A Review of Environmental Impacts and Environmental Applications of Shredded Scrap Tires

Transcription

1 A Review of Environmental Impacts and Environmental Applications of Shredded Scrap Tires Angela Pakes, PE, LEED AP and Tuncer Edil, PE, PhD.D.GE, Dist M. ASCE Presentation at the 2017 TRB Summer Workshop Duluth, MN - July 19, 2017 Recycled Materials Resource Center at the University of Wisconsin- Madison 1

2 Form of Scrap Tires in Use Whole Halved Shredded or Chips Granulated or Crumb Alone Mixed with Soil Recycled Materials Resource Center at the University of Wisconsin- Madison 2

3 Applications for Scrap Tires Geotechnical Embankment fill Retaining wall backfill MSE backfill Bridge abutment fill Insulation layer in pavement (against frost) Vibration damping layer Drainage layer Geoenvironmental Reactive leachate collection layer * Reactive barrier Septic tank leach field Nutrient barrier in golf course or athletic fields Other Artificial reef * Floating breakwater Artificial turf * Recycled Materials Resource Center at the University of Wisconsin- Madison 3

4 A Typical Elemental Analysis Element Weight Percent: Carbon 83% Hydrogen 7% Ash 6% Oxygen 2.5% Sulfur 1.2% Nitrogen 0.3% Ash Hydrogen Element Weight Percent Oxygen Sulfur Nitrogen Carbon Carbon Hydrogen Ash Recycled Materials Resource Center at the University of Wisconsin- Madison 4 Oxygen Sulfur Nitrogen

5 Rubber Compounding Composition (Dodd et al. 1983) Component Weight Percent Styrene- Butadiene Copolymer (SBR) 62.1 Carbon Black 32 Extender Oil 1.9 Zinc Oxide 1.9 Stearic Acid 1.2 Sulfur 1.1 Accelerator 0.7 Recycled Materials Resource Center at the University of Wisconsin- Madison 5

6 Evaluation of Leachate Characteristics Batch Tests Water Leach Tests (WLT) - ASTM D 3987 Toxicity Characteristic Leaching Procedure (TCLP) Large- scale Tank Batch Tests Column Leach Tests (CLT) Field Lysimeter Tests Recycled Materials Resource Center at the University of Wisconsin- Madison 6

7 Factors Affecting Leachate Characteristics The aquatic environment in which the tire chips are exposed (ph, salinity) The age of the tires The size of the tires The time of exposure of the tire to the liquid Circulating or static liquid? Recycled Materials Resource Center at the University of Wisconsin- Madison 7

8 Compounds Leached from Tire Chips Compound Grefe 1 (1988) RMA 1 (1990) TCTC 2 (1990) Miller/Chadick 3 [mg/kg] [mg/kg] [mg/kg] (1993) [mg/kg] As 0.02 Park et al. 4 (2003) [mg/kg] Ba Cd Cr Pb Fe Mn 1.5 Zn Se Hg NO 2 - /NO Toluene Carbon Disulfide Phenol 0.01 Benzene 0.63 Recycled Materials Resource Center at the University of Wisconsin- Madison 8

9 Large Scale Batch Tank Tests Three different types of water were used: - Ground water - Marsh water - Deionized water 100 kilogram tires used in each tank 3 control tanks (184 liters) without tires Nitrile Gasket Closed Holes 610 mm 150 mm Figure 1. Stainless Steel Tank 910 mm Sampling Ports Recycled Materials Resource Center at the University of Wisconsin- Madison 9

10 Compound [mg/l] Inorganic Compounds in Tank Tests- First Sampling PAL* Tank 1 (GW) Tank 2 (GW+T) Tank 3 Tank 4 (MW+T) Tank 6 (DI+T) Tank 5 (DI) Total From Tires (MW) Total From Tires Total From Tires As 5 1 <1 <1 Ba < Ca <100 Cd 0.5 <0.08 Cr 10 <2 <2 <2 <2 <2 <2 <2 0 Cu 130 <8 <8 13 Fe 150 < Pb Mg <30 Mn Ni 20 Se 10 2 <1 <1 Na <700 Zn < < TOC** 0 < < *No exceedance of PALs **TOC units are in mg/kg Recycled Materials Resource Center at the University of Wisconsin- Madison 10

11 Organic Compounds in Tank Tests- First Sampling VOCs [mg/l] WI PALS* Tank 1 (GW) Tank 2 (GW+Tire) Tank 3 (MW) Tank 4 (MW+Tire) Tank 5 (DI) Tank 6 (DI+Tire) Acetone Benzene Ethylbenzene Methyl- Ethyl Ketone Methyl- Isobutyl Ketone Toluene Trichloroethylene *Initial exceedance of PALs In the second sampling for VOCs there were no contaminants found that exceeded any PAL Recycled Materials Resource Center at the University of Wisconsin- Madison 11

