ENVIRONMENTAL HEALTH SERIES
Water Supply
and Pollution Control
EVALUATION OF THE USE
OF ACTIVATED CARBONS
AND CHEMICAL REGENERANTS
IN TREATMENT OF WASTE WATER
AWTR-11
U. S. DEPARTMENT OF HEALTH
EDUCATION, AND WELFARE
Public Health Service
-------
Advanced Waste Treatment
Research Publications
Although over-all guidance of AWTR research projects
is provided by the AWTR Program, the results obtained, opin-
ions expressed, and conclusions reached by the contractors are
theirs and are not necessarily endorsed by the Department of
Health, Education, and Welfare. Except for editorial review
and abridgments as necessary, these reports appear as re-
ceived from the contractors.
Report
Number
AWTR-1 Summary Report, June 1960 - December
1961 * W62-9
AWTR-2 Preliminary Appraisal of Advanced
Waste Treatment Processes W62-24
AWTR-3 Ultimate Disposal of Advanced-Treatment
Wastes 999-WP-3
Part 1. Wet Oxidation
Part 2. Incineration
AWTR-4 Waste-Water Renovation 999-WP-4
Part 1. A Design Study of Freezing
and Gas Hydrate Formation
Part 2. Feasibility Tests of
Freezing
AWTR-5 Contaminant Removal from Sewage Plant
Effluents by Foaming 999-WP-5
AWTR-6 Cost of Purifying Municipal Waste Waters
by Distillation 999-WP-6
AWTR-7 Advanced Waste Treatment by Distillation 999-WP-9
(Continued on inside back cover. )
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EVALUATION OF THE USE
OF ACTIVATED CARBONS
AND CHEMICAL REGENERANTS
IN TREATMENT OF WASTE WATER
R. L. Johnson, F. J. Lowes, Jr.,
R. M. Smith, and T. J. Powers
for
The Advanced Waste Treatment Research Program
Basic and Applied Sciences Branch
Robert A. Taft Sanitary Engineering Center
A report submitted in fulfillment of a contract between the
Public Health Service and Dow Industrial Service. (Contract
Number SAph 76290 for the period December 26, 1960 to
February 28, 1961. ) Submitted December 1962.
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Division of Water Supply and Pollution Control
May 1964
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The ENVIRONMENTAL HEALTH SERIES of reports was
established to report the results of .scientific and engineering
studies of man's environment: The community, whether urban,
suburban, or rural, where he lives, works, and plays; the air,
water, and earth he uses and re-uses; and the wastes he pro-
duces and must dispose of in a way that preserves these natural
resources. This SERIES of reports provides for professional
users a central source of information on the intramural re-
search activities of Divisions and Centers within the Public
Health Service, and on their cooperative activities with State
and local agencies, research institutions, and industrial organ-
izations. The general subject area of each report is indicated
by the two letters that appear in the publication number; the
indicator's are
WP - Water Supply
and Pollution Control
AP - Air Pollution
AH - Arctic Health
EE - Environmental Engineering
FP - Food Protection
OH - Occupational Health
RH - Radiological Health
Triplicate tear-out abstract cards are provided with
reports in the SERIES to facilitate information retrieval.
Space is provided on the cards for the user's accession number
and additional key words.
Reports in the SERIES will be distributed to requesters,
as supplies permit. Requests should be directed to the
Division identified on the title page or to the Publications
Office, Robert A. Taft Sanitary Engineering Center, Cincinnati
26, Ohio.
Public Health Service Publication No. 999-WP-13
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ADVANCED WASTE TREATMENT
RESEARCH PROGRAM
The Advanced Waste Treatment Research Program of the
Public Health Service has two ultimate goals: One is to help
abate our Nation's growing water pollution problems, and the
other, more startling in concept, is to renovate waste water
for direct and deliberate re-use.
Conventional water and waste treatment practices have
little or no effect on many simple inorganic salts and permit an
ever-increasing number and amount of highly complex, syn-
thetic organic wastes to contaminate drinking water supplies.
If we are to protect these water supplies for the future, it is
mandatory that new technologies for water and waste treatment
be developed.
Advanced Waste Treatment may be looked upon as a two-
step process: (1) Separating concentrated contaminants from
the purified water "product, " and (2) disposing of the concen-
trated contaminants in a way that will render them forever
innocuous. This "permanent disposal" of separated wastes is
essential so that useable surface or ground waters will not be
contaminated and so that the same contaminants need not be
removed again and again from water supplies.
In one step, then, advanced waste treatment, i.e., water
renovation, could alleviate both water pollution and water
supply problems - problems of increasing concern both in this
country and in the rest of the world. The importance of ad-
vanced waste treatment was recognized by Congress in its 1961
amendments to the Federal Water Pollution Control Act (Public
Law 87-88). This act directs the Secretary of Health, Educa-
tion, and Welfare . .to develop and demonstrate practicable
means of treating municipal sewage and other water-borne
wastes to remove the maximum possible amounts of physical,
chemical, and biological pollutants in order to restore and
maintain the maximum amount of the Nation's water at a
quality suitable for re-use. "
It is too early to predict accurately the cost of advanced
waste treatment technology, but the need is inevitable. Because
of population increase and industrial expansion, we are ap-
proaching the time when our rivers and streams will no longer
be able to assimilate our wastes and when there will be no
more developable supplies of fresh water. Whatever the cost
of this technology, one thing is certain - it must be the very
lowest science and engineering can achieve. Anything more
will impose an inexcusable, perhaps intolerable burden on our
country's economic growth and on its ability to compete in
tomorrow's world.
iii
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CONTENTS
Page
Abstract vii
Introduction 1
Phase 1. Studies on Waste-Water Adsorption by-
Activated Carbon 4
Experimental Procedures 5
Materials and Equipment 5
Source of Conventionally Treated Waste Water. 5
Pilot Plant for Producing Activated-Carbon
Feed 5
Pumping Equipment 6
Activated Carbons 7
Methods 8
Evaluation of Commercially Available,
Activated Carbons 8
Analytical Techniques 13
Chlorides 13
Chemical Oxygen Demand 13
Alkylbenzenesulfonate 13
Suspended Solids 14
Results 14
Discussion 14
Phase 2. Regeneration Studies 16
Experimental Procedures 16
Materials and Equipment 16
v
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Page
Activated Carbon 16
Ftegenerant Application Apparatus ...... 16
Evaluation of Chemical Oxidants 16
Methods 16
Activated-Carbon Exhaustion 16
Preparation of Oxidant Feed Stocks 18
Analytical Procedures 18
Results 20
Discussion 28
Phase 3. Additional Hydrogen Peroxide Studies 29
Experimental Procedures 29
Materials and Equipment 29
Methods 30
Results 31
Discussion 33
General Discussion of Total Project Phases 34
Conclusions 36
Economic Considerations 36
References 45
vi
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ABSTRACT
The capacities of six activated carbons for the soluble
organics in filtered secondary effluent were obtained by use of
a continuous-flow, column-type test. Results varied from 7 to
13 grams COD per 100 grams of carbon. Because of the manner
in which the test was carried out, only the carbon with the
smallest capacity was loaded to the maximum extent possible.
The chemical regeneration of exhausted carbon was in-
vestigated by use of nine inorganic oxidizing agents. Only
hydrogen peroxide was capable of restoring measurable adsorp-
tion capacity after more than two cycles of exhaustion and re-
generation. The economic feasibility of chemical regeneration
is not promising.
vii
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EVALUATION OF THE USE OF ACTIVATED CARBONS
A-IN D CHEMICAL REGENERANTS
IIS TREATMENT OF WASTE WATER
Introduction
Current water shortages and the prospect of more have
prompted investigations into sources of potable water other
than those represented by fresh-water supplies from lakes,
streams, and underground. Present municipal use of fresh
water is estimated at 150 gallons per capita per day while only
30 years ago this figure was 100 to 120 gallons per capita per
day. This growth in municipal use plus an increase in popula-
tion and the tremendous increase also expected in industrial
usage make it evident that our water requirements of the future
are certain to be much greater than those of the present. This
growth in water requirements must be faced with the knowledge
that our fresh-water supply is a relatively fixed amount. In
view of these stark predictions, it becomes almost imperative
to use our available water over and over again. Re-use of
water by industry is presently practiced in several sections of
the country. Chanute, Kansas, for example, re-used waste
water after treatments during a 5-month drought in the winter
of 1956; Lyndon, Kansas, re-used waste water during the fall
of 1956.6
Unfortunately, with every re-use of water, contaminants
are added that resist conventional processing. These are
called "refractory" contaminants. Pollution of natural waters
by these refractory materials has attained a certain scientific
and public notoriety. The ever-increasing industrial expansion
in plastics, dyes, organic chemicals, insecticides, fertilizers,
and synthetic fibers has obviously been responsible for many
of these pollutants.
The effect of many of these contaminants in respect to
the re-use of water is not known. Fish kills that result from
pollution of natural waters are, of course, well known and
highly publicized. Foaming of natural water, resulting from
contamination with surfactants, has also received much public-
ity. The effects of many other refractory materials, especially
over long periods of time, are not known. Tolerance levels
1
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2
USE OF ACTIVATED CARBONS
have not been established for many of the compounds that can
reach surface waters. For example, of over 500, 000 synthe-
sized organic chemicals, only several dozen have been deter-
mined safe by the Food and Drug Administration for addition to
foods. ^ Many of these refractory materials give no indication
of their presence and many cannot be completely removed from
water supplies or waste waters by conventional waste treatment
methods. * ' ^3. ^4, ^5 Hurwitz, et al. ^ have followed
the assimilation of alkylbenzenesulfonate (ABS) in receiving
streams and found a very slow and incomplete removal by nat-
ural waters. Culp and Stoltenberg 10 have reported synthetic-
detergent concentrations in the Marais des Cygnes River as
great as 6. 6 milligrams per liter below the waste-water treat-
ment plant outfall at Ottawa, Kansas. Although records indicate
no human illness associated with organic chemical pollution in
the past, this is no guarantee that there will be none in the
future.
