Linear alkylbenzenes in sewage sludges and sludge amended soils

l&'at. Res. Vol. 26. No. 5, pp. 613-624. 1992 printed in Great Britain. All rights rescued

0043-1354/92 $5.00 +0.00 Copyright C 1992 i~rgamon Press pie

LINEAR ALKYLBENZENES IN SEWAGE SLUDGES AND SLUDGE AMENDED SOILS M. S. HOLT* and S. L. BERNSTEINt Shell Research Ltd, Sittingbourne Research Centre, Sittingbourne, Kent, England (First receit'ed April 1991; accepted in ret'ised form October 1991)

Abstract--Linear alkylbenzene sulphonates (LAS), manufactured by the sulphonation of linear alkylbenzenes (LAB), became the major anionic surfactant material used in detergent formulations in the 1960s and they have maintained that status to the present day. Commercially produced LAS may contain !-3% unreacted LAB which are only biodegraded under aerobic conditions. As a result any LAB removed by adsorption onto sewage solids during primary treatment, and which is subjected to anaerobic digestion, will be present on the sludge at the end of the treatment process. Some of the sewage sludge generated is disposed of to agricultural land. A monitoring exercise to determine the concentration and isomer distribution of linear alkylbenzenes in sewage sludges and sludge amended soils is described. Concentrations of LAB in various sludges ranged from 116 to 388/~g g-t (dry wt). In fields spread with sludge prior to 1989 the concentration of LAB was generally < 5 ng g- t soil (dry wt). Comparison of these data with the estimated total cumulative load based on known sludge application history indicates losses of > 99% for the majority of sites. Time course experiments indicate rapid removal of LAB from sludge amended soils. Calculated half lives for the various alkyl homologues are similar (12-15 days). Phenyl isomer distribution in soils suggests, however, preferential biodegradation of the external isomers. This is confirmed in time course samples which show half lives of 4.5 days for the 2-phenyl isomers and 20 days for the 6/7-phenyl isomers. Key words--linear alkylbenzene, linear alkylbenzene sulphonate, sewage sludge, biodcgradation, half lives

INTRODUCTION

Linear alkylbenzene sulphonates (LAS) are the most widely used anionic surfactants. They are manufactured by reacting alkylbenzene with sulphuric acid or sulphur trioxide to give the sulphonic acid, which is then neutralised to give the desired salt, often the sodium salt. The precursor for LAS is linear alkylbenzene (LAB). The commercial production of LAB results in a mixture of homologues with various alkyl chain lengths depending on the nature of the feedstock. Furthermore, as a result of the alkylation process, each of the alkyl homologues consist of a mixture of isomers in which the phenyl group can be attached to any of the C atoms except the terminal carbon. Those having the phenyi attachment near the end of the alkyl chain (e.g. 2-, 3-, and 4-C~,) are referred to as external isomers and those having the phenyl attachment toward the middle of the alkyl chain (e.g. 5-, 6- and 7-Ctz) are referred to as internal isomers. The absence of I-phenylalkanes is attributed to the instability of the primary carbonium ion intermediate (Swischer et al., 1961). Consumption of LAB in Western Europe is approx. 420,000t/yr. Worldwide consumption of LAB is estimated to be 1.81 million t/yr. The en*Author to whom all correspondence should be addressed. tPresent address: Halliburton NUS Environmental Lid, Leatherhead, England.

vironmental acceptability of LAS is supported by numerous biodegradation, fate and toxicity studies (Schoberl, 1989; Berna et ai., 1989; Kimerle, 1989). There is, however, relatively little known about the fate of unreacted parent linear alkylbenzene (LAB) which may be present in commercially produced LAS at concentrations of 1-3% and as a result may find its way, possibly via sewage treatment systems, into the aquatic and terrestrial environments. Environmental monitoring studies have shown LAB to be present in suspended particulate matter in waste water treatment plant effluents (Eganhouse and Kaplan, 1982) at concentrations of 25-2200~g i -~ and in sewage sludges (Eganhouse et al., 1988) at concentrations of 17-430/Jg g-~ solids (all concentrations are expressed on a dry weight basis unless stated otherwise). The distribution of LAB in urban riverine environments around Tokyo was studied by Takada and lshiwatari (1987). They reported concentrations of 0--15.8 , g g-~ in fiver sediments and total suspended LAB concentrations in river water samples of 37-721 ng I - ' . The average suspended LAB concentration of waste water influents and effluents at the treatment plants examined were 1970__. 1330 and 61 ± 39 ng I - ' , respectively. The ratio of dissolved LAB to suspended LAB in sewage influents was reported to be 1.5: I. LAB in marine sediments around Port Phillip Bay (Australia) of 0-19 ~g g-~ were reported by Murray et al. (1987). These values were generally lower than

