- Email: [email protected]
Metals and polybrominated diphenyl ethers leaching from electronic waste in simulated landfills
Journal of Hazardous Materials 252–253 (2013) 243–249
Contents lists available at SciVerse ScienceDirect
Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat
Metals and polybrominated diphenyl ethers leaching from electronic waste in simulated landfills Peeranart Kiddee a,b , Ravi Naidu a,b,∗ , Ming H. Wong c a b c
Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, Adelaide, 5095, Australia Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, Mawson Lakes Campus, Adelaide, 5095, Australia Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, China
h i g h l i g h t s • • • •
Simulated landfill columns provided realistic results than lab based column study. Column leachates showed significant seasonal effect on toxic substances. Toxic substances in the landfill leachates pose environmental and health hazards. A better management of e-waste is urgently needed.
a r t i c l e
i n f o
Article history: Received 2 January 2013 Received in revised form 18 February 2013 Accepted 7 March 2013 Available online 15 March 2013 Keywords: E-waste Simulated landfill column Heavy metals PBDEs Leachate
a b s t r a c t Landfills established prior to the recognition of potential impacts from the leaching of heavy metals and toxic organic compounds often lack appropriate barriers and pose significant risks of contamination of groundwater. In this study, bioavailable metal(oids) and polybrominated diphenyl ethers (PBDEs) in leachates from landfill columns that contained intact or broken e-waste were studied under conditions that simulate landfills in terms of waste components and methods of disposal of e-wastes, and with realistic rainfall. Fourteen elements and PBDEs were analysed in leachates over a period of 21 months. The results demonstrate that the average concentrations of Al, Ba, Be, Cd, Co, Cr, Cu, Ni, Pb, Sb and V in leachates from the column that contained broken e-waste items were significantly higher than the column without e-waste. BDE-153 was the highest average PBDEs congener in all columns but the average of PBDEs levels in columns that contained intact e-waste were (3.7 ng/l) and were not significantly higher than that in the leachates from the control column. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Electronic waste (e-waste) is the fastest growing stream of all waste types and is complex as it consists of a great variety of materials [1]. Some of the constituents of e-waste contain toxic substances [2] that can potentially contaminate the ecosystem and threaten human health. Numerous researchers have demonstrated that toxic metals and polyhalogenated organics including polybrominated diphenyl ethers (PBDEs) can be released from ewaste, posing serious risks of harm to the environment and humans [3–5]. E-waste disposal to landfills can pose serious contamination risks if they are not suitably managed. Leachates from landfills can contain large concentrations of dissolved and suspended organic
∗ Corresponding author at: CERAR-Centre for Environmental Risk Assessment and Remediation, Building X, University of South Australia, Mawson Lakes, SA, 5095, Australia. Tel.: +61 8 8302 5041; fax: +61 8 8302 3124. E-mail addresses: [email protected], [email protected] (R. Naidu). 0304-3894/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2013.03.015
substances, inorganic compounds and heavy metals. However, the concentrations of toxic substances in leachates depend on the characteristics of the wastes and stages of weathering in a particular landfill [6]. E-waste provides approximately 70% of heavy metals, including 40% of the lead, to the waste stream infiltrate of landfills [7], and also contributes up to 30% of PBDEs [8]. There is potential for transport of pollutants through soils and groundwater within and around landfill sites [9]. Organic and putrescibles materials in landfills decompose and percolate through soil as landfill leachate. Disposal of ever increasing quantities of e-waste is of serious concern because e-waste contains significant amounts of toxic substances [10], and they may interact with organic compounds in leachates, and landfills were not originally designed to receive ewaste. However, there are disagreements between legislators and local councils regarding the environmental impacts of disposal of electronic wastes, particularly in landfills. Some argue that old landfills that do not have appropriate barriers to minimise leaching and more modern landfills receiving electronic wastes cause groundwater contamination. However, others claim that modern landfills
244
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
are designed to securely isolate and protect pollutants found in e-waste from reaching the environment [11]. A technique designed to assess the potential toxicity of leachates from e-waste disposal is the Toxicity Characteristic Leaching Procedure (TCLP) which simulates landfill leaching in terms of a worst case eventuality. The TCLP test determines if a solid waste has physical and chemical properties that make it likely to be a toxic hazardous waste. Electronic devices are considered to be hazardous waste under provisions of the Resource Conservation and Recovery Act (RCRA) if TCLP extracts contain specified elements at higher than regulated concentrations, which are 5 mg/l of As, 100 mg/l of Ba, 1 mg/l of Cd, 5 mg/l of Cr, 5 mg/l of Pb, 0.2 mg/l of Hg, 1 mg/l of Se and 5 mg/l of Ag [12]. There have been a number of studies used to classify the hazards of e-wastes by the TCLP test. Jang and Townsend [13] found that the concentrations of Pb in TCLP extracts ranged from 0.53 to 5.0 mg/l for printed circuit boards and from 1.7 to 6.0 mg/l for cathode ray tubes. Townsend et al. [10] found Pb concentrations in leachates above 5 mg/l from many types of electronic devices including laptops, mobile phones, mice, remote controls and smoke detectors. Li et al. [14] found that Pb is the predominant toxic heavy metal, at concentrations of 150–500 mg/l in leachate from printed wire boards of personal computers. Some studies show that the TCLP may not be an appropriate measure for the assessment of pollutant leachability from waste disposal in landfills and this further complicates the debates on the safety of the disposal of e-wastes to landfills. Numerous studies have shown that the TCLP underestimates pollutant leaching compared to actual landfills [15–17], but specific studies on e-wastes found Pb to be much more leachable in the TCLP compared to leachates from municipal solid waste (MSW) landfill [10,13,14]. Leaching in laboratory tests such as the TCLP may not accurately represent actual processes occurring in inner landfills. Leachate quality from landfills depends on several factors such as waste composition, biochemical changes, physicochemical processes and seasonal variation. This paper describes research using columns under conditions that more closely simulate actual landfills in terms of waste components and method of disposal of e-wastes, and with realistic precipitation to generate leachate. Fourteen elements and PBDEs were analysed in leachates from our column studies. The objectives of this investigation were to determine the effects of e-wastes on the concentrations of potential pollutants in leachates by comparing the concentrations of metal(oids) and PBDEs in leachates from large columns that simulate landfills that (a) contain no e-waste, (b) those that have whole e-waste items such as TV sets, computers etc. as disposed in older landfills, and (c) those that have broken e-waste items, under conditions of natural precipitation (rainfall). Much effort was directed towards ensuring that these column studies were conducted under conditions as similar as possible to actual landfills.
2. Materials and methods 2.1. Simulated landfills Three simulated landfill were built as large diameter columns in an open area at Mawson Lakes, South Australia. Each column was constructed of high density polyethylene (HDPE), 2 m high and 1.8 m in diameter (Fig. 1(a)). An outlet and tap were located close to the outside edge of each column with a maximum of 200 mm clearance under the base column. The columns were placed on a concrete base that had a slight slope and the tap was located on the lower side for leachate drainage. The tops of the three columns were open and received only rainfall. Each column had 5 holes each with 50 mm adaptor sockets on their sides, 300 mm apart, and with
Fig. 1. Column design.
removable plugs for monitoring temperature. The columns had a 100 mm layer of gravel at the bottom and geotextile fabric was laid on the surface of the gravel. A homogeneous layer of municipal solid waste (MSW) and e-waste was placed in the columns up to approximately 1.35 m in height and then covered by 50 mm of gravel (Fig. 1(b)). The gravel was used to reduce smells from the waste, minimise edge flow of the rainwater, and to allow rainwater to percolate through the waste. 2.2. Waste preparation and column loading Bulk e-waste MSW mixtures were prepared by mixing a large sample of MSW with e-waste to produce proportions of MSW components for each of the columns shown in Table 1. The MSW composition proportions were devised to correspond with those found in a detailed survey of the three main landfills in Adelaide, South Australia. The classification of the waste followed the American Society for Testing and Material (ASTM) method D5231-92 [18]. MSW components were classified into a minimum of 13 categories including: paper, glasses, plastics, metals, food wastes, wood, garden wastes, textiles, leather, tyres and rubber, e-waste, construction and demolition (C&D), and others such as medicines, cosmetics, napkins, rock, soil, and fines. The selected types of ewaste were based on criteria including consumption ratio, disposal level rating, level of recycling or reuse, toxicity, product stewardship arrangements, ease of collection/material separation and recycling and market availability in Australia [19]. Column 1 was a control that was filled with MSW only, whereas columns 2 and 3 were filled with MSW mixed with 8% (29.5 kg) e-waste. Column 2 contained intact items of e-waste that consisted of 1 CRT television (size 14 in.), 1 computer CRT monitor, 1 CPU and 3 fluorescent tubes and most of e-waste items were intact and there was no size reduction. Column 3 was filled with broken items that consisted of CRTs from televisions and computer monitors, circuit boards from CPU and fluorescent tubes. The e-waste and MSW were mixed to be as homogenous as possible. 2.3. Effect of rainfall on leachate generation The three simulated landfill columns were open at the top and in an open area. The columns received only natural precipitation to generate leachate. The data for rainfall were taken from Australian Government Bureau of Meteorology in Parafield Airport Station, some 2 km from the columns. The leachate volumes were measured and drained out until empty every month. Pearson correlation analysis was performed using the SPSS statistical package to analyse the correlation between rainfall volume and leachate production.