According to Middleton, 28 many different kinds and quan-
tities of synthetic organic chemicals are being detected in both
raw and treated water. He further states that repeated expo-
sures over long periods of time to even small concentrations
of these materials may represent a public health threat of
major proportions. Usually, the first recognized indication of
pollution is the development of tastes and odors in treated
water, but many of the compounds that produce these tastes and
odors have not been identified except in broad classifications.
Middleton et al. 27 ancj others, ' > 33 by using activated
carbon, have attempted to identify these compounds and other
organics present in surface and treated waters. Phenolic,
antibiotic, sugar beet, distillery, slaughterhouse, and pulp and
paper wastes are known sources of some tastes and odors. 2
Activated carbon has been used since 1927 for removal of
tastes and odors in water. 3 it is usually applied, in a water
slurry, at a rate of from 20 to 40 pounds per million gallons,
though doses have varied from 2 to 1, 800 pounds per million
gallons. 34 Harrison has described in some length the
installation and operation of the Bay City, Michigan, water
plant where powdered carbon slurries are used. Recent work
Q 7 2.0 *31
by Vaughn et al., ° Lieber, u and Renn and Barada*31 has
shown that synthetic detergents can be removed from waste
water and raw water by the use of activated carbon. A carbon
dosage of 240 milligrams per liter has removed 97 percent of
a 20-milligrams-per-liter synthetic-detergent concentration
from raw water. 37
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AND CHEMICAL REGENERANTS
3
Complete descriptions of the use of activated carbon in
water treatment for the removal of tastes and odors are avail-
able. 9, 17 Eckenfelder 12 recently showed that activated
carbon could be used to remove detergents satisfactorily from
a public automatic-laundry waste.
The preparation of activated carbon involves two basic
procedures, char formation and activation. In some cases,
both operations are done in one step while in others the char is
transported and activated in a separate reaction. Char forma-
tion is accomplished with hardwood by heating and drying it to
decrease its weight by 15 to 20 percent through water loss.
Activation is then carried out by slowly increasing the temper-
ature to 250°C where it is held until tars distill off. Finally,
the temperature is increased to 400°CJ and calcium, magnesium,
or zinc chloride are added. Carbonization will take place in a
temperature range of 400 to 900°C within which activated carbon
is produced.
The removal of organic materials from water and waste
water by activated carbon is accomplished by adsorption.^
18, 22 ]y[any other adsorbents are commercially available but
have had limited application in this field.
In water treatment for the removal of tastes and odors,
powdered, activated carbon is almost universally used. In this
type of treatment the carbon is used only once and then discard-
ed. Where powdered-carbon dosages would be prohibitive in
cost, granular, activated carbon may be used. Granular car-
bon is used until it becomes exhausted, and then it is regener-
ated. Regeneration can be accomplished by the elution of the
adsorbed material by a suitable solvent, by heating, or by
other chemical means.
When activated carbon is used for the removal of free
chlorine, after excess chlorination, it is used as a reducing
agent as well as adsorbent. ^ The free chlorine is converted to
chloride ion. The behavior of various oxidizing agents with
activated carbon has been determined by Behrman and Gustaf-
son. The carbon reacts in one of three ways:
1. It adsorbs and decomposes the oxidizing agent;
2. it adsorbs the oxidizer, which reacts with the carbon;
3. it adsorbs the oxidizer with no reaction of either the
carbon or oxidizer.
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4
USE OF ACTIVATED CARBONS
No published data have been found concerning the specific
use of activated carbon in waste-water treatment for removal
of soluble organic matter. Consequently, there is a lack of pub-
lications on chemical oxidation regeneration of activated carbon
exhausted by waste water.
The investigations described here have three objectives:
1. Determine the capacity of carbon to adsorb materials
from a municipal waste water that has been subjected
previously to conventional methods through the
secondary-treatment process.
2. Determine if commercially available chemical oxi-
dants can regenerate an activated carbon that has
exhaustively adsorbed soluble municipal-waste
materials.
3. Describe some of the conditions necessary for
optimum performance of the best chemical oxidant
resulting from a regeneration of exhausted, activated
carbon.
PHASE 1.
STUDIES ON WASTE-WATER ADSORPTION
BY ACTIVATED CARBON
The purpose of this phase of the project, was to determine
the capacity of activated carbon to adsorb soluble materials
from wastes previously subjected to conventional treatments.
If feasible, comparative evaluations of several activated
carbons would be made to select a single carbon for further
experimentation.
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AND CHEMICAL REGENERANTS
5
Experimental Procedures
MATERIALS AND EQUIPMENT
Source of Conventionally Treated Waste Water
The Midland Waste-Water Plant serves the City of Mid-
land, Michigan, and treats approximately 15 percent of the
domestic waste water of The Dow Chemical Company. The daily
flow rate ranges from 2. 1 to 3.5 million gallons. These figures
are based on the average daily flow and do not include ultimate
high or low figures. Waste water gets only primary treatment
here. The suspended solids coming into the plant average, dur-
ing a year (1961), 171 milligrams per liter as calculated on daily
samplings. The suspended solids as effluent from the plant to
the Tittabawasee River average 77 milligrams per liter. The
BOD average of the raw-waste-water influent to the plant is 178
milligrams per liter; the effluent BOD to the river, 108.
Pilot Plant for Producing Activated-Carbon Feed
Since the plant utilizes only primary waste-water treat-
ment, an activated-sludge pilot plant model was fabricated to
obtain secondary effluent. It was designed to simulate the nor-
mal behavior of large-scale, conventional treatment processes.
Operation was controlled so that the analytical data obtained
would compare favorably with the results of a full-scale second-
ary-treatment plant. Careful adjustments of air, influent flow
(primary effluent), and sludge wasting were maintained to pro-
duce adequate oxygenation, flocculation, and COD removal for
the batch collection of treated secondary waste. To provide
such a waste, a small, activated-sludge-settling tank unit of
6. 5-gallon capacity was constructed by following the design of
Ludzack's unit as used at the Taft Center. This unit was
operated at a flow rate of 60 to 70 milliliters per minute and
was supplied 15 psi compressed air, at the rate of 2 to 2. 5
liters per minute.
At this hydraulic rate, minimum detention time in the
unit was about 6.5 hours, with approximately 5. 25 hours in the
aeration zone. In view of the strictly domestic nature and com-
parative weakness of Midland waste water, this detention time
should produce a stable effluent. The mixed-liquor suspended
solids were maintained at about 1,000 milligrams per liter by
daily wasting of mixed liquor.
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6
USE OF ACTIVATED CARBONS
The activated sludge was produced by operating the unit
at full capacity on primary-waste-water effluent for several
weeks. Analyses of suspended solids were made sufficiently
often to determine the increasing mixed-liquor suspended solids.
Performance data of the unit are listed in Table 1.
Table 1. PERFORMANCE DATA FOR PILOT SCALE
ACTIVATED-SLUDGE UNIT
Days
Suspended sol
operation
mg/liter
0
27.5
1
289
3
165
4
150
5
105
8
316
10
595
11
270
12
410
15
620
17
1,100
After 17 days of operation, the activated-sludge unit sta-
bilized satisfactorily and operated without problems throughout
the experimental program. This pilot scale, secondary-waste-
water treatment system was further supplemented by a tertiary
filter, consisting of graded gravel and one layer of very fine
sand, and finally of glass wool.
Approximately 70 percent removal of COD from raw waste
water was accomplished by passage through the Midland primary-
treatment plant, activated-sludge pilot plant unit, and tertiary
filter. The remaining 30 percent COD provided the source of
polluted influent for the activated-carbon experiments.
The tertiary-treated waste water was collected and stored
in a 40-gallon drum. In a 48-hour period, an ample supply of
tertiary waste water was made available for a thorough study of
the adsorptive properties of a carbon type. Figure 1 illustrates
diagrammatically the waste treatment system utilized through-
out the program.
Pumping Equipment
Piston pumps, manufactured by A & F Machine Products
Company, were used to pump the tertiary-effluent waste water
through the activated-carbon columns. Multiple heads on these
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AND CHEMICAL REGENERANTS
7
pumps permitted the comparative evaluation of as many as six
activated-carbon columns during one exhaustion experiment.
The flow rates of these pumps could be accurately regulated for
a flow of from 10 to more than 100 milliliters per minute.
ANAEROBIC
SLUDGE
GRAVEL
MIDLAND
RAW SEWAGE
SAND FILTER
SIPHON
FLOW TIMER 0-200 cm3 min
SECONDARY SEWAGE TREATMENT
PILOT PLANT
GLASS WOOL
SAND
SEDIMENT WELL
STONES
AEROBIC ACTIVATED SLUDGE
AERATION STONE
SLUDGE DRAIN
A
TERTIARY SEWAGE
COLLECTION TANK
15 psi AIR SUPPLY
AIR COMPRESSOR
_ TERTIARY SEWAGE
TO MULTIPLE-HEAD
~ " PISTON PUMPS
Figure 1. Midland sewage treatment plant and pilot plant unit.
Activated Carbons
The following commercially available, activated carbons
were selected for potential adsorptive abilities to remove COD
from tertiary waste water:
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8
USE OF ACTIVATED CARBONS
Activated-carbon
identity
Mesh size
Manufacturer
Pittsburgh
Barnebey Cheney
Cliffs Dow
Atlas
American Norit
West Virginia
8 x 30
8 x 12
10 x 30
12 x 20
8 x 20
Pittsburgh Chemical Company
Barnebey Cheney Company
Cliffs Dow Chemical Company
Atlas Chemical Company
C- 190 x 30
Ft. W. Greeff & Co., Inc.
