaCl) and limestone (CaCO 3 ) to form sodium carbonate and calcium chloride. Sodium chloride Calcium chloride Forty percent of sodium chloride was produced by solution mining in the United States in 2008, and most of this is used in brine form by the industrial chemical industry. In addition, sodium chloride is precipitated from seawater or natural saline brines using solar evaporation and vacuum pan evaporation. Produced synthetically by the Solvay Process.

17 Current Recovery Processes Zero Liquid Discharge Evaporators, crystallizers, spray dryers Primary purpose is to increase water recovery, not extract salt Not commonly implemented at domestic water treatment plants Would need more complicated process to eliminate impurities in concentrate Image of a Layne EVRAS Crystallizer from:

18 Current Research on Selective Recovery The University of New Mexico is conducting research and development on a conventional treatment process that can recover salts from RO concentrate. The proposed treatment train consists of a sequential ion exchange IX process followed by 2 nd stage RO. Process removes all cations and anions from the 1 st stage RO concentrate stream and replaces them with sodium and chloride. IX regenerated by concentrate from second stage RO As the IX columns are regenerated, they will release the cations and anions from the resin phase. Salts can be generated by combining these solutions under special conditions.

19 Current Research on Selective Recovery Methods Proposed RO Concentrate Treatment Train (Patent Pending)

20 Conclusions Significant challenges exist for recovering and marketing salts form RO concentrate Creating a product that does not meet a recognized demand Lack of local market in area of water treatment plant Difficulty in meeting purity requirements for use Plentiful sources of supply natural and synthetic Economics benefits currently outweighed by cost As treatment processes become more efficient, selective recovery will become more viable

21 Questions and Comments

Water Softening for Hardness Removal. Hardness in Water. Methods of Removing Hardness 5/1/15. WTRG18 Water Softening and Hardness

Water Softening for Hardness Removal. Hardness in Water. Methods of Removing Hardness 5/1/15. WTRG18 Water Softening and Hardness Water Softening for Removal 1 in Water High concentration of calcium (Ca2+) and magnesium (Mg2+) ions in water cause hardness Generally, water containing more than 100 mg/l of hardness expressed as calcium