United States
Environmental Protection
Agency
Solid Waste And
Emergency Response
(OS-220)
Directive 9200.5-252FS
November 1989
&EPA Innovative Technology
Slurry-Phase Biodegradation
TECHNOLOGY DESCRIPTION
Slurry-Phase Biodegradation (SPB) is
potentially effective in treating various or-
ganic contaminants. It involves the com-
mingling of excavated contaminated soil
and sludge with bioactive microorganisms
mass concentration. The residence time in
the reactor varies with the soil or sludge ma-
trix, the physical and chemical nature of the
contaminants, contaminant concentrations,
and the efficiency of the bio-oxidation reac-
tions. Upon completion of the process, the
slurry is dewatered and the treated soil is re-
Figure 1: Schematic Diagram of a Typical Slurry-Phase
Biodegradation Treatment Facility
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in a mobile batch reactor or an in-ground re-
actor. A typical treatment facility is shown
in Figure 1.
Prior to treatment, large-grained con-
stituents such as stones and rubble are
physically removed from the waste. The
remaining waste is mixed with water to
create the desired slurry composition (50
weight percent solids maximum). The slurry
water may be contaminated ground water,
surface water, or another water source that is
brought on-site. The slurry is then mechani-
cally agitated in a reactor chamber which
creates arid maintains the appropriate ambi-
ent environmental conditions (e.g., nutrient
supply, temperature range, oxygen content,
and pH level) needed for maximum bio-oxi-
dation of the target contaminants. Microor-
ganisms may be added initially to seed the
reactor and/or atHfd continuously during
treatment to maintain the appropriate bio-
effectiveness of this treatment on general
contaminant groups is provided in Table 1.
Factors limiting treatment effect! veness
include the inherent biodegradability of the
target contaminant, dissolved oxygen con-
tent, operating temperature, soil/sludge char-
acteristics, and the presence of reaction-in-
hibiting compounds such as heavy metals,
chlorides, or even biodegradation by-prod-
ucts. Site-specific characteristics and their
potential impact on the SPB process are
listed in Table 2.
Variables governing the biodegradation
process and resulting effectiveness can vary
greatly between laboratory and actual field
conditions. Therefore, in order to accurately
model the effectiveness of SPB treatment, it
is necessary to conduct bench- or pilot-scale
tests at each site of interest.
Table 1
Effectiveness of Biodegradation
Treatment on General Contaminant
Group* for Soil and Debris
deposited on-site.
Advantages of SPB include the follow-
ing: biodegradable organic compounds may
be transformed into non-toxic compounds
or mineralized; elaborate or sophisticated
equipment is not required; and batch opera-
tion may allow more accurate mass-balance
determinations. The major disadvantages
are that the treatment time can be relatively
slow and SPB is ineffective against inor-
ganic wastes. Applications and limitations
of the SPB technology are discussed below.
STTE CHARACTERISTICS AFFECTING
TREATMENT FEASIBILITY
SPB has the potential to (treat a wide
range of contaminants such as pesticides,
fuels, creosote, pentachlorophenol (PCP),
polychkvinatedbiphenyls(PCBs), and some
halogeriatedvolatiieorganks. Theprojected
Treatablllty
Groups
HOogmMd votattn
HatogmMd Mntvotota
Non-htiogwoMd
PC84
DtodnMFurm
Oiganccymta*
Effectiveness
Insufficient DJU
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Tabto2
Slta-Spacif te Characteristics and Impacts on
Sturry-Phas* Blodegradalton Treatment
QianctMtetfet
Impacting Proecu
FwaiMHty
VariaMawact*
competitor)
Waur sofabilty
Tamparatur* outslda
15* -70*0 rang*
Nutrtanl oaf Idancy
pH outslda
4.8 • 8.5 ring*
Mcrobial popuftUJon
Waurdtochargas
tndalrtmfcttmt
Praaanea at «t»vn»d
• HMvymauli
• Highly cntorlnattd
organic*
• Soma pasttddaa,
ftaroicidM
• inorganic sans
SoiMiudga composlton
(la.. c*y. humus)
R*Mon*for
ItA^mftHmt
rOfVmW
•MkotA^A
•TrtfMcx
by variation In bbtoglctl aaMy
Conumkwntt win tow lobbMy art
hardarioblodagrada
proosaa
La/gar, mom dVarta mterobW
population peasant In mis rang*
Lack of adaquata nutrlants (or
Motoglcal aaMy
InhMlen el Biological actMty
InaufNcrant population racufts In low
Wodagradallon rala*
Potantw anvtoraMntaf andtor
rtaatt Impact*
pamcte tta tor propar starry
cofflpoatlon
Can b* highly toxic lo
Clay and hufflus aovo oonianvnanii
ffloraUgMy
Action* to
IfnJmto
IH1D9CT8
Norw;
or tongv •^>o
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