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
245
Table 1 The composition of MSW in simulated landfill columns. Component
Paper Glasses Plastics Metals Food Waste Wood Yard Waste Textiles Leather Tyres and Rubber C&D E-waste Others Total
Column 1
Column 2
Column 3
No e-waste
e-waste (Whole items)
e-waste (Broken items)
Percent
Weight (kg)
Percent
Weight (kg)
Percent
Weight (kg)
27.3 5.1 24.4 9.6 8.7 6.9 5.7 5.1 0.8 2.9 0.9 0.0 2.6 100
100.7 19.0 90.1 35.4 32.0 25.4 21.0 18.7 2.9 10.7 3.4 0.0 9.7 368.7
25.1 4.7 22.5 8.8 8.0 6.3 5.2 4.7 0.7 2.7 0.8 8.0 2.4 100
92.6 17.4 82.9 32.6 29.4 23.3 19.3 17.2 2.7 9.8 3.1 29.5 8.9 368.7
25.1 4.7 22.5 8.8 8.0 6.3 5.2 4.7 0.7 2.7 0.8 8.0 2.4 100
92.6 17.4 82.9 32.6 29.4 23.3 19.3 17.2 2.7 9.8 3.1 29.5 8.9 368.7
2.4. Analysis of leachate Leachate samples were collected monthly for the analyses of pH, oxidation-reduction potential (ORP), electrical conductivity (EC), total dissolved solid (TDS), total organic carbon (TOC), aluminium (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V) zinc (Zn), and polybrominated diphenyl ethers (PBDEs) from each of the three columns over a 21-month period. After collection of the samples, the leachate was drained from the columns until empty every month. The statistical analysis of one-way ANOVA at 95% confidence limits was used to compare the data of control columns with the others. 2.4.1. General analysis An AquareadTM multi-parameter water quality metre was used to measure pH, ORP, EC and TDS of fresh leachate samples drained the columns in the field. The metre was calibrated in the laboratory before use in the field. Additional filtered samples were analysed for TOC with a total organic carbon analyser (TOC-5000A, Shimadzu Corp., Japan). Quality assurance of the TOC analyses was assessed using duplicates and a standard reference solution. 2.4.2. Metal(oids) The concentrations of Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sb, V and Zn were determined in leachate samples by inductively coupled plasma mass spectroscopy (ICP-MS, Agilent 7500, USA). Prior to analysis the leachate samples were centrifuged at 10,000 revolutions per minute (RPM) with a SORVALL SA-60 rotor for half an hour and filtered through 0.45 m filters. Quality assurance and control of metal(oids) analyses were ensured by analysis of sample duplicates and standard reference solutions at regular intervals. 2.4.3. PBDEs 2.4.3.1. Chemicals and reagents. Standard solutions of PBDE (mixed standard of 27 congeners) and individual surrogate BDE-139 for sample spiking were obtained from Wellington Laboratories, Ontario, Canada. Dichloromethane (DCM), hexane, acetone, anhydrous sodium sulphate and florisil were obtained from Thermo Fisher Scientific Australia. Glassware used for analysis was washed with detergent and warm tap water and rinsed with acetone and DCM. 2.4.3.2. Extraction and cleanup. In preparation for PBDEs analysis, 400 ml leachate samples or 100 ml (in cases when the leachate samples collected were less than 400 ml) were spiked with 200 g/l
surrogate standard of BDE-139 and extracted 3 times with 40 ml of DCM. The extracts were concentrated and reduced in volume to approximately 1 ml. The extracts were purified by passing them at a rate of 1–2 ml per min through solid phase extraction (SPE) cartridges conditioned with 2 g of florisil and 5 ml of DCM, and eluted with 10 ml of hexane: dichloromethane (1:1, v/v), followed by 10 ml of DCM, and finally collected in 40 ml amber vials. The samples were concentrated to near dryness under a gentle stream of nitrogen and taken up into 200 l of hexane. Lastly, the samples were transferred into 2 ml GC vials with 200 l inserts for analysis. 2.4.3.3. Gas chromatographic analysis. PBDEs were determined using a GC-ECD Agilent 6890 N gas chromatograph with auto sampler 7683B (Agilent Technologies). A DB-5HT column (0.25 mm id, 0.1 m film thickness) was used for separation. The GC oven temperature programme was: initial temperature 110 ◦ C for 3 min followed by a programme to 200 ◦ C at 15 ◦ C/min and ramped to 220 ◦ C at 2 ◦ C/min, and finally increased to 350 ◦ C at 3 ◦ C/min, then held for 4 min. Nitrogen was used as the carrier gas. Splitless injection was used and the injected volume was 1 l. 2.4.3.4. Quality assurance/quality control. The quality of analytical processes was confirmed by checking the reproducibility of calibration, blanks, sample duplicates and recovery processes. For each batch of 10 samples a solvent blank and a procedural blank were processed to check for contamination. The recovery process was tested by spiking and ranged between 60% and 70%. Interference in solvents, blanks and extraction equipment were avoided by preventing contamination. 3. Results and discussion 3.1. Relationship between rainfall, leachate volume and analyses studied Leachates were generated by rainwater percolating through the waste in the columns and the volumes of leachates from each of the three columns each month were similar. During the operational period the leachate volumes produced were on average 26% of the rainfall entering the columns. The volume of leachate produced is compared with the rainfall in Fig. 2. Linear regression analysis showed a strongly positive correlation between monthly rainfall and leachate volumes (p < 0.01, r2 = 0.98, n = 21) with the rainfall accounting for 98% of variance in the volume of leachate generated. Simple linear correlation analyses between rainfall and metal(loids) analyses of the leachates showed that, with the
246
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
300 250 200 150 100 50
Jul-12
Jun-12
Apr-12
May-12
Mar-12
Jan-12
Feb-12
Dec-11
Oct-11
Nov-11
Sep-11
Jul-11
Rainfall (l)
Aug-11
Jun-11
Apr-11
May-11
Mar-11
Jan-11
Feb-11
Dec-10
Nov-10
0
Leachate generation (l)
Fig. 2. Comparison between rainfall and leachate generation during operation period.
Fig. 3. Comparisons between rainfall and the concentrations of Sb in three columns over 21 months.
Column 1 pH
Jul-12
Jun-12
Apr-12
May-12
Mar-12
Jan-12
Feb-12
Dec-11
Oct-11
Column 2 pH
Nov-11
Sep-11
Jul-11
Aug-11
Jun-11
Apr-11
May-11
Mar-11
Jan-11
Feb-11
Dec-10
9 8 7 6 5 4 3 2 1 0 Nov-10
exception of Sb, none of the analyses showed any significant relationship with rainfall. The concentration of Sb in all columns was negatively correlated with rainfall (p < 0.01, r2 = −0.30 in column 1, r2 = −0.42 in column 2 and r2 = −0.32 in column 3). Thus, the concentrations of Sb decreased with time and with an increase in rainfall (Fig. 3) and leachate volume. This suggests depletion of Sb in leachates with increasing rainfall and points to a fixed amount of mobile Sb in the wastes and limited replenishment of this fraction compared to other analysts. The temperatures of waste inside each of the three columns were nearly at ambient temperature, which varied with seasonal fluctuations from 16 to 32 ◦ C in summer months to lows of 9–20 ◦ C in winter months. This observation is consistent with those of Li et al. [20], and supported by Yesiller and Handson [21], that the temperatures of wastes at shallow depths are affected by seasonal variations.
Column 3 pH
Fig. 4. pH values in three columns over study period.
