:LEAI
'VATHP
WATER POLLUTION CONTROL RESEARCH SERIES • 17040 EUE 07/71
Amenability
of Reverse Osmosis Concentrate
to Activated Sludge Treatment
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes
the results and progress in the control and abatement
of pollution in our Nation's waters. They provide a
central source of information on the research, develop-
ment, and demonstration activities in the Environmental
Protection Agency through inhouse research and grants
and contracts with Federal, State, and local agencies,
research institutions, and industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications
Branch, Research Information Division, Research and
Monitoring, Environmental Protection Agency, Washington,
D. C. 20460.
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AMENABILITY OF REVERSE OSMOSIS
CONCENTRATE TO ACTIVATED SLUDGE TREATMENT
by
Rex Chainbelt Inc.
The Ecology Division
Milwaukee, Wisconsin 53201
for the
ENVIRONMENTAL PROTECTION AGENCY
Project #17040 EUE
July 1971
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents neces-
sarily reflect the views and policies of the
Environmental Protection Agency, nor does mention
of trade names or commercial products constitute
endorsement or recommendation for use.
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 • Price $1.26
ii
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ABSTRACT
This report documents a laboratory-scale feasibility study for the
treatment of domestic sewage. The objective of the study was to
produce potable water from chemically clarified sewage via reverse
osmosis (RO) and to determine the amenability of the RO concentrate
to biological treatment.
Pilot-scale tubular and spiral wound RO units were utilized in this
study. It was determined that chemical clarification of the raw
sewage was necessary even with the tubular RO systems. The chemicals
recommended for the pretreatment (based on jar tests) were ferric
chloride and alum. Reverse osmosis produced a water of excellent
quality with regard to inorganic ions. However, a significant amount
of the dissolved organic materials passed through the cellulose
acetate membranes, necessitating further upgrading of product water
for potable use. Qualitative investigations on the RO permeate
indicated that 70% of the organic matter permeating through the CA
membranes from Milwaukee sewage was apparently ethanol (C^ELOH).
Bench-scale activated sludge feasibility tests conducted on the RO
concentrate indicated that it was feasible to treat it biologically.
Soluble TOG removals of 87 to 9270 in 4 to 10 hours of aeration along
with good settling characteristics for MLSS concentrations up to
6000 mg/1 were achieved. A treatment schematic that will provide
potable water at 937» recovery and would also reduce the pollutional
discharge to streams was proposed.
This report was submitted in fulfillment of Grant No. 17040 EUE under
the partial sponsorship of the Environmental Protection Agency.
iii
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TABLE OF CONTENTS
PAGE
ABSTRACT ill
I CONCLUSIONS 1
II RECOMMENDATIONS 3
III INTRODUCTION 5
IV LITERATURE REVIEW 7
V TEST EQUIPMENT AND PROCEDURES 9
VI TEST RESULTS & EVALUATIONS 19
Pretreatment Investigation 19
Reverse Osmosis Evaluations 23
Activated Sludge Feasibility Results 40
Permeate Investigation Results 49
VII APPLICABILITY OF REVERSE OSMOSIS IN THE RENOVATION
OF WASTE WATER 57
Proposed Treatment Scheme 57
Economics of the Proposed Treatment Scheme 60
VIII ACKNOWLEDGEMENTS 63
IX REFERENCES 65
X APPENDICES
I - Pretreatment Investigation Data 67
II - Biological Oxidation Data 86
III - Permeate Investigation Data 98
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LIST OF FIGURES
FIGURE PAGE
1 BASIC ELEMENTS OF A REVERSE OSMOSIS SYSTEM 10
2 TUBULAR CONFIGURATION 12
3 SPIRAL WOUND CONFIGURATION 13
4 SCHEMATIC FLOW DIAGRAM FOR EXPERIMENTAL RO UNIT 14
5 RECOMMENDED MODULE ARRANGEMENT FOR REVERSE OSMOSIS 16
6 LOGRITHMIC VARIATION OF FLUX RATES 28
7 LABORATORY CONCENTRATE RECYCLING PROCEDURE 32
8 BIOLOGICAL TREATMENT EFFICIENCY CURVES 43
9 OXYGEN UPTAKE RATE CURVE - CHEMICALLY TREATED SEWAGE
CONCENTRATE 45
10 VARIATION OF SETTLING VELOCITY WITH MIXED LIQUOR
SUSPENDED SOLIDS 47
11 TYPICAL SETTLING CURVES FOR RO CONCENTRATE -
CHEMICALLY TREATED SEWAGE 48
12 TYPICAL CHROMATOGRAM FOR RO SAMPLES OF MILWAUKEE SEWAGE 50
13 CARBON ADSORPTION ISOTHERM FOR MILWAUKEE SEWAGE RO
PERMEATE 55
14 RECOMMENDED TREATMENT SCHEME 58
II-l TYPICAL OXYGEN UPTAKE CURVE FOR RO CONCENTRATE -
SETTLED SEWAGE 89
I1-2 TYPICAL SETTLING CURVE FOR RO CONCENTRATE - SETTLED
SEWAGE 90
III-l CHROMATOGRAM - RO PERMEATE OF 1/13/71, MILWAUKEE STP 101
III-2 CHROMATOGRAM - RO PERMEATE OF 1/20/71, MILWAUKEE STP 102
III-3 CHROMATOGRAM - DISTILLED WATER 103
III-4 CHROMATOGRAM - RO PERMEATE OF 1/20/71, MILWAUKEE STP 105
III-5 CHROMATOGRAM - RO FEED OF 1/20/71, MILWAUKEE STP 108
III-6 CHROMATOGRAM - RO BRINE OF 1/20/71, MILWAUKEE STP 109
III-7 CHROMATOGRAM - BIO-TREATED EFFLUENT OF 1/20/71 RO
BRINE, MILWAUKEE STP 110
III-8 CHROMATOGRAMS - MILWAUKEE STP SAMPLES 111
III-9 CHROMATOGRAM - RAW SEWAGE, MENOMONEE FALLS STP 112
111-10 CHROMATOGRAM - RAW SWAGE, BROOKFIELD STP 113
III-ll CHROMATOGRAM - RAW SEWAGE, KENOSHA STP 115
III-12 CHROMATOGRAM - RAW SEWAGE, RACINE STP 116
111-13 CHROMATOGRAMS - RO FEED AND PERMEATE OF 3/8/71,
RACINE STP 117
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LIST OF TABLES
TABLE PAGE
1 JAR TEST RESULTS WITH FERRIC CHLORIDE 20
2 JAR TEST RESULTS WITH ALUM 21
3 JAR TEST RESULTS WITH LIME 22
4 JAR TEST RESULTS WITH POLYELECTROLYTES AND OTHER
CHEMICAL COMBINATIONS 24
5 COST OF CHEMICAL TREATMENT 26
6 WATER QUALITY DATA FOR THE FLUX DECLINE
STUDY EXPERIMENTS 30
7 WATER QUALITY DATA - SETTLED SEWAGE FEED WATER 33
8 COMPARISON OF CONCENTRATE QUALITIES AT 90% FEED WATER
RECOVERY 34
9 WATER QUALITY DATA - SETTLED SEWAGE FEED WATER 36
10 WATER QUALITY DATA - CHEMICALLY TREATED & SETTLED
SEWAGE FEED WATER 38
11 RESULTS OF ATOMIC ABSORPTION ANALYSIS ON RO CONCENTRATE 42
12 BIOLOGICAL OXIDATION DATA, CHEMICALLY TREATED SEWAGE
CONCENTRATE 46
13 WATER QUALITY DATA FOR RACINE SEWAGE 52
14 CARBON ADSORPTION ISOTHERM TEST DATA 54
1-1 WASTE CHARACTERISTICS FOR VARIOUS TREATMENT PLANTS
FOR MAY, 1970 68
1-2 WASTE CHARACTERISTICS OF THE SAMPLES UTILIZED IN
JAR TESTS 69
1-3 JAR TESTS WITH FeClg 70
1-4 JAR TESTS WITH ALUM 73
1-5 JAR TESTS WITH LIME 76
1-6 JAR TESTS WITH PRIMAFLOC A-23 77
1-7 JAR TESTS WITH ALUM & A-23 78
1-8 JAR TESTS WITH ALUM & C31 79
1-9 JAR TESTS WITH FeCl3 & A-23 80
I-10 JAR TESTS WITH FeCl3 & C31 81
1-11 JAR TESTS WITH FeCl3 & HERCOFLOC 822A 82
1-12 JAR TESTS WITH FeCl3 & 675A 83
1-13 JAR TESTS WITH FeCl3 & ALUM 84
1-14 JAR TESTS WITH FeCl3 & PRIMAFLOC C7 85
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LIST OF TABLES (CONT.)
