Leaching of Copper, Chromium and Arsenic from CCA Treated Wood i Leaching of Copper, Chromium and Arsenic from CCA Treated Wood i n Sanitary Landfill Leachate n Sanitary Landfill Leachate Brajesh Dubey Brajesh Dubey 1 , Timothy Townsend , Timothy Townsend 1 1 and Helena Solo and Helena Solo-Gabriele Gabriele 2 1 Department of Environmental Engineering Sciences, University of Department of Environmental Engineering Sciences, University of Florida, Gainesville, FL 32611 Florida, Gainesville, FL 32611-6450, E 6450, E-mail: mail: bkdubey@ufl.edu bkdubey@ufl.edu, ttown@ufl.edu , ttown@ufl.edu 2 Department of Civil, Architectural and Environmental Engineerin Department of Civil, Architectural and Environmental Engineering, University of Miami, Coral Gables, FL 33124 g, University of Miami, Coral Gables, FL 33124-0630, E 0630, E-mail: hmsolo@miami.edu mail: hmsolo@miami.edu The objective of the research presented here is to assess the potential leaching of discarded chromated copper arsenate- (CCA-) treated wood products in MSW landfills. The objective of the research presented here is to assess the potential leaching of discarded chromated copper arsenate- (CCA-) treated wood products in MSW landfills. Sample Collection  The un-weathered samples were created by purchasing southern yellow pine dimensional lumber from a retail outlet and sending coupons of this wood to different treatment facilities for wood preservation (CCA and CCA-R).  Weathered samples of CCA treated wood were collected from a variety of demolition sites and waste disposal facilities. Detail of sample collection is presented in Table 1. Sample Collection  The un-weathered samples were created by purchasing southern yellow pine dimensional lumber from a retail outlet and sending coupons of this wood to different treatment facilities for wood preservation (CCA and CCA-R).  Weathered samples of CCA treated wood were collected from a variety of demolition sites and waste disposal facilities. Detail of sample collection is presented in Table 1. Laboratory Leaching Procedures Eight leaching fluids were utilized in this study. Six out of the eight leaching fluids were prepared from landfill leachates collected from the landfills in Florida. The other two leaching protocols used were TCLP and the SPLP. The TCLP test is a standardized method used to determine if a solid waste is a TC hazardous waste. The SPLP test is used to predict leaching under conditions where rainfall is expected to be the prime leachant; it has been used to estimate the leaching that might occur in an inert landfill like a construction and demolition (C&D) debris landfill. Laboratory Leaching Procedures Eight leaching fluids were utilized in this study. Six out of the eight leaching fluids were prepared from landfill leachates collected from the landfills in Florida. The other two leaching protocols used were TCLP and the SPLP. The TCLP test is a standardized method used to determine if a solid waste is a TC hazardous waste. The SPLP test is used to predict leaching under conditions where rainfall is expected to be the prime leachant; it has been used to estimate the leaching that might occur in an inert landfill like a construction and demolition (C&D) debris landfill. Materials and Methods Materials and Methods Materials and Methods Landfill Leachate Collection Leachate samples were collected from six MSW landfills in Florida. The landfill details are described in Table 2. The landfills are designated as sites A through F. Leachate samples were collected from the sump of the landfill leachate collection system. It was bailed using a Teflon bailer at all sites except at sites B and E where they were collected using the existing pumping system installed at the landfill. The leachate samples were collected in HDPE containers, transported to the laboratory and stored at 4 o C until further analyses. Landfill Leachate Collection Leachate samples were collected from six MSW landfills in Florida. The landfill details are described in Table 2. The landfills are designated as sites A through F. Leachate samples were collected from the sump of the landfill leachate collection system. It was bailed using a Teflon bailer at all sites except at sites B and E where they were collected using the existing pumping system installed at the landfill. The leachate samples were collected in HDPE containers, transported to the laboratory and stored at 4 o C until further analyses. Landfill site Metric tons (per day) Operation status of the landfill Acres of lined cell collected for Site A Site B Site C Site D Site E Site F 600 750 1200 550 366 800 Closed Both active and capped cells