vVEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81-043 Apr 1981
Project Summary
Removal of Phenolic
Compounds From Wood
Preserving Wastewaters
Bruce K. Wallin, Arthur J. Condren, and Roy L. Walden
Laboratory and pilot-scale studies
were undertaken to develop
economically feasible technologies
for the treatment of wastewaters from
wood preserving operations. Of prime
concern was the removal of phenol
and its chlorinated derivatives, in
particular, pentachlorophenol.
Screening analysis of the wastewater
indicated that pentachlorophenol was
the only chlorinated derivative con-
sistently present in concentrations of
approximately 100 mg/l.
Treatment technologies investi-
gated for the treatment of these
wastewaters included:
1. adsorption;
2. biological oxidation;
3. chemical oxidation;
4. coagulation;
5. extraction; and
6. pH adjustment.
Each of the above, alone or in
combination, was capable of yielding
a measurable reduction in the concen-
tration of total phenols and penta-
chlorophenol in the untreated waste-
water.
Two technologies yielded consis-
tently high levels of treatment:
pH adjustment of the waste-
water, followed by adsorption
with bentonite clay and final
polishing by the polymeric
adsorbant, XAD-4; and
2. pH adjustment of the waste-
water, followed by extraction
with a mixture of #2 fuel oil and a
co-solvent such as still bottoms
from amyl alcohol production.
Total annual operating costs for
systems treating a typical 10,000 gpd
of wastewater were calculated to be
$40,000 and $23,600, respectively,
for the two aforementioned technol-
ogies.
This report was submitted in fulfill-
ment of Contract No. 68-03-2605,
Work Directive No. 2, Parts 1 and 5,
by the Edward C. Jordan Co., Inc.,
under the sponsorship of the U.S.
Environmental Protection Agency.
This report covers the period Novem-
ber 20, 1978 to May 20, 1980, and
work was completed as of May 20,
1980.
This Project Summary was develop-
ed by EPA's Industrial Environmental
Research Laboratory. Cincinnati, OH.
to announce key findings of the
research report that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
at back).
Introduction
The U.S. Environmental Protection
Agency has been involved in extensive
investigations of toxic compounds being
discharged from industrial facilities.
Primary emphasis has been on the 65
"priority" pollutants, which are con-
tained in the Settlement Agreement of
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1976 and in the Clean Water K
1977 (PL 95-217). Phenolics and U,
chlorinated derivatives are a part of thiL
group and are commonly found in the
wood products industry's wastewater
streams.
The initial objective of this study was
to evaluate the treatability of 2,4,6-
trichlorophenol, parachlorometacresol,
2-chlorophenol, 2,4-dichlorophenol,
and pentachlorophenol in the wood
products industry's wastewater The
wood preserving industry was selected
for this program because wastewater
from wood preserving facilities is
usually low in volume but high in con-
centrations of chlorinated phenolics. A
chemical screening of the wastewater
revealed that it had a high organic con-
tent, but more significantly, it contained
pentachlorophenol in concentrations
exceeding 100 mg/l. The program's
focus then shifted primarily to penta-
chlorophenol to the virtual exclusion of
all else, since only trace levels of other
chlorinated phenolics were found.
In conjunction with the treatability
aspect, the program was intended also
to explore atypical pretreatment
schemes that would reduce chlorinated
phenolics, namely pentachlorophenol,
in typical wood preserving wastewater
to levels at which the wastewater could
be discharged to a POTW without
causing an upset Owing to constraints
imposed by time and financial resources,
it was not the objective of this program
to investigate all aspects of each treat-
ment scheme (e g., residual catalyst
after PCP removal, toxicity of the
removal concentration, adsorptive
capacity of the regenerated resin). The
objective here was also not to improve
the phenol-contaminated wastewater
to drinking water quality, nor was it
within the bounds of the study to make
any conclusions concerning the toxicity
of the residual pentachlorophenol con-
centration in the wastewater that would
be discharged to the POTW.
The physical/chemical properties of
pentachlorophenol, as distinguished
from those of phenol, were important in
considering the pretreatment systems
which would be capable of reducing
concentrations to an acceptable level.