3.2. General analytical results The results for leachates from each of the three columns are shown in Table 2. The pH values ranged from 6.1 to 8.0 (Fig. 4). In the first month of leachate sample collection the pH values of all three column leachates were lower than the next batches of leachate samples, which had pH values of 6.2, 6.2 and 6.1 in columns 1, 2 and 3, respectively. After the second month until the end of the
study period, pH values of the leachates fluctuated between 6.7 and 8.0. These results contrast with those reported by Spalvins et al. [22] who found that leachate pH in simulated columns containing MSW remained in the acidic range for their entire study period of 400 days and stabilised at a pH of approximately 5. However,
Table 2 Average and range of analyses from three simulated landfill columns over 21 months. Parameters
pH ORP (mV) EC (mS) TDS (mg/l) TOC (mg/l) Al (g/l) As (g/l) Ba (g/l) Be (g/l) Cd (g/l) Co (g/l) Cr (g/l) Cu (g/l) Fe (g/l) Ni (g/l) Pb (g/l) Sb (g/l) V (g/l) Zn (g/l) PBDEs (ng/l)
Average
Range
Column 1
Column 2
Column 3
Column 1
Column 2
Column 3
7.3 −5.1 1285 1150 141 80.1 18.4 72.7 0.07 0.24 6.5 5.0 25.1 514 14.3 6.7 4.4 12.5 12.4 3.2
7.4 −8.2 1182 962 126 55.7 24.7 64.8 0.04 0.17 6.5 2.5 18.8 407 11.6 5.5 4.4 14.5 9.7 3.7
7.4 −25.5 1406 1167 160 91.0 24.4 88.3 0.07 0.26 9.7 5.3 25.6 400 21.6 9.3 5.0 17.9 11.6 3.3
6.2–8.0 (−)154.5–134.5 609–3292 340–3139 13.7–1765 8.6–826.0 5.4–70.7 12.4–437.0 0.007–0.7 0.004–1.0 0.9–64.1 1.2–11.6 0.8–53.6 27.4–3260 4.9–46.9 0.4–38.0 0.8–8.0 1.6–53.3 0.7–128.7 0.3–8.9
6.2–8.0 (−)173.5–115.4 464–3273 301–3093 10.6–1532 4.4–479.4 7.2–71.2 11.9–261.3 0.003–0.3 0.003–0.7 0.8–53.0 0.9–7.8 1.0–36.1 13.6–2927 3.7–35.3 0.2–33.6 0.9–8.5 2.5–53.8 0.784.4 0.3–8.0
6.1–8.0 (−)183.0–85.6 723–3448 469–3230 15.8–1930 2.1–943.7 4.9–73.0 22.8–510.4 0.008–0.8 0.008–1.4 1.6–73.3 1.8–11.8 1.0–56.9 22.2–2061 7.0–63.3 0.8–47.2 1.4–10.7 2.8–75.2 0.5–83.5 0.2–8.4
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
leachate pH from simulated columns containing excavated landfill wastes ranged from 7.2 to 8.1. They attributed these pH changes to the two primary phases of waste decomposition in a MSW landfill: an acidic phase and a methanogenesis phase. The pH and organic carbon content are the parameters normally used to characterise which phase the leachate represents. The pH values recorded in our study may be attributed to the differences in the design of the simulation columns from that of Spalvins et al. [22] that allowed the development of highly reducing conditions, whilst the rate of leachate flow through the column in the current study may have prevented methanogenesis because of the absence of food wastes and cardboard. Oxidation-reduction potential (ORP) values of the leachates were more negative in the first five months of sampling in all three columns and tended to increase to slightly less negative and to positive values in the sixth month (detailed results not shown). After that ORP fluctuated between (−) 116 and 134 mV in all columns. Oxidation-reduction potential (ORP) values in the control column were higher than those of columns 2 and 3 (Table 2). Column 3, with broken e-waste, had lower average ORP values than column 2 that had whole e-waste items. EC, TDS and TOC indicated downward trends with time. EC and TDS decreased moderately with small fluctuations. TOC had the highest level in the first month, at over 1500 mg/l, and sharply dropped to around 100 mg/l in the third month with a slightly decreasing trend with a small fluctuation (detailed results over time not shown). TOC reflects the presence of dissolved organic matter in leachates [23,24]. During the first month the leachates enriched in dissolved organic matter with the soluble fraction decreasing with time. Most of EC, TDS and TOC values in column 3 (broken e-waste components) were higher than columns 1 and 2 (Table 2). These results are not surprising given the higher surface area of the broken e-waste components compared to whole items. The statistical analysis showed that pH, TDS and TOC in control (column 1) were statistically different (p < 0.05) to the columns that contained e-waste but EC and ORP in the control were statistically similar (p < 0.05) to the others.
247
3.3. Metal(oids) A summary of the data for the metal(oids) in the simulated landfill column leachates is shown in Table 2. Fourteen elements were analysed from November 2010 to June 2012. Iron was detected at the highest concentrations in all leachates. In general, the concentrations of metal(oids) in leachates that contained e-wastes were significantly higher than the control column containing MSW only. The average concentrations of Al, Ba, Be, Cd, Co, Cr, Cu, Ni, Pb, Sb and V in leachates from column 3 that contained broken items of e-waste were significantly (p < 0.05) higher than that in leachates from other columns. Concentrations of As, Cd, Sb and V detected in leachates from columns 2 and 3 that included e-waste items were higher than the control column. The average concentrations of Al, Ba, Be, Co, Cr, Cu, Ni and Pb found in the control column were less than in column 3 that contained broken items of e-waste higher, but higher than column 2 that had whole e-waste items. It is difficult to explain why slightly elevated concentrations of metal(oids) were recorded in the leachates from control column (column 1) compared to column 2 which contained unbroken components of e-wastes. One reason perhaps may be the presence of slightly more metal and yard wastes in the control column compared to columns 2 and 3. The statistical analysis showed that concentrations of Ba, Co, Pb and Sb in control (column 1) were significantly different (p < 0.05) to the columns that contained e-waste (see Fig. 5(a–d)) and there was no significant differences in Al, As, Be, Cd, Cu, Fe Ni and V in control relative to the other columns. The main heavy metal of concern in e-waste, and the most problematic from a monitoring perspective, is Pb [13,22,25]. The values of Pb ranged between 0.4–38.0, 0.2–33.6 and 0.8–47.3 g/l in columns 1, 2 and 3, respectively, demonstrating that the concentrations of Pb in the column filled with broken e-waste items exceeded that in leachates from the control column, confirming Spalvins et al. [22] results. Spalvins et al. [22] reported that the concentrations of Pb were 7–66 g/l in columns containing e-waste and <2–54 g/l in a control column, so their Pb concentrations were greater than in the present study.
80
600 500 400 300 200 100 0
60 40 20 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12 Jun-12 Jul-12
0
Ba (µg/l) Column1
Ba (µg/l) Column2
Co (µg/l) Column1
Ba (µg/l) Column3
a: The concentration of Ba
Co (µg/l) Column2
Co (µg/l) Column3
b: The concentration of Co 12 10 8 6 4 2 0
50 40 30 20 10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12 Jun-12 Jul-12
0
Pb (µg/l) Column1
Pb (µg/l) Column2
c: The concentration of Pb
Pb (µg/l) Column3
Sb (µg/l) Column1
Sb (µg/l) Column2
d: The concentration of Sb
Fig. 5. The concentration of Ba, Co, Pb and Sb in three columns during the study period.
Sb (µg/l) Column3
248
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
4 DecaBDE
3.5
NonaBDE
3
OctaBDE 2.5
HeptaBDE
2
HexaBDE
1.5
PentaBDE TetraBDE
1
TriBDE 0.5
DiBDE
0
MonoBDE column 1
column 2
column 3
Fig. 6. The level of average PBDEs congeners in each landfill columns (ng/l).
This difference in the concentration of Pb may be attributed to the nature of e-wastes used by Spalvin et al. [22] in their study which could have been different from that used in the present study.
TCLP leachates from e-wastes have the potential to release high concentrations of toxic chemicals (such as Pb), but simulated column studies as in the present study show significantly lower concentrations than would be expected from TCLP extractions. However, considerable caution must be exercised when dealing with long-term landfills given the potential for extensive weathering of e-wastes potentially leading to greater concentrations of toxic substances that observed in our 21-month column study. In contrast to columns, extensive weathering of e-wastes is likely to occur in landfills due to the presence of moisture as it percolates slowly through the wastes- with the residence contact time between the moisture and wastes being significantly longer than that recorded in columns. Slow leaching allows enough contact time for contaminant solubilisation while quick flushing after a dry period is less likely to transport chemicals out of the landfill. Needless to say the procedure established in the present study can be used to further manipulate contact time between moisture and wastes thus enhancing landfill conditions. Management of leachates percolating through the column together with longer term considerations allowing further weathering of e-wastes may generate results similar to that found in landfills.