Active Active Closed Both active and capped cells 125 104 34 20 27 12 Table 2: Leachate sampling site details Table 2: Leachate sampling site details Objective Objective Objective Pressure treated wood products contain heavy metals to prevent biological decay. Scrap treated wood from construction activities and demolished treated wood structures are typically disposed in landfills. To examine the potential mobility of metals from pressure treated wood disposed in landfills, wood samples were leached using leachate from lined landfills and the concentrations of arsenic, chromium and copper were measured. Both un-weathered and weathered chromated copper arsenate- (CCA-) treated wood sample were evaluated. Results were compared to leaching measured using the toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP). Pressure treated wood products contain heavy metals to prevent biological decay. Scrap treated wood from construction activities and demolished treated wood structures are typically disposed in landfills. To examine the potential mobility of metals from pressure treated wood disposed in landfills, wood samples were leached using leachate from lined landfills and the concentrations of arsenic, chromium and copper were measured. Both un-weathered and weathered chromated copper arsenate- (CCA-) treated wood sample were evaluated. Results were compared to leaching measured using the toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP). Introduction Introduction Introduction Leaching of arsenic, copper and chromium  The mean As concentration in the un-weathered CCA treated wood leachate was 7.41 mg/L for TCLP and 7.17 mg/L for SPLP. The weathered wood leachates had As concentration in the range of 3.0 to 6.6 mg/L for TCLP and 3.2 to 7.6 mg/L for SPLP. The As concentration in the extract using the landfill leachate was in the range of 1.49 to 5.91 mg/L for un-weathered samples and 1.97 to 6.57 mg/L for weathered treated wood samples.  In general the As and Cr concentrations leached using the landfill leachate samples varied somewhat among the sites, but tended to be similar or somewhat lower than the TCLP and SPLP concentrations.  Copper leaching was greatest when extracted with the landfill leachate. Leaching of arsenic, copper and chromium  The mean As concentration in the un-weathered CCA treated wood leachate was 7.41 mg/L for TCLP and 7.17 mg/L for SPLP. The weathered wood leachates had As concentration in the range of 3.0 to 6.6 mg/L for TCLP and 3.2 to 7.6 mg/L for SPLP. The As concentration in the extract using the landfill leachate was in the range of 1.49 to 5.91 mg/L for un-weathered samples and 1.97 to 6.57 mg/L for weathered treated wood samples.  In general the As and Cr concentrations leached using the landfill leachate samples varied somewhat among the sites, but tended to be similar or somewhat lower than the TCLP and SPLP concentrations.  Copper leaching was greatest when extracted with the landfill leachate. The un-weathered CCA-treated wood, and five out of eight weathered CCA- treated wood samples exceeded the TCLP limit for arsenic. If CCA-treated wood was not otherwise exempt from classification as a hazardous waste, the discarded CCA- treated wood would frequently require management as a hazardous waste. Some CCA- treated wood is disposed in lined landfills. If all the CCA-treated wood are disposed in lined landfills, the potential increased concentration of arsenic in the leachate may exist. While this option for CCA-treated wood disposal is preferred option over disposal in an unlined landfill, increased arsenic concentrations in the leachate may occur leading to increase cost of disposal. The un-weathered CCA-treated wood, and five out of eight weathered CCA- treated wood samples exceeded the TCLP limit for arsenic. If CCA-treated wood was not otherwise exempt from classification as a hazardous waste, the discarded CCA- treated wood would frequently require management as a hazardous waste. Some CCA- treated wood is disposed in lined landfills. If all the CCA-treated wood are disposed in lined landfills, the potential increased concentration of arsenic in the leachate may exist. While this option for CCA-treated wood disposal is preferred option over disposal in an unlined landfill, increased arsenic concentrations in the leachate may occur leading to increase cost of disposal. Conclusions Conclusions Conclusions This research was sponsored by the Florida Center for Solid and Hazardous Waste Management. The authors thank the landfill operators for allowing leachate sampling for the study. The following graduate students assisted with this project: Ajay Seth