TABLE PAGE
II-l BIOLOGICAL OXIDATION DATA - SETTLED SEWAGE CONCENTRATE 88
II-2 SETTLING TEST DATA - SETTLED SEWAGE CONCENTRATE 91
II-3 CHEMICALLY TREATED SEWAGE CONCENTRATE - BATCH KINETIC
RUN #1 BIO-OXIDATION DATA 92
I1-4 CHEMICALLY TREATED SEWAGE CONCENTRATE - BATCH KINETIC
RUN #2 BIO-OXIDATION DATA, UNIT 1 93
II-5 CHEMICALLY TREATED SEWAGE CONCENTRATE - BATCH KINETIC
RUN if 2, BIO-OXIDATION DATA, UNIT 2 94
II-6 CHEMICALLY TREATED SEWAGE CONCENTRATE - BATCH KINETIC
RUN #2 BIO-OXIDATION DATA, UNIT 3 95
II-7 CHEMICALLY TREATED SEWAGE CONCENTRATE - BATCH KINETIC
RUN #2 BIO-OXIDATION DATA, UNIT 4 96
II-8 CHEMICALLY TREATED SEWAGE CONCENTRATE - BATCH KINETIC
RUN if3 BIO-OXIDATION DATA 97
III-l KNOWN COMPOUNDS TESTED 107
III-2 QUANTITATIVE ANALYSIS RESULTS OF THE LARGEST
CHROMOTOGRAM - PEAK (B) 119
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SECTION I
CONCLUSIONS
This study has demonstrated the potential use of Reverse Osmosis in
the treatment of domestic waste waters. An excellent quality effluent
water was produced relative to inorganic ion rejection. However, the
product water from RO must be further upgraded for potable use since
some of the soluble organic material passes through the RO membranes.
It was also demonstrated that it is feasible to treat the RO brines
biologically. Specific conclusions which can be drawn from this study
are:
1. Prior chemical treatment of the raw sewage will be necessary
even when tubular RO systems are utilized.
2. Ferric chloride and alum were concluded to be the most
suitable chemicals for the pretreatment of raw sewage.
3. Reverse osmosis produced an excellent quality product water
with regard to inorganic ions (approximately 100 mg/1 TDS).
A. Approximately 40-50% of the soluble organic material oermeated
through the cellulose acetate membranes at high feed water
recoveries.
5. The RO product waters will have to be nost treated to meet
the water quality standards for maximum organic material in
potable waters.
6. Qualitative investigations on the RO permeate indicated that
approximately 70% of the organic matter permeating through the
RO membranes was apparently ethanol (C^H^OH) for Milwaukee
sewage. However, organics passing through the RO membranes may
be appreciably different for other sewages.
7. Significantly less fouling of the membranes was observed with
chemically clarified sewage as compared to settled sewage
through laboratory recycling test procedures.
8. Water recovery rates of 92% were achieved in the laboratory
without any precipitation problems in the RO concentrate.
9. It was demonstrated that the RO concentrates can be successfully
treated biologically. TOC removals in the range of 87 to 93%
were obtained in A to 10 hours aeration time depending upon
the suspended solids level maintained.
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10. Metallic ion concentrations in the concentrates were found
to be well below levels, toxic to activated sludge biota.
11. Mixed liquor suspended solids concentrations of up to
6000 mg/1 could be maintained with good settling characteris-
tics.
12. An average oxygen uptake rate that can be utilized for design
purposes was 30 to 40 mg/l/hr.
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SECTION II
RECOMMENDATIONS
Based on the results of this study, it is recommended that:
1. A split flow treatment scheme consisting of chemical treatment,
reverse osmosis, activated carbon anc1 ozone oxidation be utilized
for the treatment of domestic sewage. The above combination of
treatment concepts is expected to provide high recovery of reusable
and potable water as well as reduce pollutant discharges to streams.
2. A prototype scale RO system be constructed and that the field
evaluations be conducted in accordance with the proposed split flow
treatment scheme. Also, special emphasis be placed on the evaluation
of the flux decline characteristics due to the presence of soluble
organic material.
3. The RO concentrates be treated via activated sludge process and a
prototype unit be constructed to substantiate the laboratory findings
in the field on a continuous flow basis.
4. Post treatment investigations on RO permeates be continued on sewages
from various treatment plants other than Milwaukee.
5. Hollow fiber RO configuration be evaluated and compared to other RO
configurations for the treatment of chemically clarified domestic
waste waters.
6. A detailed cost analysis for using reverse osmosis to treat municipal
waste waters be prepared.
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SECTION III
INTRODUCTION
The ever increasing demand for fresh water combined with an increased
emphasis on a more complete abatement of water pollution has forced
the water purveyors of the nation to study ways and means of utilizing
our waters more efficiently. A logical way of improving this effi-
ciency is through multiple use of the water supplies.
To achieve this objective, the conventional waste treatment practices
must be modified and/or supplemented with advanced wastewater treatment
technology that will provide reusable and potable water. The domestic
wastewaters are normally dilute organic-bearing wastes and typically
have dissolved solids concentrations in the range of 500-1500 mg/1. The
primary concern in the application of the newer technology is the
removal of nutrients, dissolved mineral salts, oxygen-demanding organics
and undesirable bacteria and viruses presently being discharged as a
result of incomplete conventional waste treatment. Removal of these
contaminants can be accomplished with a variety of processes such as
reverse osmosis, activated carbon, ion exchange, biological and
chemical oxidation and disinfection. Most of these processes except
reverse osmosis can remove only a portion of the pollutants. For
example, organic contaminants can be adsorbed over activated carbon
but dissolved inorganics are not; while ion exchange can remove the
dissolved inorganics, the soluble organics pass through. However,
reverse osmosis is a process which is capable of separating the
dissolved organics and inorganics from an aqueous solution in addition
to the removal of bacteria and viruses. The promising potential of
the reverse osmosis process in the waste treatment area has consistently
been described in recent literature (1, 2, 3, 4, 5). The continual
development and refinement of RO membranes and hardware has now made it
possible to study the feasibility of utilizing this process for muni-
cipal wastewater treatment. The specific objectives of this study were:
1. To establish the pretreatment steps required to allow RO to
function efficiently when treating municipal wastewaters.
2. To determine whether the waste concentrate from the RO process
is amenable to activated sludge treatment.
3. To evaluate the quality of the RO product water with regard to
its reuse as a potable water supply.
To accomplish the stated objectives of the project, the test program was
divided into the following five phases:
1. Pretreatment investigations
2. RO evaluations
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3. Biological system evaluations
4. Permeate quality investigations
5. Preliminary cost information
Raw sewage samples from various treatment plants in the Milwaukee area
were utilized in this study. The feasibility evaluations in the
various phases were conducted with laboratory scale pilot plant equip-
ment. Based on the results of the laboratory scale investigations, a
treatment schematic was developed and proposed for a large scale field
program.
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SECTION IV
LITERATURE REVIEW
There has been a limited amount of work done in the area of reverse
osmosis application to municipal wastewater treatment. Mostly, it
has been in the form of pilot plant investigations. Initial investi-
gations in this area were started when preliminary tests by Aerojet
General Corporation in 1962 indicated that the cellulose acetate
membrane was an effective barrier for both organic and inorganic solutes.
Subsequent work was conducted on filtered municipal secondary effluent
with a flat plate test cell (6). The results indicated greater than
95% removals of total dissolved solids (TDS) and chemical oxygen demand
(COD). However, severe flux decline problems were experienced. Further
pilot plant testing was conducted at Pomona, California with the spiral-
wound configuration on secondary and activated carbon treated effluents
by Gulf Environmental Systems under various contracts sponsored by
EPA (7). Results of these tests again showed high organic and inorganic
solute rejections at lower feed water recoveries. However, significant
fouling of the membranes was again noticed due to the soluble organic
material present in the filtered secondary effluent. Various flushing
and membrane cleaning techniques were utilized for reducing the membrane
fouling and for restoring the flux losses. A cleaning technique utiliz-
ing an enzyme-based detergent was considered to be the most effective.