W. Virginia Pulp & Paper Co.
METHODS
Evaluation of Commercially Available, Activated Carbons
Although it is well known that activated carbon can adsorb
many organic materials from aqueous solutions, experimental
work to determine the adsorptive capacity of activated carbon
for the soluble organics present in secondary-treatment plant
effluents has not been performed or at least has not been report-
ed in the literature. It was necessary, therefore, to evaluate
the various carbons for their adsorptive capacity on these ma-
terials ,
At the time of the writing of this contract, it was stipu-
lated that all work on the carbons would be carried out on an
actual effluent from a secondary-treatment plant. This posed
many problems owing to the extreme variability of such a waste
stream. By taking this variability into account, it was conclud-
ed that at least a composite, of 24 hours' duration, would have
to be used for the studies of adsorptive capacity. Moreover,
since most individual constituents in such a stream are present
only in minute amounts, only a general determination of organ-
ic matter could be utilized for evaluating the capacity. Such a
test is the COD (Chemical Oxygen Demand). The sensitive
modification, for dilute samples, was used throughout this
study.
Initial studies were made to determine the adsorptive ca-
pacity of the previously mentioned carbons for the soluble
organics in the tertiary-waste-water effluent (sand-filtered,
pilot plant effluent). By adsorptive capacity is meant the per-
cent, by weight> of the carbon's weight that it could adsorb
without exhaustion. These studies were made with 1-inch-
diameter columns.
The use of columns was based on the phenomenon that an
organic "front" moves downward through a bed and that total
exhaustion is not accomplished until the total bed has had this
"front" pass through it. The use of batch systems was con-
«PO BII-74*-*
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AND CHEMICAL REGENERANTS
9
sidered for this phase of the evaluation. The carbon would
then, however, be only in equilibrium with the organic constit-
uents in the waste, while still having adsorptive capacity remain-
ing. It is also quite difficult, if not impossible, to scale up to
column conditions from batch observations. Since this entire
study was geared to conditions that would approximate actual
field operation, it was felt that this was a valid decision..
The columns used for this phase of study were 100-milli-
meter burets. The carbon, generally 15 grams, was placed in
the buret on a bed of glass beads, and the feed was percolated
downward through this column. The feed rate was 30 cubic
centimeters per minute, which amounts to 30 to 60 bed volumes
per hour based on carbon density. Grab samples of feed and
effluent were taken at frequent intervals (15 to 60 minutes) for
the first 4 hours and approximately once every 8 hours there-
after until the study was completed. The flow that occurred
between the sampling periods was recorded. A study was termi-
nated when the influent and effluent COD were within 5 milligrams
per liter of each other, or when 180 liters of waste had been
passed through the bed.
It is common knowledge that the organic content of waste
water varies hour by hour; hence, the composition of effluent
from a plant treating waste water would also vary. For instance,
the chloride concentration would vary when thawing snow would
carry salt into the combined sewer system; ABS would be high
on certain days; COD would be high about 1:00 p.m. and lowest
about 3:00 a.m.
It was felt that we could eliminate much of this variability
if we used composited effluent as feed. This was the reason for
collecting effluent to use for this study rather than accept the
actual tertiary effluent on a continuous basis from the unit.
A definite problem that arose later as a result of this decision
was the gradual degradation of the influent COD concentration
owing to biological action in the stored waste. This degradation
was accelerated as the waste was stored at room temperature.
It was obvious that sand filtration had not eliminated the micro-
organisms that caused this COD reduction. A solution to this
problem in future studies would be the pasteurization or steril-
ization of the waste prior to storage. This degradation amounted
to as much as 40 percent of the original COD when the waste was
stored for a period of 4 days in the laboratory. We did not de-
termine what fraction of the COD was being degraded, nor what
effect the lack of these materials during the later stages of an
individual test had on the carbon's capacity or adsorption pattern.
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10
USE OF ACTIVATED CARBONS
The degradation was accounted for in computation of the
adsorptive capacity of the carbons. The influent and effluent
COD's were plotted, as shown in Figures 2 through 7, and the
area between the curves was computed. Since one test, that on
Barnebey Cheney KC-5, was run for only 143 liters, the rela-
tive adsorptive capacities for all the carbons were computed at
a total flow of 140 liters. The adsorptive capacity was deter-
mined by dividing the area between the curves by the weight of
carbon used for the test. Note that carbons were not of uniform
size, and this may have affected adsorption capacity.
so
40
30
?
a
8
20
10
30 cm3 -nin FLOW
100
150
170
160
WASTE VOLUME, liter*
1 575
Figure 2, Pittsburgh 8 x 30 mesh, .^ = 10.5% by weight adsorbed COD.
15.000
Asa precautionary measure, possible COD residues in
each batch of new, activated carbon were determined. Since
manufacturing processes could possibly leave organic fragments,
the interference was of concern. High-purity distilled water
was percolated through activated-carbon samples, collected, and
analyzed for chlorides and COD. In no case was a measurable
COD found; chlorides were less than 10 milligrams per liter in
the first liter of wash water and absent thereafter. The back-
ground interference was, therefore, considered insignificant.
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AND CHEMICAL REGENERANTS
11
INFLUENT
EFFLUENT
30 cm^/min FLOW
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
WASTE VOLUME, litari •
} 215
Figure 3. Barn«b*y Chenty KC-5, = 8.1%.
50
40
30
20
INFLUENT
EFFLUENT
10
100 no 120 130 140
30
50
60
70
80
130 160
10
30
40
90
WASTE VOLUME, lit*.
Figur* 4. CI lift Dow 10 x 30 mesh, ^ = 13.4%,
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12
USE OF ACTIVATED CARBONS
60
50
40
30
20
JNFLUENT
EFFLUENT
10
too
120
110
130
140 150
160
WASTE VOLUME, litau
Figure 5. Atlas 12 x 20 mesh, = 8.795.
40
30
20
INFLUENT
EFFLUENT
10
100
120 1 30 140 150 140
WASTE VOLUME, !it#r»
Figure 6, American Norit 8 x 20 mesh, jj'qqq = 7.0%.
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AND CHEMICAL REGENERANTS
13
Analytical Techniques
Chlorides
Chlorides were run by using the Mohr technique as out-
lined on page 78 of Standard Methods 38 with the modification of
using 0. 1 normal AgNOg rather than 0. 0141. This was con-
sidered sufficient for this work since the only reason for run-
ning chlorides was to correct the COD data for their presence.
With this normality, 0. 1 milliliter is equivalent to 0. 35 milli-
gram of CI" per liter, or to only 0. 07 milligram of COD per
liter {with 0. 23 x CI" equivalent to 1 milligram of COD per
liter). No greater accuracy was required owing to limitations
of the COD test used.
30
20
£
E
d
8
!0
Figure 7. West Virginia C-190 x 30 mesh, = 11.1%.
i i i I i i i i i i i i i i—i—r
INFLUENT
EFFLUENT
TO 20 30 3fl SO 40 70 80 TO 100 MO !?0 130 MO f» 160 170
WASTE VOLUME, litm
Chemical oxygen demand
Chemical oxygen demand was determined by the dichro-
mate reflux method as described on pages 399-402 in Standard
Methods. The modification for dilute samples, outlined on page
402, was used. Silver sulfate was not used as a catalyst because
comparative studies, with and without this agent, did not show
appreciable variation in final values.
Alkylbenzenesulfonate
ABS was run in accordance with the proposed method
found on page 245 in Standard Methods. This method is for use
in water supplies but is considered sufficiently accurate for use
in these tests. Neither the error due to the presence of chlo-
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14
USE OF ACTIVATED CARBONS
rides nor the possible errors due to other interferences were
investigated.
Suspended solids
Suspended matter was determined by filtration through
asbestos mat by vacuum in a Gooch crucible. Suspended solids
on both activated sludge and tertiary waste water were run by
this method as outlined on page 327 in the Eleventh Edition of
Standard Methods. Results were recorded as total milligrams
of suspended matter per liter.
Results
Figures 2 through 7 illustrate the change in influent and
effluent with time for each of the activated carbons evaluated.
The area between the two curves represents the amount of COD
retained by the carbon.
The percent by weight of the adsorbed COD after 140 liters
of tertiary effluent has been treated was calculated, and the data
are shown in Table 2.
Tefelo 2. PERCENT BY WEIGHT OP ADSORBED COD
Wf % adsorbed Prom
Carbon identity COD Figure
Pittsburgh 8 x 30 meih 10.5 2
Barnebey Cheney 8 * 12 8.1 3
CI iff¦ Dow 10 x 30 meih 13,4 4
Atla» 12 x 20 mesh 8.7 5
American Norit 8 x 20 me*h 7.0 6
We»t Virginia C-190 + 30 11.1 7
Discussion
Liquid-phase adsorption data obtained from different
sources seldom correlate because of the effect of the variable
medium enhancing the natural differences in carbon activity.
Furthermore, the relative adsorption of different materials is
not the same at all concentrations, and correlation among con-
centrations used by various investigators becomes difficult. In
general, it has been found that the higher molecular-weight
materials are adsorbed more effectively on activated carbon
than are those of lower molecular weight.
-------
AND CHEMICAL REGENERANTS
15
Much of the adsorptive power of activated carbon has been
attributed to crystal formation within the substrate. For instance,
diamond powder adsorbs methylene blue but not succinic acid,
while graphite adsorbs succinic acid but not methylene blue.
Activated carbon, however, adsorbs both succinic acid and meth-
ylene blue, and from this, it has been inferred that both crystal
types are present in the active carbon. In general, it has been
found that a single solute is more easily removed from a solu-
111 14 *30
tion than are several materials in the same solvent. ' * '
Other work has shown considerable preferential adsorption of
one ol the materials from a solution.
