NCD980602163_19800912_Warren County PCB Landfill_SERB C_Biological Methods for the In Situ Cleanup of Oil Spill Residues-OCR

l
Preprint
BIOLOGICAL METHODS FOR THE IN SITU CLEANUP OF
OIL SPILL RESIDUES
Or. Curtis S. McDowell, Howard J. Bourgeois, Jr., Thomas G. Zitrides
Po lybac Corporation, Allentown, Pennsylvania
Presented at:
CO-OP 1980
Coastal and Off-shore Oil Pollution Conference
The French/American Experience
Fairmount Hotel
New Orleans, Louisiana
September 10, 11, 12, 1980
,
INTRODUCTION
Current techniques for dealing with land-or beach-based spills of oil
or oily materials generally rely on the removal of contaminated soil or sand
to a secured landfill. This approach, however, is impractical for very large
spills or where a spill occurs in an area remote from such a landfill. To
complicate matters, many land-based spills contaminate nearby surface waters,
creating a separate and more severe problem. Chronic historical contamination
with oily materials, such as might occur in a railroad maintenance yard, can
yi e 1 d both contaminated surf ace water runoff and groundwater contamination.
Recent developments in applied industrial microbiology have made in situ
biological clean-up of spills and spill residues a safe, low-cost alternative
to transport of contaminated soil. This approach can, in some instances, be
us ed to deal with the surface water problem. Fermentation technology has led
to the development of stable microbial strains with enhanced capabilities for
degrading crude and refined petroleum products (Tracy and Zitrides, 1979),
pesticides and herbicides (Zitrides, 1978), and .other organic chemicals
(Walton and Dobbs, 1980). This technology has been used for several years in
flow-through industrial wastewater treatment systems for treatment of complex
organic wastes from refineries and chemical plants (McDowell and Zitrides,
1979).
This new approach to spill clean-up involves the application of one of
several commercially available, dried mutant bacterial formulations with known
specificity for the hydrocarbon or hydrocarbon mixture in question. If the
spill involves a hydrophobic substance such as a hydrocarbon mixture, a biode-
gradable emulsifier is also applied to enhance the interfacial contact between
the aqueous phase and the hydrocarbon phase in order to accelerate the rate of
clean-up. A balanced mixture of nitrogen and phosphorus is applied as nutri-
1
ents. The actual methodology required to contact the microorganisms with
the contaminants depends on the nature of the spi 11; however, a 11 methods
rely on aerobic oxidation and thus require and adequate supply of oxygen for
success.
ADAPTED MUTANT MICROORGANISMS
Adapted, mutant microorganisms which can degrade complex organics and
hydrocarbons have been developed using techniques which are well established
in the field of microbiology (Pelczar and Reid, 1972). For example,
techniques of adaptation and mutation are routinely used in the fermentation
industry to produce mutant strains which enhance the production of antibiotics
(Elander, 1976, and Calan, 1970). Essentially, mutant strains reduce the time
required to produce a given quantity of antibiotic, thereby increasing
production. Increased production of penicillin was achieved by these
techniques, for example (Merrick, 1976).
Adaptation and mutation of selected parent strains involves several
steps. Several strains which are known to degrade a specific organic chemical
or functional group are exposed to successively increasing concentrations of
that substrate. The fastest growing strains, and those which are least
inhibited by high concentrations of substrate, are carefully isolated and
further adapted. Microorganisms showing the highest growth rates are then
irradiated to induce genetic changes in the cell. Genetic alterations
further increase the growth rate and fix the desired biochemical capability.
Adaptation of the strains at high concentrations of a preferred substrate
can induce increased production of the specific enzymes required to degrade
that substrate. This increased capacity for producing a specific enzyme is,
in many cases, achieved at the expense of the microbe I s ability to produce
other enzymes, however. Therefore, an adapted mutant put back into an envi-
2
ronment where the preferred substrate is not as readily available or is some-
times unavailable, may have a disadvantage in competing with less specialized
organisms for non-preferred, but available, substrates. When the preferred
substrates are present, however, the mutant wi 11 prol iterate and generally
will out-grow strains indigenous to the natural biological population. (In
terms which are most familiar to the biochemical engineering community,
selection, adaptation, and mutation produce organisms which have a higher
maximum growth rate, Umax' and/or a lower saturation constant Ks).
