N 1
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-074 Nov. 1983
&ERA Project Summary
Land Treatability of Refinery and
Petrochemical Sludges
K. W. Brown, L. E. Deuel, Jr., and J. C. Thomas
The land disposal of API separator
sludges was investigated with regard
to decomposition rates of organic
constituents and the possible impact
of these materials on plants and sur-
face water or groundwater quality.
Two oily sludges (one from a pe-
troleum refinery and one from a pet-
rochemical plant) were studied as to
their phytotoxicity, biodegradability
in soils, water-soluble constituents,
and field mobility.
Concentrations of refinery sludge of
5% v/v and above depressed ryegrass
emergence and yield. The pet-
rochemical sludge suppressed emer-
gence and yield proportional to the
amount of sludge applied, and the
suppression lasted longer than that
of the refinery sludge.
Biodegradation rates were greatest
when small applications of sludge
were made at frequent intervals. Op-
timum application rates for both
wastes was 5% to 10% (wt/wt).
The water-soluble compounds in
both sludges were low in degradabil-
ity, potentially toxic, and extremely
mobile in high concentrations. These
results indicate a need for careful
management of land treatment sites
to avoid groundwater contamination.
Gas-liquid chromatography (GLC)
combined with column chromatogra-
phy is recommended for effective
monitoring of oily wastes applied to
soils.
This Project Summary was devel-
oped by EPA's Municipal Environ-
mental Research Laboratory, Cincin-
nati, OH, to announce key findings
of the research project that is fully
documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
Soil disposal may prove to be the most
economical and environmentally sound
means of disposing of many of our
complex industrial wastes. Such dis-
posal can be effective provided that
application rates and scheduling do not
result in conditions that allow undesir-
able components or degradation pro-
ducts to run off or leach through the soil,
and provided no materials accumulate to
toxic levels in the soil.
Soil disposal of many wastes is effec-
tive because the soil has large surface
areas in which to absorb and inactivate
waste components. And if the soil is
properly managed, it also presents an
ideal medium for microbial decomposi-
tion because of the presence of oxygen,
water, and the nutrients needed for de-
gradation of organic constituents.
Oily wastes are often separated from
reusable constituents or more easily dis-
posed of materials by the use of API
separators at petrochemical plants and
depots. Certain fractions of the materials
accumulate as sludge in these pits and
must be periodically dredged or pumped
out. These wastes have classically been
disposed of by deep-sea dumping, deep-
well injection, incineration, landfilling,
and back-lot dumping. But all of these
techniques have either economical or
environmental drawbacks that limit their
utility.
This report investigates the soil dis-
posal of API separator sludges with re-
gard to decomposition rates or organic
constituents and the possible impact of
these materials on plants and surface
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water or groundwater quality. Because
of the complexity of the study, it was
divided into four sections: phytotoxicity,
biodegradation, water-soluble con-
stituents, and field mobility of contam-
inants.
Phytotoxicity
In the phytotoxicity study, measure-
ments were made of the impact of two
oil-water separator sludges on the emer-
gence and yield of ryegrass (Loluim
multiflorum Lem.) grown on four diverse
soils in the greenhouse. One sludge
was from a petroleum refinery, and the
other was from a petrochemical plant.
Each was applied at rates of 0%, 596,
1096, and 2096 v/v to each of the four
soils to determine the influence of ap-
plication rates. After growth periods of
approximately 6 weeks, the grass was
harvested, and the soil-sludge mixture
was air-dried, cultivated, and reseeded.
Eight harvests were made in sequence.
Soil wettability was measured twice to
evaluate physical problems.
Concentrations of refinery sludge of
596 v/v and above depressed ryegrass
emergence and yield through two mech-
anisms: phytotoxic constituents and
impaired water relations. The phytotoxic
constituents initially acted to retard plant
growth. Several months were required
for the sludge to degrade sufficiently to
allow normal plant growth. Subsequent
yield reductions resulted from the im-
paired water relations associated with
residual hydrophobic hydrocarbons. This
impairment was evidenced by the in-
creased water adsorption times of the
sludge-treated soils.
The petrochemical sludge had higher
concentrations of both organic carbon
and aromatics, and it suppressed emer-
gence and yield proportional to the
amount of sludge applied. The suppres-
sion lasted longer than that caused by
the refinery sludge. Seedling emergence
from soils treated with 2096 refinery
sludge did not differ from that in the
unamended control by the second plant-
ing; but the corresponding treatments
with the petrochemical sludge resulted
in depressed emergence for the first
five replantings. Grass yield from the
2096 refinery sludge treatment required
1 3 months to reach control levels. The
corresponding petrochemical treatment
yield reaches only 47% of the control
levels 17 months after application.
Biodegradation
The biodegradation rates of the two
sludges were studied using a soil re-
spirometer as a model for field studies.