There are no valid theories that allow selection of the best
active carbon in any single case without experimentation. Most
of the materials now marketed have been the result of continued
improvement for a particular job. In sugar production, one
material is used to decolorize beet sugar while a different one
is used for cane sugar, and yet both remove color from essen-
tially an aqueous, sucrose solution. Most activated-carbon
manufacturers, therefore, offer their products in reference to
a specific demand. In some cases as many as 50 carbons from
one manufacturer are sold with each available in several mesh
sizes.
No attempt was made to obtain the most superior activated
carbon for adsorption of refractory contaminants from Midland,
Michigan, tertiary waste. The main objective was to determine
the extent to which activated carbon could adsorb those contami-
nants that demonstrated COD values in the tertiary waste. All
activated carbons evaluated showed measurable adsorptive
capacities for COD materials.
The compilation of calculated-percent-adsorbed COD by
weight for the various carbons evaluated {Table 2) should not
be construed as valid for comparative purposes. These data
were accumulated at various times, for example. Hence, there
were undoubtedly differences in the degree and nature of the
refractory contaminants in the waste water. In turn, these
differences would affect the point at which equilibrium between
the carbon adsorptive capacity and total COD in the waste wbuld
exist. The results listed should, therefore, serve only as a
possible indication of differences among activated carbons in
waste removal efficiency.
Cliffs Dow activated carbon was selected for use in the
second phase of the project. This decision was induced solely
by the ease of procurement of necessary quantities of the acti-
vated carbon selected.
-------
16
USE OF ACTIVATED CARBONS
PHASE 2.
REGENERATION STUDIES
The purpose of this series of experiments was to screen
commercially available chemical oxidants for their ability to
regenerate activated carbon partially exhausted by passage of
a sand-filtered, activated-sludge effluent through carbon columns.
Experimental Procedures
MATERIALS AND EQUIPMENT
Activated Carbon
Cliffs Dow 10 x 30-mesh activated carbon was used for the
screening of oxidative regenerants. This particular carbon
appeared to have adsorptive capacities for components of the
utilized tertiary waste water that were sufficiently great to per-
mit comparative oxidant screening,
Regenerant Application Apparatus
The equipment required to feed the chemical oxidant to
the exhausted, activated carbon is shown in Figure 8. Essentially,
the apparatus consisted of a reservoir for oxidant solutions and
a pumping apparatus to force the oxidant solution up through the
exhausted carbon column.
Evaluation of Chemical Oxidants
Chemical oxidants evaluated as regenerants for the ex-
hausted, activated carbon were as follows: Chlorine, bromine,
potassium permanganate, sodium dichromate, sodium persul-
fate, potassium persulfate, sodium peroxide, hydrogen peroxide,
and ozone.
METHODS
Activated-Carbon Exhaustion
To expedite the screening of oxidative regenerants, it was
felt necessary to alter the procedure for exhaustion of the
-------
AND CHEMICAL REGENERANTS
17
activated carbon. The dynamic status of the collected tertiary -
treated waste water in respect to time further prompted a change
in the technique. The flow of tertiary-treated waste water through
2-llt.r BOTTLE
llll ,«.•
l\ \
OXIDANT
IH
WATER
SOLUTION
PISTON PUMP
5/8 In. HEAD SET
AT 100 cmVmln
2-mm l,D. GLASS TUBE
RUBBER STOPPER
1 in. OF GLASS WOOL
50.0 g CLIFFS DOW
10 x 30-MESH ACTIVATED
CARBON
1 in. OF GLASS WOOL
2 In. OF GLASS CHIPS
18 in. x 1 in. I.D.
CARBON COLUMN
2-mm 1,0, STOPCOCK
Figure 8. Carbon column with packing and rogonoration application.
the activated-carbon column was increased from 30 to 100 cubic
centimeters per minute. The amount of carbon exposed was also
-------
18
USE OF ACTIVATED CARBONS
increased from 15 to 50 grams. Several runs following these
changes substantiated the belief that satisfactory exhaustion of
the activated carbon could be achieved within the confines of an
8-hour working day. More efficient planning of experiments as
well as more rapid data accumulation were realized by these
changes.
If other factors are ignored, these changes in rate of flow
and amount of carbon exposed altered the calculated percent COD
adsorbed. A 25 percent increase was noted. By using area inte-
gration calculations to obtain an average efficiency value, the
slower flow rate through 15 grams of carbon gave 52 percent
COD adsorbed. The increased flow rate of 100 cubic centimeters
per minute through 50 grams of carbon gave 77 percent COD ad-
sorbed.
Differences in the tertiary waste water in respect to time,
variations in the procedures of exhausting the carbon, and even
changes in personnel would all affect these calculations. The
25 percent increase is, therefore, only approximate, but does
indicate that flow rate and amount of carbon especially will affect
the adsorptive efficiency of carbon exposed to tertiary wastewater.
This point was not pursued further.
Preparation of Oxidant Feed Stocks
No routine procedure of preparation or concentration of
the various chemical oxidants could be established. Differing
solubilities, stability, and source of supply all dictated that each
oxidant had to be considered individually. For example, sodium
dichromate is very soluble in water, and ozone is, of course,
an extremely unstable gas. In general, a "reasonable" concen-
tration was selected that would be expected to have some oxida-
tive effect on the materials adsorbed on the carbon.
Analytical Procedures
The unstable and reactive nature of many of the oxidants
was well known. Since, however, the objective was to compare
oxidants for contemplated use as regenerants of exhausted carbon
under practical conditions, no attempt was made to control the
variables that may affect the oxidant efficiency. Only the con-
stants of carbon amount and influent flow rate were controlled.
Different conditions of exposure of exhausted carbon to the oxidants
could, therefore, significantly alter the results. It should also
be remembered that the carbon, was exhausted by a municipal
waste over which no control of variability was possible.
-------
AND CHEMICAL REGENERANTS
19
In spite of an awareness of these variables a comparative
consideration of the regenerative efficiencies of the candidate
oxidants was desirable. The method used consisted of analyses
of the tertiary-waste-water COD removed by a virgin carbon
sample as compared with the COD removed from the same tertiary
waste water by the "regenerated" carbon. In these experiments
a regenerated carbon is identified as a 50-gram amount of Cliffs
Dow activated carbon that had previously been exhausted by
Midland tertiary waste water and then subjected to oxidant ex-
posure by the method previously described.
To make realistic comparisons of the regenerative effi-
ciencies of the oxidants, a standardized sampling procedure was
necessary. At a flow rate of 100 cubic centimeters per minute,
a total of 42 liters of tertiary-waste-water feed could be passed
through the carbon columns within the practical confines of a
working day. Grab samples of the feed and column effluents were
obtained at the first liter of throughput and at each sixth liter
thereafter. The exception was the sampling at the 42d liter.
The regenerative efficiencies of the oxidants were deter-
mined in percent by integrated area calculations. At any sam-
pling point the efficiency percentile could be calculated as follows:
x 100 (1)
oxidant efficiency
COD of influent
COD of regenerated-carbon effluent
COD of virgin-carbon effluent, and
any sampling point.
The efficiency values can then be fitted into the following
integrated area formula:
Avg regenerant 3E + 6(E0 + E„ -- + EJ + 5. 5E_+ 2. 5E (2)
% efficiency(Eq)~ = - - -
where E, ® Ei at 1 liter throughput
E„ = Ei at 7 liters throughput
Eg = E2 + 6 liters throughput, etc.
Eg = E7 + 5 liters throughput.
In Table 3, for example, COD values and efficiency calculations
were determined for chlorine water.
E: -Xi - Zi
Xi - Yi
where E «
X =
Z =
Y =
i =
-------
20 USE OF ACTIVATED CARBONS
Tabla 3. COO VALUES AND EFFICIENCY CALCULATIONS FOR CHLORINE WATER
Throughput,
lltara
COO ramovad by
virgin carbon,
ppm
COD ramovad by
raganaratad carbon,
ppm
Raganaratlva
•fflelancy, %
1
-------
AND CHEMICAL REGENERANTS
21
adsorptive capacity induced by chlorine was considered
to be very poor. The regeneration, based on the aver-
age of 11 single ERC determinations, was calculated to
only 15 percent recovery.
2. Bromine. A saturated (approximately 0, 35%)solution
of bromine was fed through exhausted carbon columns.
The apparent adsorption of bromine on the carbon
caused gross errors in the COD analyses of the grab
samples of carbon effluent. Approximately 25 liters
of wash water {or tertiary-treated waste) was required
to rid the carbon completely of bromine. Consequently,
no worthwhile data were obtained on the efficiency of
bromine as a regenerant for waste-exhausted, activated
carbon. The meager results that were accumulated
indicate that bromine is no more efficient than chlorine.
3. Potassium permanganate. The high water solubility
of KMn04 prompted the arbitrary selection of a 10 per-
cent solution of this oxidizing agent. The recovery of
adsorptive capacity by the carbon averaged 16 percent
for a single ERC. Potassium permanganate also dis-
colored all components of the apparatus. The low
recovery plus the staining discouraged further investi-
gations with this oxidant.
4. Sodium dichromate. The percent recovery of adsorp-
tive capacity by the carbon on the first ERC with
Na2Cr2(>7 was superior to those obtained with any of
the previous oxidants. Sixty percent recovery was
demonstrated on the first ERC. The recovery dropped
off grosBly on the second ERC; only 15 to 20 percent
recovery was evident. No measurable regeneration
was observed on the third ERC.
It was also noted that the characteristically yellow
color of Cr207 showed that this chemical had an affinity
for the carbon. The dichromate was difficult to remove
and showed up in the column effluent during a second
ERC even after the passage of 20 liters of treated waste
water.
5. Potassium per sulfate. The results obtained with
K^S^O^poInteTouFtHat the average recovery of ad-
sorptive capacity by the carbon on the first ERC was
49 percent. Data on second ERC experiments showed
a drop of regenerative restoration to 20 percent.