Microorganisms having the capacity to degrade complex organic chemicals
such as pentachloropheno l (Kirsch and Etzel, 1973), monosubstituted phenols
and benzoic acids (Haller, 1978), and carboxymethyl tartronate (Barth et al.,
1978) are frequently isolated and identified. Similarly, strains having
generalized capabilities for the aliphatic and aromatic hydrocarbons which
make up petroleum and, having an ability to function under saline1 or non-
saline2 conditions, have been developed using the adaptation-mutation techni-
ques similar to those used in the fermentation industry. These classes of
organic compounds include such important chemicals as industrial surfactants,
crude and refined petroleum products, pesticides and herbicides, chemical
intermediates, and solvents (Krupka and Thibault, 1980). FIGURES 1-5
illustrate the performance advantage of mutant strains over the parent strains
in degrading halo-phenols, cyanides, aryl halides, aliphatic amines, and
detergents, respectively.
ENGINEERING CONSIDERATIONS FOR IN SITU CLEAN-UP
Several factors are critical to the engineering design of a
1PETROBACR Mutant Bacterial Hydrocarbon Degrader
2PHENOBACR Mutant Bacterial Hydrocarbon Degrader
3
Fl GURE 1
HALOPHENOLS DEGRADATION TIME
BY PARENT ANO MUTANT PSEUOOMONAS IGI 309C.
2.4.6-TRIBROMOPHENOL
(, ,nr ?ll() mq I
2.5-0IBROMOPHENOL
C, ,nt ?00 m4 I
2 4-0IBROMOPHENOL
Cone ?O<l m4 I
p-BROMOPHENOL
(.()ll(' ?llO tnq I
m-BROMOPHENOL
C,1111 ?tltl1114 I
o-BROMOPHE NOL
C•><>r ?Ollmq I
PENTACHLOROPHENOL
0 (., >nc ;>O() >114 I .z 6 2 4 6 TRICHLOROPHENOL
ll-t·, "'l ;>on mq , .-3 2.3.S-TRICHLOROPHENOL
~llllC ,1()( I mg I
;., . S -OICHLOROPHE NO
Cone ?001114 I
2.4 OICHLOROPHENOL
C,,nc 20() nlQ I
'
I
I
I
I
I
I
I
I
I
111() fl
1 ( )(I I)
l (l(l {)
'. ()() . [ l
--
1· ,. T 1'~~! ~~ . '
'l ' ll
l(l() ll , .. ., l.:
IHi' ()
1., t · ll
110() l)
1()1.) p
1100 0
IL)()·[)
1()0 ' C,
l100", D
>DO : .. ll
t>-CHLOROPHENOL
C,,nc 200 mg ·I
______________ 100 .. D
100· .D
m-cHLoAoPHeNoL ~■ml■■Hllic>Ci":"o ______ __,1()(J .o Cone 200 mo I Ill 1 00 . ll
o-CHLOROPHENOL
Cnnc ?()() mq I -----~100 · ll
100 l)
PHENOL 100 · D Cone 500mg 1 ... -~,oo~ .... ~D ....... .J ·,
u 30 60
TIME IN HOURS
I
I
I
I
I
14 I l
',H (l
1 . D
?ti ll
100· D
no D
l?O
CJPARENT
MICROORGANISMS
-MUlANT
MICROORGANISMS
0 -RING DISRUPTION
POLYBAC
CORPORATIO~,
505 Park Avenue
NY• NY• 10022
[phone]
FIGURE 2
CYANIDES DEGRADATION TIME
BY PARENT AND MUTANT MICROORGANISMS 10 209C.