3.4. PBDEs Acknowledgements Only limited information is available in the literature on PBDEs in simulated landfill columns. The average and range of the sums of the PBDEs ( PBDEs) in leachates from simulated landfill columns are shown in Table 2, and there was no effect of e-waste on PBDEs. PBDEs were detected from MonoBDEs to DecaBDEs in all PBDEs levels in the simulated landsimulated landfill columns. fill columns fluctuated between 0.3–8.9, 0.3–8.0 and 0.2–8.4 ng/l, respectively and PBDEs average value were 3.2, 3.7 and 3.3 ng/l, respectively. HexaBDEs, especially: BDE-153 had the highest average PBDEs congener in the three columns (Fig. 6). However, these results vary from the recently published studies on PBDEs in landfill leachates in which e-waste was reported to contribute approximately 30% of PBDEs [26] in the leachates. These differences may be attributed to either the release of PBDE’s from material other than e-wastes in landfill leachates or the short duration of the current study and as a consequence limited weathering of e-wastes. PBDE’s detected in the leachates are nevertheless of much concern given the increasing regulatory pressure to control persistent and bioaccumulative chemicals more effectively following 2001 Stockholm convention. Indeed, many of the old landfills in South Australia are not adequately lined and, there is potential for these leachates to migrate into the subsurface soil and ground water over a period of time- this would be considered the primary environmental concern. 4. Conclusions It is apparent that e-waste disposal at the rate tested here in simulated modern sanitary MSW landfills is not likely to result in Pb leachate concentrations reaching levels of regulatory concern, although it cannot be said that higher volumes of e-wastes would still yield the same result. However, the results from this study demonstrate that the average concentrations of Al, Ba, Be, Cd, Co, Cr, Cu, Ni, Pb, Sb and V detected in column which contained broken e-waste items were higher than the column without e-waste. The average of PBDEs levels in columns that contained e-waste had similar concentrations as the control column. Of much concern is the fact that these toxic substances leached throughout the 21-month study period indicating slow and continuous loading of groundwater even though concentrations of the analysts studied were low. Old landfills may still need to be remediated to prevent potential contamination of groundwater.
The authors acknowledge financial support from CRC CARE, the Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia and Thai Government fellowship for this study. We thank CERAR’s friends and UniSA’s staff for their assistant to set landfill simulation columns. References [1] S. Zhang, E. Forssberg, Mechanical separation-oriented characterization of electronic scrap, Resour. Conserv. Recycl. 21 (1997) 247–269. [2] D. Pant, D. Joshi, M.K. Upreti, R.K. Kotnala, Chemical and biological extraction of metals present in E waste: a hybrid technology, Waste Manage. 32 (2012) 979–990. [3] E. Williams, R. Kahhat, B. Allenby, E. Kavazajian, J. Kim, M. Xu, Environmental, social and economic implications of global reuse and recycling of personal computers, Environ. Sci. Technol. 42 (2008) 6446–6454. [4] J.M. Czuczwa, R.A. Hites, Environmental fate of combustion-generated polychlorinated dioxins and furans, Environ. Sci. Technol. 18 (1984) 444–450. [5] B.H. Robinson, E-waste. An assessment of global production and environmental impacts, Sci. Total Environ. 408 (2009) 183–191. [6] S.R. Qasim, W. Chiang, Sanitary Landfill Leachate: Generation, Control and Treatment, CRC Press, United States of America, 1994. [7] E. Grossman, High Tech Trash: Digitatl Devices, Hidden Toxics, and Human Health, ISland Press, Washington, DC, 2006. [8] M. Danon-Schaffer, J. Grace, R. Wenning, M. Ikonomou, W. Lukemburg, PBDEs in landfill leachate and potential for transfer from electronic waste, OHCs 68 (2006) 1759–1762. [9] A. Kasassi, P. Rakimbei, A. Karagiannidis, A. Zabaniotou, K. Tsiouvaras, A. Nastis, K. Tzafeiropoulou, Soil contamination by heavy metals: measurements from a closed unlined landfill, Bioresour. Technol. 99 (2008) 8578–8584. [10] T.G. Townsend, K. Vann, S. Mutha, B. Pearson, Y.-C. Jang, S. Musson, A. Jordan, RCRA Toxicity characterization of computer CPUs and other discarded electronic devices, Department of Environmental Engineering Sciences, University of Florida, Florida, 2004, p. 79. [11] SWANA, The Environmental Consequence of Disposing of Products Containing Heavy Metals in Municipal Solid Waste Landfills, Solid Waste Association of North America, Silver Spring, MD, 2004. [12] T.G. Townsend, K. Vann, S. Mutha, B. Pearson, Y.-C. Jang, S. Musson, A. Jordan, RCRA Toxicity characterization of electronic wastes, Hazard. Waste Consultant 23 (2005) 16–18. [13] Y.-C. Jang, T.G. Townsend, Leaching of lead from computer printed wire boards and cathode ray tubes by municipal solid waste landfill leachates, Environ. Sci. Technol. 37 (2003) 4778–4784. [14] Y. Li, J.B. Richardson, A.K. Walker, P.-C. Yuan, TCLP Heavy metal leaching of personal computer components, J. Environ. Eng. 132 (2006) 497–504. [15] K. Hooper, M. Iskander, G. Sivia, F. Hussein, J. Hsu, M. Deguzman, Z. Odion, Z. Llejay, F. Sy, M. Petreas, B. Simmons, Toxicity characteristic leaching procedure fails to extract oxoanion-forming elements that are extracted by municipal solid waste leachates, Environ. Sci. Technol. 32 (1998) 3825–3830. [16] A. Ghosh, M. Mukiibi, W. Ela, TCLP underestimates leaching of arsenic from solid residuals under landfill conditions, Environ. Sci. Technol. 38 (2004) 4677–4682.
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249 [17] C.E. Halim, J.A. Scott, H. Natawardaya, R. Amal, D. Beydoun, G. Low, Comparison between acetic acid and landfill leachates for the leaching of Pb(II), Cd(II), As(V), and Cr(VI) from cementitious wastes, Environ. Sci. Technol. 38 (2004) 3977–3983. [18] ASTM International, Standard test method for determination of the composition of unprocessed municipal solid waste, D5231-92 (2008), American Society for Testing and Materials, US, 2008. [19] Hyder Counsulting, Waste Recycling in Australia Final Report, Prepared for the Department of Environment, Water, Heritage and the Arts, 2008, p. 137. [20] Y. Li, J.B. Richardson, R. Mark Bricka, X. Niu, H. Yang, L. Li, A. Jimenez, Leaching of heavy metals from e-waste in simulated landfill columns, Waste Manage. 29 (2009) 2147–2150. [21] N. Yesiller, J.L. Handson, Analysis of temperatures at a municipal solid waste landfill, in: Christensen et al. (Ed.) Sardinia 2003, Ninth International Waste
[22] [23] [24] [25]
[26]
249
Management and landfill Symposium, CISA, Environmental Sanitary Engineering Centre, Italy, 2003, pp. 1–10. E. Spalvins, B. Dubey, T. Townsend, Impact of electronic waste disposal on lead concentrations in landfill leachate, Environ. Sci. Technol. 42 (2008) 7452–7458. I.M.-C. Lo, Characteristics and treatment of leachates from domestic landfills, Environ. Int. 22 (1996) 433–442. M. Osako, Y.-J. Kim, S.-i. Sakai, Leaching of brominated flame retardants in leachate from landfills in Japan, Chemosphere 57 (2004) 1571–1579. S.E. Musson, Y.-C. Jang, T.G. Townsend, I.-H. Chung, Characterization of lead leachability from cathode ray tubes using the toxicity characteristic leaching procedure, Environ. Sci. Technol. 34 (2000) 4376–4381. M. Danon-Schaffer, J. Grace, R. Wenning, M. Ikonomou, W. Lukemburg, PBDEs in landfill leachate and potential for transfer from electronic waste, Organohalogen Compd. 68 (2006) 1759–1762.