Laboratory scale reverse osmosis tests on municipal wastewaters were
conducted by Aerojet-General Corporation (8). These tests were
conducted in assemblies representing two different membrane geometries:
sheet and tubular. Behavior and response of the reverse osmosis process
to carbon-treated secondary effluent, alum-treated secondary effluent,
secondary effluent, alum treated primary effluent, raw sewage and
digester supernatant were evaluated. High removals of dissolved organics
and inorganics were reported. The principal cause of flux decline was
attributed to the membrane fouling by finely dispersed solids and the
effect of the dissolved organic substances was considered to be of lesser
relative importance. The effects of the flocculent, dispersant, chelat-
ing, enzyme and acid on reducing product water flux decline were compared.
Pretreatment of the municipal wastewater feed by flocculation with alum,
followed by rapid sand filtration was considered to be the most effective
of all the preconditioning methods studied. Evaluation of the flat-
plate configuration in the treatment of municipal wastewaters was also
made at Lebanon, Ohio by the EPA staff. The results of these pilot plant
investigations have been well summarized by Smith, ejt al^ (9). It was
concluded that excellent separation of both the inorganic and organic
contaminants could be achieved in treating the secondary or carbon-treated
effluents by reverse osmosis. However, organic fouling of the membranes
was experienced in all runs and was considered the principal cause of
the flux declines that occurred. It was clearly indicated that for
reverse osmosis to become competitive, it will have to be employed near
the primary end of the treatment train. The need for the evaluation of
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the proper pretreatment requirements preceding RO and an investigation
of the treatment and disposal of the concentrated brines was clearlv
indicated. Also, the performance of the tubular RO systems needed
to be evaluated towards the primary end of the treatment train because
of their capability of handling larger amounts of suspended material.
It is apparent from the above discussion that many technical areas
require further investigation in order to successfully apply reverse
osmosis to the treatment of municipal wastewaters.
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SECTION V
TEST EQUIPMENT AND PROCEDURES
The equipment and procedures employed in the various phases of this
project, except in the permeate investigation phase, are described
below. The description of the apparatus for the permeate investigation
phase is presented in Appendix III. The laboratory procedures utilized
for all analyses except TOC and atomic absorption were performed in
accordance with Standard Methods (10). The TOC and AA analyses were
performed in accordance with the guidelines published by EPA (11) and
the instrument manufacturer (12, 13).
Pretreatment Equipment
Jar test procedures were utilized for studying the chemical flocculation
of the raw wastes from various treatment plants during the pretreatment
investigations phase. Flocculation procedure consisted of one minute
rapid mix @ 100 rpm followed by five minutes of slow mixing at 10-15
rpm with a Phipps and Bird stirrer. This was followed by one hour of
sedimentation time. The optimum chemical dosages were determined on
the basis of the reduction in the turbidity of the flocculated and
settled effluent. A Hellige turbidimeter (Model 925A) was utilized
for all turbidity measurements.
RO Equipment
The basic elements of a reverse osmosis system are shown in Figure 1.
It may be seen from this figure that the RO process produces two
liquid streams. One stream, highly concentrated with the materials
originally present in the feed stream, is called the concentrate or
brine, while the water which has passed through the membrane is called
the permeate or product water. The basic elements shown in Figure 1
are common to all reverse osmosis systems. The essential difference
between various system configurations lies in the method of packaging
the membranes.
There are only three forms which are commercially available in large
quantities. These are tubular, spiral-wound and the hollow-fiber
membranes. These systems have been described in great detail in
earlier literature (14). However, since this study was made with the
tubular and spiral-wound RO systems, some pertinent remarks about
these are in order.
In tubular systems, the cellulose acetate membrane is formed in a
tubular shape generally one-half inch in diameter and several feet
long. There are a number of different tubular systems which are
commercially available. In some systems the membrane is cast directly
onto a supporting tube, while in others the membrane is cast separately
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3
I
High-Low
PH Control
Feed
Water\ / \ /
V V
Low Pressure
High
RO
Membrane
Bank
pressure
Control
Pump
J
%
High Salinity
Control
\ /
V „
^
r\
High Pressure
Control
Product Water
Permeate Flow
Back Pressure
Valve
Brine or
Concentrate Flow
FIGURE 1
BASIC ELEMENTS OF A REVERSE OSMOSIS SYSTEM
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and later inserted into a supporting tube. Some suppliers utilize
the supporting tubes made of porous fiberglass material and the
tubes serve as the pressure vessel. Others have supporting tubes made
out of some sort of plastic or cardboard and a separate pressure
vessel is provided. The individual bundles of tubes (modules) are
then grouped together to form the membrane bank portion of the RO
System.
The tubular system marketed by Calgon-Havens Industries was utilized
in this study. Modules of two membrane types were used. The looser
membrane was designated as Type 300 or 310 with lower salt rejections
and higher flux rates, while the tighter membrane was designated as
Type 500 or 510 with higher salt rejections and lower flux rates. In
the earlier part of the study the older type modules (300 and 500)
were utilized for flux decline studies while later evaluations of the
water quality data were performed with the new type modules (310 and
510). The essential difference between these modules was in the
method of inter-connection of the individual tubes within each module.
The tubes in the old module were connected by separate turn arounds
at both ends while for the new module, these were connected internally
by means of a molded integral head (sealed by 0-rings between the tubes
and the molded head). Each module consisted of 18 porous fiberglass
tubes. The membrane is cast onto the inside of the tubes. The porous
fiberglass tube acts both as the membrane support and the pressure
vessel. Each module contains an effective membrane area of 16.9 sq ft.
A sketch of the tubular module and a single tube is shown in Figure 2.
Each new module (310 & 510) was also equipped with 18 turbulence pro-
motors (also called volume displacement rods) inside the tubes to
minimize the concentration polarization effects by increasing the
effective velocity through the tubes.
A limited amount of RO data was also obtained with the spiral-wound
configuration. This configuration has the advantage of a high membrane
area to volume ratio. The spiral wound module utilized in this study
is marketed by Gulf Environmental Systems. The membrane used was a
newly developed high flux membrane. The module in this system consists
of one or more leaves wrapped around a product water take-off tube.
These leaves consist of the membrane, a porous, incompressible product
water side backing material, and a brine side flow spacer. The membrane
is bonded along the two sides, at the end, and around the product water
tube, forming a sealed envelope that encloses the backing material
except at the product water tube open end. The brine side flow spacer
is placed on the membrane, and several layers are then wrapped around the
product water tube to form a cylindrical module. Modules are then placed
in a suitable pressure vessel. The modules utilized in the study contained
a useful membrane area of 50 sq ft. A spiral wound module is shown in
Figure 3.
A flow diagram of the pilot RO system utilized is shown in Figure 4.
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"f
Single Tube
Turbulence
Promotor Rod
i
»-•
N)
Complete Tubular Module
FIGURE 2
TUBULAR CONFIGURATION
-------
Roll to
Assemble
Feed Side
Spacer
W-
Permeate
Out
Permeate Flow
(After Passage Through
Membrane)
Feed Flow
Permeate Side Backing \
Material With Membrane on
Each Side and Glued Around
Edges and to Center Tube
FIGURE 3
SPIRAL WOUND CONFIGURATION
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r-tXH
4 Modules in Series (Typical)
Membrane Type 510
Permeate - Membrane Type 510
•iXH
-XH
Membrane Type 310
O
Pressure Out Gauge
Permeate - Membrane Type 310
i—IXJ
Manual By Pass Valve
Pressure "In" Gauge
^"^
Back Pressure Regulator
High-Low Pressure Cut Out Switch
High Pressure Safety
i - 1 Relief Valve
Feed
Concentrate
Discharge
Moyno Pump
FIGURE 4
SCHEMATIC FLOW DIAGRAM FOR EXPERIMENTAL RO UNIT
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The system consists of feeding the wastewater through the modules under
a positive head by a Moyno pump. The pump speed is controlled by a
variable drive and this controls the pump flow rate. A half-inch
diameter stainless steel coil using a recirculation of cold tap water was
incorporated in the feed tank to control the feed water temperature to
approximately 70°F.