HCN __________________________ P_.1 6C.l)
Cone?~ mgil 1100· •. o
NaCN 1--------------------------r,Pl 58".D
Cone 2~ mc;i1I 1100~.D
DICHLOROPHENYL t--------------------------.19::'\.D ISOCYANATE -■■■1'iwJ5'" _________________ __,
Cone !>OOmg•I 1 100,.D
PHENYL ISOCYANATE ------------------------190'\.0 Cone 500 mg1I -■■■fi1ooocr·.::i.0S-________________ _
PHTHALONITRILE
Cone 500 mg1I
________________ Pl 68",0
• -• .:. 'ii ~ • • • 100·,.o
PHENYLNITRILE 95 ;.O Cone 500 mg,I ·••■■r1iooo:0°:;;:i,.0D ________________ _
PHE NY LACETONITRILE
Cone 500 mg/I
... 100-'\.""D _______________ __.
METHACRYLONITRILE' 93\.D Cone 500mg/l ~-...,100,.,,...
0
,,""0 _________ __.
0 10
D PARENT
MICROORGANISMS
P · MICROORGANISMS
Pul!:>ONED •
20 JO
TIME IN HOURS
-MUTANT MICROORGANISMS
0 · DISRUPTION
40
8S'7..0
50
POLVBAC
CORPORATION
505 Park Avenue
NY• NY• 10022
[phone]
HElACHLOROBENZENE
Cone ;,(JU mq I
FIGURE 3
ARYL HALIDES DEGRADATION TIME
BY PARENT AND MUTANT PSEUDOMONAS SP ~ 30-C.
o•~.D o·w
1245~ETRACHLOROBENZENE
Conr. ?00 mq:1
30't 0
80'1.0
0 z -. i=.. ci'.
~
0 w
1.2 3.4-TRICHLOROBENZENE
Cone ?00 mq · I
t 3.5-TRICHLOROBENZENE
Cone. ?OO mq I 10<1. D
33",.0
14 ·i.o
I 781.0
I 2 4-TAICHLOROBENZENE -■■!Jl■lll■■■■-ioch'.c,--------------'' g;,-~.O Cone ?00 r ,q I 100·1.D
1.2.3 TRICHLOROBENZENE
Cone ?O(l m4 I
_________________ 187'~0
p-OICHLOROBENZENE
Cone ?00 m4 I
100·:..o
---------------100--..0
m OICHLOROBENZENE •n■■llll■ioc~,------------' 100~ .. o Cone ?00 mq , 1 OO~ .D
o-OICHLOROBENZENE f l('O'i D
Cone ?0() mq 'I •ml'l■llll■11,oo~·.::'E,[)1 ______ __.
I
MONOCHLOROBENZENE I 10C ;.D
Cu"c ?UO m-, I 11■:J··vl.Y~HXl>m'~,00 _______ ..,
l
0 JO
D PARENT
MICROORGANISMS
•
6C•
TIME IN HOURS
-MUTANT MICROORGANISMS
90
0 · RING DISRUPTION
POLYBAC
CORPORATION
505 Park Avenue
NY• NY• 100~2
[phone]
TRI-N-ALL YLAMINE
Cone ;>OOmq I
D1 -N-ALL YLAMINE
Cone 700 m911
N-ALL YLAMINE
Cone 200 m911
N-DODECYLAMINE
Cone 200 mg · I
N-HEXYLAMINE 0 Cone 200 mg/I z ::> ~ N-AMYLAMll,IE
~ Cone 20'J mg•I
0 N·BUTYLAMINE u Cone 200 mg/I
TRI-N-PROPYLAMINE
Cone 200 mq:1
Dl-N-PROPYLAMINE
Cone 200 rr.o , 1
N-PROPYLAMINE
Cone 200mg/l
TRIETHYLAMINE
Cone 200mg11
FIGURE 4
ALIPHATIC AMINES DEGRADATION TIME
BY PARENT AND MUTANT AEROBACTER SP IU 30'"C.