Nevertheless, provided the best regeneration
-------
22
USE OF ACTIVATED CARBONS
so far when the carbon was subjected to a second ERC.
Unfortunately, no regeneration of the carbon was
apparent on the third ERC.
6. Sodium persulfate. Essentially equivalent toK2S20g
on the initial ERC (55%), Na2S208 was much less
efficient in regenerative ability on the second ERC.
The average recovery on a second ERC was less than
20 percent.
7. Sodium peroxide. This chemical was selected for
evaluation because, in addition to its well-known oxi-
dizing properties, it had a sodium ion available. An
interesting theory was considered that a possible
saponification of adsorbed fatty acids could occur in
conjunction with the oxidizing effect.
Sodium peroxide gave favorable results on the first
ERC. The recovery of adsorptive capacity was calcu-
lated to be 60 percent. This promising recovery rate
decreased, however, to less than 20 percent on the
second ERC and to an unmeasurable percentile on the
third ERC.
8. Ozone. The instability of ozone necessitated genera-
tion of the gas and immediate feed into the exhausted
carbon column. The amount of ozone was governed by
the generating apparatus and the time of exposure.
The amount of molecular ozone fed to the 50 grams of
carbon was 2. 5 grams.
The carbon-regenerating capacity of ozone was demon-
strated to be very limited. The first ERC resulted in
only 25 percent recovery.
9. Hydrogen peroxide. Regeneration of exhausted, acti-
vated carbon with hydrogen peroxide was done initially
with a 30 percent aqueous solution. This experiment
was carried out in an explosion-proof hood because of
the danger involved in combining concentrated H2O2
with organic matter. This form of treatment proved
inconvenient because of the high instability of 30 percent
H2°2; no EEC results were measured.
Six percent dilutions of the stock H2Q2 reagent were
evaluated on another exhausted carbon cylinder. It
was observed, however, that the 6 percent H2Q2
solution effervesced, which, in turn, indicated
-------
AND CHEMICAL REGENERANTS
23
instability. Because the 3 percent H2°2 solutions
were known to be the most stable aqueous form of
this oxidant, further investigations were performed
with this concentration. It was noted during the appli-
cation of H2O2 that oxygen gas was evolved but that
3 percent solutions caused less flow blockage due to
this effervescence. Seventy-one percent recovery was
realized on the first ERC whereas 47 percent recovery
was found on the second ERC, The third ERC gave a
20 percent recovery. No adsorptive capacity was noted
on the carbon sample when subjected to a fourth ERC.
It is thought that oxidants will remove some organics
selectively and leave others on the pores. This theory
would account for the arithmetic reduction of adsorp-
tive capacity of the 3 percent H2O2-treated carbon.
The results obtained during the evaluation of each oxidant
are pictured in Figures 9 through 16. For comparison, the re-
sults obtained in the screening of chemical oxidants for regener-
ation of tertiary-waste-exhausted, activated carbon are compiled
in Table 4.
Table 4. OXIDANT REGENERATION EFFICIENCIES ON WASTE-EXHAUSTED,
ACTIVATED CARBON, CUFFS DOW, 10 x 30 MESH
Oxidant
concentration, %
Average efficiency, X
Oxidant
First ERC
Second ERC
Third ERC
Chlorine water
0.46
15
0
Bromine water
3.50
< 10
0
KMnO .
4
10.0
16
0
*SCr2°7
10.0
61
<20
K2S2°8
0.75
49
20
0
Na252°8
0.75
55
<20
0
°3
4.0
25
0
n-2°2
1.0
60
<20
0
H2°2
3.0
71
50
<20
-------
24
USE OF ACTIVATED CARBONS
l
i—i—i—i—i—i—i—i—i—i—i—I—i—r
i—i i i
• ___ INFLUENT TMTIMTT &EHA.6E
EFFLUENT CI* MjD 13L TREATMENT
. , EFFLUENT CONTROL
I I I I I I I I I I I I. .1, i . J. 1
2 4 it ie 13 U 16 « JO 22 a 26 »30 » it It X « O
FLOW OF SEVAGE, ((>«. . TOO aiVmln
Figur* 9- Percent recovery chlorine water, 50.0 g, Cliffs Dow, 10 x 30 me*h,
15% average efficiency.
i i i i j i i j i ; i i r
1—i—r
4 1—
I Mh
t
30 _
INFLUENT TERTIARY
EFFLUCNT (CMfCa TREATMENT
EFFLUENT CONTROL
j i i \ i i t ' ' j i j i i i i ' i ' i
3 i s 4 io u u <4 ii » 55 55555 55»x m Jo«
FLOW OF SEWAGE, titer* . 100 anVnli,
Figure 10. Percent recovery of KMnO^, 6 liters, 50.0 g, Cliffs Dow, 10 x 30 moth,
16% average efficiency.
WO B11~74f~*
-------
AND CHEMICAL REGENERANTS
25
50
40
30
JO
10
INFLUENT TERTIARY SEWAGE
EFFLUENT N <120207 TREATMENT
EFFLUENT CONTROL
FLOW OF SEWAGE, lit*" • 100 cm3/mii
Figure II. Percent recovery NajC^Oy, 50.0.9, Cliff* Dow, 10 * 30 mesh,
60% average efficiency.
60
SO
-• INFLUENT TERTIARY SEWAGE
_ EFFLUENT KjSjOj TREATMENT
— EFFLUENT CONTROL
10
10
FLOW OF SEWAGE, lluti . 100 cm3/mm
Figure 12. Percent recovery I^SjOg, 50.0 g, Cliffs Dow, 10 x 30 mesh,
49% average efficiency.
-------
USE OF ACTIVATED CARBONS
influent
NajSjOj EFFLUENT
CONTROL EFFLUENT
FLOW OF SEWAGE, lit«« . 100 cm3/mln
Figure 13. Percent recovery Noj^Og, 50.0 g, Cllfft Dow, 10 x 30 mesh,
55% average efficiency.
INFLUENT TERTIARY SEWAGE
EFFLUENT NojOj TREATMENT
EFFLUENT CONTROL
FLOW OF SEWAGE, )H«r. . 100
igure 14. Percent recovery \\ 50.0 g, Cliff* Dow, 10 x 30 mesh,
activated carbon, 60% average efficiency.
-------
AND CHEMICAL REGENERANTS
27
O 20
INFLUENT TERTIARY SEWAGE
EFFLUENT OZONE TREATMENT
EFFLUENT CONTROL
7
4
A
e
W 12 14 16 18 20 22 24 26 28 30 32 34 3< 38 40 42
FLOW OF SEWAGE, liters « 100 em3/mm
Figure 15. Percent reeovety oxone, 50.0 g. Cliffs Dow, 10 x 30 mesh,
25% average efficiency.
70
1 ^4-¦¦ I "I )
50
40
30
30
INFLUENT TERTIARY SEWAGE
EFFLUENT HjOj TREATMENT
EFFLUENT CONTROL
10
FLOW OF SEWAGE, ll»«« . 100 tmVmln
Figure 16. Percent recovery of .3% 2 Uteri, Cliffs Dow, 10 x 30 mesh,
activated carbon; phase 2 about 20° C, 70% average efficiency.
-------
28
USE OF ACTIVATED CARBONS
Discussion
None of the evaluated chemical oxidants achieved complete
regeneration of the Cliffs Dow activated carbon that had been
exhausted by tertiary waste water from Midland, Michigan,
municipal waste water, under the experimental conditions used
during this investigation.
This inability to regenerate the active carbon completely
to its original state could arise from any of a number of causes
that were not investigated. Some of the phenomena that could
contribute to the incomplete regeneration of the active carbon
are: Site poisoning, reaction rate with the contaminant, the
blocking of micropores either by gas or oxidation products, dif-
fusion of oxidant or product, degradation of active sites by oxi-
dant, or reaction kinetics.
Still other factors could affect any comparative efforts to
select the most effective chemical oxidant of those evaluated.
For example, the effect of temperature, oxidant concentration,
and time of exposure of the carbon to the oxidant could alter the
apparent superiority of one candidate oxidant over another.
The results obtained in this phase of the investigation indi-
cate, therefore, only that hydrogen peroxide appeared to be
superior to any of the other chemical oxidants in the screening
method used. The apparent superiority of hydrogen peroxide
seems to be supported by the 47 percent regenerative efficiency
on the second ERC. Furthermore, hydrogen peroxide was the
only evaluated oxidant that provided a measurable regenerative
efficiency on the third ERC.
None of the chemical oxidants screened was totally in-
effective, as indicated by the percentile restoration of carbon
adsorptive capacity on the first ERC. Distilled water was found
to induce some percentage of recovery but only below 5 percent.
All the oxidants gave higher percentile degrees than this.
Oxides of metals, represented by KMnO^ and Na2Cr207,
did not appear to be satisfactory regenerants for the exhausted
carbon. The dichromate demonstrated good regeneration, 60
percent on the first ERC, but dropped off considerably on the
second. The permanganate presented an even poorer regenerative
picture. Metallic ion residues, accumulating during the use of
either of thesfe two chemicals, could also pose a disposal problem.
-------
AND CHEMICAL REGENERANTS
29
Neither halogen, chlorine, or bromine was sufficiently
effective for further consideration as a regenerant. The two
persulfates, K2S20g and Na2S20g, provided a surprising degree
of regeneration on the first ERC. Here again, however, resi-
dues of the sulfates would occur in the effluent during the use
and present an additional-problem. Second ERC calculations,
moreover, demonstrated that these persulfates were incapable
of regenerating more than 20 percent.
The selection of hydrogen peroxide, then, as the best
oxidant of those screened was based on: (1) The best regener-
ation obtained on the second ERC, and (2) the lack of residual
problems.
PHASE 3.