Contents lists available at SciVerse ScienceDirect
Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat
Metals and polybrominated diphenyl ethers leaching from electronic waste in simulated landfills Peeranart Kiddee a,b , Ravi Naidu a,b,∗ , Ming H. Wong c a b c
Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, Adelaide, 5095, Australia Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, Mawson Lakes Campus, Adelaide, 5095, Australia Croucher Institute for Environmental Sciences, and Department of Biology, Hong Kong Baptist University, Kowloon Tong, China
h i g h l i g h t s • • • •
Simulated landfill columns provided realistic results than lab based column study. Column leachates showed significant seasonal effect on toxic substances. Toxic substances in the landfill leachates pose environmental and health hazards. A better management of e-waste is urgently needed.
a r t i c l e
i n f o
Article history: Received 2 January 2013 Received in revised form 18 February 2013 Accepted 7 March 2013 Available online 15 March 2013 Keywords: E-waste Simulated landfill column Heavy metals PBDEs Leachate
a b s t r a c t Landfills established prior to the recognition of potential impacts from the leaching of heavy metals and toxic organic compounds often lack appropriate barriers and pose significant risks of contamination of groundwater. In this study, bioavailable metal(oids) and polybrominated diphenyl ethers (PBDEs) in leachates from landfill columns that contained intact or broken e-waste were studied under conditions that simulate landfills in terms of waste components and methods of disposal of e-wastes, and with realistic rainfall. Fourteen elements and PBDEs were analysed in leachates over a period of 21 months. The results demonstrate that the average concentrations of Al, Ba, Be, Cd, Co, Cr, Cu, Ni, Pb, Sb and V in leachates from the column that contained broken e-waste items were significantly higher than the column without e-waste. BDE-153 was the highest average PBDEs congener in all columns but the average of PBDEs levels in columns that contained intact e-waste were (3.7 ng/l) and were not significantly higher than that in the leachates from the control column. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Electronic waste (e-waste) is the fastest growing stream of all waste types and is complex as it consists of a great variety of materials [1]. Some of the constituents of e-waste contain toxic substances [2] that can potentially contaminate the ecosystem and threaten human health. Numerous researchers have demonstrated that toxic metals and polyhalogenated organics including polybrominated diphenyl ethers (PBDEs) can be released from ewaste, posing serious risks of harm to the environment and humans [3–5]. E-waste disposal to landfills can pose serious contamination risks if they are not suitably managed. Leachates from landfills can contain large concentrations of dissolved and suspended organic
∗ Corresponding author at: CERAR-Centre for Environmental Risk Assessment and Remediation, Building X, University of South Australia, Mawson Lakes, SA, 5095, Australia. Tel.: +61 8 8302 5041; fax: +61 8 8302 3124. E-mail addresses: [email protected], [email protected] (R. Naidu). 0304-3894/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jhazmat.2013.03.015
substances, inorganic compounds and heavy metals. However, the concentrations of toxic substances in leachates depend on the characteristics of the wastes and stages of weathering in a particular landfill [6]. E-waste provides approximately 70% of heavy metals, including 40% of the lead, to the waste stream infiltrate of landfills [7], and also contributes up to 30% of PBDEs [8]. There is potential for transport of pollutants through soils and groundwater within and around landfill sites [9]. Organic and putrescibles materials in landfills decompose and percolate through soil as landfill leachate. Disposal of ever increasing quantities of e-waste is of serious concern because e-waste contains significant amounts of toxic substances [10], and they may interact with organic compounds in leachates, and landfills were not originally designed to receive ewaste. However, there are disagreements between legislators and local councils regarding the environmental impacts of disposal of electronic wastes, particularly in landfills. Some argue that old landfills that do not have appropriate barriers to minimise leaching and more modern landfills receiving electronic wastes cause groundwater contamination. However, others claim that modern landfills
244
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
are designed to securely isolate and protect pollutants found in e-waste from reaching the environment [11]. A technique designed to assess the potential toxicity of leachates from e-waste disposal is the Toxicity Characteristic Leaching Procedure (TCLP) which simulates landfill leaching in terms of a worst case eventuality. The TCLP test determines if a solid waste has physical and chemical properties that make it likely to be a toxic hazardous waste. Electronic devices are considered to be hazardous waste under provisions of the Resource Conservation and Recovery Act (RCRA) if TCLP extracts contain specified elements at higher than regulated concentrations, which are 5 mg/l of As, 100 mg/l of Ba, 1 mg/l of Cd, 5 mg/l of Cr, 5 mg/l of Pb, 0.2 mg/l of Hg, 1 mg/l of Se and 5 mg/l of Ag [12]. There have been a number of studies used to classify the hazards of e-wastes by the TCLP test. Jang and Townsend [13] found that the concentrations of Pb in TCLP extracts ranged from 0.53 to 5.0 mg/l for printed circuit boards and from 1.7 to 6.0 mg/l for cathode ray tubes. Townsend et al. [10] found Pb concentrations in leachates above 5 mg/l from many types of electronic devices including laptops, mobile phones, mice, remote controls and smoke detectors. Li et al. [14] found that Pb is the predominant toxic heavy metal, at concentrations of 150–500 mg/l in leachate from printed wire boards of personal computers. Some studies show that the TCLP may not be an appropriate measure for the assessment of pollutant leachability from waste disposal in landfills and this further complicates the debates on the safety of the disposal of e-wastes to landfills. Numerous studies have shown that the TCLP underestimates pollutant leaching compared to actual landfills [15–17], but specific studies on e-wastes found Pb to be much more leachable in the TCLP compared to leachates from municipal solid waste (MSW) landfill [10,13,14]. Leaching in laboratory tests such as the TCLP may not accurately represent actual processes occurring in inner landfills. Leachate quality from landfills depends on several factors such as waste composition, biochemical changes, physicochemical processes and seasonal variation. This paper describes research using columns under conditions that more closely simulate actual landfills in terms of waste components and method of disposal of e-wastes, and with realistic precipitation to generate leachate. Fourteen elements and PBDEs were analysed in leachates from our column studies. The objectives of this investigation were to determine the effects of e-wastes on the concentrations of potential pollutants in leachates by comparing the concentrations of metal(oids) and PBDEs in leachates from large columns that simulate landfills that (a) contain no e-waste, (b) those that have whole e-waste items such as TV sets, computers etc. as disposed in older landfills, and (c) those that have broken e-waste items, under conditions of natural precipitation (rainfall). Much effort was directed towards ensuring that these column studies were conducted under conditions as similar as possible to actual landfills.
2. Materials and methods 2.1. Simulated landfills Three simulated landfill were built as large diameter columns in an open area at Mawson Lakes, South Australia. Each column was constructed of high density polyethylene (HDPE), 2 m high and 1.8 m in diameter (Fig. 1(a)). An outlet and tap were located close to the outside edge of each column with a maximum of 200 mm clearance under the base column. The columns were placed on a concrete base that had a slight slope and the tap was located on the lower side for leachate drainage. The tops of the three columns were open and received only rainfall. Each column had 5 holes each with 50 mm adaptor sockets on their sides, 300 mm apart, and with
Fig. 1. Column design.
removable plugs for monitoring temperature. The columns had a 100 mm layer of gravel at the bottom and geotextile fabric was laid on the surface of the gravel. A homogeneous layer of municipal solid waste (MSW) and e-waste was placed in the columns up to approximately 1.35 m in height and then covered by 50 mm of gravel (Fig. 1(b)). The gravel was used to reduce smells from the waste, minimise edge flow of the rainwater, and to allow rainwater to percolate through the waste. 2.2. Waste preparation and column loading Bulk e-waste MSW mixtures were prepared by mixing a large sample of MSW with e-waste to produce proportions of MSW components for each of the columns shown in Table 1. The MSW composition proportions were devised to correspond with those found in a detailed survey of the three main landfills in Adelaide, South Australia. The classification of the waste followed the American Society for Testing and Material (ASTM) method D5231-92 [18]. MSW components were classified into a minimum of 13 categories including: paper, glasses, plastics, metals, food wastes, wood, garden wastes, textiles, leather, tyres and rubber, e-waste, construction and demolition (C&D), and others such as medicines, cosmetics, napkins, rock, soil, and fines. The selected types of ewaste were based on criteria including consumption ratio, disposal level rating, level of recycling or reuse, toxicity, product stewardship arrangements, ease of collection/material separation and recycling and market availability in Australia [19]. Column 1 was a control that was filled with MSW only, whereas columns 2 and 3 were filled with MSW mixed with 8% (29.5 kg) e-waste. Column 2 contained intact items of e-waste that consisted of 1 CRT television (size 14 in.), 1 computer CRT monitor, 1 CPU and 3 fluorescent tubes and most of e-waste items were intact and there was no size reduction. Column 3 was filled with broken items that consisted of CRTs from televisions and computer monitors, circuit boards from CPU and fluorescent tubes. The e-waste and MSW were mixed to be as homogenous as possible. 2.3. Effect of rainfall on leachate generation The three simulated landfill columns were open at the top and in an open area. The columns received only natural precipitation to generate leachate. The data for rainfall were taken from Australian Government Bureau of Meteorology in Parafield Airport Station, some 2 km from the columns. The leachate volumes were measured and drained out until empty every month. Pearson correlation analysis was performed using the SPSS statistical package to analyse the correlation between rainfall volume and leachate production.