••• llfi1'3l0o>T·;.OD----------------J 41 :, 0
67 ', D ••• fii,oom· •. or---------------'
·•Fc100XY·:;:J,.o:, ___________ ___. 78 [)
0 30 60 90
TIME IN HOURS
120
WPARENT
MICROORGANISMS
-MUTIINT
MICROORGANISMS
0 · DEGRADATION
POLVBAC
CORPORATION
505 Park Avenue
NY• NY• 10022
[phone]
FIGURE 5
BIOOEGRAOATION OF ABS-LAS SUBSTRATES BY ADAPTED
AND MUTATED PSEUOOMONASsp IN WORNE MEDIA AT 25"C
,.
13
2 ,,
~ II
! ,o
~ '
~ . a ... z i :~ u • r
A SOO•UW "LK>L 8£ .. Z£N( SULl()NATf
0 soo,ur,o ALKYL 11£ .. ll .,£ SULl()NAT(
• ~ll01Ut.4N000f{'tl BtN/fNf ~11\FO~AT(
• ~oo,uu Al l>UOI C ., Ill"" ... su, • 0"• I(
I 1 J t ~ I 7 I I 10 11 11 1) U I~ 16 17 19 tt ;.'0 ')I
TIME IN DAYS
•
OXYGEN UPTAKE BY UNADAPTED. ADAPTED. ANO
MUTANT PSEUOOMONAS IP IN WORNE MEDIA
CONTAINING O.OI SOLUTION OF SODIUM
ALKYL BENZENE SULFONATE AT 2s·c
"' It ~ ::. ~ u j
l ... "' c( ... A. :,
0
110
'10
IIO ·~ ,,o
,:,o
,10
110
100
10
110
'IO
to
~
«l
30
10
10
MUTANT
,o 10 :,o AO !10 10 ,o 10 to ,00110120130uo •~•60
TIME IN MINUTES
POLVBAC
CORPORATION
505 Park Avenue
~y •NY• 10022
[phone]
system for in situ biodegradation of a land-or beach-based spill:
1. Biodegradability of the material
2. Solubility of the material
3. Quantity of material spilled
4. Environmental contamination and site geo 1 ogy
5. Nutrient requirement
6. Oxygen requirement
7. Temperature effects
BIODEGRADABILITY OF THE MATERIAL
As mentioned earli~r, mutant bacterial formulations have been developed
to degrade the most complex organic materials including industrial surfactants,
crude and refined petroleum products, pesticides and herbicides, and solvents.
The supplier of these products3 maintains an up-to-date library of information
on the relative bio-degradability of a wide range of organic chemicals by
various mutant strains (FIGURES 1-5). This information makes a simple task
of choosing the proper formulation.
Although the biodegradability of crude petroleum under laboratory condi-
tions is well documented, the source and nature of the spilled material (e.g.
heavy crude vs. light crude) and the condition of the spill or spill residue
(e.g. oxidized vs. unoxidiz~d, salt contaminated vs. uncontaminated) will
affect the efficiency of biodegradation. Under these circumstances, it is
necessary to undertake a laboratory investigation of the kinetics of bio-
degradation of the material by the various available bacterial products.
3Polybac Corporation, 1251 South Cedar Crest Boulevard, Allentown,
Pennsylvania
4
Modern, automated respirometric techniques have been developed to establish
the fol lowing:
1. biodegradation rates (kinetics)
2. potential for inhibition of these rates under various conditions
3. oxygen and nutrient requirements
4. temperature effects
The simplest form of such a laboratory program can be completed 24 hours from
the time a sample is received. The sample may be a one-gallon container of
the "pure" organic or it may be a one-cubic foot samp 1 e of contaminated soi 1.
The laboratory test program is designed to suit the needs of the client, both
from a technical standpoint and an economic standpoint.