In a typical experiment the pretreated waste water was pumped to the
membrane bank from the feed water tank. Both the concentrate (brine)
and the permeate (product water) were recirculated to the feed tank.
Measurements were recorded for TDS, temperature, pressure, pH and flow
rates for the feed, brine, and product streams. Composite permeate
samples of the individual membrane types were obtained at the low pressure
end of each module row for desired laboratory analysis. In cases where
a concentrate stream at higher feed water recovery level was desired,
the concentrate was continuously recirculated to the feed tank while the
permeate was wasted until the desired recovery level was achieved.
For designing reverse osmosis systems at high feed water recovery
levels, the generally recommended module arrangement is shown in
Figure 5. This consists of three banks of modules connected in series.
Within each bank the modules are connected in parallel. Each bank has
a decreasing number of modules to compensate for the product water
which has been removed and still maintain turbulent flow conditions.
The product water TDS would be highest in bank 3 since approximately
90% of the raw water has been removed and the TDS in the influent to
bank 3 is approximately four times as high as the influent to bank 1.
Overall salt rejection when the product water streams from various
banks are blended should be in the 80% to 90% range.
For the experiments undertaken during this study, the feed water
recoveries attainable from the pilot RO unit without recycling of the
brine ranged between 20 and 40% depending upon feed flow, type of membrane
and the membrane area utilized. In order to evaluate the water quality
data at higher feed recovery levels, a computer program available at
Rex Chainbelt, Inc. was utilized. The computer program utilizes the
actual data obtained at the lower feed water recoveries of the test unit
and enables an approximate prediction of the product and brine water
qualities at higher recoveries. The program is applicable for any
module configurations similar to that shown in Figure 5 and for any
number of membrane banks that may have to be utilized to achieve the
desired recovery level.
Activated Sludge Experiments
The biological oxidation experiments were conducted in four rectangular
ten-liter plexiglass units approximately 7" x 10" x 12" (15). Each unit
was equipped with one inch diameter spherical air stones. Air was
supplied from the plant air header carrying a pressure of up to 100 psig.
The air flow was controlled to each of the units through a needle valve.
No attempt was made to measure the air volumes to the units. Conditions
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Raw Water Inlet
Bank 1
Bank 2
50% Raw
Water Flow
25% Raw
Water Flow
Product Water Stream
85% to 90% of Raw Water Flow
FIGURE 5
Back Pressure Valve
Bank 3
Waste Stream
[yfyl __ (Rlowdown)
VSl*"~ 10% to 15% of
Raw Water Flow
12% Raw
Water Flow
RECOMMENDED MODULE ARRANGEMENT FOR REVERSE OSMOSIS
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were adjusted to ensure sufficient dissolved oxygen onlv.
The activated sludge (A.S.) feasibility and design information was
obtained by the batch kinetic procedures described by Boyle and Polkowski
(16) and based on the work done by McKinney (17) and Eckenfelder (18).
Briefly, the procedure consists of acclimating the activated sludge
biota to the wastewater for periods up to four weeks so that sufficient
sludge is accumulated to operate several aeration reactors at various
mixed liquor solid levels. Normally the reactors are set up in such
a fashion that various combinations of high and low substrate, high
and low solids and one reactor in the endogenous phase can be operated.
Total Organic Carbon (TOG), mixed liquor suspended and volatile suspended
solids, oxygen uptake rates, pH and settling rates were recorded at
frequent time intervals on samples drawn from various reactors.
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SECTION VI
TEST RESULTS & EVALUATIONS
Pretreatment Investigation
Raw sewage samples were obtained from six different sewage treatment
plants in the Milwaukee area. The raw sewage characteristics of these
wastes for the month of May, 1970 are shown in Appendix I (actual plant
data). The waste characteristics varied over a wide range. The
average BOD ranged from 64 to 296 mg/1. Grab samples of the raw sewages
from various plants were obtained on different week days for jar tests.
The laboratory analysis of these samples is also shown in Appendix I.
The results of the jar tests with various chemicals and chemical combin-
ations are shown in Tables 1 to 4. The chemicals utilized in this study
were ferric chloride, alum, lime and a variety of anionic, cationic
and nonionic polyelectrolytes. The selection of the optimum chemical
dosage was based on the reduction in the turbidity and the pH of the
flocculated and settled effluent. Waste samples from all the six treat-
ment plants were utilized for investigations with ferric chloride and
alum. The chemical dosages investigated ranged from 25 to 200 mg/1
for ferric chloride (Table 1) and 75 to 400 mg/1 for alum (Table 2).
The settled effluent from the jar tests appeared quite clear for turbid-
ities below 20 and 25 JTU for both the chemicals. For a ferric chloride
dosage of 150 mg/1 or higher all the effluent samples were extremely
clear and had turbidity readings below 15 JTU as well as pH values
between 6.0 and 6.7. However, for ferric chloride dosages less than
150 mg/1 the clarity of the settled effluent varied from one sewage
sample to another. Also, in later experiments, when 50 to 800 gallons
of sample was used, a ferric chloride dosage of 150 mg/1 resulted in
effluent turbidities of only 1 to 4 JTU. Therefore, a dosage of 150
mg/1 was considered optimum for the chemical treatment of raw sewage
with ferric chloride.
Wastewater samples treated with alum indicated that a minimum alum
dosage of 200 mg/1 was required to bring about any significant reduction
in the turbidity (Table 2). The clarity of the settled effluent varied
considerably for alum dosages between 200 and 250 mg/1. For alum
dosages higher than 250 mg/1 the turbidity of the treated effluent was
below 17 JTU in most cases and the pH ranged from 6.1 to 6.8. Therefore,
an alum dosage between 250 and 300 mg/1 was considered optimum. Raw
wastewater samples treated with lime (CaO) were visually turbid in most
cases and had very high pH values (>9.0). Lime dosages utilized for
this investigation spanned over a wide range of 100 to 1000 mg/1
(Table 3). The investigations with lime were discontinued early in
the study because of its unreliability in producing a visually clear
supernatant and the extra cost of pH adjustment involved in reducing
the effluent pH (necessary for RO treatment with the cellulose acetate
membranes).
-19-
-------
TABLE 1
JAR TEST RESULTS WITH FERRIC CHLORIDE (Fed )
FeCl3
Dosage Origin of
mg/1 Waste*
0 (raw waste)
25-75
100
100
125
125
150
175-200
1 to 6
1 to 6
1, A
2,3,5,6
4
1,2,3,5,6
1 to 6
1, 6
No. of
Samples
Utilized
14
30
5
9
2
12
10
4
Effluent
pH
6.9-8.1
6.5-7.2
6.6-7.0
6.3-6.8
6.6, 7.0
6.1-6.8
6.0-6.7
6.3-6.6
Effluent
Turbidity
JTU
49->100
25
20-31
13-25
28, 31
11-21
8-15
7-11
* Sewage Treatment Plants:
1. Brookfield
2. Jones Island (Milwaukee)
3. Kenosha
4. Puetz Road (South Milwaukee)
5. Racine
6. Waukesha
-20-
-------
TABLE 2
JAR TEST RESULTS WITH ALUM (A12(S04)3'18H20)
Alum
Dosage Origin of
mg/1 Waste *
0 (raw waste)
75-150
200
225
250
275
300
400
1 to 6
1 to 6
1 to 6
1 to 6
1 to 6
1 to 6
1 to 6
1, 6
No. of
Samples
Utilized
14
6
14
12
14
12
12
2
Effluent
PH
6.9-8.1
—
6.5-7.2
6.4-6.9
6.3-6.9
6.2-6.8
6.1-6.8
6.2-6.5
Effluent
Turbidity
JTU
49->100
>38
20-40
20-28
15-23
8-20
7-17
11-12
* Sewage treatment plants :
1. Brookfield
2. Jones Island (Milwaukee)
3. Kenosha
4. Puetz Road (South Milwaukee)
5. Racine
6. Waukesha
-21-
-------
TABLE 3
JAR TEST RESULTS WITH LIME (CaO)
Lime
Dosage
rag/1
Origin of
Waste*
0 (raw sewage) 1, 6
100-450
500
500
500-1000
500-800
800-1000
1, 6
1, 6
6
1
6
6
No. of
Samples
Utilized
4
10
3
1
5
3
2
Effluent
pH
7.6, 7.8
8.9-9.5
10.2, 9.6
9.1
9.0-12.0
9.0-11.6
11.0
Effluent
Turbidity
JTU
>65
>35
>32
8
>35
6-8
18, 40
* Sewage treatment plants:
1. Brookfield
2. Jones Island (Milwaukee
3. Kenosha
4. Puetz Road (South Milwaukee)
5. Racine
6. Waukesha
-22-
-------
The results of the jar tests with various polyelectrolytes and chemical
combinations are summarized in Table 4. Most polyelectrolytes and
their combinations with ferric chloride or alum did not produce any
encouraging results. The settled effluent turbidities with logically
selected dosages of chemical combinations that might have given some
economic advantage compared to the treatment cost with ferric chloride
or alum alone were generally higher than 20 JTU. A comparison of the
chemical treatment costs in C/1000 gallons for various chemicals and
dosages along with the unit prices for the chemicals is shown in
Table 5. It can be seen that for most optimum chemical dosage combin-
ations with polyelectrolytes the treatment costs are generally higher
than those with FeCl3 or alum alone. However, it should be noted
here that a combination of ferric chloride and alum did produce a
desirably clear effluent. For FeCl3 dosages between 15 and 50 mg/1
and alum dosages between 100 and 125 mg/1, the turbidity of the
settled effluent ranged between 11 and 25 JTU (Table 4). The effluent
pH was between 6.5 and 6.7 and therefore was within the desirable
range for RO treatment. Such a combination of ferric chloride and
alum may also produce some reduction in the cost of chemical treatment
as compared to FeCl- or alum alone.