Pentachlorophenol consists of a ben-
zene ring (CeH6) with all six hydrogen
sites substituted by one hydroxyl group
(OH) and five chlorine atoms (CU). The
resulting compounds, CeCUOH, is mildly
acidic, boils at 309°C, and is soluble in
50°C water at 30 mg/l Oils or emul-
c
.o
•8
.0
CU
(J
to
ID
Oc
t3
tb
i/i
<0
5)
b
ol
2,4-Dichlorophenol
a 2,4,6-Trichlorophenol
0 Pentachlorophenol
Figure 1. Phenolic resistance to
biodegradation (2).
sions in wastewater can provide a
"carrier" effect, allowing pentachloro-
phenol to far exceed its normal solubility
in water. Table 1 summarizes the
physical properties of several phenolic
compounds. Figure 1 presents phenolic
structures for several compounds.
A review of available literature
assisted the investigators in identifying
treatment techniques foi investigation.
Investigations were divided into two
phases, preliminary bench-scale treat-
ability studies and an evaluation of
batch treatment techniques.
Unlike phenol, which is quite
unstable and easily oxidized either
chemically or biologically, pentachloro-
phenol is stable and resistant to oxida-
tion In some instances, though, when
wastewater containing pentachloro-
phenol in concentrations which a
biomass can tolerate is run through a
biological treatment system, pentachlo-
rophenol is adsorped onto the biofloc.
Disposal of the sludge, now laden with
pentachlorophenol, then presents a
hazardous waste problem. Alkyliniza-
tion of the sludge, a relatively common
practice, would more than likely release
the pentachlorophenol intotheenviron-
ment If the sludge were incinerated,
2,3,7,8-tetrachlorodibenzo-p-dioxm, a
thermal degradation product of penta-
chlorophenol, could be released into the
atmosphere.
These rather ominous prospects
make such treatment techniques as
solvent extraction and batch polymeric
resin adsorption, two schemes investi-
gated during this study, more appealing
from the standpoint of avoiding the
creation of a hazardous waste problem
while improving water quality
In the preliminary bench-scale
studies the investigators traveled to a
wood preserving facility on the west
coast to evaluate treatment technol-
ogies, described m the literature,
designed to lower pentachlorophenol
concentrations Treatment schemes
tested included pH reduction, acid
cracking, chemical coagulation, chemi-
cal oxidation, ultrafiltration, resin
adsorption, and solvent extraction
After conducting the preliminary
bench-scale studies, the investigators
reported to representatives of the EPA.
Table 1. Physical Properties of Several Phenolic Compounds
Compound
Phenol
o-Chlorophenol
m-Chlorophenol
p-Chlorophenol
2,4-Dichlorophenol
2,4,6-Trichlorophenol
Pentachlorophenol
o-Cresol
m-Cresol
p-Cresol
p-Chloro-m-Cresol
2. 4, 6- Trichloro-m-Cresol
Boiling Point
°C
182
173
214
220
210
246
309
191
201
202
196
265
Solubility in H2O
mg/l @ 25° C
93,000
28.000
26.000
27,000
4,500
900
30(50°C)
25.000
26,000
23,000
insol.
si. sol.
Ka x 10'°
1.1
77.0
16.0
6.3
Large
Very Large
Very Large
0.63
0.98
0.67
Unknown
Unknown
Ka = thermodynamic acid dissociation constant
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At this time, mid-course corrections
were suggested It was suggested that
the program emphasis be shifted to
focus on only those pretreatment
systems that would both lower pervta-
chlorophenol concentrations to levels
acceptable for discharge to a POTW and
be economically feasible for wood pre-
servers
To meet the revised criteria, pretreat-
ment schemes had to be both efficient
and economically feasible, which
essentially eliminated from considera-
tion the more elaborate treatment
technologies (e.g., reductive degrada-
tion, electrochemical oxidation, ion
exchange, rotary vacuum filtration with
activated carbon) The effectiveness of
these cannot be denied, but the cost of
installing and operating any one of them
makes it economically impractical for
wood preservers.
Batch treatment systems were set up
at the southern facility to provide some
indication of which methods were cost
effective. Technologies tested at the
southern facility included batch biolog-
ical treatment, chemical and polymeric
coagulation, resin adsorption, acid
cracking, bentonite clay, solvent extrac-
tion, and filtration. As at the west coast
facility, a combination of these were
tested The size of the batch treatment
reactors ranged from several litersto 50
gallons, depending on the pretreatment
system being tested.
Summary and Conclusions
Processes for the treatment of waste-
waters from two wood preserving
facilities were investigated at the
laboratory and pilot scale levels In-
cluded were various chemical, physical,
and biological operations selected
specifically for the removal of phenol
and its chlorinated derivatives. Of the
treatment technologies investigated,
two systems consistently lowered the
concentrations of pentachlorophenol in
the wastewater from 100 mg/l to less
than 1 mg/l.