Biodegradation rates were measured by
C02 evolution and residual hydrocarbon
analysis. The microbial population was
determined after 6 months of incuba-
tion of the waste-soil mixture. Parame-
ters studied included soil texture, soil
moisture, mineral nutrient amendments,
application rates, application frequency,
and temperature. Maximum degradation
rates were achieved with Norwood sandy
clay at a temperature of 30C. The great-
est rate of biodegradation per unit of
waste applied occurred when small ap-
plications were made at frequent inter-
vals. Addition of mineral nutrients effec-
tively increased the biodegradation rates
of both the refinery and the petrochemi-
cal sludges. The soil microcosm was
stimulated by small applications of
waste, but reduced numbers of microor-
ganisms were found when the applica-
tion rates exceeded 5 g/100 g of soil
for either sludge. Thus a comparison of
degradation rate and the microbial pop-
ulation indicates that the optimum appli-
cation rate for both wastes is 596 to
1096 (wt/wt).
Water-Soluble Constituents
A study of the water-soluble constitu-
ents of the refinery sludge was performed
using Bastrop sandy loam, Nacogdoches
clay loam, and Norwood loam. The sludge
was extracted with water, and the water-
soluble fraction (WSF) was partitioned
into benzene. Concentrated extracts were
applied to soil thin-layer chromatographic
(soil TLC) plates and eluted with deionized
water. Soil column leaching studies sup-
plemented the soil TLC, and the analyses
of column leachates and soil TLC were
performed using gas-liquid chromatog-
raphy.
Analysis of the WSF yielded largely
mono- and diaromatic hydrocarbons
such as phenols and naphthalenes. Most
of the WSF was highly mobile as a
group on soil TLC plates where the sol-
utes moved with the wetting front. Since
the waste constituents were concen-
trated to achieve resolution, the mobility
may have been a result of concentra-
tions in excess of the adsorption capacity
of the soil. No significant mobility dif-
ferences occurred among the three soils
because of the extreme mobility of the
WSF. Compounds of increased polarity
and molecular weight exhibited de-
creased movement in all soils. Soil
column results were inconclusive be-
cause of confounding by soluble soil
organic matter.
The low degradability and the potential
toxicity of the soluble compounds in
conjunction with their extreme mobility
when applied at high concentration sug-
gests that careful management of land
treatment sites will be needed to assure
that groundwater contamination does
not occur.
Field Mobility Study
The field mobility study was conducted
to evaluate the fate of two land-treated
oily wastes under conditions that dupli-
cated field conditions as nearly as pos-
sible. Controlled applications were made
of the refinery sludge and the petro-
chemical sludge to large undisturbed
soil monoliths under field conditions.
Soil samples were taken periodically to
determine degradation and residual or-
ganics, and leachate was collected and
monitored for potential groundwatpr con-
taminants. The same four soils were
used as in the phytotoxicity study.
Degradation rates for neither sludge
were measurably influenced by soil pH
or cationic distribution.
Soil texture profoundly affected the
depth of migration. Depth of penetration
was inversely related to the degradation
rates observed when fertility was not a
limiting factor. The deeper the migra-
tion, the slower the decomposition. With-
holding nitrogen fertilizer reversed the
trend and retarded decomposition in the
zone of incorporation. This observation
is an anomaly attributed to nutrients
leached from the surface profile and to
the attendant nutritive requirements re-
lated to the material balance within a
given depth interval. Hydrocarbon levels
within surface horizons were materially
greater than subsurface horizons requir-
ing a greater nutritive level.
Climatic factors were normalized over
soils because of the juxtaposition of the
field-installed lysimeters. Degradation
rates were diminished for both refinery
and petrochemical sludges over the win-
ter months corresponding to the lowered
soil temperatures.
Gas-liquid chromatogrphy (GLC) analy-
sis together with column chromatogra-
phy was an effective means of monitor-
ing the fate of complex waste hydrocar-
bons applied to soils.
Significant amounts of water moved
through all the soil profiles during the
study period, buy hydrocarbons were not
found in detectable concentrations in
leachate from any of the lysimeters.
Leachate collected as long as 2 years
after waste application remained free of
hydrocarbons.
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Conclusions and Recommen-
dations
Though oily sludges applied to land
may initially be phytotoxic and reduce
the yield of the vegetation that manages
to emerge, the toxicity diminishes with
time. Thus soils used for land treatment
of oily sludges can eventually be reveg-
etated.
A comparison of degradation rate with
the microbial population indicates that
the optimum application rate for both
the refinery and petrochemical sludges
is 5% to 10% (wt/wt).
The water-soluble compounds in both
sludges are potentially toxic, low in de-
gradability, and extremely mobile when
applied at high concentrations. Thus
careful management of land treatment
sites is recommended to prevent
groundwater contamination.
The mobility of waste organics and
their degradation products in soil are
not well understood. GLC analysis com-
bined with column chromatography can
be effectively used to monitor these
wastes in soils. Additional information
should be developed on the fate and
mobility of organic wastes in the soil so
that land treatment facilities can be de-
signed and managed to protect our
groundwater resources.
The full report was submitted in fulfill-
ment of Grant No. R805474013 by the
Texas Agricultural Experiment Station
under the sponsorship of the U.S. Envi-
ronmental Protection Agency.
K. W. Brown, L E. Deuel, Jr., and J. C. Thomas are with Texas Agricultural
Experiment Station, College Station, TX 7784O.
Robert E. Landreth is the EPA Project Officer (see below).
The complete report, entitled "Land Treatability of Refinery and Petrochemical
Sludges," (Order No. PB 83-247 148; Cost: $19.00. subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
•frUS GOVERNMENT PRINTING OFFICE 1983-659-017/7216
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