ADDITIONAL
HYDROGEN PEROXIDE STUDIES
Hydrogen peroxide appeared to be the most favorable oxi-
dative regenerant for exhausted carbon as based on the previous
investigations. During the contract time remaining, it was de-
sirable to try to determine some of the optimum conditions for
the use of hydrogen peroxide as an exhausted carbon regenerant.
Experiments were also conducted to determine if ABS in tertiary-
treated waste water comld be adsorbed on activated carbon and if
the carbon's capacity for this material could be restored with
h2o2.
Experimental Procedures
MATERIALS AND EQUIPMENT
The previous evaluations of H2O2 as a regenerant for waste-
exhausted carbon were conducted only at ambient temperatures.
To consider the effect of an elevated temperature on the
efficiency, the apparatus shown in Figure 17 was used.
-------
30
USE OF ACTIVATED CARBONS
The same apparatus was used to determine the minimal
volume of H2O2 solution necessary for the regeneration of ex-
hausted carbon.
The materials necessary for ABS analyses were taken
from Standard Methods, Eleventh Edition, page 246. The analysis
required a Beckman Model B Spectrophotometer at a wave length
setting of 650 microns.
THERMOMETER
CARBON CYLINDER
2-liter BOILING
FLASK
PISTON PUMP
e 100 cra^/min
RHEOSTAT
Figure 17. Elevated temperature apparatus, 60° C, 3% solution, HjOj application.
METHODS
Hydrogen peroxide solutions with concentrations as great
as 85 percent can be obtained commercially. The stock H2O2
solution used in the experiments was a 30 percent solution pro-
duced by Merck and Company.
-------
AND CHEMICAL REGENERANTS
31
It was advisable to try to find the smallest concentration of
^2^2 wou^ provide satisfactory regeneration of waste-
exhausted carbon. Dilutions of hydrogen peroxide were prepared
down to a 1 percent concentration.
Comparative regeneration data were compiled for each of
these concentrations. Moreover, the volume of carbon was
varied at a constant 3 percent concentration of hydrogen peroxide.
Only two temperatures were compared for effect on hydro-
gen peroxide's regenerative abilities. An elevated temperature
of 60°C was selected; results at this temperature were compared
with those obtained at 20°C. The hydrogen peroxide concentra-
tion (3%) and volume (2 liters) were identical for both temperature
evaluations.
Results
Determination of limiting concentration and solution volume
of hydrogen peroxide for regeneration of waste-exhausted carbon*
is summarized in Table 5.
Table 5. PERCENT EFFICIENCY OF HYDROGEN PEROXIDE FOR REGENERATION OF
WASTE-EXHAUSTED CARBON
^2®2 *°'u,'0n
Vol urn#
Efficiency
concentration, %
used, liter
Temperature, "C
1st cycle, %
30
2
20
No result*
6
2
20
69
4
2
20
69
3
2
20
71
3
2
60
54
3
1
20
72
3
0.5
20
79
3
0.25
20
71
2
2
20
70
1
2
20
68
Analyses were made at various times throughout 1961 for
total apparent ABS in Midland waste treatment waters. The
results of this monitoring are listed in Table 6.
* Calculations of the efficiency percentage were identical to the method utilized for
evaluation of the various oxidants in Phase 2.
-------
32
USE OF ACTIVATED CARBONS
The soluble surfactants in Midland waste waters caused
slight foaming on the head of the pilot plant aeration tank. No
foam difficulties were encountered owing to the rapid natural
breakdown of the foam produced.
Table 6. ALKYLBENZENESULFONATE ANALYSES (DAILY FOR 1 WEEK)
Date Total apparent ABS, mg/!iter
2/9/61 2.96
2/10/61 2.80
2/11/61 3.04
2/12/61 2.48
2/13/61 3.04
2/14/61 3.24
2/15/61 2.86
Random samplei
10/6/61 2.20
12/1/61 2.00
12/5/61 2.50
Analyses for ABS were done on the three treatment effluents to
determine if treatment degradation of surfactants occurred
(Table 7).
Table 7. ABS ANALYSES OF THREE TREATMENT EFFLUENTS
Date
Midland plant
primary treatment
ABS, mg/Nter
10/6/61 10:00 AM
Effluent
2.0
10/6/61
Secondary ptlot
plant effluent
2.10
10/4/61
Composite >omple of
collected watt®
2.40
An experiment was designed to determine if Cliffs Dow
10 x 30-mesh, activated carbon would adsorb ABS from waste
waters. Thirty-seven liters of Midland, Michigan, tertiary
waste water were pumped through 50-gram samples of Cliffs
Dow activated carbon. Samples of 1-liter volume were taken of
the tertiary waste water as well as of the carbon effluent. These
samples were tested for milligrams of ABS per liter by the
aforementioned methods. Results of ABS analyses during an ERC
are recorded in Tables 8 and 9.
WO •! 1—741—4
-------
AND CHEMICAL REGENERANTS
33
TableS, ABS ANALYSES, DECEMBER 1, 1961
SampN
COD, mg/l Iter
Throughput,
literi
ABS, mg/l Iter
8:00 a.m, tertiary-wo it*-water inf
12:00 Noon, tertiary-waite-water inf
3:00 p.m. tertiary-waste-water inf
Effluent from carbon column
1st liter, 100 cm3/tn!n
13th liter, 100 cm^/min
25th liter, 100 cm^/min
43d liter, ]00 em^/min
41.1
41.0
43.1
3.3
9.7
11.1
17.2
1
19
37
1.55
1.95 Avg -
2.00 1.83 mg/l Iter
0.06
0.20
0.7
0.7
Table 9. COD AND ABS ANALYSES, DECEMBER 5, 1961 (AFTER REGENERATION WITH
1% HYDROGEN PEROXIDE, 2 LITERS VOLUME)
Somple COD, mg/l Iter ABS, mg/l iter
9(00 e.m. tertiary inf 39,7 2.05
12)00 Noon tertiary inf 40,0 2.51
3:00 p.m. tertiary inf 37,9 2.51
lit liter effluent 19.3 0.00
13th liter effluent 23»6 0.30
25th liter effluent 26.4 0.70
43d liter effluent 28.2 0.70
Discussion
The accumulated data from this supplementary hydrogen
peroxide study were insufficient to determine specifically the
exact volume, concentration, and temperature of hydrogen per-
oxide that would provide maximum regeneration of exhausted
carbon. For instance, the rates of oxidation generally double
for each 7 percent increase in temperature. Our data do not,
however, support this statement since a lower efficiency was
obtained when the H2O2 solution was maintained at 60°C than
when it was maintained at 20°C. This lower efficiency most
likely resulted from the deterioration of H2O2 at the elevated
temperature. We would expect that physical variations within
these conditions would have considerable effect on the efficiency
of hydrogen peroxide. The data listed tend to indicate this.
-------
34
USE OF ACTIVATED CARBONS
According to the results, activated carbon can adsorb ABS
from a municipal waste water after conventional waste treatment.
Furthermore, the data suggest that hydrogen peroxide can re-
generate exhausted, activated carbon to the extent that more ABS
can be removed from a waste-water stream,. No evidence was
obtained to show that ABS was removed from the exhausted carbon
by hydrogen peroxide; this possibility does, however, exist.
GENERAL DISCUSSION
OF TOTAL PROJECT PHASES
Literatur'e studies indicated that many carbons and chars
are prepared from almost any material that was at one time
either carbohydrate or cellulosic. These carbons are prepared
by many different methods of activation for specific purposes.
The carbon types may be classified on the basis of adsorptivity
of gas or liquids. Most of these materials show selective ad-
sorption properties; for example, a carbon may effectively
remove H2O2 from air, but it may be of no value in removing the
same compound from aqueous solution.
In choosing one carbon for the extraction of a contaminant
from a liquid, there is no theoretical basis for the choice other
than that of screening the carbons for effectiveness. The results
of initial investigations of the adsorptive capacities of activated-
carbon types showed that refractory organic compounds in Mid-
land, Michigan, effluent {primary plus small, fabricated,
secondary unit) waters could be removed by several activated-
carbon types. The treatment processes at Midland Waste-Water
Treatment Plant plus the fabricated pilot plant treatment unit
removed 97 percent of the original suspended solids from the raw
waste water and lowered the COD by 70 percent. Most of the
remaining organics could be removed by adsorption on activated-
carbon beds.
The screening studies of activated carbon done under this contract
indicate a maximum COD loading of about 0. 14 gram COD per
gram of carbon under the experimental conditions utilized. Con-
siderable variation was, however, noted among the active carbons
tested.
It was further found that the carbon selected for regener-
ation studies was reactivated in a declining manner; that is,
restored activity was always less than that found on the previous
regeneration, The declining regeneration is thought to be
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AND CHEMICAL REGENERANTS
35
partially attributable to the concentration of regenerant used in
these studies as well as to temperatures and other experimental
variables. The results of ERC studies of oxidants indicate that
hydrogen peroxide solutions produce the best regenerative effects
on Cliffs Dow carbon exhausted with Midland waste water. All
oxidants tested had some regenerative abilities. A general
screening program of oxidants showed that hydrogen peroxide
had the most favorable over-all regenerative ability. The choice
of hydrogen peroxide was made on this basis as well as for ease
of application and ready availability.
To make an economic study on the feasibility of activated-
carbon adsorption and chemical reactivation for advanced waste
treatment, liberties must be taken with the project data. Pro-
visional acceptance of the following statements must be given:
Cliffs Dow activated carbon gave the best adsorption of
COD. This carbon costs $0, 15 per pound.
Hydrogen peroxide was the best regenerant for activated
carbon exhausted by tertiary waste water. This oxidant
costs $0. 53 per pound {based on January 1963 average
price of 50% H2O2, $0,265 per pound, delivered).
One part of H2O2 is required to regenerate 3.3 parts of
carbon to 70 percent of the initial capacity.