613

M. S. HOLT and S. L. BEa.NS'r~.N

614

those reported (Eganhouse et al., 1983) for coastal sediments in the U.S.A. of 1-33 p g g-~. An aquatic environmental safety assessment of LAB has recently been completed by Gledhiil et al. (1990). Laboratory and environmental studies have been carried out to determine the adsorption of LAg onto sewage sludges during biological treatment. No such information exists for LAB. The aerobic biodegradation of LAB has been demonstrated by Bayona et al. (1986) and by Takada and lshiwatari (1990). Neither LAS nor LAB are known, however, to be biodegraded under anaerobic conditions and therefore any LAB removed by adsorption onto sewage solids during primary settlement of the sewage, and which is then subjected to anaerobic digestion, will be present on the sludge at the end of the biological treatment. In the U.K. some 45% of this sludge is disposed of to agricultural land. The concentrations and fate of LAS in sludge amended soils have been reported (Holt et al., 1989; Berna et al., 1989). The aims of this study were: (I) to determine the distribution of LAB in sewage sludges and sludge amended soils (2) to measure the rate of disappearance of LAB in sludge amended soils (3) to compare the estimated total cumulative load based on known sludge applications with concentrations of LAB found.

pressedcake

(3) Analytical 15g soil, 0.1-2.0g (dry wt) anaerobic sludge or 25ml centrifuged solids from activated sludge were Soxhlet extracted with 100ml HPLC grade methanol for 4h. Methanol pre-extracted Whatman glass fibre thimbles were used. The entire methanol extract was passed through a preconditioned SPE strong anion exchange column (SAX, Analyticbem) at a flow rate of i drop/s. This ensured that the LAS were retained on the column and were separated from the LAB which passed straight through the column. Details of the analytical procedure for LAg are given elsewhere (Holt et al., 1989). The methanol extract containing the LAB was mixed with an equal volume of 1.7 M NaCI. The LAB were back extracted into 10 ml hexane, a procedure which was repeated 3 times. The hexane fractions were pooled and dried with anhydrous sodium sulphate and were concentrated to I ml by rotary evaporation at 20~C. The hexan¢ fraction was transferred to a silica column (160 x 10mm). The silica 60 (0.063-0.200 mm) 70-230 mesh was previously activated overnight at 450~C (Takada and lshiwatari, 1985) and wet packed in dried hexan¢. LAB were eluted from the column with hexane at I ml/min. The first 20 ml of eluent were discarded and the LAB collected in the 20-70ml fraction which was then evaporated to I ml prior to GC/MS analysis. A flow chart indicating the extraction, clean-up and analysis of LAg and LAB is shown in Fig. I.

Soil/sludge J I Soxhlet MeOH ] ~z 4hr [

EXPERIMENTAL (I) Soil sampling Sampling sites were selected following discussions with both the Thames Water Authority (TWA) and the Southern Water Authority (SWA). The parameters taken into account in selecting sampling sites have been detailed before (Holt et al., 1989) but included: (!) frequency of applications (2) concentrations of applications (3) different soil types. Representative samples from each location were collected, using a screw auger with a bit 200 mm Ions and 22 mm dia, by sampling at least 25 times at regular intervals along a W-shaped path. After drying, the samples were ground in a mortar and pestle to pass through a 1 mm dia sieve. A total of 17 fields from 9 farms at locations in Kent, West Sussex, Surrey and Hertfordshire were sampled between May and November 1989 to establish the concentration of LAB in sludge amended soils. The disappearance of LAB with time following subsurface injection of sewage sludge onto agricultural land was determined at 3 farms in W. Sussex. Soil samples were collected immediately prior to sludge application and at intervals over 105 days. Samples of sludge to be applied were collected in pre-washed (chromic acid followed by methanol) I ]itre glass bottles and immediately preserved with I% formaldehyde. (2) Sludge sampling Grab samples of activated sludge from Canterbury Sewage Treatment Plant (STP) were collected on I I July 1989, 23 August 1989 and 26 September 1989. Anaerobically digested sludge was collected from Ashford STP on 17 May 1989 and Sittingbourne STP on 13 July 1989. These samples were immediately preserved with !% formaldehyde. Raw

solids)

(32% from Queenborough STP was sampled on 17 October 1989.

( • 99%) 1 J olid phase extraction anion exchange rosin LAB pass straight through SPE column

~

Elute with "~henol HCl LAS analysis

I Add equal volume of 1.7 M NeCI back extract I 3x 10 ml H.xen. I

(98.8%)l i Rotary evaporate J (95.3%) [Activated silica ]

~Elut. with~ 0 - 20 ml discard

HoxIno

i' 20 - 70 ml I L,containing LAB (91.3%) l Rotary .vaporer. ] ~ 189 8%) GC/MS

Fig. I. Schematic outline of LAB extraction and clean-up (figures in parentheses represent percentage recovery).