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
245
Table 1 The composition of MSW in simulated landfill columns. Component
Paper Glasses Plastics Metals Food Waste Wood Yard Waste Textiles Leather Tyres and Rubber C&D E-waste Others Total
Column 1
Column 2
Column 3
No e-waste
e-waste (Whole items)
e-waste (Broken items)
Percent
Weight (kg)
Percent
Weight (kg)
Percent
Weight (kg)
27.3 5.1 24.4 9.6 8.7 6.9 5.7 5.1 0.8 2.9 0.9 0.0 2.6 100
100.7 19.0 90.1 35.4 32.0 25.4 21.0 18.7 2.9 10.7 3.4 0.0 9.7 368.7
25.1 4.7 22.5 8.8 8.0 6.3 5.2 4.7 0.7 2.7 0.8 8.0 2.4 100
92.6 17.4 82.9 32.6 29.4 23.3 19.3 17.2 2.7 9.8 3.1 29.5 8.9 368.7
25.1 4.7 22.5 8.8 8.0 6.3 5.2 4.7 0.7 2.7 0.8 8.0 2.4 100
92.6 17.4 82.9 32.6 29.4 23.3 19.3 17.2 2.7 9.8 3.1 29.5 8.9 368.7
2.4. Analysis of leachate Leachate samples were collected monthly for the analyses of pH, oxidation-reduction potential (ORP), electrical conductivity (EC), total dissolved solid (TDS), total organic carbon (TOC), aluminium (Al), arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), antimony (Sb), vanadium (V) zinc (Zn), and polybrominated diphenyl ethers (PBDEs) from each of the three columns over a 21-month period. After collection of the samples, the leachate was drained from the columns until empty every month. The statistical analysis of one-way ANOVA at 95% confidence limits was used to compare the data of control columns with the others. 2.4.1. General analysis An AquareadTM multi-parameter water quality metre was used to measure pH, ORP, EC and TDS of fresh leachate samples drained the columns in the field. The metre was calibrated in the laboratory before use in the field. Additional filtered samples were analysed for TOC with a total organic carbon analyser (TOC-5000A, Shimadzu Corp., Japan). Quality assurance of the TOC analyses was assessed using duplicates and a standard reference solution. 2.4.2. Metal(oids) The concentrations of Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Ni, Pb, Sb, V and Zn were determined in leachate samples by inductively coupled plasma mass spectroscopy (ICP-MS, Agilent 7500, USA). Prior to analysis the leachate samples were centrifuged at 10,000 revolutions per minute (RPM) with a SORVALL SA-60 rotor for half an hour and filtered through 0.45 m filters. Quality assurance and control of metal(oids) analyses were ensured by analysis of sample duplicates and standard reference solutions at regular intervals. 2.4.3. PBDEs 2.4.3.1. Chemicals and reagents. Standard solutions of PBDE (mixed standard of 27 congeners) and individual surrogate BDE-139 for sample spiking were obtained from Wellington Laboratories, Ontario, Canada. Dichloromethane (DCM), hexane, acetone, anhydrous sodium sulphate and florisil were obtained from Thermo Fisher Scientific Australia. Glassware used for analysis was washed with detergent and warm tap water and rinsed with acetone and DCM. 2.4.3.2. Extraction and cleanup. In preparation for PBDEs analysis, 400 ml leachate samples or 100 ml (in cases when the leachate samples collected were less than 400 ml) were spiked with 200 g/l
surrogate standard of BDE-139 and extracted 3 times with 40 ml of DCM. The extracts were concentrated and reduced in volume to approximately 1 ml. The extracts were purified by passing them at a rate of 1–2 ml per min through solid phase extraction (SPE) cartridges conditioned with 2 g of florisil and 5 ml of DCM, and eluted with 10 ml of hexane: dichloromethane (1:1, v/v), followed by 10 ml of DCM, and finally collected in 40 ml amber vials. The samples were concentrated to near dryness under a gentle stream of nitrogen and taken up into 200 l of hexane. Lastly, the samples were transferred into 2 ml GC vials with 200 l inserts for analysis. 2.4.3.3. Gas chromatographic analysis. PBDEs were determined using a GC-ECD Agilent 6890 N gas chromatograph with auto sampler 7683B (Agilent Technologies). A DB-5HT column (0.25 mm id, 0.1 m film thickness) was used for separation. The GC oven temperature programme was: initial temperature 110 ◦ C for 3 min followed by a programme to 200 ◦ C at 15 ◦ C/min and ramped to 220 ◦ C at 2 ◦ C/min, and finally increased to 350 ◦ C at 3 ◦ C/min, then held for 4 min. Nitrogen was used as the carrier gas. Splitless injection was used and the injected volume was 1 l. 2.4.3.4. Quality assurance/quality control. The quality of analytical processes was confirmed by checking the reproducibility of calibration, blanks, sample duplicates and recovery processes. For each batch of 10 samples a solvent blank and a procedural blank were processed to check for contamination. The recovery process was tested by spiking and ranged between 60% and 70%. Interference in solvents, blanks and extraction equipment were avoided by preventing contamination. 3. Results and discussion 3.1. Relationship between rainfall, leachate volume and analyses studied Leachates were generated by rainwater percolating through the waste in the columns and the volumes of leachates from each of the three columns each month were similar. During the operational period the leachate volumes produced were on average 26% of the rainfall entering the columns. The volume of leachate produced is compared with the rainfall in Fig. 2. Linear regression analysis showed a strongly positive correlation between monthly rainfall and leachate volumes (p < 0.01, r2 = 0.98, n = 21) with the rainfall accounting for 98% of variance in the volume of leachate generated. Simple linear correlation analyses between rainfall and metal(loids) analyses of the leachates showed that, with the
246
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
300 250 200 150 100 50
Jul-12
Jun-12
Apr-12
May-12
Mar-12
Jan-12
Feb-12
Dec-11
Oct-11
Nov-11
Sep-11
Jul-11
Rainfall (l)
Aug-11
Jun-11
Apr-11
May-11
Mar-11
Jan-11
Feb-11
Dec-10
Nov-10
0
Leachate generation (l)
Fig. 2. Comparison between rainfall and leachate generation during operation period.
Fig. 3. Comparisons between rainfall and the concentrations of Sb in three columns over 21 months.
Column 1 pH
Jul-12
Jun-12
Apr-12
May-12
Mar-12
Jan-12
Feb-12
Dec-11
Oct-11
Column 2 pH
Nov-11
Sep-11
Jul-11
Aug-11
Jun-11
Apr-11
May-11
Mar-11
Jan-11
Feb-11
Dec-10
9 8 7 6 5 4 3 2 1 0 Nov-10
exception of Sb, none of the analyses showed any significant relationship with rainfall. The concentration of Sb in all columns was negatively correlated with rainfall (p < 0.01, r2 = −0.30 in column 1, r2 = −0.42 in column 2 and r2 = −0.32 in column 3). Thus, the concentrations of Sb decreased with time and with an increase in rainfall (Fig. 3) and leachate volume. This suggests depletion of Sb in leachates with increasing rainfall and points to a fixed amount of mobile Sb in the wastes and limited replenishment of this fraction compared to other analysts. The temperatures of waste inside each of the three columns were nearly at ambient temperature, which varied with seasonal fluctuations from 16 to 32 ◦ C in summer months to lows of 9–20 ◦ C in winter months. This observation is consistent with those of Li et al. [20], and supported by Yesiller and Handson [21], that the temperatures of wastes at shallow depths are affected by seasonal variations.
Column 3 pH
Fig. 4. pH values in three columns over study period.