By using the above figures, calculations can be made of
the cost required to regenerate carbon by chemical oxidation.
On a pound-for-pound basis, it would cost $0. 53 to regenerate
activated carbon costing $0.50. Obviously, these figures indi-
cate that it would be cheaper to discard the exhausted carbon
than to attempt to regenerate it by means of chemical oxidants.
If further calculations are made on the basis of 70 percent oxi-
dant efficiency and declining efficiencies with multiple loading
and regeneration steps, the economics appear even more un-
favorable.
It is apparent that this uneconomical aspect of chemical -
oxidant regeneration of carbon for use in advanced waste treat-
ment could be altered if cheaper carbon and a cheaper, more
efficient chemical regenerant could be found.
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36
USE OF ACTIVATED CARBONS
CONCLUSIONS
1. Activated carbon removed refractory contaminants from a
tertiary-treated, municipal waste water.
2. Chemical oxidants partially regenerated activated carbon
that had been exhausted by exposure to sand-filtered
secondary effluent.
3. On a comparative basis, hydrogen peroxide displayed the
most favorable over-all regenerative ability of the oxidants
evaluated.
4. Because of only partial regenerative ability demonstrated
by chemical oxidants, the adsorptive capacities of activat-
ed carbon were eventually destroyed.
5. Alkylbenzenesulfonate was adsorbed by activated carbon
from a sand-filtered, municipal-waste-water, secondary
effluent.
6. The data accumulated in this project suggested that chemi-
cal-oxidant regeneration of activated carbon exhausted by
tertiary-treated waste water is not economically feasible.
ECONOMIC CONSIDERATIONS
It has been determined that activated carbon can adsorb
refractory contaminants from tertiary, municipal waste. Further-
more, the exhausted carbon can be regenerated by chemical
oxidants. To make an economic study of the feasibility of the
use of activated carbon in advanced waste treatment, however,
more information must be accumulated.
Time limitations prevented a thorough research into the
best and most economical carbon type for use in waste treatment.
The carbon type, in turn, may have a significant influence on the
ultimate selection of a regenerant.
The following economic guide lines have been compiled as
a criterion for selection of a carbon and a regenerant for ad-
vancpH wastp trpat.mfint.
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AND CHEMICAL REGENERANTS
37
The cost of COD removal from waste effluents with acti-
vated carbon has been treated in this evaluation on a purely
operating basis since the unit process may be of a number of
different types, and capital requirements would vary widely de-
pending on the unit process involved and volumes handled. No
attempt has been made to evaluate the inorganic removal.
An equation was derived that gives the cost per pound of
COD removal on the assumption of a constantly declining regener-
ation of the activated carbon. The following equation is the basis
of this analysis:
Cost ~ (Cost of carbon) + n (Cost of regeneration)
n (3)
S (Regeneration factor)n (Initial loading)
n = 0
Wherein
Cost = the cost per pound of the total COD removal if the
carbon was discarded after the nth regeneration.
Cost of carbon = the price per pound of the active carbon
used in the COD removal.
Cost of regeneration = the cost of regenerating 1 pound
of active carbon regardless of its capacity or
recovery. Assume no loss of carbon during
regeneration.
Regeneration factor = the fraction of initial adsorption
recovery obtained at the first regeneration and
assumed constant for succeeding regenerations.
Initial loading = weight of contaminant adsorbed on a unit
weight of activated carbon.
n = an integer defining the number of times a particular-
carbon is regenerated.
An example of the use of this formula may be illustrated by
assuming conditions given in Figure 20.
Cost of carbon = 10 cents per pound
Cost of regeneration = 1 cent per pound
80 percent declining regeneration
10 percent initial loading
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38
USE OF ACTIVATED CARBONS
Cost at nth regeneration =
(Cost of carbon ) + n (Cost of regeneration)
2 (Regeneration factor)11 (Initial loading)
n - 0
„ . . Al, _ (10 cents/lb) +4 (1 cent/lb)
Cost at 4th regeneration ^ (0~T)
14 cents per pound
(4)
(0.80 + 0.81 + 0.fl2 + 0.83 + 0. 84) (0. 1)
= 14centertb 41.5cents/lb
The cost for COD removal under these assumed conditions
is thus seen to be 41. 5 cents per pound for all of the COD re-
moval from solution up to the 5th regeneration, The carbon is
assumed to be reloaded after the 4th regeneration.
For an estimation of the costs of activated carbon two
situations must be considered. The first is when a displacement
regeneration occurs wherein only a fixed fraction of the active
sites is reactivated by the specific regenerant, and the second
is when a decreasing regeneration is encountered. Both types of
reactivation have been noted in the literature. The marked differ-
ence between the case of site poisoning and declining regeneration
is indicated in Figure 18 where the dotted lines indicate various
levels of declining regeneration and the solid lines indicate a
comparative degree of initial site poisoning. This analysis is
made on the basis of a quantity of carbon that initially removed
100 pounds of COD and is meant to indicate only differences in
the mode of regeneration.
Ip the case of site poisoning, the initial activity is de-
creased to some fixed lower value in the first few regenerations
owing to the poisoning of one type of active site and its conse-
quent inactivation for future adsorptions. These cases are often
encountered in the removal of products from biochemical pro-
cesses. The COD adsorption from waste-water effluents would
probably act more like a case of declining regeneration because
of the spectrum of components that would allow for a continuing
poisoning as a function of use. The site-poisoning case would,
however, constitute a minimum cost situation.
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AND CHEMICAL REGENERANTS
39
95ft MS
DECLINING REGENERATION
SITE POISON
500 600
COO REMOVAL, lb
1,000
1,100
Figure 18. COD removal as a function of type of regeneration (assume initial carbon
capacity of 100 lb COD).
Figure 19 indicates the cost per pound of COD removal
(as COD) for six differently priced, activated carbons as a
function of the number of regenerations for site poisoning.
Figures 20 through 24 indicate the relation of the cost of
regeneration and the cost of activated carbon to the cost of COD
removal for declining regeneration.
Circles in Figure 20 indicate where the cost of COD re-
moval is minimum for each carbon cost. As the cost of carbon
increases, the need for regeneration increases and the number
of regenerations to obtain the minimum cost is increased.
A comparison between Figures 20 and 23 indicates the im-
portance of high initial loading on the total cost of COD removal.
It should be noted, however, that the number of regenerations
required to obtain minimum cost depends upon the price of acti-
vated carbon and the cost of reactivation, and is independent of
the initial loading.
Figure 24 shows the cost of COD removal by a 10-cent and
a 30-cent carbon at three costs of regeneration and clearly indi-
cates the importance of low-priced, activated carbons. From
this figure it can be seen that a cheaper COD removal can be
achieved when the 10-cent carbon is discarded after 2 regener-
ations at 5 cents per pound for each regeneration than is achieved
with a 30-cent carbon after 10 regenerations at only 1 cent per
pound.
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40
USE OF ACTIVATED CARBONS
3.00
2.50
2.00
UJ
1.00
0.50
20 k
0
10
9
0
2
3
5
7
8
1
4
6
NUMBER OF REGENERATIONS
Figure 19. Effect of cost of carbon on COD removal (atsum* 10% initial
COD loading, 20% poison, 1 cent/lb regeneration cost).
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AND CHEMICAL REGENERANTS
2.50
2.00
1.00
0.50
9
10
0
8
2
A
3
4
5
7
NUMBER OF REGENERATIONS
Figure 20. Effect of coat of regeneration on cost of COD removal (10% initial loading,
80% declining regeneration, 1 cent/lb regeneration cost).
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42
USE OF ACTIVATED CARBONS
3.00
2.50
2.00
UJ
1.00
0.50
8
10
0
9
5
6
7
2
3
4
NUMBER OF REGENERATIONS
Figure 21. Effect of cost of regeneration on the cost of COD removal (10% loading,
80% declining regeneration, 3 cents/lb regeneration cost).
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AND CHEMICAL REGENERANTS 43
3.00
2.50
2.00
20 m
1.00
O.JO
NUMBER OF REGENERATIONS
Figure 22, Effect of cost of regeneration on the cost of COD removal (10% loading,
60% declining regeneration, 5 cents/lb regeneration cost).
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44
USE OF ACTIVATED CARBONS
I
v
§
i
§
0
Figure 23. Effect of cost of corbon on COD removol at high initial loading (30% initial
loading, 80% declining regeneration, 1 cent/lb regeneration cost).
3,00
30-CENT CARBON
10-CENT CARBON
2.00
3!
>
i
ji
I
.00
0.30
I CENT
NUMBER OF REGENERATIONS
Figure 24. Effect of cost of regeneration on COD removal from 10-cent and 30-cent
carbon (oiivme 10% initial loading, 80% declining regeneration and
variable cost at regeneration).
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AND CHEMICAL REGENERANTS
45
REFERENCES
1. Amiot, R., Adsorption par le Charbon de Melanges
Binaires in Solution Aqueous, Compt. rend, 199,
636-638, 1934.
2. A.W.W.A., Water Quality and Treatment, Second Edition,
American Water Works Association, New York, 1951,
pp. 233-234.
3. A.W.W.A., Water Quality and Treatment, Second Edition,
American Water Works Association, New York, 1951,
pp. 240-249.
4. Barry, H. M., Fixed-Bed Adsorption, Chemical
Engineering, &]_, 105-120, 1960.
5. Behrman, A. S., and Gustafson, H., Behavior of
Oxidizing Agents with Activated Carbon, Industrial and
Engineering Chemistry, 27_, 426-429, 1935.
6. Berger, B. B., Public Health Aspects of Water Reuse
for Potable Supply, Journal of the American Water Works
Association, J52, 599-606, 1960.
