ORGANIC COMPOUNDS IN MUNICIPAL LANDFILL

ORGANIC COMPOUNDS IN MUNICIPAL LANDFILL LEACHATES.

Nicklas Paxéus GRYAAB- Göteborg Regional Sewage Works, Karl IX:s väg S-418 34 Göteborg, Sweden.

ABSTRACT Leachates from three municipal landfills in the Göteborg area of western Sweden were characterised in terms of their content of individual organic compounds. Two of the investigated landfills were still in use during the time of this study. The third landfill was closed down in the mid-seventies. More than 200 individual organic compounds and classes of compounds were identified in the leachates with concentrations ranging from less than one up to several hundred µg/L. Among the compounds common to all three landfills were plasticizers (phthalates, benzenesulfonamides), phosphate esters, substituted phenols, chlorinated phenols, phenolic antioxidants and siloxanes as well as the compounds formed during the degradation of organic wastes (dihydro-dioxin, pyrazines and several sulphur-containing odorous volatiles). Dioxanes and dioxolans found in the leachates have not been previously reported. Compounds originated from previously disposed oil contaminated wastes dominate the leachate from an old closed landfill. Its replacement, a new regional landfill has a leachate dominated by alcohols and ethers. This difference is attributed to regional measures in waste management.

KEYWORDS Analysis; gas chromatography; landfill; leachate; mass spectrometry; organic compounds; pollutants. INTRODUCTION A major part of organic matter in leachates is composed of high-molecular weight humic-like material predominantly associated with colloids (Welander and Henrysson, 1998; Bae et. al., 1999; Jensen and Christensen, 1999). Rather few studies deal with individual organic compounds and there are differences in the reported compounds (Harmsen, 1983; Schultz and Kjeldsen, 1986; Först et al., 1989; Murray and Back, 1990; Öman and Hynning, 1993; Bauer et al., 1998; Welander and Henrysson, 1998; Benfenati et al., 1999; Rügge et al., 1999). The discrepancy might be attributed to the previous history of the landfill, heterogeneity of leachates, different sampling procedures and analytical techniques applied for screening. The aims of the present work were: (1) to identify and quantify individual organic compounds in leachates from three municipal landfills in Göteborg region and (2) to compare landfill leachates in terms of their content of organic compounds (common compounds and landfill specific compounds). A possible origin of the compounds found in the leachates is discussed. METHODOLOGY Landfills cites and sampling. Landfill A, active since the mid-seventies, has an area of 8 ha. The annually received waste (in tons) consisted roughly of wet fly ash (14,000) and wet bottom ash/slag (77,000) from incineration, wet screenings from a WWTP (2,700) and industrial wastes (10,000). Leachate water flow is about 180,000 m3/y. Typi-