Ferric chloride and alum were concluded to be the most suitable
chemicals for the pretreatment of raw sewage because of the following
advantages:
1. Very clear supernatant
2. Effluent pH between 6.0 and 7.0 (required no pH adjustment for
further RO treatment)
3. Good settling characteristics
4. Versatility of these chemicals
5. Low cost of chemical treatment (3.5 to 5.5 C/1000 gal)
Reverse Osmosis Evaluations
Raw sewage (screened through mesh No. 8) from the Milwaukee Sewage
Treatment Plant was utilized for the RO evaluations. Milwaukee sewage,
which can be considered typical to that of any metropolitan area, is
a high strength mixture of domestic sewage and industrial wastes, and
has an average BOD of approximately 200 mg/1. The reverse osmosis
evlauations consisted of utilizing two feed water sources, i.e.
settled sewage and chemically treated settled sewage. Raw sewage
samples (representing grab samples) from 50 to 1200 gallons were
brought to Rex laboratories in a truck in batch loads. A sample after
1 to 2 hour sedimentation in the laboratory constituted the settled
sewage, while a sample after flocculation with ferric chloride and
1 to 2 hour sedimentation constituted the chemically treated settled
sewage. The old tubular modules (types 300 and 500) were utilized for
the flux decline evaluation studies (because of the non-availability
of the new modules at that time), while the new modules (Types 310 and
510) were used for the evaluation of the permeate and concentrate quality
data.
-23-
-------
TABLE 4
JAR TEST RESULTS WITH POLYELECTROLYTES AND OTHER CHEMICAL COMBINATIONS
Range of
Chemical Dosages
No. of
Ranre of
Optimum
Chemical Dosage
Effluent Characteristics with Optimum
Chemical Dosage
Investigated
mg/1
Dow A23:
0.15-5.0
Alum: 150-225
& A23: 0.5-2.0
Alum: 100-200
& C31: 0.5-2.0
FeCl3: 25-75
& A23: 0.25-20
FeCl3: 25-50
C31: 0.5-4.0
Origin of
Waste*
1, 6
2, 4
2, 4
2,3,4,5
2,3,4,5
Samples
Utilized
34
18
15
24
27
mg/1
(if any)
none
175-200
& 0.5-1.0
150-200
& 0.5-1.0
50-75
& 0.25-1.0
50
& 0.5-2.0
Turbidity
j>H JTU
>7.0 >28
6.4-7.0 18-28
6.5-7.0 18-20
6.6-6.9 22-42
6.8-7.0 11-35
Remarks
No clarity achieved
No exceptional clarity
High chemical costs
No exceptional clarity
High chemical costs
Medium clarity, wide
variation in effluent
quality
Medium clarity, wide
Variation in effluent
quality
FeCl3: 25-50
C7: 0.25-1.5
25-50
Herco 822A:
0.25-2.0
FeCl3: 25-50
Herco 810C:
0.5-3.0
3, 5
3, 5
3, 5
12
10
16
none
none
none
>30
>30
6.6-7.2 >24
No clarity achieved
No clarity achieved
No clarity achieved
-------
TABLE 4 (cont.
JAR TEST RESULTS WITH POLYELECTROLYTES AND OTHER CHEMICAL COMBINATIONS
Range of
Chemical Dosages
No. of
Range of
Optimum
Chemical Dosage
Effluent Characteristics with Optimum
Chemical Dosage
1
NO
U1
Investigated Origin of Samples
mg/1 Waste* Utilized
FeCl-: 25-50
675A: 0.25-1.0 3, 5 12
FeCl3: 25-50
905N: 0.5-2.0 3, 5 12
FeCl.: 10-50
Alum: 50-125 3, 5 18
mg/1 Turbidity
(if any) pH JTU Remarks
none 6.8-7.1 22-44 No clarity achieved
none 6.8-7.0 >35 No clarity achieved
15-50 6.5-6.7 11-25 Good clarity. Econoi
& 100-125 ical chem. dosages
* Sewage treatment plants
1. Brookfield
2. Jones Island (Milwaukee)
3. Kenosha
4. Puetz Road (South Milwaukee)
5. Racine
6. Waukesha
-------
TABLE 5
COST OF CHEMICAL TREATMENT
I
to
Chemical $/ton
FeCl3 90.0
Alum 40.0
Lime 16.6
A23
C31
822A
675A
810C
905N
C7
$/lb
-
-
-
1
•
1
1
1
1
1
-
-
-
.35
38
.25
.51
.45
.40
.00
.25
—
—
—
.282
.08
.261
.315
.303
.292
.209
.50
—
—
—
.565
.16
.523
.630
.606
.585
.418
1.0 10.0 25.0 50.0 75.0 100 150 200 250 300 500
.375 .94 1.88 2.82 3.75 5.64 7.50 —
.42 .84 1.26 1.68 2.51 3.35 4.2 5.04 —
.65 .98 1.30 1.62 1.94 3.24
1.13 --
.32
1.04 —
1.26 —
1.21 —
1.17 — — —
.835 —
-------
Evaluation of Flux Decline Rates
Two experiments were made to evaluate the flux decline characteristics
of the tubular RO system for the two feed water sources without any
disinfection of the RO feed. The pretreatment for experiment #1
consisted of treating the raw sewage with 150 mg/1 ferric chloride
followed by one hour sedimentation. The pretreatment for Experiment #2
consisted of 1.5 hours sedimentation and a pH adjustment of the settled
sewage effluent with sulfuric acid to a value below 7.0 (required for
cellulose acetate membranes). No pH adjustment in experiment #1 was
necessary because of the use of FeClo which lowered the feed pH
between 6.0 and 7.0. Experiment #1 was concluded at the end of 480
hours of test duration while experiment #2 lasted slightly over 200
hours. Both these experiments were made on batch samples by recycling
the concentrate and product water streams to the feed water tank. No
disinfectants to control bacteria growth or chemical dispersing
agents to control precipitation or any kind of flushing procedures
were utilized during these test runs. A feed flow rate of 1.3 gpm per
module row(3 modules in series) was maintained, which resulted in feed
velocities between 1.5 to 2.0 ft/sec. Operating pressures of 600 psi
at the inlet and a feed water recovery of approximately 25% were
utilized in these experiments.
The variation of the flux rates on a log-log scale is shown in
Figure 6 for the two membrane types as well as the feed water type.