In the first system, the wastewater
was first acidified to a pH of 4.0 ± 0.1,
then bentonite clay was added. A
polymeric adsorbant, amberlite XAD-4
was used in the final polishing process.
In the second system a mixture of No. 2
fuel oil and a cosolvent (amyl alcohol
still bottoms) was used to extract penta-
chlorophenol from the waste stream.
Reductions were consistently in excess
of 99 percent. Since No. 2 fuel oil is used
often in the preserving process, as it
was at this facility, it is conceivable that
a facility could operate this extraction
process without incurring any
additional chemical expense, except
possibly for the cosolvent. Trials with
No. 2 fuel oil alone yielded removal ef-
ficiencies in the vicinity of 97 percent,
which may be high enough to allow the
wastewater to be discharged to a
POTW. For both systems to function
consistently, the wastewater first had to
be subjected to free oil separation and
flow equalization.The following
summarizes the findings of other inves-
tigations, based on reductions in total
phenol and/or pentachlorophenol con-
centrations.
pH Adjustment
Lowering the pH of the wastewater
with sulfuric acid was found to induce
the formation of colloidal material. Sub-
sequent removal of this colloidal mate-
rial resulted in slight reductions in total
phenol concentrations as measured by
the modified lowry procedure described
in the Project Report. Pentachloro-
phenol concentrations, however, were
consistently reduced from approxi-
mately 100 mg/l to less than 20 mg/l.
Biological Oxidation
Biological oxidation was not found to
be an effective treatment technique be-
cause bioadsorption rather than bio-
transformation was found to be the
primary removal mechanism. Removal
rates continued to diminish as the
adsorptive capacity of the biomass was
approached
Chemical Oxidation
At high doses, chlorine yielded sub-
stantial reductions in the compounds of
concern. Hydrogen peroxide, on the
other hand, had little effect. The high
chemical demand observed precludes
the use of chemical oxidation as a viable
treatment alternative
Coagulation
Coagulation with alum, ferric
chloride, and/or polymers resulted in
modest pollutant reductions. These
reductions were not deemed sufficient
to justify coagulation as a sole treat-
ment technology.
Applicability of Technologies
In turning now to the applicability of
the programs' findings to the wood pre-
serving industry as a whole, it should be
understood that the utility of any single
pretreatment option is contingent upon
both the volume and chemical make-up
of the waste stream. Because wood
preserving processes are so variant,
each facility must be evaluated in terms
of its preserving process, its waste
stream, and the capital available for
investing in a pretreatment system The
systems devised for wood preservers in
connection with this study would prob-
ably not be transferable to the leather
tanning industry or to the paper indus-
try, not because a No. 2 fuel oil - cosol-
vent mixture would not remove penta-
chlorophenol from leather tanning or
paper industry effluent just as
effectively as it would from wood pre-
serving wastewater, but because
neither of these industries uses No. 2
fuel oil in its production process (non-
combustion) as do some members of the
wood preserving industry The
advantage of the fuel oil extraction
process is that the pentachlorophenol
can be removed from the wastewater
without creating an additional waste
and without bringing large capital and
operating expense to bear on the wood
preserver.
Recommendations
If results obtained during these
investigations are to be verified, a
continuously flowing pilot-scale system
must be established. Because this study
was done on a quick response basis
with limited financial resources,
researchers could not investigate all
aspects of each pretreatment scheme
(e.g., residual catalyst after pentachlo-
rophenol removal, toxicity of removal
concentrations, utility or necessity of
catalysts other than amyl alcohol still
bottoms). Instead, the project provided
an overview of the many economically
achievable approaches to removing
pentachlorophenol from wastewater
and identified two systems especially
successful in lowering pentachloro-
phenol concentrations in wood pre-
servers' wastewater to levels that
would allow it to be discharged to the
POTW without causing an upset.
: US GOVERNMENT PRINTING OFFICE 1981 757-012/7060
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Bruce K Walhn, Arthur J Condren, and Roy L Wa/den are w/th the Edward C
Jordan Co , Inc , Portland, ME 0417 2
Donald L. Wilson and Brian West fall are the EPA Project Officers (see below)
The complete report, entitled "Removal of Phenolic Compounds from Wood
Preserving Wastewaters, "(Order No PB81 -172637, Cost $12 50,subjectto
change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone 703-487-4650
The EPA Project Officers can be contacted at
Industrial Environmental Research Laboratory
U S Environmental Protect/on Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Protection
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