cal values for the leachate are COD 130 mg O2/L, TOC 50 mg C/L, PCB less than 0.1 µg/L, AOX ca 0.4 mg/L. Landfill B, active since 1964, has an area of 8 ha. The annually received waste (in tons) consisted roughly of sewage sludge (900), industrial waste (5,000), construction waste (1,500), household and garden waste (1,000). Leachate water flow is about 67,000 m3/y. Typical values for the leachate are COD 240 mg O2/L, PCB less than 0.1 µg/L, AOX ca 0.2 mg/L. Landfill C, has been active in 1938-1978, receiving all kind of wastes like household, construction, industrial, chemical, sludges, cadaver etc., has an area of 25 ha. Leachate water flow is about 115,000 m3/y. Typical values for the leachate are COD 230 mg O2/L, TOC 77 mg C/L, PCB 0.44 µg/L, AOX 0.1 mg/L. Apparatus and materials. Multi-bed adsorbent Carbotrap tubes from Supelco Inc. and non-end-capped C18 SPE columns from International Sorbent Technology, Inc. were used. The solvents used were of analytical grade or better. The Dynamic Thermal stripper (DTS) and Thermal Desorption Unit (TDU) from Dynatherm Analytical Instruments, Inc. used are described in detail by Hazard et al. (1991). The TDU was used both to refocus organic compounds to the narrow-bore tube (Carbotrap 301) and as an injector port of the GC (Hewlett Packard 5890). A 60m x 0.25mm ID column coated with 0.25µm chemically bonded phase DB-5 (J&W Scientific, Ca.) was used. The GC temperature program: 5°C held in 3 minutes, then to 35° C at 4° C/min, then to 300°C at 3°C/min and held at 300°C for 15 min. The mass-spectrometer (INCOS 50, Finnigan MAT) was operated in EI mode, scanning from 33 to 450 u in 1 sec. Identification was performed by searching in the NIST and Wiley libraries. Estimates for the concentrations of compounds not available as standards were performed (1) assuming the same response factor as standards with related structure or (2) by calculating the total area of the compound in question and comparing it with the area of d8-naphthalene, added to eluates prior to injection. Sample preparation procedure. Samples of leachates were collected in March 1996 at three different occasions. The samples were transported to the laboratory in closed glass bottles for immediate treatment and analysis.Volatiles were concentrated from 20 mL using DTS. Less volatile compounds were concentrated from 1L leachate using SPE. The elution procedure was previously reported by Schröder (1993). RESULTS AND DISCUSSION Organic compounds identified in the leachates are shown in Table 1. From 209 identified compounds 35 are classified as Priority Pollutants. Apart from the compounds given in the table about 20 substances present in leachates could not be positively identified due to a lack of their reference spectra. Individual organic compounds. Hydrocarbons and their metabolites. The hydrocarbons found in all of the leachates were predominantly cyclic structures with only a few alcanes and alkenes present in trace concentrations. The hydrocarbons given in the table represent three main groups: (1) monocyclic non-aromatic (cyclo-hexanes/–hexenes) and aromatic (benzene, substituted benzenes) six-ring hydrocarbons, (2) bicyclic non-aromatic (decalins, terpenes) and aromatic (tetralins, naphthalenes, indenes, biphenyls) compounds and (3) polyaromatic hydrocarbons (PAH). Terpenes (nos. 15, 16, 17, 20) and related compounds (nos.18, 19, 21, 101, 102) may principally be biosynthesised on site during degradation of organic matter. However, several of these compounds are also widely used and are persistent to biotransformations under the methanogenic conditions found in the landfills. One of these is pinene, which is a widely used odorant and is a consistuent of turpentine. The other is camphor, which is used in laquers and varnishes, in the manufacture of plastics (celluloid) and as a plasticizer for cellulose esters and ethers. A large group of compounds found in leachates originates from disposed wastes containing petroleum-based solvents and/or rude naphthenic oils. Thus, benzene (C6) and short-chain alkyl benzenes (C7-C8, e.g. toluene, ethylbenzene and xylenes) have previously been widely used as components in laquers, varnishes and other commercial products. Deposition of wastes containing degreasing agents (white spirits) may explain the presence of C9-C11 benzenes in the leachates. Pure deca- and tetralin are often used instead of turpentine in laquers, floor waxes etc. and as degreasing agents. Since a formation of naphthenes, decalins and tetralins under the conditions of landfills is not likely, the presence of these compounds in the leachates suggests a previous disposal of wastes containing low aromatic solvents (or wastes contaminated with rude naphthenic oils). Other constituents normally present as impurities

Table 1.Organic compounds found in municipal landfill leachates and their estimated concentrations (µg/L). (★ - Priority Pollutants ”- ” - not fond). No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