The lower initial flux rates for the settled sewage experiment compared
to those for the chemically treated sewage were due to the sequence
of these two experiments, whereby the flux rates had already been
reduced in the former experiment. Flux decline slopes for the chemi-
cally treated sewage were -0.06 for membrane type 300 and -0.027 for
membrane type 500. The corresponding slopes for settled sewage were
-0.13 and -0.10. The comparative slopes for these two membrane types,
when a nonfouling inorganic solution was utilized, were -0.06 and -0.01
(19). These reference slopes with the inorganic solution are typical
of the compaction slopes for the respective membranes. It is clear
from Figure 6 that the flux decline rates for the settled sewage are
much higher than the chemically treated and settled sewage. The
continued steep decline of flux rates in Experiment #2 (settled sewage)
indicated significant fouling of the membranes due to the presence of
higher amounts of organic material compared to the flux decline rates
observed in Experiment #1 (chemically treated sewage) for which the
predominant cause of flux decline can be attributed to membrane compac-
tion. It should be noted that some flaky materials were loosened and
were observed in the concentrate when the membranes were flushed at
the end of the experiment with chemically treated sewage. This indi-
cated some deposition of the organic material on the membranes in
Experiment #1 although it was not as significant as in Experiment #2.
Also, it may be recognized that the flux decline slopes shown may not
be truly representative of the slopes expected in the field for a full
scale system because of the utilization of laboratory scale batch
-27-
-------
Membrane Type 300
Chemically Clarified Sewage
10 15 25 40
80 100
200 300
500
Time, hours
Membrane Type 500
Chemically Clarified Sewage
25 40
Time, hours
80 100
200 300
500
Figure 6
LOGARITHMIC VARIATION OF FLUX RATES
-------
recycling procedures. But the steeper flux decline shown for the
settled sewage as compared to the chemically treated sewage is quite
representative of the membrane fouling phenomenon. The longer test
durations up to 500 hours also demonstrate the effect of the membrane
compaction characteristics. However, it is recommendedthat a larger
capacity RO system at higher feed water recoveries on a continuous
flow stream be utilized for more exact information on flux decline
rates.
The looser membranes (Type 300) showed only a two gallon per day per
sq ft or 25% higher initial flux rate (10.5 gal/sq ft/day for type
300 and 8.5 gal/sq ft/day for type 500) as compared to tighter
membranes (Type 500) for Experiment No. 1. The difference in the flux
rates for the two membranes was less than 10% within 500 hours
(Experiment No. 1). Similar differences in flux rates were observed
for the two membranes in Experiment No. 2. However, it should be
noted that the modules utilized in these experiments had already been
used earlier for over 3000 hours under various investigations. The
difference in flux rates for the two membranes was considerably higher
when these membranes were new, (approximately 13.0 gfd for type 300
compared to 9.0 gfd for type 500), but after 3000 hours of operation,
the initial flux rates had been reduced to the present levels.
Typical feed and product water quality data and the percent salt
rejections for the flux decline evaluation experiments is shown in
Table 6. Permeate quality for membrane type 500 was significantly
better compared to type 300 as shown by the higher total solid and
total organic carbon rejections in both the experiments. Therefore,
as a result of the poorer salt rejections and only slightly greater
flux rates, the use of membrane type 300 was discontinued. As
expected, the percent salt rejections for membrane type 500 remained
approximately the same in the two experiments. However, from the
permeate quality shown in Table 6, it is clear that a significant
amount of total organic carbon (between 15 and 30 mg/1) was passing
through the tighter membrane type 500 at a feed water recovery of
approximately 25% and this content would increase at higher feed
water recoveries. Hence, it was indicated that further treatment of
the RO permeate would be warranted in order to utilize this water for
domestic purposes.
Additional experiments were continued to evaluate the permeate and the
brine water quality obtained via the tight membrance type 500 or
510 at high feed water recoveries of up to 90% with settled and
chemically treated sewages. It was decided to utilize a large batch
(approximately 1000 gallons) of raw waste for the evaluation of the
water quality data and also to produce sufficient RO concentrate that
could be further utilized for activated sludge feasibility investigations.
-29-
-------
TABLE 6
WATER QUALITY DATA FOR THE FLUX
DECLINE STUDY EXPERIMENTS
Total Solids
TOC
Experiment #1
Raw Sewage
Chemically Treated
& Settled (RO Feed)
Product Water:
Membrane Type 500
Membrane Type 300
_E
7
6
5
5
H
.5
.2
.5
.9
Turbidity
JTU
100
9
<1
<1
mg/1
883
740
65
215
%
Rejection
___
91
71
mg/1
177
72
16
24
%
Rejection
___
78
67
Experiment //2
Raw Sewage
Settled Sewage
(RO Feed*)
7.
7.
7
7
>200
158
965
764
212
122
__.
Product Water:
Membrane
Membrane
Type
Type
500
300
6.
6.
0
6
<1
<1
54
206
93
73
27
39
78
68
*pH adjusted to 7.0 with sulfuric acid.
Test Conditions:
Temperature - 65 to 75°F
Pressure - 600 psi
Feed pH - 6.0 to 7.0
Feed Recovery - Approx. 25%
-30-
-------
Experiments with Settled Sewage for Water Quality Evaluation
A sedimentation period of two hours was allowed for the raw waste.
A concentration test was performed on the settled effluent whereby the
brine was returned to the feed tank while the permeate was continuously
wasted. A schematic of the laboratory concentration procedure is
shown in Figure 7. Such a concentration system enabled the simulation
of the brine water quality at high feed water recovery levels. This
system was utilized until a tenfold concentration of the feed water
(as shown by the 90% reduction in the original feed water volume) was
achieved. The water quality data as obtained from the laboratory
analysis of the raw waste, the RO feed after sedimentation and pH
adjustment, and the brine at the 90% simulated feed water recovery is
shown in Table 7.
From the brine analysis shown in Table 7, it is seen that the concen-
trations of the various constituents in the brine are significantly
less then the expected concentrations (approximately 10 times the
feed concentrations). A comparison of this data was then made with
the computed water quality data obtained via a computer program avail-
able at Rex. This program computes the water quality data at high feed
water recoveries from the results obtained at low recoveries through the
pilot plant operation. The comparisons shown in Table 8 could only be
made for a limited number of constituents for which the product water
analyses were available at the lower feed water recovery. It is seen
that the computed brine has a significantly higher concentration of
various constituents compared to the simulated brine water quality.
The reason for such a discrepancy can be attributed to the limitations
on the information generated through the concentrate recycling procedure.
A schematic comparison of a full size multiple bank PO system designed
for a high recovery ratio and the recycling procedure utilized in the
laboratory can be made by comparing Figures 5 and 7. Actually, what
is happening in the recycling procedure is that a larger amount of
dissolved material is passing through the membranes in the permeate
than would actually be passed in a full size multiple bank RO system
designed for higher feed water recoveries. The reason for such a high
amount of material in the permeate of the recycling procedure can be
attributed to the low flux rates of the tubular system whereby it took
over 70 hours to reduce the feed volume from 975 gallons to 97.5 gallons
to achieve the 90% recovery level. Hence, due to the increased salt
passage into the permeates, the salt concentrations in the simulated
brine become lower than the computed salt concentrations for the
corresponding concentrate.
However, it should be kept in mind that the concentrate recycling
procedure does have the advantage of producing a reasonably concentrated
waste stream in the laboratory that can be utilized for further brine
treatment feasibility investigations without incurring the expenses for
a full size RO system. Moreover, quite reliable permeate and concen-
trate quality data at high feed water recoveries can be obtained through
-31-
-------
Membrane Bank
(Low Product to Feed
Recovery Ratio)
Recycle
Brine
Constant Volume Permeate
Removed
FIGURE 7
LABORATORY CONCENTRATE RECYCLING PROCEDURE
-32-
-------
TABLE 7
WATER QUALITY DATA - SETTLED SEWAGE FEED WATER*
Analysis
pH, units
Total Solids
Volatile Total Solids
Suspended Solids
Volatile Suspended Solids
Total Organic Carbon
Total Inorganic Carbon
Chemical Oxygen Demand
Total Nitrogen (Kjeldahl)
Nitrate as N
Nitrite as N
Ammonia as N
Total PO^ as P
Ortho P04 as P
Total Hardness as CaCO-j
Sulfates
Chlorides
Total Iron
Total Alkalinity as CaC03
Turbidity JTU
Raw
Sewage
8.5
996
420
160
35
196
46
537
30.5
1.56
0.91
255
200
126
0.7
275
165
Concentrate
90 Percent
Simulated Feed
Water Recovery
7.2
7196
1705
308
235
810
100
2260
170
0.20
0
7.5
5.55
1.93
2200
2600
975
8.6
1025
>500
NOTE: All results in mg/1, except where noted.