LAB in sludges GC~MS conditions Capillary GC was performed on a Carlo Erba Model SFC 300 interfaced to a Finnigan INCOS 50 mass spectrometer (electron impact mode). Separation was achieved under the following conditions: Column: 50 m x 0.22 mm CP Sil 5 CB (0.11 mm film thickness). Mobile phase: helium at 120 kPa inlet pressure. Injection: on column. 2 #I in hexane. Temp. prog.: start temp 80°C, hold for 2 min, then at 30:C rain -~ to II0°C, then at I-~Crain-' to 175~C and finally at 25~C rain -~ to 300:C. Detector temp.: 310°C. LAB were quantified by selective ion monitoring by comparing the integrated areas of the mass fragements m/: 91,105. 119, and 133 in samples with the areas obtained for the components of Dobane 83.

615

after elution from the silica column was 96%. The overall recovery after the final rotary evaporation was 89.8%. Recoveries at each step in the analytical procedure are given in Fig. 1. To check recoveries of LAB through the analytical procedure the methanol extracts were spiked with 5.34/zg l-phenyloctane, 5.01/~g I-pbenyldodecane, 5.02/zg i-phenyltridecane and 5.0/~g ["C] 2-phenyldodecane. Recoveries had mean values of 90.5 (+3.1), 80.5 (-+4.1) and 84.5% (_+3.6), respectively, for the I-phenyl isomers. The average recovery of [ ~'C] 2-phenyldodecane from 20 analyses was 83.7% (-+4.7). (2) LAB and LAS concentrations in sludges

The concentrations of LAB in the various sludges are given in Table !. The concentrations range from 116 to 388 #g LAB g-~ dry solids for the anaerobically digested and raw sewages. In contrast, the concentration of LAB on activated sludge was significantly lower and ranged from 58 to 78/~ g g- '. These Chemicals n-Hexane was purchased from Sigma Chemicals. results are in agreement, therefore, with the published All other solvents were HPLC grade from Rathburns data on the concentrations of LABs in anaerobic Chemicals. Marion A (10.2% A.M.) LAS anayltical stan- sewage sludges by Eganhouse et al. (1988). They dard was supplied by Huls Chemicals. Germany and reported concentrations of 17--430/zg g-t dry solids Dobane 83 (LAB) by Shell Chemicals, U.K. "C ring labelled 2-phenyldodecane specific activity 41.2#Ci/mg for 6 treatment plants in the U.S.A. with the lowest was prepared at Shell Research, Sittingbourne. ['4C] Hex- concentration (17/zg g - ' ) found in sludge from an adecane specific activity 268/zCi/mg was obtained from activated sludge plant. Takada and lshiwatari (1987) Amersham. I-Phenyloctane, I-phenyldodecane and I-phen- also reported a similar concentration of LAB (60.8 # g lytridecane were purchased from Aldrich Chemicals. g-~) in activated sludge. In addition, work carried out by Crathorne et al. (1989), indicates levels of 276/zg g - ' in anaerobic sludge from a plant treating RF~UI.TS AND DISCUSSION predominantly domestic waste and 535/zg g - ' from (I) Recovery of LAB from soil samples a plant treating predominantly industrial waste in the Soil samples (10g) were spiked by equilibrating U.K. them for 1 h (Matthijs and De Henau, 1985) with A histogram of the percentage of the C~--C~3alkyl an aqueous solution (10 ml) containing 160/zg LAS homologues of LAB in sludges is shown in Fig. 3 and and I. 1/z g [ ~4C] 2-phenyldodecane and formaldehyde indicates no major differences in homologue distri(I ml of 40% v/v solution). Following equilibration bution in any of the sludges. There is, however, a and centrifugation the liquor phase was removed and distinct difference in the isomer distribution pattern analysed for LAB. Greater than 99*/, of the radio- for anaerobically stabilised sludge and the activated label was adsorbed onto the soil. Soxhlet extraction sludge unit (see Fig. 4). The anaerobic sludges have with methanol resulted in 100% recovery of the LAB a pattern similar to that found in domestic laundry after 2 h. detergents whereas the activated sludge has predomRecovery of the [t4C] 2-phenyldodecane through inantly the internal isomers. the SAX column was 98.6% and in the back extracThe concentrations of LAS on the various sludges tion into hexane was 98.8*/,. Without the addition of analysed are given in Table 2. The concentrations of NaCI the recovery was only 70%. Recovery after LAS range from 9.3 to 18.Stag g-t for raw and rotary evaporation at 20°C was 96.3%. anaerobically digested sludge and are similar to those The optimum conditions for silica gel chromatog- values reported in earlier work. The concentration raphy were examined using ["C] hexadecane and of LAS in activated sludge (Canterbury STP) was [l'C] 2-phenyldodecane dissolved in I ml n-hexane. between 62 and 98/zg g-i which is only slightly The mixture was applied to the top of the silica gel higher than previously reported for an activated column and eluted with n-hexane at I mlmin -~. sludge (Holt et al., 1989). The ratio of LAS in the Fractions (2 ml) were collected and the amount of aqueous phase to that bound on the sludge was radioactivity determined by liquid scintillation count- between 24:1 and 100:I for the raw and anaerobiing. Figure 2 illustrates a typical elution curve ob- cally digested sludges but was only !.5: ! in activated tained. Consequently the 0--20ml fraction was sludge (Table 2). discarded and the 20-70ml fraction collected for Similarly, the ratio of LAS:LAB in raw and LAB analysis. Recovery of ["C] 2-phenyldodecane anaerobically digested sludges varies significantly Liquid scintillation counting The amount of radioactivity in liquid samples was determined by scintillation counting in Optiphas¢ Safe (15 ml) in a plastic vial. The vials were counted in an LKB 1219 Rackbeta liquid scintillation counter.