7. Braus, H., Middleton, F. M., and Walton, G., A Study
of the Concentration and Estimation of Organic Chemical
Compounds in Raw and Filtered Surface Waters,
Analytical Chemistry, 23, 1160-1164, 1951.
8. Brown, G. G., Unit Operations, John Wiley & Sons, Inc.
New York, 1950, pp. 398-409.
9. Colebaugh, D., Filicky, J., and Hyndshaw, A., Factors
Influencing the Efficiency of Activated Carbon, Journal
of the American Water Works Association, 43, 322-326,
1951.
10. Culp, R. L., and Stoltenberg, H. A., Synthetic Detergent
Pollution in Kansas, Journal of the American Water Works
Association, 45, 1187-1195, 1953.
11. Deitz, V. R., United States Cane Sugar Refiners and Bone
Char Manufacture and National Bureau of Standards,
Bibliography of Solid Adsorbents, Washington, D. C,, 1944.
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46
USE OF ACTIVATED CARBONS
12. Eckenfelder, W. W., Presentation as member of panel
symposium on the Water Renovation and Desalination
Program meeting of American Institute of Chemical
Engineers, New York City, December 6, 1961.
13. Ettinger, M. B., Proposed Toxicity Screening Procedure
for Use in Protecting Drinking Water Quality, Journal
of the American Water Works Association, 52, 687-694,
1960.
14. Freundlich, H., and Masius, M, , Absorption in a Solu-
tion of Several Substances, van Bemmelen Gedenboek,
88-101, 1910.
15. Harrison, L. B., Activated Carbon at Bay City's
Filtration Plant, Journal of the American Water Works
Association, 23, 1388-1392, 1931.
16. Harrison, L. B., Use of Granular Activated Carbon at
Bay City, Journal of the American Water Works Associ-
ation, 32, 593-608, 1940.
17. Hassler, J. W., The History of Taste and Odor Control,
Journal of the American Water Works Association, 32,
2124-2152, 1941.
18. Hassler, J. W., Activated Carbon, Chemical Publishing
Company, Inc., Brooklyn, New York, 1951.
19. Hurwitz, E., Beaudoin, R. E., Lothian, T., and
Sniegowski, M., Assimilation of ABS by Activated Sludge
Treatment Plant-Waterway System, Journal of the Water
Pollution Control Federation, Z2, 1111-1116, 1960.
20. Lieber, M., Syndet Removal from Drinking Water Using
Activated Carbon, Water and Sewage Works, 107,
299-301, 1960.
21. Ludzack, F. J., Laboratory Model Activated Sludge Unit,
Journal of the Water Pollution Control Federation, 32,
605-609, 1960.
22. Mantell, C. L., Chemical* Engineers Handbook, Section 14,
McGraw-Hill, New York, 1950.
23. McGauhey, P. H., and Klein, S. A. , Removal of ABS by
Sewage Treatment, Sewage and Industrial Wastes, JT1,
877-899, 1959.
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AND CHEMICAL REGENERANTS
47
24. McKinney, R. E,, and Donovan, E. J., Bacterial
Degradation of ABS, II, Complete Mixing Activated
Sludge, Sewage and Industrial Wastes, 3_1, 690-696, 1959.
25. McKinney, R. E., and. Svnaons, J. M., Bacterial
Degradation of ABS, I. Fundamental Biochemistry,
Sewage and Industrial Wastes, SU, 690-696, 1959.
26. Middleton, F. M., Braus, H., and Ruchhoft, C. C.,
The Application of the Carbon Filter and Countercurrent
Extraction to the Analysis of Organic Industrial Wastes,
Proceedings of the 7th Purdue Industrial Waste Conference,
Series No. 79, 439-454, 1952.
27. Middleton, F. M. , and Lichtenberg, J. J., Measurement
of Organic Contaminants in the Nations' Rivers., Industrial
and Engineering Chemistry, 52_, 99A-102A, 1960.
28. Middleton, F. M., Advanced Waste Treatment - A
Challenge to the Community, Statement read as part of
panel discussion on the Water Renovation and Desalination
Program meeting of American Institute of Chemical
Engineers, New York City, December 6, 1961..
29. Nellenstevn, F. J., De Activiteit van Grafiet en Diamant
en de Modificaties der Amorphe Koolstof, Chemical
Weekbald, 22, 291-293, 1925.
30. Ockrent, C,, Selective Adsorption by Activated Charcoal
from Solutions Containing Two Organic Acids, Journal of
Chemical Society, 33, 613-130, 1932.
31. Renn, C., and Barada, M., Adsorption of ABS on
Particulate Materials in Water, Sewage and Industrial
Wastes, 31, 850-854, 1959.
32. Ruchhoft, C. C. Middleton, F. M., Braus, H., and
Rosen, A., Taste and Odor Producing Compounds in
Refinery Gravity Oil Separator Effluents, Industrial and
Engineering Chemistry, 46, 284-289, 1954,
33. Ryckman, D. W. , Burbank, N. C. , and Edgerley, D. ,
Methods of Characterizing Organic Materials of Taste
and Odor Significance from Missouri River Waters,
American Chemical Society Convention, September, 1959.
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48
USE OF ACTIVATED CARBONS
34. Sigworth, E. A., Activated Carbon - Its Value and Proper
Points of Applications, Journal of the American Water
Works Association, 29, 688-698, 1937.
35. Sipyagin, A. S. , and Serkin, E. S., Regeneration of
Activated Carbons, Zhur, Sakhur, Prom., _4, 176-181,
C. A, 24, 6052, 1930.
36. Syverson, G. , and Timmer, R., Laundering Spent Carbon
for Reuse, Food Engineering, 3^2, 107-108, 1960.
37. Vaughn, J. C. , and Falkenthal, R. E., Detergents in
Water Supplies, Industrial and Engineering Chemistry,
48, 241-245, 1956.
38. Standard Methods for the Examination of Water and
Waste Water, Eleventh Edition, American Public Health
Assoc., Inc., New York, 1960.
•N
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I
;i
-f
I
I
i
'i
ii
'I
i
!
i
i
t-
l
t
BIBLIOGRAPHIC: Johnson, R. L., F. J. Lowes. Jr.,
R. M. Smith, and T. J. Powers. Evaluation of
the use of activated carbons and chemical regener-
ants in treatment of waste water. PHS Publ.
Mo. 000-WP-13. 1964. 48 pp.
ABSTRACT: The capacities of six activated carbons
for the soluble organic* in filtered secondary
effluent were obtained by use of a continuous-flow,
column-type test. Results varied from 7 to 13
grams COD per 100 grants of carbon. Because
of the manner in which the test was carried out,
only the carbon with the smallest capacity was
loaded to the maximum extent possible.
The chemical regeneration of exhausted carbon
wan investigated by ut>e of nine jtiturgamc oxid-
izing agents. Only hydrogen peroxide was capable
of restoring measurable adsorption capacity after
more than two cycles of exhaustion and regenera-
tion. The economic feasibility of chemical
regeneration is not promising.
BIBLIOGRAPHIC: Johnson, R. L., F. J. Lowes, Jr.,
R. M. Smith, and T. J. Powers. Evaluation of
the use of activated carbons and chemical regentr-
ants in treatment of waste water. PHS Publ.
No. 999-WP-I3. 1SS4. 48 pp.
ABSTRACT: The capacities of six activated carbons
for the soluble organic* in filtered secondary
effluent were obtained by use of a continuous-flow,
column-type test. Results varied from 7 to 13
grams COD per 100 grams of carbon. Because
of the manner in which the test was carried out,
only the carbon with the smallest capacity was
loaded to the maximum extent possible.
The chemical regeneration of exhausted carbon
was investigated by use of nine inorganic oxid-
ising agents. Only hydrogen peroxide was capable
of restoring measurable adsorption capacity after
more than two cycles of exhaustion and regenera-
tion. The economic feasibility of chemical
regeneration is not promising.
ACCESSION NO.
KEY WORDS:
Advanced Waste
Treatment
Waste-Water
Renovation
Adsorption
Activated Carbon
Regeneration
Economics
ACCESSION BIO.
KEY WORDS:
Advanced Waste
Treatment
Waste-Water
Renovation
Adsorption
Activated Carbon
Regeneration
Economics
»!
I
BIBLIOGRAPHIC: Johnson, R. L., P. J. Lowes, Jr.,
R. M. Smith, and T. J. Powers. Evaluation of
the use of activated carbons and chemical regener-
ants in treatment of waste water. PHS Publ.
No. Bfle-WP-13. 1064. 48 pp.
ABSTRACT: The capacities of six activated carbons
for the soluble organic* in filtered secondary
effluent were obtained by use of a continuous-flow,
column-type test. Results varied from 7 to 13
grams COD per 100 grams of carbon. Because
of the manner in which the test was carried out,
only the carbon with the smallest capacity was
loaded to the maximum extent possible.
The chemical regeneration of exhausted carbon
was investigated by use of nine inorganic oxid-
ising agents. Only hydrogen peroxide was capable
of restoring measurable adsorption capacity after
more than two cycles of exhaustion and regenera-
tion, The economic feasibility of chemical
regeneration is not promising.
ACCESSION NO.
KEY WORDS;
Advanced Waste
Treatment
Waste-Water
Renovation
Adsorption
Activated Carbon
Regeneration
Economics
-------
(Continued from inside front cover, )
Report
Number
AWTR-8 Ultimate Disposal of Advanced-
Treatment Waste 999-WP-10
Part 1. Injection
Part 2. Placement in
Underground Cavities
Part 3. Spreading
AWTR-9 Adsorption of Biochemically Resistant
Materials from Solution. 1 999-WP-ll
AWTR-10 Feasibility of Granular,
Activated-Carbon Adsorption
for Waste-Water Renovation 999-WP-12
AWTR-11
Evaluation of the Use of Activated
Carbons and Chemical Regenerants
in Treatment of Waste Water 999-WP-13
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