*Sample No. 1, RO treatment with tubular membrane type 510
**Supernatant after 2 hour sedimentation and pH adjustment with H
-33-
-------
TABLE 8
COMPARISON OF CONCENTRATE QUALITIES AT 90% FEED WATER RECOVERY*
Concentrate Quality Concentrate Quality
Obtained Through Calculated Through
the Experimental The Computer
Analysis Simulation Program
Total Dissolved Solids 6886 8950
Total Organic Carbon 810 1405
Chemical Oxygen Demand 2260 3590
NOTE: All results expressed in mg/1.
*Sample No. 1, RO treatment with tubular membrane type 510.
-34-
-------
the computer program mentioned.
Another experiment was made on a second sample of the raw sewage from
the Milwaukee Sewage Treatment Plant following two hour sedimentation
and pH adjustment. The feed and the product water quality data were
obtained at a low feed water recovery of 20 percent. This data was
then utilized to predict the permeate quality, overall percent salt
rejections and the concentrate quality at a feed water recovery of
91.4% with the help of the computer program. The results of the
laboratory analysis as well as the calculated data at higher feed water
recovery is shown in Table 9.
The permeate and concentrate water qualities shown in Table 9 can be
considered to be typical of the two streams obtained through the reverse
osmosis treatment of any high strength domestic waste at high feed
water recovery ratios. It can be seen that although the TDS content
in the permeate is only 70 mg/1, the 6005, the TOG and the COD contents
are extremely high at 108, 67 and 182 mg/1, respectively. Also, the
overall soluble TOG rejection is of the order of only 50%. This further
illustrates the poor organic rejections shown by cellulose acetate
membranes (CA) at high recovery ratios.
From the experiments described above it may appear the the physical
handling of settled sewage through the tubular RO systems can be done
without a significant number of problems, but actually several mechan-
ical problems were encountered during the course of the experiments.
It appears that a flow scheme in which the primary effluent is directly
utilized for RO treatment, would present a great risk to the life of the
mechanical as well as the membrane hardware. The amenability of even
the tubular RO system to plugging was demonstrated during the second
experiment with the settled sewage. It was found that in spite of the
removal of the larger solids, sufficient suspended material in the form
of gum, grease and other floating organic material remained in the
settled supernatant and had a tendency to conglomerate and block the
flow through the tubular system. In one instance of a plugged module,
it was found that the fine suspended organic material had conglomerated
with hair in the presence of grease to plug the tubular system.
Moreover, in the new Havens tubular system, the solids handling capacity
has become further limited because of the introduction of the turbulence
promoter rods provided for minimizing the concentration polarization
effects. Therefore, it is considered essential that prior additional
treatment over and above plain sedimentation of the raw sewage will be
needed before RO treatment.
Experiments with Chemically Treated Sewage
A ferric chloride dosage of 150 mg/1 was utilized for the chemical
flocculation of the raw waste and following a two hour sedimentation
period, the settled effluent was treated by reverse osmosis. Since
the main objective of the experiments was to evaluate the water quality
-35-
-------
TABLE 9
WATER QUALITY DATA - SETTLED SEWAGE FEED WATER
Laboratory Analysis Results
Analysis
Raw 2
Sewage
8.2
1912
963
1043
684
869
525
—
1202
508
76
—
—
—
—
—
—
—
—
—
—
—
—
—
360
—
RO 3
Feed 20%
6.5
1345
458
321
273
1024
308
444
740
300
24
110
20
335
260
75
18.7
21
10.3
3.2
250
230
0.9
0.4
142
1.2 x 105
Product
Water @
Recovery
5.9
30
14
0
0
30
53
74
85
31
3
29
3
10
5
5
0
1.1
0.12
0.01
2.5
11
0.16
0.1
12
0
Calculated Data Through Computer
Program P 91.4% Feed Recovery
pH, units
Total Solids
Total Volatile Solids
Suspended Solids
Volatile Suspended Solids
Total Dissolved Solids
BOD 5
BOD21
COD
TOC
TIC
Soluble TOC
Soluble TIC
Total Hardness as CaCOo
Calcium as
Magnesium as
Organic Nitrogen as N
Ammonia as N
Total Phosphate as P
Ortho Phosphate as P
Sulfate
Chloride
Total Iron
Ferrous Iron
Alkalinity as CaCOo
Total Coliforms, ///ml
1. Sample No. 2; RO treatment with tubular membrane type 510. 2. Screened through mesh No. 8.
3. Supernatant after 2 hours sedimentation & pH adjustment with sulfuric acid. 4. All results in rag/1,
Product
Water
70
36
0
0
70
108
151
182.6
67
6.4
54
6.2
23
12
11
0
2.5
0.3
0.02
6
25
0.3
0.2
26.6
0
% Rejection
by Membrane
94.8
92.3
100
100
93.1
65.0
65.9
75.3
77.5
73.4
50.9
68.8
93.1
95.5
85.0
100
88.0
97.0
99.0
97.6
89.0
64.0
52.8
81.2
100
Concentrate
Quality
—
—
—
—
11175
2439
3560
6671
2776
212
706
166
3651
2901
753
218
218
117
36
2847
2409
7
2.6
1370
—
-------
data at high feed water recoveries and since considerable difficulties
had been experienced earlier in obtaining a representative brine
sample at high recoveries with the tubular system in batch experiments,
an alternate method of achieving the same objective was adopted. It
was indicated through some cursory experiments that recently developed
high flux cellulose acetate membranes marketed by Gulf Environmental
Systems with the spiral wound configuration had over 300% greater flux
rates with comparable rejections shown by the tubular membrane type 510.
Also, the clarity of the chemically treated sewage was found to be
suitable as feed to the spiral wound modules for short term feed
concentration tests. With the switch over to the spiral wound membrane,
it took only six hours to concentrate 800 gallons of chemically treated
sewage compared to over 50 hours for corresponding amounts with the
tubular system. Samples of raw, chemically treated sewage and the RO
product water at a feed water recovery of 35% were analyzed in the
laboratory. The results were also subjected to a computer program
discussed earlier and the product and brine water quality at 92% feed
water recovery level was calculated. The results of the laboratory
analyses as well as the calculated data of the higher feed water
recovery are shown in Table 10. From the brine qualities shown in
this table, it is clear that, because of the short duration of the
concentration experiment the computer calculation and laboratory
analysis results match quite closely (within 10% compared to approximate-
ly 25% for TDS in Table 8 for the tubular system).
The product water at the high feed water recovery of 92% was again found
to be of extremely good quality as far as inorganic content was concerned.
The permeate was calculated to have a TT)S concentration of 140 mg/1,
which is well below the recommended public health standard for dissolved
solids (500 mg/1). However, a high amount of organic material was again
found to be permeating through the CA membranes as shown by the calcu-
lated BOD, COD and TOC values in Table 10. At this point in time, an
interesting observation was made relative to the brine and permeate
qualities at high feed water recoveries.
