- Research & Technology
Transformations of
Tetrachloroethene and
Trichloroethene in
Microcosms and
Groundwater
Frances Parsons, Paul R. Wood, and Jack DeMarco
Co- and tna»-l^-dichJoroetkeM wan fowi In well water st a «tte coatanrijutcd wtth
trttbkjroeth£!vt from a hairing rtcrttfe tank, although neither aopooad *ms used to the
vicinity na* was present u an hnpuiity in the tricMoMcthene in the storage tank.The me of
tetnthfowetheiie and trichkuroetbene (a dry cleaning and oeUl reBabblng phnU is
widespread. Severn ehkrroethtne cmnywmdtthsl are found in southern Florida fiiimidwilei'
uuy have been formed fro® these solvents vta jnkrobial mftaboltrro In the groundwater
ottfaxisenL to this stndy, depletion of tetjwhloroedjene and appearance of dv and
buu-l,2-dkti!orocUien« ami cMcroethent wo* observed follow^ tncabatkmcf tefcrachlo-
nxtheve tn microcosms aratatnlnj nrudt freffl the aqviftr redstrge b&tin.
Public drinking water m Dade and
Broward counties in southeastern Flor-
ida Is drawn from wells sunk less than
45 an <150 ft) deep into the Blscayne
Aquifer, which >3 & shallow, uncoofirud
aquifer composed of porous calcareous
rock. The aquifer is rechareed primarily
by rain falling in the Everglades, a
greminoid wetland. The roflected surface
water, which is continuous with ground-
water, enters the rock substratum
through a bed of muck, a saprist histosot
formed of decomposed Indigenous vege-
tation.1 Organic solutes leached from
the muck are present in groundwater at
concentrations up to 17 mg/L Turbidity
values of 00 ntu art not uncommon.
During the past five years, chloroeth-
ene arid as-and rrans-l^-dkhbroethene
were found to groundwater in southern
Florida where these substances are
lection produced trihaknðane
concentrations greater than 300 ^g/L,4
chloroethene ami cis- and trans-l£-di-
chloroethene have not been detected as
by-products of water treatment. Local
Industries do not use these compounds,
but several industries use tetrachlo-
roethene and trichloroethene as de-
greasers. and these have spilled hrto
groundwater.
Because the muck bed of the recharge
basin Is microbiological!? active in de-
composing organic matter, it was epecu-
56 KES8AHCU AND TECHNOLOGY
lated that mucb mtenwr^anistns could
also act on exotic organic compounds,
eg., tetrachloroethene and trichloroeth-
ene. The research described in thi3 arti-
cle was an attempt to simulate local
aquifer conditions in the laboratory and
to subject b known contaminant of local
groundwater to the activity of native
microorganisms.
Tetrachloroethene was injected into
static microcosms, which were repre-
sentative of the recharge basin and
composed of muck and surface water in
sealed septum bottles. During three
weeks of incubation, the contents of
these bottles were analyzed periodically
by eaa chromatography (GQ for products
^biotransformation, Results of analyses
of well water from the site of an indus-
trial Bpili of trichloroethene io to ground-
water^were compared with the results of
the laboratory models (microcosms) that
contained tetrachlorbethene, because die
latter results indicated that tetrachlo-
roethene was biatransformed to tri-
chloroethene and that both tetrachlo-
roethene and trichloroethene were bio-
transformed to chloroethene, ds- and
trana-W-dichloroethene, end dichtoro-
methsne
The results of this study, which Indi-
cated successive transformation of tet-
rachloroethene to triehloToetbene and
then to chloroetbena, els- and trarts-1,2-
dkbloroetheue, and dkhlororn ethane,
have two implications for researchers in
the field of drinking water supply.
First, the source of any contaminant
must be identified before the contam-
ination can be remedied. With the real-
ization that a contaminant may be a
biotransformation product of a different,
precursor contaminant, a researcher
may more readily identify the source.
Second, treatment methods developed
to remove one contaminant (Le.. a parent
ineffective in removing its biotrans-
formation products as time and succes-
sion advance.
Thus, researchers may be required to
search for the source of a contaminant
different from the one found in the
water and concurrently prepare to re-
move a third, which groundwater mi-
crotnota may make in the future from
the existing contaminant.
Materials and netted*
Samples of freshwater sediments were
assayed to determine their ability to
transform tetrachloroethene in two
chronological experimental phases.
Phase 1 was on assay of muck and
surface water from the Everglades,
South Florida's wetland; phase 2 was an
assay of muck, surface water, and marls
from five other sites in the Everglades.
Muck used in the initial experiment
was collected from a pristine site in the
Everglades and, while still wet, was
passed through a 2-mm standard sieve-,
10 raLof the sieved muck was placed in
each of seven BO-mL septum bottles.
Surface water, which had covered the
mods in situ and had been collected at
the same time, was added to fill each
bottle, and 10 mL of a methanol solution
containing 100 fig of tetrachloroethene
was injected Into the fluid in each bottle.
JOURNAL A WWA

