Building lifetime relationships with our clients and employees. Management Alternatives for Reverse Osmosis Leachate Treatment Concentrate David Pannucci(1) and Arie Kremen(2) (1) Progressive Waste Solutions (2) Cornerstone Environmental FNYSWA Spring Conference The Sagamore, Bolton Landing, New York May 17, 2016 Leachate Disposal Cost (Cap & Op Ex) $0.45 $0.40 Old and closed Operating Landfills Landfills $0.35 $0.30 $0.25 $0.20 $0.15 $0.10 $0.05 $0.00 © 2016 Cornerstone. All rights reserved. MSW Leachate Characteristic Composition Specific Leachate Production: 180 – 200 gallon/acre/day Young Medium Old Age (yr) <1 1-5 >5 pH <6.5 6.5-7.5 >7.5 COD (mg/l) >15,000 3,000-15,000 <3,000 BOD5/COD 0.5-1.0 0.1-0.5 <0.1 TOC/COD <0.3 0.3-0.5 >0.5 NH3-N (mg/l) <400 400 >400 Metals (mg/l) >2.0 <2.0 <2.0 Organic Compounds 80% VFA 5-30% VFA, HA, HA, FA FA (VFA – Volatile Fatty Acid, HA – Humic Acid, FA – Fulvic Acid) © 2014 Cornerstone. All rights reserved. Evolution of Organic Constituents Landfill Age young medium old Landfill Gas Leachate McBean and Rovers (1998) Statistical Procedures for Analysis of Environmental Monitoring Data and Risk Assessment, Prentice-Hall Publishing Co. © 2016 Cornerstone. All rights reserved. Contaminant Classification • BOD Biodegradable • COD Biochemical Organics Recalcitrant • BOD/COD Nutrients Nitrogen, Phosphorus • Ammonia Trace Organic Pollutants, • Benzene, Vinyl chloride, … Pollutants Heavy Metals • Arsenic, Lead, …. • Total Dissolved Solids (TDS) Salts Chloride, Sodium, Potassium, Calcium • Electrical Conductance © 2014 Cornerstone. All rights reserved. Solid Separation: Size Comparison Dissolved Colloid Particulate © 2016 Cornerstone. All rights reserved. Reverse Osmosis Osmosis: movement of water through a semi-permeable membrane to equalize solute concentration Reverse Osmosis: application of external pressure, forces water to the low concentration side Reverse Osmosis vs. Filtration: filtration relies of size exclusion, whereas RO is also relying diffusion and pressures 7 © 2015 Cornerstone. All rights reserved. Dissolved Organics in Leachate Effluent Filtration Reverse Osmosis Effluent 1.5μm .45μm .22μm 100kDa 30kDa 10kDa 5kDa 3kDa 1kDa 500Da Source: John T Novak, PhD Virginia Polytechnic Institute © 2014 Cornerstone. All rights reserved. RO Design Rules of Thumb • Recovery is a design parameter Concentration Recovery Factor • Higher recoveries: 50% 2 Lower concentrate volume 75% 4 80% 5 Lower quality permeate 83% 6 Accelerated membrane fouling and scaling • Fouling, buildup of particles and colloids on membrane © 2015 Cornerstone. All rights reserved. Membrane Performance Species Rejection* Feed/Concentrate Permeate Concentration Recovery Concentration Ammonium 80-90% (pH<7.8) Chloride 92-98% 100 ppm 0% 20ppm Sodium 92-98% Potassium 92-96% Calcium 93-99% Iron 96-98% 80% Sulfate 96-99% 200 ppm 50% Rejection 40ppm Borate 30-50% Membrane Cyanide 90-99% Magnesium 93-98% Phosphate 96-98% * Polyamide composite membrane at 25°C 400 ppm 75% 80ppm © 2015 Cornerstone. All rights reserved. Real World Example Concentration Parameter (mg/l) Leachate Concentrate Seawater: Factor NH3-N 1,831 4,951 2.70 NO3, NO2-N 0.251 0.797 3.18 BOD 3,509 7,405 2.11 COD 7,934 20,032 2.52 TDS 15,150 38,606 2.55 >35,000 Sulfate 120 12,812 107 Conductivity (μS/cm) 40,971 60,956 1.47 >50,000 Concentration Factor (avg.) 2.6 Recovery (calculated) 62% = 푅푅푅푅푅푅푅푅 푃푅푅푃푅푃푃푅 퐹퐹푅퐹⁄퐹푅푅퐹퐹�퐹 퐹퐹푅퐹 © 2015 Cornerstone. All rights reserved. Concentrate Management Options • Offsite disposal • Onsite treatment • Multistage RO • Evaporation • Solidification/Resource Recovery • Eutectic Freeze Crystallization © 2015 Cornerstone. All rights reserved. Offsite Disposal • Compared to sanitary wastewater, RO concentrate is … concentrated: RO typ. Sanitary Enrichment Parameter (mg/) Concentrate Wastewater Factor NH3-N 4,951 20 x250 BOD 7,405 250 x30 TDS 38,606 500 x75 Conductivity (μS/cm) 60,965 500 x120 • Requires large design-flow POTW to rely on dilution • Subject to monitoring and discharge limitations, e.g.: • Metals, Volatiles, recalcitrant COD, Dissolved Organic Nitrogen • Cost © 2015 Cornerstone. All rights reserved. Cascading RO Stages Objective: Reduce concentrate volume Constraint: Maintain membrane cross-flow velocities Diminishing returns, increasing