3.2. General analytical results The results for leachates from each of the three columns are shown in Table 2. The pH values ranged from 6.1 to 8.0 (Fig. 4). In the first month of leachate sample collection the pH values of all three column leachates were lower than the next batches of leachate samples, which had pH values of 6.2, 6.2 and 6.1 in columns 1, 2 and 3, respectively. After the second month until the end of the
study period, pH values of the leachates fluctuated between 6.7 and 8.0. These results contrast with those reported by Spalvins et al. [22] who found that leachate pH in simulated columns containing MSW remained in the acidic range for their entire study period of 400 days and stabilised at a pH of approximately 5. However,
Table 2 Average and range of analyses from three simulated landfill columns over 21 months. Parameters
pH ORP (mV) EC (mS) TDS (mg/l) TOC (mg/l) Al (g/l) As (g/l) Ba (g/l) Be (g/l) Cd (g/l) Co (g/l) Cr (g/l) Cu (g/l) Fe (g/l) Ni (g/l) Pb (g/l) Sb (g/l) V (g/l) Zn (g/l) PBDEs (ng/l)
Average
Range
Column 1
Column 2
Column 3
Column 1
Column 2
Column 3
7.3 −5.1 1285 1150 141 80.1 18.4 72.7 0.07 0.24 6.5 5.0 25.1 514 14.3 6.7 4.4 12.5 12.4 3.2
7.4 −8.2 1182 962 126 55.7 24.7 64.8 0.04 0.17 6.5 2.5 18.8 407 11.6 5.5 4.4 14.5 9.7 3.7
7.4 −25.5 1406 1167 160 91.0 24.4 88.3 0.07 0.26 9.7 5.3 25.6 400 21.6 9.3 5.0 17.9 11.6 3.3
6.2–8.0 (−)154.5–134.5 609–3292 340–3139 13.7–1765 8.6–826.0 5.4–70.7 12.4–437.0 0.007–0.7 0.004–1.0 0.9–64.1 1.2–11.6 0.8–53.6 27.4–3260 4.9–46.9 0.4–38.0 0.8–8.0 1.6–53.3 0.7–128.7 0.3–8.9
6.2–8.0 (−)173.5–115.4 464–3273 301–3093 10.6–1532 4.4–479.4 7.2–71.2 11.9–261.3 0.003–0.3 0.003–0.7 0.8–53.0 0.9–7.8 1.0–36.1 13.6–2927 3.7–35.3 0.2–33.6 0.9–8.5 2.5–53.8 0.784.4 0.3–8.0
6.1–8.0 (−)183.0–85.6 723–3448 469–3230 15.8–1930 2.1–943.7 4.9–73.0 22.8–510.4 0.008–0.8 0.008–1.4 1.6–73.3 1.8–11.8 1.0–56.9 22.2–2061 7.0–63.3 0.8–47.2 1.4–10.7 2.8–75.2 0.5–83.5 0.2–8.4
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
leachate pH from simulated columns containing excavated landfill wastes ranged from 7.2 to 8.1. They attributed these pH changes to the two primary phases of waste decomposition in a MSW landfill: an acidic phase and a methanogenesis phase. The pH and organic carbon content are the parameters normally used to characterise which phase the leachate represents. The pH values recorded in our study may be attributed to the differences in the design of the simulation columns from that of Spalvins et al. [22] that allowed the development of highly reducing conditions, whilst the rate of leachate flow through the column in the current study may have prevented methanogenesis because of the absence of food wastes and cardboard. Oxidation-reduction potential (ORP) values of the leachates were more negative in the first five months of sampling in all three columns and tended to increase to slightly less negative and to positive values in the sixth month (detailed results not shown). After that ORP fluctuated between (−) 116 and 134 mV in all columns. Oxidation-reduction potential (ORP) values in the control column were higher than those of columns 2 and 3 (Table 2). Column 3, with broken e-waste, had lower average ORP values than column 2 that had whole e-waste items. EC, TDS and TOC indicated downward trends with time. EC and TDS decreased moderately with small fluctuations. TOC had the highest level in the first month, at over 1500 mg/l, and sharply dropped to around 100 mg/l in the third month with a slightly decreasing trend with a small fluctuation (detailed results over time not shown). TOC reflects the presence of dissolved organic matter in leachates [23,24]. During the first month the leachates enriched in dissolved organic matter with the soluble fraction decreasing with time. Most of EC, TDS and TOC values in column 3 (broken e-waste components) were higher than columns 1 and 2 (Table 2). These results are not surprising given the higher surface area of the broken e-waste components compared to whole items. The statistical analysis showed that pH, TDS and TOC in control (column 1) were statistically different (p < 0.05) to the columns that contained e-waste but EC and ORP in the control were statistically similar (p < 0.05) to the others.
247
3.3. Metal(oids) A summary of the data for the metal(oids) in the simulated landfill column leachates is shown in Table 2. Fourteen elements were analysed from November 2010 to June 2012. Iron was detected at the highest concentrations in all leachates. In general, the concentrations of metal(oids) in leachates that contained e-wastes were significantly higher than the control column containing MSW only. The average concentrations of Al, Ba, Be, Cd, Co, Cr, Cu, Ni, Pb, Sb and V in leachates from column 3 that contained broken items of e-waste were significantly (p < 0.05) higher than that in leachates from other columns. Concentrations of As, Cd, Sb and V detected in leachates from columns 2 and 3 that included e-waste items were higher than the control column. The average concentrations of Al, Ba, Be, Co, Cr, Cu, Ni and Pb found in the control column were less than in column 3 that contained broken items of e-waste higher, but higher than column 2 that had whole e-waste items. It is difficult to explain why slightly elevated concentrations of metal(oids) were recorded in the leachates from control column (column 1) compared to column 2 which contained unbroken components of e-wastes. One reason perhaps may be the presence of slightly more metal and yard wastes in the control column compared to columns 2 and 3. The statistical analysis showed that concentrations of Ba, Co, Pb and Sb in control (column 1) were significantly different (p < 0.05) to the columns that contained e-waste (see Fig. 5(a–d)) and there was no significant differences in Al, As, Be, Cd, Cu, Fe Ni and V in control relative to the other columns. The main heavy metal of concern in e-waste, and the most problematic from a monitoring perspective, is Pb [13,22,25]. The values of Pb ranged between 0.4–38.0, 0.2–33.6 and 0.8–47.3 g/l in columns 1, 2 and 3, respectively, demonstrating that the concentrations of Pb in the column filled with broken e-waste items exceeded that in leachates from the control column, confirming Spalvins et al. [22] results. Spalvins et al. [22] reported that the concentrations of Pb were 7–66 g/l in columns containing e-waste and <2–54 g/l in a control column, so their Pb concentrations were greater than in the present study.
80
600 500 400 300 200 100 0
60 40 20 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12 Jun-12 Jul-12
0
Ba (µg/l) Column1
Ba (µg/l) Column2
Co (µg/l) Column1
Ba (µg/l) Column3
a: The concentration of Ba
Co (µg/l) Column2
Co (µg/l) Column3
b: The concentration of Co 12 10 8 6 4 2 0
50 40 30 20 10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12 Jun-12 Jul-12
0
Pb (µg/l) Column1
Pb (µg/l) Column2
c: The concentration of Pb
Pb (µg/l) Column3
Sb (µg/l) Column1
Sb (µg/l) Column2
d: The concentration of Sb
Fig. 5. The concentration of Ba, Co, Pb and Sb in three columns during the study period.
Sb (µg/l) Column3
248
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249
4 DecaBDE
3.5
NonaBDE
3
OctaBDE 2.5
HeptaBDE
2
HexaBDE
1.5
PentaBDE TetraBDE
1
TriBDE 0.5
DiBDE
0
MonoBDE column 1
column 2
column 3
Fig. 6. The level of average PBDEs congeners in each landfill columns (ng/l).
This difference in the concentration of Pb may be attributed to the nature of e-wastes used by Spalvin et al. [22] in their study which could have been different from that used in the present study.
TCLP leachates from e-wastes have the potential to release high concentrations of toxic chemicals (such as Pb), but simulated column studies as in the present study show significantly lower concentrations than would be expected from TCLP extractions. However, considerable caution must be exercised when dealing with long-term landfills given the potential for extensive weathering of e-wastes potentially leading to greater concentrations of toxic substances that observed in our 21-month column study. In contrast to columns, extensive weathering of e-wastes is likely to occur in landfills due to the presence of moisture as it percolates slowly through the wastes- with the residence contact time between the moisture and wastes being significantly longer than that recorded in columns. Slow leaching allows enough contact time for contaminant solubilisation while quick flushing after a dry period is less likely to transport chemicals out of the landfill. Needless to say the procedure established in the present study can be used to further manipulate contact time between moisture and wastes thus enhancing landfill conditions. Management of leachates percolating through the column together with longer term considerations allowing further weathering of e-wastes may generate results similar to that found in landfills.