COMPOUNDS

Cyclic hydrocarbons Cyclohexanes, methylCyclohexanes, C2 (ethyl-/dimethyl-) Cyclohexanes, C3 (trimethyl- /ethylmethyl- ) Cyclohexanes, C4 Cyclohexanes, methyl-, methylethylideneCyclohexenes, methylCyclohexenes, dimethylCyclohexenes, methyl-, methylethylBicyclic compounds Tetralin Methyl-tetralins Di-methyl-tetralins Tri-methyl-tetralins Tetra-methyl-tetralins Tetra-methyl-di-ethyl-tetralins Bicyclo[2.2.1]hept-ene-2,3-dimethylFenchene Camphene Camphene hydrate Camphor Pinene Isocineole Aromatic hydrocarbons Benzene ★ Benzene, chloro- ★ Benzene, dichloro- ★ Toluene ★ Ethylbenzene ★ Xylenes ★ Substituted benzenes C9 C10 C11 C12 Styrene ★ Styrenes, methylStyrenes, dimethylStyrenes, trimethylToluenes, allyl1H-Indene 1H-Indenes, 2,3-dihydro-, methyl1H-Indenes, 2,3-dihydro-, dimethylNaphthalene ★ Naphthalenes, methyl ★ Naphthalenes, di-methyl- ★ Naphthalenes, tri-methyl- ★ Naphthalenes, tetra-methylNaphthalene, 1,4-dihydro-, trimethyl1,1'-Biphenyl ★ 1,1'-Biphenyls, methyl-

A

B

C No.

-

-

2 4

-

-

10 4

-

-

198 0.3 2 68

0.1 0.4 1.3 0.2 -

0.4 4.0 37 12 0.1 0.2 1.5 1.0 0.2 0.1 -

34 8 3 2 1 10 3 28 29 134 4 98

4 0.1 0.1 1.0 0.2 0.3

3 1 8 1 2 2

110 62 57 17 179 310

0.1 0.1 0.1 0.2 0.4 0.1 0.4 0.1 -

0.5 0.4 0.5 1 0.4 5 0.3 0.2 0.5 8 0.1 -

623 309 169 55 11 135 17 1 0.2 3 22 46 400 200 176 48 4 22 11

48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97

COMPOUNDS

1,1'-Biphenyls, dimethylPhenanthrene ★ Phenanthrene, tetra-methylAnthracene Anthracenes, methylAcenaphthene Acenaphthylene 9H-Fluorene ★ 9H-Fluorenes, methylFluoranthene ★ 10,11-Dihydrobenzo[k]fluoranthene Pyrene ★ Phenazine/1,10-Phenanthroline Alcohols and ethers 2-Butanol, 2-methylEthane, 1,2-dimethoxy2-Butanol, 2,3-dimethyl Methanol, dibutoxyEthanol, 2-(2-butoxyethoxy)2-Propanol, 1-(2-ethoxypropoxy)3-Hexanol, 3,5-dimethyl2,4,7,9-Tetramethyl-5-dicyne-4,7-diol t-Butyl-phenylcarbinol 1,3-bis(2-propanol)benzene 4,4'-Dimethoxystilbene Cyclic ethers 1,4-Dioxin,2,3-dihydro1,3-Dioxolanes, methyl1,3-Dioxolanes, dimethyl1,3-Dioxolanes, ethylmethyl1,4-Dioxane ★ 1,4(1,3)-Dioxanes, methyl1,4(1,3)-Dioxanes, dimethyl1,3-Dioxanes, trimethyl1,3-Dioxanes, tetramethylKetones and ene-ones 3-Buten-2-one 2-Butanone (MEK) 2-Butanone, 3-methyl3-Buten-2-one, 3-methyl3-Pentanone (DEK) 2-Pentanone 2-Pentanone, 4-methyl- (MIBK) 2-Pentanone, 3-methyl2-Pentanones, dimethyl3-Pentanones, dimethylHexanones Methylcyclohexanones Cyclohexanones, dimethylCyclohexanones, trimethyl2-Allyl-2-methylcyclohexanone Acetophenone Acetophenone, dimethyl-

A

B

C

128 27 27 2 5 2 9 1 114 2 2 1 48 3 1 46 10 - 13

4 3 54 95 7 1 5 1 -

0.6 1 0.1 1 1 2 3 34 11 8 3 2 16 92 3 1 4 1

2 3 1 3 36 3 37 7 7

8 10 46 18 7 1 5 3 4 6 5

5 3 2 5 4 1 5 42 56 22 44 3 17 1 1 7

8 0.6 0.6 52 - 18 0.8 1.4 7 - 10 - 48 9 - 45 9 1 6 3 2 4 3 3 10 -