SOLUBILITY OF THE MATERIAL
A factor often overlooked in discussions of this topic is the solubility
of the material in question. Recent research on hydrocarbon uptake by micro-
organisms has reaffirmed that microorganisms consume .2..!l.lx soluble organic
molecules and that when they are p 1 aced in the presence of an i nso 1 ub 1 e
material , they actually synthesize and secrete a natural emulsifier to first
pseudo-solubilize the hydrocarbon thus making it available for consumption
(Goma et al., 1976). This concept has led to the development and subsequent
application of synthetic biodegradable emulsifiers4 for the clean-up of spills
of hydrophobic materials such as crude and refined petroleum products. These
emulsifiers rapidly pseudo-solubilize the hydrocarbons and therefore assist in
their rapid assimilation by the mutant microorganisms which exist in the
aqueous phase.
4POLYBACR E Biodegradable Emulsifier
5
QUANTITY OF MATERIAL SPILLED
This information may or may not be easy to obtain depending on the
circumstances of the spill, however, it is useful in two areas:
1. application of a material balance at the spill site
2. determination of the nutrient requirement for biodegradation
For example, consider a roadside spill of 5,000 gallons of home-heating oil
into a drainage ditch. If 4,500 gallons of the oil is removed 11 intact11 by
pumping, then it is known that 500 gallons remain. This 500-gallon deficit
may not be all that apparent in a surface view of the contaminated soil,
which indicates it may be presenting itself as a groundwater contamination
problem.
ENVIRONMENTAL CONTAMINATION AND SITE GEOLOGY
A good understanding of the extent of contamination and the geology of
the site is essential in choosing the proper approach to clean-up. Important
questions include:
1. Has groundwater contamination already occurred?
2. Is there a direct geologic link between the surface and the
ground aquifer?
3. Have surface waters been contaminated?
4. What is the potential for contaminating surface waters during the
clean-up?
These quest ions and a myriad of others are best answered by a spi 11 control
contractor with expertise in surface and subsurface hydrology. Often an
emergency sampling program is re qui red to answer quest ions on the extent of
contamination and the possibilities for migration.
6
NUTRIENT REQUIREMENT
In the previous example of the heating oil spill, the 500-gallon deficit
quantity may be a candidate for in situ biodegradation. Bacteria, like all
forms of 1 ife, require nitrogen and phosphorus as nutrients. Most soils do
not contain sufficient amounts of nitrogen and phosphorus for thorough biode-
gradation of an oil spill. Therefore, even after inoculation with the
appropriate bacterial strains, success is not guaranteed without a supplemental
supply of nitrogen and phosphorus. A simple technique for calculating
nutrient requirements for a given spi 11 1 i es in an understanding of the
nitrogen and phosphorus content of the bacterial ce 11 in re 1 at ion to its
carbon content:
. C : N : P = 100 : 15 : 3
If it is assumed that all of the carbon in the 500 gallons of heating oil
winds up as bacterial cells, then one can easily calculate the nitrogen and
phosphorus which must be used in any clean-up scheme. A product is now
available which contains the proper balance of nitrogen and phosphorus
required in a form readily available for microbial uptake5.
OXYGEN REQUIREMENT
The mutant microorganisms used in spill clean-up perform optimally under
aerobic conditions where they use oxygen as the terminal electon acceptor in
oxidation of organic molecules. Many microorganisms can also consume organic
molecules under anaerobic conditions where oxygen is not available, however,
the metabo 1 i c pathways used are much 1 ess efficient and thus have other
adverse side effects (e.g. the production of toxic or noxious end products).
5POLYBACR N Biodegradable Nutrients
7
Spi 11 s often contaminate just the upper layer of soil. Even in these
situations, an oxygen limitation on degradation rate can occur. The problem
of oxygen supply is easily solved by tilling the soil as is common in
agricultural practice and by insuring that the site does not become unundated
with water. In actuality, the oxygen used by the microorganisms must first be
dissolved in the interstitial water droplets of the soil since the viable
microorganisms are present in the aqueous environment only. For this reason,
it is important that the contaminated soil be kept moist (but not soaked)
during the clean-up.