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The bottles were immediately capped
and shaken for 30 s to distribute the
tetrachl&roethene. To establish initial
values, all seven were sampled for GC
analysis by removing 2.0 mL of the
supernatant fluid with syringes. Each of
the seven replicate bottles was sampled
again after 7,14, and 21 days incubation
at 25°C. Thu procedure, which resulted
in increasing heads pace in the micro-
cosm. was not used in later worfc.
A control of sieved muck and surface
water was prepared without tetrachbro-
ethene. Tetrachloroethene was added to
& sterile control of 10 :oL muck and $0
mL surface water and to a Bterfle control
of distilled water. The sterile controls
were prepared by autoclavicg them at
121°C for 15 mln. The three controls
were also sampled and analyzed for
tetrachtoroethene and sterility initially
and again after 7, 14. and 21 days
Incubation at 25°C. Sterility was deter-
mined by streaking autndaved material
on plates of a nutrient solid medium and
by inoculating, incubating, and then
observing tbioglycollate broth tubes for
microbial growth.
In phase 2, samples of Everglades
sediments ware assayed for transfor-
mation capability according to the same
scheme used in phase 1, except that
duplicate test bottles, rather than seven
replicates, were prepared and analysed
for each of the five sample sites and the
tetrachloroethene inoculum was in-
creased to 250 pg/60-mL bottk by adding
2S jig of a 10-pg/mL methanol solution
of tetrachloroetbene. For each sediment
sample, $ control bottle without tctra-
chloroethene was used to evaluate the
possibility of generation of chlorinated
compounds by indigenous sediment
organisms. One autoclaved control bottle
for each sample site was also used to
detect abiotic changes, and a bottle of
sterile distilled water was injected with
tetrachkjroethene to test for spontaneous
hydrolysis effects.
Fluid contents of the bottles were
analyzed for chlorinated organic com-
pounds by using GC with packed col-
umns*-f and the puree-and-trap methods
of Beliar and Lir.htenberg5 and Dress man
and McParren.'
ftavits end dfea&sioa
Averaged values of chloroethene com-
pounds obtained in the phase 1 experi-
ment are shown in Table 1. [hiring the
21-day experimental period, tetrachloro-
ethene decreased from an average value
of 67 (100 pg was added) to 28 pg
while tnehkroetheoa, which was pres-
ent as a contaminant in the tetrachtoro-
ethene. increased from 1.1 pg to 4.7 pg.
Ci»- and trans-l,2-dichk»roethene. di-
chlororaethane, and chloroethene were
all undetected initially. The detection
limit was about 0.03 fig. After 21 days
these four compounds were found at the
TABLE 1
Compotrnd and Test Bottle
Concentration in Boniest M • Fonction
of tncutvttlon Tunt—^/60 ml
0d»jr8
7 days
14 d«ys
SI day*
Trtrwhkroethene




Meek
47,0 ± 1L1
6&e±i£4
47.J *2Si
27eiflkl
Wmehttd crack}
8334U
88,0 ±i66
8X012.12
83.0 = 0
TrieMaroettene




Muck
M0 ±0.80
£81*1.70
3.11 ±2^0
4 72 ±110
AotodAvod miKk
150 ±030
09i ±ae
1.W10
U»±0
Ci»l ,2-dicli !nn*thene




Hade
f
o»±ao8
2.13 ±09}
&£0±0 16
Antodarcd muck
i
s
»
f
Tnma-l>diohl«ro«btne


tt.ll ± C10
n --1-
raUCK
I
«•
cxts±c.a?
Auwdtewdntuck
1
*
1
9
DkMer*n«thanetT


0.15±0j0o
Mucfr
9
m
OJEtaOB
Antodtved meek
I
t
s
i
Chloroethene




Mw±
1
m
aoe*o.o8
1.70 ±120
ftntoelivoj muck
S
i
f
8
•Battles spited wltfi lDQcgtelrac&laroeshcm
tValues are nw«na of seven repteata ± ttttuiirf derfetim. Itoipitaad mudi control yitlded
co tMorfared oMBpeundi; SBUhAwiter antra! gatt v»1wb fran 851» 105 rg that wee
unretotad to time.
JVttaes *re	of two GC orttlyto.
gLeu tfwn <103 n? rt/U, deletion Smit
"*Dttect»b!e, not moacuratle
ttDicWonmwtfuBe aiid 1,1-dfchlorowieM were not distinguished, thete nines couU Indode bwb
following levels rift-l,2-
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TABLE2
Gmctntretionjojchlorinatedctmpoumtia
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TABLES
Jmvbatim* of Uracklontthene end mart in staled battles
Compeued
Amauatt In Spike
Htf
Amctwt hi Muck MiancoammJ
ft
TenciJcrtethece
2SC.Q
«iio+ao
Tnchloroethrae
4j0
4.7 ±11
Ctsl^dicftlorsjthcra:
Trace
7-3*2/4
Trwn-liKiichlsroetfwse
Trace
0.071 ICS
DWitoroaethine


gr 1 J^lichlororthow
W
tiilS
•Ujooasait ven; iocutatcd fsr 11 den 1tfter hcog nnted vttii 290 <4 tetrtcbbraecb«ne.
thctudine impurities
tMoo value for five totUes tstaadart drdatfan
quality of nutrients and the environ-
mental conditions 
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