616

M.S. HOLT and S. L. BERNSTEIN hexlKl~an•

16000

14000

i

12000

6O000

10000

50000

i @ C

8000

40000 e,

¢Sl

6000

30000

4000

20000

2000

10000

lO

20

30

40

50

60

?

70

Vol(ml}

Fig. 2. Elution pattern for hcxadecane and 2-phenyldodecanc.

between aerobically treated and anaerobically treated sludges. In anaerobic sludges the LAS:LAB ratio was between 60:1 and 100:1 but in activated sludge it was I:1.

(3) Concentrations of LA B and LAS in sludge amended soils T h e fields sampled in this section o f the study had all been surface spread with primary a n d / o r surface

activated anaerobically digested sludge which had been gravity thickened to approx. 4.5% dry solids a n d had been stored for approx. 3 months. Fields receiving sludge prior to 1989. Nine fields from 5 different farms were sampled to establish the c o n c e n t r a t i o n s o f LAB in the top 20 cm o f the soil. Table 3 gives the c o n c e n t r a t i o n s found, together with the k n o w n sludge application history a n d the total estimated cumulative L A B loads resulting from the

Table I. Concentrations of LAB in sewage sludges

Sludge Ashford digester influcnt Ashford digested sludge Earlswood digested sludge 5 July 1989 Earlswood digested sludge

30 August 1989 Crawley raw sludge 30 August 1989 Mixed Earlswood and Crawley 13 May 1989 Sitlingbourne digested sludge Quecnborough pressed cake Canterbury activated sludge II July 1989 23 August 1989 26 September 1989 ND = not determined.

Solids

LAB on

LAB in

content (El")

solids (/Jg g- ')

liquor (/Ag I "')

LAB ratio solid:liquor

Total

LAB (mE I -*)

13.9 21.2 31.4

157.9 169.5 116.0

ND ND ND

ND ND ND

ND ND ND

31.9

251.0

94.9

84: I

8. I 0

30.9

206.0

59.3

107:1

6.43

36.8

155.0

38.5

148;I

5.74

29.6 320.0 4.4

387.9 167.1 58.3

ND -ND

ND ND ND

ND ND ND

2.8 4.8

77.2 77.8

ND 0

ND --

ND 0.37

617

LAB in sludges

, lul

lal

60-

6O

44.0 40 31.6

34.6

32.8

20

18.5

2O 0.4

N

~! 0

2.3 k'x\\\\'x~l

0.7

Ibl

Ib) 60-

80

40.7

40

m

28.3 21.4 20

~

22 .~ 2O

13.4

13.5

N N

2.2 0

0

14.7

Ic)

Icl

60

60

39.8

40 27.8

40

~

24.8

22.3

21.8

718

5

4 Phenyl isomer

20 12.3

~

1.8 ~NNN\N~

9

10

11 12 Alkyl chain length

Fig. 3. Alkyl homologue distribution of LAB in sludge. (a) Activated sludge. (b) anaerobically digested sludge and (c) raw sludge.

Sludge

0

13

2

Fig. 4. Phenyl isomer distribution of LAB in sewage sludges. (a) Activated sludge. (b) anaerobically digested sludge, (c) raw sludge.

