United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
i\\
Research and Development
EPA-600/S2-83-060 Oct. 1983
&ERA Project Summary
Wet Oxidation and Ozonation
of Specific Organic Pollutants
C. Robert Baillod and Bonnie M. Faith
This study was undertaken to assess
the applicability of wet oxidation and
ozonation to the treatment of waste-
water containing five specific pollu-
tants typical of the 114 organic com-
pounds included on the EPA priority
pollutant list. The pollutants, phenol; 2-
chlorophenol; 4-nitrophenol; 1,2-di-
methylphthalate and 1,2-dichloroethane
were selected for study on the basis of
their occurrence, structure, water
solubility, and volatility. The ability of
the wet oxidation and ozonation proc-
esses to oxidize these pollutants in
aqueous solution was studied using
batch laboratory-scale experiments. In
the case of wet oxidation, efforts were
made to determine the influence of
temperature, pH value, catalyst, and
reaction time on the degree of pollutant
destruction. In addition, an economic
evaluation was made of a wet oxidation
process designed to treat a refractory
petrochemical waste stream. For ozon-
ation, information was developed on
the degree of pollutant destruction as
influenced by ozone dosage and contact
time. For both processes, the fate of
pollutants were studied by measuring
products of incomplete oxidation. The
ozonation results showed that 1,2-
dichloroethane was rapidly volatilized
and the remaining four pollutants could
be removed to less than detectable
concentrations, in 5 to 10 minutes, at
initial ozone usage rates of 3.9 to 5.9
moles of ozone per mole of compound
removed. The wet oxidation results
indicate that all five pollutants could be
oxidized under the conditions of tem-
perature (204° C to 260° C) and oxygen
pressures studied. The removal rates for
each substance depended on tempera-
ture, pH, and catalyst and were ade-
quately described by semi-empirical,
first-order kinetics. For both processes.
a significant amount of organic carbon
remained in solution after the specific
pollutants had been removed. This
carbon was slowly oxidized and con-
sisted primarily of organic acids and
aldehydes. A wet oxidation process was
designed to treat a 37.8 l/min (10
gal/min) of a high COD (70,000 mg/l)
petrochemical waste which was inhib-
itory to a biological treatment process.
A detailed economic evaluation of this
process indicated that an investor's
interest rate of 20 percent could be
attained at a treatment charge of $69
per 1000 gallons ($17.81 per cubic
meter) or $0.16 per pound of COD
removed ($.35 per Kg COD removed).
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory. Cincinnati, 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).
Experimental Results
Semi-batch ozonation experiments
showed that:
Phenol, 2-chlorophenol, 4-nitrophenol
and 1,2-dimethylphthalate could be
removed to less than detectable con-
centrations (in 5 to 10 minutes)
through ozonation at initial ozone
utilization ratios of 3.9 to 5.9 moles of
ozone per mole of specific pollutant.
However, the removal rates were
limited by the rate of ozone mass
transfer. During the initial stages of the
ozonation experiments, reaction in the
diffusive film enhanced the mass
transfer rate.
A significant amount of total organic
carbon remained in solution after the
specific pollutants had been removed
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and this carbon was slowly oxidized.
Increasing the initial pH from 6 to 10: a)
increased the specific pollutant removal
rate for phenol and 4-nitrophenol, but
decreased the rate for 2-chlorophenol,
and b) decreased the total organic
carbon removal rates for phenol and 2-
chlorophenol.
Batch wet oxidation experiments showed
that:
All five specific pollutants studied could
be oxidized under the conditions of
temperature and oxygen pressured
studied. The removal rates depended
on the substances and on temperature
and were adequately described by
semi-empirical first-order kinetics.
Alkaline pH levels markedly increased
the rate of specific pollutant removal
and only slightly increased the rate of
total organic carbon removal. However,
over the one-hour reaction period,
alkaline pH levels gave markedly lower
removals for total organic carbon and
chemical oxygen demand.
Cupric ion acted as a catalyst and
increased the rate and extent of
removal of specific pollutants and total
organic carbon.
A significant amount of total organic
carbon remained in solution after the
specific pollutants had been removed
and this carbon was slowly oxidized.
More than three-fourths of this carbon
was accounted for by low molecular
weight acids, acetaldehyde and acetone.
Bioassay tests using Daphnia magna
indicated that wet oxidation achieved
90 to 99 percent detoxification for
phenol, 2-chlorophenol and 4-nitro-
phenol.
Although acetic acid was a major end
evident during ozonation. Conversely,
oxalic acid was a relatively minor product
during wet oxidation, but was very
significant in ozonation.
C. Robert Baillod and Bonnie M. Faith are with Michigan Technological University,
Houghton. Ml 49931.
Ronald J. Turner is the EPA Project Officer (see below).
The complete report, entitled "Wet Oxidation and Ozonation of Specific Organic
Pollutants," (Order No. PB 83-254 060; Cost: $16.00, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
GOVERNMENT PRINTING OFFICE 1983-659-017/7202
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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