and Lakmini Wadanambi. Thanks are also extended to Dr. Yong-Chul Jang, Marnie Ward, Heng Li, Pradeep Jain and Thabet Tolaymat for their help. This research was sponsored by the Florida Center for Solid and Hazardous Waste Management. The authors thank the landfill operators for allowing leachate sampling for the study. The following graduate students assisted with this project: Ajay Seth and Lakmini Wadanambi. Thanks are also extended to Dr. Yong-Chul Jang, Marnie Ward, Heng Li, Pradeep Jain and Thabet Tolaymat for their help. Acknowledgements Acknowledgements Acknowledgements Sample Preparation All samples were processed to meet the TCLP requirement of having a particle size no larger than 0.95 cm at its narrowest dimension. The weathered samples were size reduced using a power drill with 8.7 mm drill bit to drill through the cross section of the wood. The drill cuttings were collected in plastic bags for later analyses. Each of the eight weathered CCA-treated wood samples used in this study represented composite cutting samples from seven individual CCA treated boards. Sample Preparation All samples were processed to meet the TCLP requirement of having a particle size no larger than 0.95 cm at its narrowest dimension. The weathered samples were size reduced using a power drill with 8.7 mm drill bit to drill through the cross section of the wood. The drill cuttings were collected in plastic bags for later analyses. Each of the eight weathered CCA-treated wood samples used in this study represented composite cutting samples from seven individual CCA treated boards. Solid waste Size reduction to less than 1 cm Leach 100 g for 18 hours at 30 RPM Filter solids from leachate Analyze leachate X mg / ml Figure 1: Laboratory leaching procedure Figure 1: Laboratory leaching procedure Sample Sample description Estimated age (yr) Standard retention Un-weathered CCA CCA Southern yellow pine 2.0 0.243 CCA-R Southern yellow pine 2.0 0.284 Weathered CCA CCA-1 Steps and walkway to temporary buildings. 1.5 0.300 CCA-2 Dimensional lumber & poles from demolished Playground 10.0 0.256 CCA-3 Blocks collected from a demolition site along the I-10 Highway. -1 0.213 CCA-4 Dimensional lumber from the demolished fence of a residence -1 0.204 CCA-5 Dimensional lumber from a demolished deck 20.0 0.476 CCA-6 Dimensional lumber from the demolished Fence of a church 10.0 0.255 CCA-7 Dimensional poles from a demolished structure in a park, Sample 1 10.0 0.263 CCA-8 Dimensional poles from a demolished structure in a park, Sample 2 10.0 0.297 UN Southern yellow pine 2.0 0.009 -1 age is not available Table 1: Sample details Table 1: Sample details Landfill leachate characterization Table 3 summarizes the analyzed parameters and the chemical characteristics of the leachates in the six landfills. The pH of the leachates ranged from 6.5 to 8.2. These pH values are typical of other Florida landfills. Conductivity readings correlated with the TDS value as expected. Landfill leachate characterization Table 3 summarizes the analyzed parameters and the chemical characteristics of the leachates in the six landfills. The pH of the leachates ranged from 6.5 to 8.2. These pH values are typical of other Florida landfills. Conductivity readings correlated with the TDS value as expected. Results Results Results Anions & cations (mg/L) Sulfide Chloride Sulfate Ammonia Calcium Potassium Sodium <0.008 31.65 0.072 0.132 0.225 7.75 296 2150 1502 402 1950 1270 7.91 33.0 11.0 2.42 17.6 141.2 20.6 1490 125 833 2630 1160 275 177 174 67 44.1 128 24 813 123 604 746 356 532 1920 367 1395 1990 1550 Organic acids (mg/L) Acetate Propionate Isobutyrate Butyrate Isovalerate Valerate Metals (mg/L) Arsenic Copper Chromium 35.0 582 273 13.5 40 366 22.60 176 32 11.3 19 13 74.0 172 129 101 100 126 <1.0 82 29 1.8 23 7.5 <1.0 159 56 0.4 13.3 59 <1.0 52 36 0.26 3.0 <1.0 <0.005 0.16 <0.005 0.07 0.06 0.03 <0.01 <0.01 <0.01 0.16 0.56 <0.01 <0.05 0.25 <0.05 <0.05 0.10 0.06 Parameters pH Conductivity (mS/cm) TDS Alkalinity (mg/L as CaCO3) COD (mg/L) Site A Site B Site C Site D Site E Site F 6.53 8.10 8.22 7.92 7.97 7.89 4.62 20.1 3.84 13.3 19.4 12.3 2620 9610 1960 5540 7960 5880 1250 6850 1550 5300 8050 4350 792 9570 1260 2150 3080 2530 Table 3: Characterization of landfill leachates Table 3: Characterization of landfill leachates 0 2 4 6 8 10 12 TCLP SPLP MSW Copper concentration (mg/L) CCA CCA-2 CCA-5 CCA-3 CCA-4 CCA-R CCA-1 CCA-6 CCA-7 CCA-8 0 2 4 6 8 10 TCLP SPLP MSW CCA CCA-2 CCA-5 CCA-3 CCA-4 CCA-R CCA-1 CCA-6 CCA-7 CCA-8 Arsenic concentration (mg/L) 0 1 2 3 4 5 6 TCLP SPLP MSW CCA CCA-2 CCA-5 CCA-3 CCA-4 CCA-R CCA-1 CCA-6 CCA-7 CCA-8 Chromium concentration (mg/L)