Table 2. Concentrations of LAS in sewagesludges Solids LAS on LAS in content solids liquor LAS ratio (gl *) (mgg-t) (rag I 't) solid:liquor

Ashford digester influent Ashford digested sludge 17 May 1989 Earlswo~xl digested sludge 5 July 1989 Earlswood digested sludge 30 August 1989 Crawley raw sludge 30 August 1989 Mixed Earlswood and Crawley 13 May 1989 Sittingbourn¢ digested sludge

3

Total LAS

(rag I t )

13.9 21.2

10.4 12.3

6.0 5.0

24 : I 51:7

150.4 264.8

31.4

11.5

ND

ND

ND

31.9

18.8

6. I

98: I

604.2

30.9

18.1

9.4

59: I

568.7

36.8

10,3

6.5

58:1

386.7

29.6

ND

ND

ND

ND

0,1 ND

1.5 : I ND

0,28 ND

Queenborough pres~d rake

320.0

Canterbury activated sludge II July 1989 23 August 1989 26 September 1989 ND - not determined.

4.4

9.3 ND

2.8 4.8

0.06 0.1

ND ND

ND ND

ND ND

M. S. HOLTand S. L. BEg.~S'I'EIN

618 Table

3. Summaryof LAB data for soils having sludge applications prior to 1989 Sludge application

Field No. 10 12 35 36 37 45 6565 6567 6568

LAB analysed (ngg -I )

Total solids (kgm -~)

< 1.0 5.0 < 1.0 47.9 < 1.0 31.5 0

0.40 0.70 2.12 1.99 2.59 1.04 1.69

Total estimated cumulative LAB in top 20 crn (ngg -j )

Removal (%)

(4) (2) (3) (3) (2) (2) (3)

373 586 1760 1658 2158 863 1407

>99.5 99. I >99.5 97.1 > 99.5 96.3 100

No. of yr applied 1978-1988 1986-1987 1986-1988 1986-1988 1986--I 987 1986-1987 1985-1988

1.9

1.69

1985-1988 (3)

1407

>99.5

3.4

0.52

1985-1988 (3)

435

99.2

sludge applications. LAB concentrations in 7 of these samples contained < 5 ng LAB g-~ soil. The other two sites contained LAB concentrations of 31.5 and 47.9 ng g- ~ soil. The determined LAB concentration was compared with the total estimated load of LAB introduced with time through sludge application to calculate the percentage loss from the soil. The estimated LAB load was calculated assuming an LAB concentration of 0.2 mg g-~ dry sludge solids (based on the LAB concentration in the eight sludges analysed in this study), the known application rates of sludge, a bulk density of 1200 kg m -3 and a 20cm soil depth. In all cases < 5 % of the estimated LAB remained in the soil. A frequency distribution of percentage LAB disappearance is shown in Fig. 5. The phenyl isomer distribution of the LAB found in these soils is similar (see Fig. 6), and consists primarily of the 7, 6, and 5-phenyl isomers. Concentrations of LAS in these soils are shown in Table 4. Some of the fields monitored had been used in a previous study (Holt et al., 1989). The field numbers have been retained to enable comparison of the data. LAS concentrations in 7 of the 9 soils were < 1/~g g-~ soil. The other two soils contained !.3/~g LAS g- soil. These results indicate that < 5% of the

estimated cumulative LAS load remained on the soil and confirm the earlier findings. The estimated loads are based on an LAS content of 6 g LAS kg- ~sludge solids (De Henau et al., 1986) and in the light of the concentrations of LAS found in our work with 16 U.K. sludges over the past 3 yr (mean concentration 10.9g LAS kg -~) they may well be an underestimate. Fields receiving sludge in 1989. The LAB concentrations in soils from 8 fields that had received a sludge application within the 6 months prior to sampling are shown in Table 5. The month during which sludge was applied and the sampling date are also shown. Concentrations of LAB found in these soils ranged from 4.7 to 387 ng g- t soil. The highest concentration was found in soil 44 which was sampled only 27 days after a surface spread sludge application (application rate was 162m 3 ha-J). Assuming 0.2 mg LAB kg sludge solids the concentration of LAB immediately after application would have been approx. 540 ng g-L The concentration found (387ng g - ' ) corresponds to 72% of that applied. The phenyl isomer distribution of LAB in these soils is similar to that in the soils which had received sludge prior to 1989 and is a further indication that it is the external isomers which disappear first. Concentrations of LAS in these soils are given in Table 6 and are in the range <0.2-8.1 pg g-~ with the highest concentration in field 44.

(4) Disappearance of LAB with time 5 4

Z

3

2 1

loo-N

II-II

N-II

II-II

>00

Percentage disappearance

Fig. 5. Frequency distribution of percentage LAB disappearance from soils (sludge applied prior to 1989).