costs 3 300 2.5 250 2 200 ppm) ( 1.5 150 1 100 Permeate (ppm) Concentrate 0.5 50 0 0 0 1 2 3 4 5 6 7 RO Stage © 2015 Cornerstone. All rights reserved. Real World Example (cont’d) Recovery Rate of 62% is result of dual stage RO with optional permeate polishing: Greater concentrate reduction not economically feasible. © 2015 Cornerstone. All rights reserved. Electrodialisys Reversal (EDR) Electric current migrates ions through an electrodialysis stack of altering cationic and anionic ion exchange membranes. • Feedstock recovery rate: 90+% (water supply); • Self-cleaning through periodic voltage reversal; • Applications: water supply, brine concentrator • Nitrate • Total Dissolved Solids • Arsenic • Sulfate • Iron • Radionuclides Contaminants • Sulfate © 2015 Cornerstone. All rights reserved. EDR-RO • Generates highly concentrated brine; • Relative to RO: higher CapEx, lower OpEx • Less susceptible to fouling and scaling; • Dual purpose Hybrid EDR-RO: • Feedstock pre-treatment (softening) • Concentrate post-treatment (brine concentration) Concentrate • No commercial installation (Leachate Concentrate); EDR RO © 2015 Cornerstone. All rights reserved. Vapor Compression Distillation (VCD) • VCD recovery exceeds 90%, in combination with crystallizer can achieve ZLD; • Processes feedstock with TDS up to 650 g/l; • Operating concept: 1. Compression increases vapor pressure 2. Increases condensation temperature 3. Vapor temperature is used to preheat feedstock; 4. Feedstock is vapor source; • Opportunity cost: $0.02/gal (LFG) • Op Ex: $0.02-$0.04/gal (VCD only) © 2015 Cornerstone. All rights reserved. Salt Crystallizers • Commodity salt crystallizers operate on neat brines; • Leachate RO concentrate contains large number of dissolved minerals; • Relatively few Mixed Salt Crystallizers (15 units) operate in North America (2011, GE); • Crystallizers are added to VCD units to achieve ZLD; • Crystallizers are constructed from high grade metals or plastics; • Crystallization is very energy intensive; © 2015 Cornerstone. All rights reserved. Misting enhanced Evaporation Residue from Leachate Evaporator (‘Misting’) © 2015 Cornerstone. All rights reserved. Thermally Enhanced Evaporation • Leachate volume by up to 95%: • Evaporation vessels; • Direct injection-devices; • Metals precipitate, fall out as salts; • Organics are volatilized and stripped by vapor; • Energy intensive, requires LFG or waste heat; • Residuals: slurry (vessel) or grit (direct injection); • Esthetic impact: steam plume; © 2015 Cornerstone. All rights reserved. Evaporation Vessel • Approx. 24 scf LFG/gal • Residual volume: 3-10% of feedstock • Residual solid content: 10-12% (slurry) • Disposal at working face • Air Quality permitting • Op Ex: $0.055-$0.065/gal • LFG Opportunity cost © 2015 Cornerstone. All rights reserved. Ammonia Recovery & Uses • Stripping: ammonium sulfate formation • Requires pH adjustment, absorption by sulfuric acid • Uses: fertilizer, agricultural spray adjuvant • Solidification: struvite precipitation (‘kidney stones’) • Requires: magnesium, phosphate, pH adjustment • Uses: fertilizer • landfilling Struvite © 2015 Cornerstone. All rights reserved. Thermodynamic Considerations 2,025 Btu/gal 8,920 Btu/gal 4 scfm LFG/gal 50°C/106°F 18 scfm LFG/gal Parameter Value Specific Heat of Water 4.2 kJ/kg/K Enthalpy of Evaporation 2,257 kJ/kg x7 Enthalpy of Fusion 334 J/kg © 2015 Cornerstone. All rights reserved. Eutectic System Thermodynamic equilibrium point where a salt and its solution transition from solid to liquid state Temperature A B Solution Eutectic T Ice & Solution Salt & Solution Ice & Salt Eutectic Point CEutectic Salt Concentration (%wt) © 2015 Cornerstone. All rights reserved. Summary • RO can achieve direct discharge limitations • Challenges: concentrate volume, TDS, and ammonia • Multiple ionic species increase complexity • With exception of evaporators, industry has limited experience treating Leachate RO Concentrate • Consider Total Cost of Ownership, incl. opportunity cost • Rights and ready access to waste heat can affect project economics © 2015 Cornerstone. All rights reserved. Questions? Comments? David Pannucci, PE [email protected] 315.539.5624 Arie Kremen, PhD [email protected] 845.695.0213 © 2015 Cornerstone. All rights reserved. .