3.4. PBDEs Acknowledgements Only limited information is available in the literature on PBDEs in simulated landfill columns. The average and range of the sums of the PBDEs ( PBDEs) in leachates from simulated landfill columns are shown in Table 2, and there was no effect of e-waste on PBDEs. PBDEs were detected from MonoBDEs to DecaBDEs in all PBDEs levels in the simulated landsimulated landfill columns. fill columns fluctuated between 0.3–8.9, 0.3–8.0 and 0.2–8.4 ng/l, respectively and PBDEs average value were 3.2, 3.7 and 3.3 ng/l, respectively. HexaBDEs, especially: BDE-153 had the highest average PBDEs congener in the three columns (Fig. 6). However, these results vary from the recently published studies on PBDEs in landfill leachates in which e-waste was reported to contribute approximately 30% of PBDEs [26] in the leachates. These differences may be attributed to either the release of PBDE’s from material other than e-wastes in landfill leachates or the short duration of the current study and as a consequence limited weathering of e-wastes. PBDE’s detected in the leachates are nevertheless of much concern given the increasing regulatory pressure to control persistent and bioaccumulative chemicals more effectively following 2001 Stockholm convention. Indeed, many of the old landfills in South Australia are not adequately lined and, there is potential for these leachates to migrate into the subsurface soil and ground water over a period of time- this would be considered the primary environmental concern. 4. Conclusions It is apparent that e-waste disposal at the rate tested here in simulated modern sanitary MSW landfills is not likely to result in Pb leachate concentrations reaching levels of regulatory concern, although it cannot be said that higher volumes of e-wastes would still yield the same result. However, the results from this study demonstrate that the average concentrations of Al, Ba, Be, Cd, Co, Cr, Cu, Ni, Pb, Sb and V detected in column which contained broken e-waste items were higher than the column without e-waste. The average of PBDEs levels in columns that contained e-waste had similar concentrations as the control column. Of much concern is the fact that these toxic substances leached throughout the 21-month study period indicating slow and continuous loading of groundwater even though concentrations of the analysts studied were low. Old landfills may still need to be remediated to prevent potential contamination of groundwater.
The authors acknowledge financial support from CRC CARE, the Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia and Thai Government fellowship for this study. We thank CERAR’s friends and UniSA’s staff for their assistant to set landfill simulation columns. References [1] S. Zhang, E. Forssberg, Mechanical separation-oriented characterization of electronic scrap, Resour. Conserv. Recycl. 21 (1997) 247–269. [2] D. Pant, D. Joshi, M.K. Upreti, R.K. Kotnala, Chemical and biological extraction of metals present in E waste: a hybrid technology, Waste Manage. 32 (2012) 979–990. [3] E. Williams, R. Kahhat, B. Allenby, E. Kavazajian, J. Kim, M. Xu, Environmental, social and economic implications of global reuse and recycling of personal computers, Environ. Sci. Technol. 42 (2008) 6446–6454. [4] J.M. Czuczwa, R.A. Hites, Environmental fate of combustion-generated polychlorinated dioxins and furans, Environ. Sci. Technol. 18 (1984) 444–450. [5] B.H. Robinson, E-waste. An assessment of global production and environmental impacts, Sci. Total Environ. 408 (2009) 183–191. [6] S.R. Qasim, W. Chiang, Sanitary Landfill Leachate: Generation, Control and Treatment, CRC Press, United States of America, 1994. [7] E. Grossman, High Tech Trash: Digitatl Devices, Hidden Toxics, and Human Health, ISland Press, Washington, DC, 2006. [8] M. Danon-Schaffer, J. Grace, R. Wenning, M. Ikonomou, W. Lukemburg, PBDEs in landfill leachate and potential for transfer from electronic waste, OHCs 68 (2006) 1759–1762. [9] A. Kasassi, P. Rakimbei, A. Karagiannidis, A. Zabaniotou, K. Tsiouvaras, A. Nastis, K. Tzafeiropoulou, Soil contamination by heavy metals: measurements from a closed unlined landfill, Bioresour. Technol. 99 (2008) 8578–8584. [10] T.G. Townsend, K. Vann, S. Mutha, B. Pearson, Y.-C. Jang, S. Musson, A. Jordan, RCRA Toxicity characterization of computer CPUs and other discarded electronic devices, Department of Environmental Engineering Sciences, University of Florida, Florida, 2004, p. 79. [11] SWANA, The Environmental Consequence of Disposing of Products Containing Heavy Metals in Municipal Solid Waste Landfills, Solid Waste Association of North America, Silver Spring, MD, 2004. [12] T.G. Townsend, K. Vann, S. Mutha, B. Pearson, Y.-C. Jang, S. Musson, A. Jordan, RCRA Toxicity characterization of electronic wastes, Hazard. Waste Consultant 23 (2005) 16–18. [13] Y.-C. Jang, T.G. Townsend, Leaching of lead from computer printed wire boards and cathode ray tubes by municipal solid waste landfill leachates, Environ. Sci. Technol. 37 (2003) 4778–4784. [14] Y. Li, J.B. Richardson, A.K. Walker, P.-C. Yuan, TCLP Heavy metal leaching of personal computer components, J. Environ. Eng. 132 (2006) 497–504. [15] K. Hooper, M. Iskander, G. Sivia, F. Hussein, J. Hsu, M. Deguzman, Z. Odion, Z. Llejay, F. Sy, M. Petreas, B. Simmons, Toxicity characteristic leaching procedure fails to extract oxoanion-forming elements that are extracted by municipal solid waste leachates, Environ. Sci. Technol. 32 (1998) 3825–3830. [16] A. Ghosh, M. Mukiibi, W. Ela, TCLP underestimates leaching of arsenic from solid residuals under landfill conditions, Environ. Sci. Technol. 38 (2004) 4677–4682.
P. Kiddee et al. / Journal of Hazardous Materials 252–253 (2013) 243–249 [17] C.E. Halim, J.A. Scott, H. Natawardaya, R. Amal, D. Beydoun, G. Low, Comparison between acetic acid and landfill leachates for the leaching of Pb(II), Cd(II), As(V), and Cr(VI) from cementitious wastes, Environ. Sci. Technol. 38 (2004) 3977–3983. [18] ASTM International, Standard test method for determination of the composition of unprocessed municipal solid waste, D5231-92 (2008), American Society for Testing and Materials, US, 2008. [19] Hyder Counsulting, Waste Recycling in Australia Final Report, Prepared for the Department of Environment, Water, Heritage and the Arts, 2008, p. 137. [20] Y. Li, J.B. Richardson, R. Mark Bricka, X. Niu, H. Yang, L. Li, A. Jimenez, Leaching of heavy metals from e-waste in simulated landfill columns, Waste Manage. 29 (2009) 2147–2150. [21] N. Yesiller, J.L. Handson, Analysis of temperatures at a municipal solid waste landfill, in: Christensen et al. (Ed.) Sardinia 2003, Ninth International Waste
[22] [23] [24] [25]
[26]
249
Management and landfill Symposium, CISA, Environmental Sanitary Engineering Centre, Italy, 2003, pp. 1–10. E. Spalvins, B. Dubey, T. Townsend, Impact of electronic waste disposal on lead concentrations in landfill leachate, Environ. Sci. Technol. 42 (2008) 7452–7458. I.M.-C. Lo, Characteristics and treatment of leachates from domestic landfills, Environ. Int. 22 (1996) 433–442. M. Osako, Y.-J. Kim, S.-i. Sakai, Leaching of brominated flame retardants in leachate from landfills in Japan, Chemosphere 57 (2004) 1571–1579. S.E. Musson, Y.-C. Jang, T.G. Townsend, I.-H. Chung, Characterization of lead leachability from cathode ray tubes using the toxicity characteristic leaching procedure, Environ. Sci. Technol. 34 (2000) 4376–4381. M. Danon-Schaffer, J. Grace, R. Wenning, M. Ikonomou, W. Lukemburg, PBDEs in landfill leachate and potential for transfer from electronic waste, Organohalogen Compd. 68 (2006) 1759–1762.