The disappearance of LAB with time was studied at three farms in the TWA area. Sludge was applied by subsurface injection in each case. Field A was treated on 19 May 1989 with a 50:50 mixture of raw and anaerobically digested sludge. Field B was dressed on il July 1989 with Earlswood raw sludge. The very dry weather between June and October made sampling to 20cm impractical. As a result samples were only collected from field A after 21 and 103 days and from field B after 56 days. Neither field A nor field C had any previous history of sludge applications. From initial concentrations of 1.19 #g g-J LAB and 116.5/~g g - ' LAS, after 103 days, the removal of LAB and LAS was 98 and 97.6% respectively. Field B had one previous application of

LAB in sludges

619

Field 12 4

m

1 0 Field 6 5 6 8 4

m

,;2 m loi i

Field 45

8 !

k

OS

`;4

Field 36 10 8

6432

6 5 4 3 2

65432

Clo

7/65 4

C12

Cll

3

C1:

Fig. 6. Phenyl isomer distribution in soils amended with sludge prior to 1989. sludge in 1987. The concentration of LAB however immediately prior to the 1989 application was below the level of detection. Immediately following the application there was i.05/zg LAB g-~ soil. After 56 days this value had dropped to 0.15/~g g-i. The

concentration of LAS during this period fell from 124.2 to < 0 . 2 p g g - ' . Sludge was applied at the third site (field C) on 30 August 1989 and samples were collected after I0, 22 and 55 days. The area of the field sampled was

Table 4. Summaryof LAS dales for soils havingsludge applicalions prior to 1989 Sludge application

Field No.

I0 12 35 36 3"I 45 656S 6~67 6568

we ~/~.-.F

LAS analysed ( ~ I I "l )

Total solids (kgm -2)

No. of yr applied

Total estimated cumulative LAS in top 20 cm (~gg -I)

0.46 0.95 1.3 0.3 0.9 0.5 <0.2 1.3 0.2

0A0 030 2.12 1.99 2.59 1.04 1.69 1.69 0.52

1978-1988 (4) 1986-1987 (2) 1986-1988 (3) 1986-1988(3) 1986-1987(2) 1986-1987 (2) 1985-1988 (3) 198~1988 (3) 198~1988 (3)

11.2 17.6 52.9 49.7 64.8 25.9 42.2 42.2 13.0

Removal (%) 95.9 94.6 97.5 99.4 98.6 98,3 99.5 96.8

98,5

M. S. HOLT and S. L. BERNSTEIN

620

Table 5. Summary of LAB data for soils having sludge applications during 1989 Sludge application LAB analy,~-'d (ng g-:)

Total solids (kgm -2 )

No. of yr applied

4

12.0

I 1.3

II

26.4

1974--1989 021 February, 7 November 1989 1979-1989 (9) June, 7 November 1989 1985-1989 (4) October, 7 November 1989 1987-1989 (2) May. 30 August 1989 1986-1989 (4) May, 23 October 1989 1986-1989 (3) July, 23 October 1989 1985-1989 (3) July, 23 October 1989 1985-1989 (4) May, 23 October 1989

Field No.

~4

2.86

387

4.08

140

43,7

2.0

6402

4,7

0.33

6553

26.2

2.39

6554

39.3

1.07

6564

19.6

1.53

Total estimated cumulative LAB in top 20 cm (ngg -~ )

Removal (%)

9500

>99.5

2383

98.9

3400

88.6

1667

97.3

280

98.3

1992

98.6

893

95.6

1276

98.5

The first month indicates the time of the last application of sludge and the date indicates the sampling date.

treated solely with raw sludge from Earlswood STP. The disappearance of LAB and LAS with time for field C are shown in Fig. 7. The reported data for LAS disappearance in sludge amended soils indicate there is no preferential biodegradation of specific alkyl chain lengths (Ward and Larson, 1989). This also seems to be the case for LAB. There is, however, a noticeable pattern in the distribution of phenyl isomers in the LAB in the soils. Isomer disappearance with time, for field C, is shown in Fig. 8. Histograms showing the phenyl isomer distribution for the time course experiments at fields A and C are shown in Figs 9 and 10, respectively. Clearly it is the internal isomers which remain in the soil the longest. Half lives and rate constants for LAB, for the LAB alkyl homologues, the phenyl isomers and LAS in field C have been calculated by linear regression analysis and from the equation: k = 2.303 log Co/C(h_l) t

where Co = initial concentration C = final concentration t = time Its2 ----h a l f life

In 2 /l,2 ='

T"

There is no significant difference in the half life values for the alkyl homologues with the overall half life for LAB around 15.3 days, in comparison to 8.3 days for LAS. There is, however, a significant difference between the half lives of the phenyl isomers, which were 4.5, 5.7, 16, 17 and 20.2 days for the 2, 3, 4, 5 and 6/7 isomers respectively when calculated by linear regression and 4.4, 5.6, 13.4, 14.4 and 16.9 days respectively when calculated from the above equations. No attempt has been made during this study to quantify the phenyl isomers of LAS.

Table 6. Summary of LAS data for soils having sludge applications during 1989 Sludge application Field No.