In cases of groundwater clean-up with mutant bacterial strains, the
contaminated water is often pumped out of the ground from one or more wells to
a tank where aeration and nutrient addition occur. The water is then pumped
back into the ground at a point "upstream" with regards to the groundwater
flow. Thus, a closed loop for biological treatment has been developed. De-
pending on the tank configuration, a number of mechanical or diffused aeration
devices are commercially available.
TEMPERATURE EFFECTS
Microorganisms generally experience a decrease in activity or growth
rates as the temperature drops. Mutant microbes are designed to provide the
optimal biodegradation rate possible at any given temperature. A rule of
thumb states that microbial growth rates double for every 10 degree centigrade
increase in temperature. FIGURE 6 illustrates the temperature dependency of
the biodegradation of crude oil by a commercially-available mutant bacterial
formul at ion6. Note that biodegradat ion does occur, al though at a reduced
rate, at a temperature as low as 5 C.
6PETROBACR Mutant Bacterial Hydrocarbon Degrader
8
100
90
...J
0 80
LU 0 ::, 70 er u
~ 60 0 z Q so I-C 0
c:( 40 er
" I.II 30 0
0
CD 20 -!?.. 0
10
FIGURE 6
CRUDE OIL BIODEGRADATION TIME
10 20 30 40 so 60 70 80 90 100 110 120 130
TIME IN HOURS
WATER 99 83'
MEDIUM GRAVITY LOUISIANA CRUDE OIL 10,
PETROJIAC Ill .os,
PETROBAC E .o,,
PETROBAC . 01 •.
140
POLVBAC
CORPORATION
505 Pai·k Avenue
NY• NY• 10022
[phone]
CASE HISTORIES
Fuel Transfer Depot -Oil Spill
An excellent example of in situ biological treatment was the recent
clean-up of oil-contaminated soil at a fuel transfer depot with about twenty
underground tanks. Poor housekeeping practices during loading operations
over the years at this site, located in a middle Atlantic state, had led to
contamination of the soil surface over a one-acre site. The clean-up was a
relatively straightforward application of this technology. First, the soil
was 11 tilled11 vigorously with conventional farm equipment to insure an
adequate supply of oxygen and good microorganism-hydrocarbon contact. The
proper nutrient balance was insured through the application of 500 pounds of
a commercially-available nutrient source. 7 Next, an aqueous solution con-
taining 80 pounds of a commercially-available biodegradable emulsifier8 was
sprayed over the contaminated soil. Finally, the area was inoculated with 50
pounds of a dry, mutant bacterial hydrocarbon degrader9 following a two-hour
rehydration period in warm water. The area was tilled regularly and reinocu-
lated over the summer mohths. The soil was kept moist naturally by the rain.
OIL SPILL -UNITED KINGDOM
Another excellent example is the ELENI V incident. The Greek tanker,
ELENI V, carrying heavy bunker fuel oil, was cut in two by a French vessel in
the North Sea and oi 1 started coming ashore near Great Yarmouth on the 7th
May. The Borough Engineer of Great Yarmouth was contacted on May 9th and
gave the go-ahead to biologically treat a section of the beach. Supplies of
7POLYBACR N Biodegradable Nutrients
8POLYBACR E Biodegradable Emulsifer
9PETROBACr Mutant Bacterial Hydrocarbon Degrader
9
a commercially-available bacterial formulation1O arrived on May 15th at Great
Yarmouth. With the aid of four County Council workmen and a portable fire
pump, the beach was sprayed with sea water and then treated with a solution of
mutant microorganisms with nutrients and emulsifiers added on May 16th. The
sea temperature was 9° C. and the air temperature was 12° C. The beach was
sprayed with sea water twice a day.
