United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
-EPA
Research and Development
EPA-600/S2-81-027 Mar. 1981
Project Summary
Evaluation of Powdered
Activated Carbon for
Removal of Trace Organics at
New Orleans, Louisiana
Michael A. Epton and James F. Becnel
Several organic contaminants of
interest to the U.S. Environmental
Protection Agency (EPA) were found
in New Orleans' finished drinking
water. A bench-scale research pro-
gram designed to determine the effec-
tiveness of powdered activated
carbon (PAC) for removing these
organic contaminants was conducted
at the City's Carrollton Purification
Plant. This investigation consisted of
the design and execution of bench-
scale simulations of full-scale plant
operations (100 million gallons per
day conventional plant, utilizing lime
and cationic polyelectrolyte for partial
softening and coagulation of
Mississippi River water). The feasibil-
ity of using PAC treatment to reduce
the concentrations of the organics
found in the drinking water was then
evaluated. Control runs and full-scale
plant profiles were included to
compare PAC-treated and conven-
tionally treated water. Additional
studies attempted to evaluate the
effects of changing the point of
chlorine addition within the normal
treatment scheme and to correlate
nonspecific analytical parameters
(fluorescence, ultraviolet absorption,
and total organic carbon (TOC) con-
centration) with specific organics.
The effect of PAC treatment on the
concentration reduction of volatile
organic compounds, including trihalo-
methanes (THM); their precursors;.
and high molecular weight contami-
nants were evaluated. To select one
PAC for further investigations, four
commercially available PAC's were
studied. At dosages of 5, 50, and 500
mg/L, the PAC added to coagulated
settled water yielded average respec-
tive removals of 2%, 21 %, and 65% of
the 385 fjg/\. 5-day THM formation
potential found in the controls. Even
at the 500 mg/L dosage, only one of
the four tested PAC's was able to
reduce the formation potential to a
level below the EPA promulgated
maximum contaminant level of 0.10
mg/L in finished drinking water. The
PAC's did not reduce the levels of the
high molecular weight organic
contaminants studied.
The effectiveness of the one
selected PAC to reduce terminal THM
concentrations was basically the same
whether added to raw or to coagulated
settled water. Its addition to raw
water yielded 37% and 82% average
reductions of terminal THM concen-
trations at respective dosages of 50
and 500 mg/L; the concentration of
the controls ranged from 204 to 225
yg/L. The full-scale plant profiles
demonstrated that conventional treat-
ment alone effected a removal of 46%
of the THM formation potential.
Therefore, only the addition of 500
mg/L PAC effected more removal
than conventional treatment.
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This Project Summary was develop-
ed by EPA's Municipal Environmental
Research Laboratory, Cincinnati, OH.
to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Plant Profiles
Two full-scale plant profiles were
conducted, the first in September 1978
and the second in April 1979. The first
corresponded to the annual low-flow
period and the second to the peak-flow
period for the Mississippi River at New
Orleans. In each profile, sample
collection sites and times were de-
signed to enable a single portion of
water to be monitored as it progressed
through the plant process stream. With
this sampling procedure, the influence
of each treatment step on the levels of
organic contaminants present in the
water could be evaluated The profiles
indicated that although TOC concentra-
tions measured in the raw river water
varied greatly, the THM formation
potentials did not. Both profiles demon-
strated overall removals of 46% of the
approximately 700/ug/LTHM formation
potential that was found in the river
each time.
In each profile, the largest portion of
the 46% overall removal of THM forma-
tion potential occurred during coagula-
tion and primary settling (27% to 40%).
Rapid sand filtration, in both cases,
provided the smallest portion of the
overall removal (1% to 8% relative to the
controls). Atrazine, a high molecular
weight herbicide that was consistently
found throughout the study, was
removed by the overall plant treatment
processes in nearly the same propor-
tions (36% to 38%) during both profiles.
Raw water concentrations of Atrazine
were 1.36 and 0.67 /ug/L in the first and
second plant profiles, respectively.
Instantaneous THM concentrations
were zero in all samples before the
chlorine addition point. After chlorma-
tion, the instantaneous THM concen-
trations at all sample locations were
significantly higher for the warm
weather profile (September) than for the
(April) cool weather profile (i e , 118
versus 108//g/L on secondary settled
water and 145 versus 11S/vg/Lonfilter
effluent).
Evaluation of Four PAC's
Bench-scale evaluations of four
commercially available PAC products
were conducted in an attempt to
determine the most suitable one for
further study. These efforts met with
mixed success Because data on
removal of TOC and high molecular
weight compounds were very erratic,
data on removal of THM formation
potential became the principal consid-
eration in selecting one PAC for further
studies.
Effect of Adding PAC
With the use of the selected PAC,
bench-scale studies were conducted to
determine whether adding PAC to raw
water would yield better removal of
THM formation potential than adding
PAC to coagulated settled water. A 500-
gallon reserve of raw river water was
constantly agitated in a stainless-steel
tank, and portions were withdrawn, as
needed, to test the various treatment
alternatives Following PAC dosage, the
percent removals for raw water and for
coagulated settled water were similar
(Table 1).
Table 1. Removals of THM
Formation Potential
PAC Dosage
fmg/Ll
Raw Water:
Control
5
50
500
A verage
THM Forma-
tion Potential
(vg/Ll
213
196
135
38
A verage
Removal of
THM Forma-
tion Potential
<%>
—
10%
37%
82%
Coagulated Settled Water:
Control 333 —
5 359 0%
50 206 38%
500 69 81%
Effect of Altering Chlorination
Would instantaneous THM concen-
trations be reduced if the plant's chlor-
mation scheme were changed from its
present form of two doses (with one
added after primary settling and the
other after secondary settling) to a
single dose after secondary settling (just
prior to filtration)? Results from two
bench-scale studies indicated that
single-step chlonnation yielded lower
instantaneous THM concentrations
This was expected since chlorine/
contact times were much shorter than
those of the double-step chlorination (at
both locations).
Confirmation of Analyses
In the course of the project, five
analyses each of river and finished
water were run by capillary column gas
chromatography. Flame lonization
detection and mass spectrometry were
used for confirmation. Seven volatile
compounds and two high molecular
weight compounds of interest were
identified in the plant finished water
(Table 2).
Table 2. Nine Organic Compounds
and Their Concentration
Ranges Found in Finished
Water
Concentration
Compound Range ffjg/L)
Cloroform
Benzene
Bromodichloromethane
Dibromochloromethane
Toluene
Xylene
J, 2 - Dichloroethane
Atrazine
Di (2-ethylhexyl) Phthalate
36.3 -
0 -
3.1 -
0
0
0
0 -
014-
0.29-
123
0.45
29.0
6.1
0.33
.38
1.5 (
5.02 *
0.55
The full report was submitted m ful-
fillment of Grant No R804404by RoyF
Weston, Inc , and the University of New
Orleans under subcontract to the New
Orleans Sewerage and Water Board
under the sponsorship of the U.S.
Environmental Protection Agency.
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Michael A. Epton and James F. Becnel are with the Sewerage and Water Board
of New Orleans, New Orleans, LA 70165.
Benjamin Lykins and Jack DeMarco are the EPA Project Officers (see below).
The complete report, entitled "Evaluation of Powdered Activated Carbon for
Removal of Trace Organics at New Orleans, Louisiana," (Order No. PB
81-161 853; Cost: $9.50, 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 Officers can be contacted at:
Municipal Environmental Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
0 U.S. OOVEflNMENT PRINTING OFFICE. IMt -757-OU/7026
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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