12 Tires and Aquatic Life Tires placed in surface water are shown to be toxic to aquatic life and this practice should be abandoned. Recycled Materials Resource Center at the University of Wisconsin- Madison 12

13 Conclusive Relative Environmental Impacts Although the levels of certain metals (e.g., Fe, Mn) increase, the impact of tire leachate on drinking water quality of groundwater is limited for a range of applications involving tires or tire shreds, so human health concerns are minimal. The compliance with the drinking water standards at a chosen point of compliance in the groundwater resulting from the initial increased tire leachate concentrations can be assessed through the advection- dispersion- reaction transport principles. The practice of tires being placed in surface water should be abandoned. Tires placed in groundwater generate leachate that is toxic to aquatic life but again, if there is enough separation zone from the surface water, the toxic effects may decrease by the time the leachate reaches the surface water. Recycled Materials Resource Center at the University of Wisconsin- Madison 13

14 Environmental Applications of Scrap Tires Recycled Materials Resource Center at the University of Wisconsin- Madison 14

15 Effect of Organic Carbon on Breakthrough Pore volumes D L = 4.6x 10-6 cm 2 /sec k = 1.0 x 10-7 cm/sec Liner thickness = 2 ft i = 3 n = 0.36 Toluene TCE Methylene chloride Years Recycled Materials Resource Center at the University of Wisconsin- Madison % organic carbon

16 Tires are like Oysters: Heavy Metal Removal by Tires Mercury removal: equivalent to powdered activated carbon (PAC); optimum ph range: 5 ~ 7 Cadmium (II) and mercury (II): an ion- exchange type removal Lead (II) removal: adsorption Other heavy metals: probably similar to PAC Recycled Materials Resource Center at the University of Wisconsin- Madison 16

17 Advantages for Tire Chip Addition All statements are in respect to microbial degradation: 1. Decrease persistent organic chemical concentration in liquid phase. 2. Furnish a longer contact time for acclimation and biodegradation. 3. Provide ideal sites for microbial consortia to grow. 4. Maintain constant liquid phase concentration by sorption/desorption. Recycled Materials Resource Center at the University of Wisconsin- Madison 17

18 So How Thick? Experimental Methods 1. Batch Sorption Test a. Gravimetric Methods b. Batch Isotherm Experiment 2. Continuous Flow Column Test 3. Large Scale Column Test 4. Full Scale Field Test Recycled Materials Resource Center at the University of Wisconsin- Madison 18

19 Tire Layer Depths for 90% Removal of Organic Compounds in Landfill Leachate Collection Layer Thickness of the Layer, cm Q r = 500 m 3 /acre/yr n = 0.5 Benzene TCE m- Xylene Pentachlorophenol Design Lifetime, Years Recycled Materials Resource Center at the University of Wisconsin- Madison 19

20 Results of Tank and Full- Scale Field Tests n Tire chips efficiently reduce the amount of VOCs present in the leachate and retard the movement of VOCs through the clay liner underlain the drainage layer. n Shredded tire chips had a positive impact on the quality of the leachate that they had made contact with. Recycled Materials Resource Center at the University of Wisconsin- Madison 20

21 Environmental Applications Significant sorption capacity of tire material renders it a potential material for environmental protection and remediation when in contact with contaminated waters and leachate Use of tires in environmental applications: Reactive drainage medium in landfills in reducing the strength of the landfill leachate, but most importantly, sorbing highly toxic volatile organic compounds Reactive slurry walls (no known application) Retaining nitrogen and phosphorus can be beneficial beneath sand- based root zones in golf courses and athletic fields Recycled Materials Resource Center at the University of Wisconsin- Madison 21

22 Conclusions 1. Hydraulic conductivities of tire chips (5-10 cm in size) were comparable to sands and gravels (> 1 cm/sec). 2. Organic chemical sorption capacities of tire chips were 2-5% of activated carbon sorption capacities for equivalent mass. 3. Sorption rates were affected by tire chip size; however, the equilibrium concentrations were almost the same. 4. Shredded tires (5-10 cm in size) can be used in landfills to retard the movement of toxic compounds. Recycled Materials Resource Center at the University of Wisconsin- Madison 22

23 Links for Further Information on Shredded Scrap Tires All links can be found on the RMRC website in the Reference Library section: Environmental Impacts and Environmental Applications of Shredded Scrap Tires Mechanical Properties And Mass Behavior of Shredded Tire- Soil Mixtures Mitigating Nutrient Leaching With a Sub- Surface Drainage Layer of Granulated Tires Recycled Materials Resource Center at the University of Wisconsin- Madison 23

24 THANK YOU! QUESTIONS? Angela Pakes, P.E., LEED AP Recycled Materials Resource Center at the University of Wisconsin- Madison 24