Within six days, the oil at the high tide level began to break up into
smaller patches and the lower part of the beach was clear of oil. Previousl y ,
soft patches where the oil had soaked into the sand and shingle, had firmed
up considerably. The air temperature was still low at 11° C. and the sea
temperature was 10° C. Generally, the weather had been cool and overcast
during the intervening six days.
The control, uninoculated section of the beach had unfortunately been
physically cleared of oil patches, but there was an area at the north end of
the untreated section which had only partly been cleared and this was used for
a comparison with the inoculated portion of beach. Sixteen days after inocu-
lation, trenches were dug into the sand at intervals to see the extent of oil
removal below the surface. The remaining soft patches were found to have a
layer of oil some 411 below the surface, but below this the sand was clear of
oil. The hard sections were clear of oil in both areas, but the untreated
area still had patches of oil below the surface.
REGULATORY ENVIRONMENT
Under current law, the use of additives at a beach spill site is under
the discretion of the Regional Response Team Coordinator, generally the Coast
Guard in the case of spills in navigable waters. Acceptance by the EPA of any
lOPETROBACR Mutant Bacterial Hydrocarbon Degrader
10
such additives prior to use is mandated under Annex X of the National Oil and
Hazardous Substance Pollution Contingency Plan. The bacterial products
described in this paper have been accepted by the EPA under Annex 10 and have
been used in several inland in situ spill clean-up operations of both crude
and refined petroleum products (Walton and Dobbs, 1980).
11
REFERENCES
Barth, E. F., Tabak, H. H., and Mashni, C. I. (1978) Biodegradation Studies of
Carboxylmethyl Tartronate. Municipal Environmental Research Laboratory, EPA-
600/2-78-115.
Calan, C. F. (1970) Improvement of Microorganisms by Mutation, Hybridization
and Selection. In Methods in Microbiology (Norrir, J. R. and Ribbons, D. W.)
Volume 3A, 435-459. Academic Press.
Elander, R. P. (1976) Mutation to Increase Product Formation in Antibiotic
Producing Microorganisms. American Society of Microbiology, 517-552.
Goma, G., Al Ani, D. and Pareilleux, A. (1976) Hydrocarbon Uptake by Micro-
organisms. Fifth International Fermentation Symposium, Berlin.
Haller, Helen D. (1978) Degradation of Mono-substituted Benzoates and Phenols
by Wastewater. Journal WPCF, 2771-2777.
Krupka, M. J. and Thibault, G. T. (1980) Biological Methods for the Detoxifi-
cation of Hazardous Organic Materials, National Conference on Hazardous and
Toxic Waste Management, New Jersey Institute of Technology, June 3, 4 and 5,
1980, Newark, New Jersey.
McDowell, C. S. and Zitrides, T. G. (1979) Accelerating the Dynamic Response
of Bacterial Populations in Activated Sludge Systems, 34th Annual Industrial
Waste Conference, Purdue Univiersity, West Lafayette, Indiana, May 8-10,
1979.
12
Merrick, M. J. (1976) Hybridization and Selection for Penicillin Production
in Aspergillus Nidulars--A Biometrical Approach to Strain Improvement. 2nd
International Symposium on Genetics of Industrial Microorganisms, 229-242.
Academic Press.
Pelczar, Michael, J., Jr., and Reid, Roger D. (1972) Microbiology. 3rd Ed.,
218. McGraw-Hill, New York.
Tracy, K. D. and Zitrides, T. G. (1979) Mutant Bacteria Aid Exxon Waste
System, Hydrocarbon Processing, October, 1979.
/
Walton, G. C. and Dobbs, D. (1980) Biodegradation of Hazardous Materials in
·' ' Spill Situations, Proceedings of the 1980 National Conference on Control of
Hazardous Materials Spills, Louisville, Kentucky.
Zitrides, T. G. (1978) Mutant Bacterial for the Disposal of Hazardous Organic
Wastewaters, Pesticide Disposal Research and Development Symposium (EPA),
Reston, Virginia, September 6-7, 1978.
13