LAS analysed (#BE")

Total solids (kErn -z)

No. of yr applied

I 1.3

1974-1989 (12) February, 7 November 1989 1979--1989 (9) June, 7 November 1989 1985-1989 (4) October, 7 November 1989 1987-1989 (2) May, 30 August 1989 1986--1989 (4) May, 23 October 1989 1986--1989 (3) July, 23 October 1989 1985-1989 (3) July, 23 October 1989 1985-1989 (4l May, 23 October 1989

4

1.2

II

0.9

2.86

,14

8.1

4.08

140

<0.2

2.00

6402

4.9

0.33

6553

3.7

2.39

6554

6.4

1.07

6564

0.8

1.53

Total estimated cumulative LAS in top 20 cm ~gg-') 285 71.5

Removal (%) 99.6 98.7

102

92.0

50

>99.6

8.4

41.6

59.8

93.9

26.8

76.3

38.3

98.0

The first month indicates the time of the last application of sludge and the date indicates the sampling date.

LAB in sludges

621

2.6

LAB 2.4 2.2 2.0 1.8

=~

1.6

m

1.4

~

1.2 1.0 0.8 0.6 0.4 0.2 ,O

Background level

! 10

0

i 20

3'0

' 40

5'O

I

6O

Time (days)

160

"

LAS

140 -

7 m '~

120 100 80

-

60

-

40 20Background level. , I

I

I

I

I

0

10

20

30 Time (days}

40

I "-~'n

50

t

60

Fig. 7. Disappearance of LAB and LAS with time in field C.

Table 7. Half lives for LAB in field C

CONCLUSIONS

Rate constant k (h - I )

Half life" (days)

Half life*' (days)

ND

ND

15.3

Homologue Cla alkyl C . alkyl C,2 alkyl C . alkyl

0.054 0.058 0.047 0.054

12.8 11.9 14.8 12.8

14.7 14.2 12.8 15.4

Isomer 2-phenyl 3-phenyl 4-phenyl 5-phenyl 6/7-phenyl LAS

O.156 0.123 0.052 0.048 0.041 ND

4.4 5.6 13.4 14.4 16.9 ND

4,5 5.7 16.0 17.0 20.2 8.3

Compound LAB

"Calculated from equations in text. *From linear regression analysis. ND - not determined.

(I) The concentrations of LAB in anaerobic sludges varied from 116 to 388pg g - ' and in activated sludge varied from 58 to 78pg g - ' dry wt. (2) The ratio of concentration of LAS: LAB in raw and anaerobic sludges varies between 60:! and 100:1 but in activated sludge is of the order of I:1. (3)LAB will reach the soil environment as a result of raw or digested sludges being applied to agricultural land. A typical sludge application in the Thames Water Authority area resulted in LAB concentrations of 0.5 pg g-m soil and in the Southern Water Authority area of 0.3 pg g-L (4) In the 9 fields spread with sludge prior to 1989 the concentration of LAB in the soils was generally

--

o

" £

0

10

20

10

15

20

25

30

35

40

45

50

.O

Fig. 8. PhenyI isomer disappearance with time for field C.

Time (days)

55

60 0

20

40

60

80

20

40

60

30 nglg

nglg

100

5

isomer isomer isomer isomer ison~r

40

50

6O

70

80

Phenyl Phenyl Phenyl Phenyl Pheny!

80

2 3 4 5 716

90 • 0 Z1 O Q

100

0

20

40

60

80

1001

nglg

100

120

140

3

3

C~o

4

Cio

2

2

8

S

5

S

4

Ctl

4

C.

2

2

•

4

Cl2

S

2

7IS E

4

Clm

Q

CI2

4

3

2

7/6

E

C~m

,It

Day 103 LAB conc.= 26.2 ng/g

Q

Cll

CI,

C~s Fig. 9. Isomer distribution with time for field A.

C~o

3

3

Day 21 LAB cone. : 146.8 nglg

s

.oJm°o °oo_ 3

3

6 4 3 2 S 6 4 3 2 S S 4 3 2 7 1 S 6 4 3 2

5

4

0oo 0

S

Dmy 0 LAB c o n e . - 1186 nglg

2

2

T.

f-

Q r" -t

O~

6

4

3

2

•

6

4

3

2

3

2

3

2

3

2

200

Clo

C.

@

•

C12

4

3

4

C13

6

S

4

4

Fig. lO. Isomer distribution with time for field C.

2 7~D 6

40

4

4

CI]

40

6

27~6

80

•

3

80

2

4

C1:

ng/g 120

3

6

Day 10 LAB conc. : 4 1 0 nglg

•

nglg 120

4

Cll

40

80

ng/g 120

160

200

160

S

Clo

im,uIIIIl IIHllm

Dmy 0 LAB conc. = 2260 ng/g

160

200

0

40

80

120

n919 160

200

240

280

3

Cio

3

C1o

2

2

I

6

6

6

4

(:11

4

CII

3

3

2

2

6

4

CI2

3

2

71• 6

4

CI3

•

6

C12

4

3

2

710 6

CI3

4

Day 55 LAB conc.: 121 ng/g

6

Day 22 LAB conc.= 296 nglg

3

3

2

2

c:h

M. S. HOLT and S. L. BER.'qSTEIN

624

< 5 ng g- i. The loss of the estimated cumulative LAB load added was < 9 9 % for the majority of soils. (5) In fields spread during 1989 (i.e. within I yr of sampling) the concentrations of LAB in soils were in the range 5--390 ng g-t. (6) The half life for LAB was approx. 15 days (cf. LAS = 8.3 days), the half lives of the individual aikyl homoiogues were of a similar order but the half lives of the phenyl isomers were significantly different ranging from 4.5 days for the 2-phenyl isomer to 20 days for the 6/7-phenyl isomer. Acknowledgements--The authors wish to express their thanks to the staff of both TWA and SWA for their help in identifying suitable sampling sites and providing the data on sludge applications. REFERENCES

Bayona J. M., Albaiges A. M., Solonas A. M. and Grifol M. 0986) Selective aerobic degradation of linear alkylbenzenes by pure microbial cultures. Chemosphere 15, 595-598. Berna J. L.. Ferret J., Moreno A.. Prats D. and Ruiz Bevia F. (1989) The fate of LAS in the environment. Tenside Deterg. 26, 101-107. Crathorne B., Donaldson K., James H. A. and Rodgers H. R. (1989) The determination of organic contaminants in U.K. sewage sludges. In Organic Contaminants in Waste Water, Sludge and Sediment (Edited by Quagheur D.). Elsevier Applied Science, Amsterdam. De llenau, H., Matthijs E. and Hopping W. D. (1986) LAS in sewage sludges, soils and sediments: analytical determination and environmental considerations. Int. J. em'ir, analyt. Chem. 26, 279.293. Eganhouse R. P. and Kaplan 1. R. (1982) Extractable organic matter in municipal wastewaters. 2. Hydrocarbons: moh.'cular characterisation. Em,ir. Sci. TechnoL 16, 541-551.

Eganhouse R. P., Blumfield D. L. and Kaplan I. R. (1983) Long-chain alkylbenzenes as molecular tracers of domestic wastes in the marine environment. Em'ir. Sci. Technol. 17, 523-530. Eganhouse R. P., Olaguer D. P., Gould B. R. and Phinney C. S. (1988) Use of molecular markers for the detection of municipal sewage sludges at sea. Mar. Envir. Res. 25, 1-22. Gledhill W. E., Saeger V. W. and Trehy M. L. (1990) An aquatic environmental safety assessment of linear alkylbenzene. £nvir. Toxic. Chem. 10, 169-178. Holt M. S., Matthijs E. and Waters J. (1989) The concentration and fate of linear alkylbenzene sulplionate in sludge amended soils. War. Res. 23, 749-759. Kimerle R. A. (1989) Aquatic and terrestrial ecotoxicology of linear alkylbenzene sulphonate. Tenside Deterg. 26, 169-176. Matthijs E. and De Henau H. (1985) Adsorption and desorption of LAS. Tenside Deterg. 22, 299-304. Murray A. P., Gibbs C. F. and Kavanagh P. E. (1987) Linear alkylbenzenes in sediments of Port Phillip Bay (Australia). Mar. Ent'ir. Res. 23, 65-76. Schoberl P. (1989) Basic principles of LAS biodegradation. Tenside Deterg. 26, 86-94. Swischer R. D., Kaelble E. F. and Liu S. K. ( 1961) Capillary gas chromatography of phenyldodecane alkylation and isomerisation mixtures. J. organ. Chem. 26, 4066-4069. Takada H. and lshiwatari R. (1985) Quantitation of long chain alkylbenzenes in environmental samples by silica gel chromatography and high resolution gas chromatography. J. Chromatogr. 346, 281-290. Takada H. and lshiwatari R. (1987) Linear alkylbcnzenes in urban riverine environments in Tokyo: distribution, source and behaviour. Envir. Sci. Technol. 21, 875-883. Takada H. and Ishiwatari R. (1990) Biodegradation experiments of linear alkylbenzenes (LABs): isomeric composition of C~z LABs as an indicator of the degree of LAB degradation in the aquatic environment. Envir. Sci. Technol. 24, 86-91. Ward T. E. and Larson R. J. (1989) Biodegradation kinetics of LAS in sludge amended soils. Ecotoxic. envir. Safety 17, 119-130.