A composite sample of product water was obtained at the 92% recovery
level from the batch recycling procedure for permeate investigation
purposes. It was found to exhibit a TOC value of only 36 mg/1 as
opposed to the calculated TOC value of 51 mg/1 (Table 10) at corres-
ponding recoveries. Also, the calculated brine TOC of 525 mg/1 was
considerably less than the analyzed TOC value of 710 mg/1 at 92%
recovery. When a mass balance on the TOC values was made, the laboratory-
analyzed values checked out within 10% accuracy. This meant that some
specific organic compounds were passing through the CA membranes and
once these had passed from the fixed volume of feed utilized in a batch
type experiment, further concentration of the feed would not be correctly
reflected in the organic quality of the permeate or brine through the
computer program. The above conclusion was further supported later in
the course of the permeate investigations when it was shown that approx-
imately 70% of the organic material permeating through the membrane was
ethanol for the Milwaukee sewage utilized. However, for purposes of the
-37-
-------
TABLE 10
WATER QUALITY DATA - CHEMICALLY TREATED & SETTLED SEWAGE FEED WATER
1
Laboratory Analysis Results
i
U)
00
I
Analysis
pH, units
Total Solids
Total Volatile Solids
Suspended Solids
Volatile Suspended Solids
Total Dissolved Solids
BOD 7
Soluble BOD7
BOD 21
COD
Soluble COD
TOC
TIC
Soluble TOC
Soluble TIC
Raw
2
Sewage
8.6
1068
364
144
106
924
262
—
403
472
—
173
61
—
—
RO -
Feed
6.6
959
286
3
3
956
177
146
239
295
291
91
21
90
20
Product
Water C
-------
TABLE 10 (Cont.) -
WATER QUALITY DATA - CHEMICALLY TREATED & SETTLED SEWAGE FEED WATER
1
Calculated Data Through Computer
LO
vO
I
Laboratory Analysis Results
Analysis
Organic Nitrogen as N
Ammonia as N
Nitrate as N
Nitrite as N
Total Phosphate as P
Ortho Phosphate as P
Total Hardness as CaC03
Calcium as CaCC>3
Magnesium as CaCO-j
Sulfate
Chloride
Total Iron
Total Alkalinity as CaC03
Phenols
Raw
Sewage ^
16.2
13.6
2.23
0.07
5.5
3.6
328
260
68
—
—
1.5
285
0.5
R0
Feed3
7.0
14.9
2.25
0.05
0.17
<0.05
318
250
68
118
334
1.1
100
0.5
Product
Water
@ 35%
Recovery
0.3
8.1
0.77
0.03
0.06
<0.05
4
2
2
1
27
<0.1
4
0.5
Concentrate
92%
Recovery
72
68
1.7
0.6
0.6
<0.05
3590
2550
1040
1240
3050
—
1250
—
Program @ 92% Feed
Product
Water
0.6
11.5
1.3
0.04
0.09
—
8
4
4
2
55
0.2
8.5
—
Percent
Rejection
by
Membrane
91.4
22.8
42.2
20.0
47.1
—
97.5
98.4
94.1
98.3
83.5
81.8
91.5
—
Recovery
Concentrate
Quality
79
54
16.2
0.2
0.9
<0.1
3650
2800
850
1440
3400
11
1125
—
1. RO treatment with high flux SDiral-wound membranes.
2. Screened through mesh No. 8
3. Supernatant after flocculation with 150 rag/1 FeCl3 anc* ^ hours sedimentation.
4. All results in rng/1 except where noted. Operating pressure - 600
-------
evaluation of Che water quality, the calculated data through the computer
program can be considered more representative for the inorganic ions
while the analyzed brine values can be considered typical of the organic
content.
Overall Evaluation of the Membrane Rejection Characteristics
The tighter membrane Type 510, exhibited a consistent rejection pattern
for the various inorganic and organic species. In general, the percent
rejection of the dissolved inorganic matter was significantly better
than that of the dissolved organic material. Among the various inorganic
ions, the rejection of the divalent ions such as calcium, magnesium,
and sulfates was considerably better than the tnonovalent ions such as
chlorides and ammonium. Following is a summary of the typical percent
rejections expected for various constituents in domestic sewage when
tighter membrane type 510 is utilized at a feed water recovery level
of approximately 92%.
Total Dissolved Solids 93%
Total Volatile Solids 92%
Total Hardness 93%
Soluble TOC 40-50%
Soluble TIC 68%
Organic Nitrogen 100%
Ammonia Nitrogen 88%
Phosphates 98%
Chlorides 89%
Sulfates 97%
Alkalinity 81%
Total Colifonns 100%
The percent rejections for the high flux spiral wound membranes(utilized
for obtaining the RO concentrate in a shorter time) were either similar
or slightly lower for most inorganic and organic constituents at corres-
ponding recovery levels. However, a significant difference in rejection
characteristics was shown for ammonia nitrogen. The percent rejection
for ammonia nitrogen was found to be only 25% at 90% recovery level by
the high flux spiral wound membrance as compared to 88% for the tight
tubular membranes.
Activated Sludge Feasibility Results
Separate experiments were conducted on the RO concentrates from the
settled sewage and the chemically clarified sewage for the evaluation
of the biological oxidation of these concentrates. Since it had
already been indicated that prior chemical clarification of the raw
sewage would be necessary even when tubular RO systems are utilized,
main emphasis of evaluation was shifted toward RO concentrates from
chemically clarified sewage. The discussion of the results of the
bio-treatment of the settled sewage concentrate along with a complete
-------
record of the biological oxidation data are presented in Appendix II.
Reverse Osmosis concentrate of the chemically treated sewage obtained
at a feed water recovery of 92% was subjected to biological oxidation.
A sample of the RO concentrate was subjected to atomic absorption
analysis for measuring any metallic ion concentration that might be
toxic to activated sludge biota. The result of this analysis is
shown in Table 11. It can be seen from this table that there are no
significant metallic ion concentrations in the RO concentrate except
zinc and silica which were found to be 6.6 and 72.3 mg/1, respectively.
The return sludge from the Milwaukee sewage treatment plant was
found to be suitable for system start-up and no acclimitization of the
A.S. biota was needed. Also, subsequent biological oxidation tests
made it clear that there were no adverse effects of zinc, silica or
any other ion buildups that might be toxic to activated sludge biota.
Batch kinetic experimental procedures were employed for A.S. feasi-
bility investigation. Initially the pilot units were operated in the
range of 3400 to 10,000 mg/1 MLSS levels. Aeration times up to 24 hours
were utilized. It was found that although biological oxidation of
the organic matter was occuring at a rapid rate, the settling proper-
ties of the activated sludge for mixed liquor solids levels at 7000
and 10,000 mg/1 were extremely poor. Therefore, the mixed liquor
solids levels were readjusted in the range of 1500 to 6000 mg/1 by
dilution for further experiments. The results of the biological
treatment efficiencies are shown in Figure 8. The biological
oxidation of the organics was measured in terms of the total organic
removals in the filtered mixed liquor samples at various aeration
time intervals and MLSS levels. By plotting the percent soluble TOC
remaining against the product of mixed liquor suspended solids (Sa)
in mg/1 and time of aeration (t) in hours, the effect of various
MLSS and aeration times is eliminated for design purposes. Thus,
if 90% soluble TOC removal is achieved at a Sa x t value of
20,000 mg/1 hrs., several design combinations can be obtained, e.g.
at a design MLSS level of 5000 mg/1, the required design aeration
time will be 4 hours while the corresponding time will be 5 hours
at a MLSS level of 4000 mg/1. The curves in Figure 8 are shown for
two sets of data. It is clear from these curves that the biological
treatment efficiency of the data taken between 3800 and 6000 mg/1
MLSS was greater than the efficiency for MLSS levels below 4000 mg/1.
Therefore, the optimum mixed liquor suspended solids levels may lie
between 4000 and 6000 mg/1 if the sludge separation characteristics
are found to be good. The highest soluble TOC removals achieved
in the optimum MLSS range were found to be of the order of 90 to 92%.
In most cases, soluble TOC removals of the order of 90% were achieved
in 4 to 10 hours aeration time depending upon the suspended solids
level maintained in the aeration chamber. There was no significant
increase in the percent soluble TOC removals beyond a MLSS x Time
value of 20,000 mg/l/hr and hence this value is recommended for
design purposes.
An important dependent parameter measured in the biological oxidation
-41-
-------
TABLE 11
RESULTS OF ATOMIC ABSORPTION ANALYSIS ON RO CONCENTRATE
Analysis Ion Concentration, mg/1
Chromium 0.0
Cadmium 0.0
Nickel 0.8
Copper 0.1
Lead 0.0
Zinc 6.6
Arsenic 0.0
Silver 0.0
Aluminum 0.02
Silicon (Si02) 72.3
Cyanide 0.0
-42-
-------
60
40
O
30
0)
w
0)
f.
20
00
c
0)
i-t
8
0)
fH
•s
10
MLSS: 1500 - 4000 mg/1
MLSS: 3800 - 6000 mg/1
MLSS x Time x 103
20
40
60
FIGURE 8
80
100
120
BIOLOGICAL TREATMENT EFFICIENCY CURVES
-43-
-------
tests was oxygen uptake rate. These rates were measured manually with
a dissolved oxvgen meter by removing a sample from the pilot unit,
measuring the uptake rate and then returning the sample to the unit.
The results of the oxygen uptake rate measurements at the high and low
mixed liquor suspended solid levels are shown in Figure 9. As expected,
the 0^ uptake rate increased markedly immediately after feeding but
stabilized to a sustainable average rate within 2 to 5 hours. These
rates are indicated by the flat portion of the curve. As food became
scarce, the rate fell off gradually until the next feeding. The
sustainable oxygen uptake rates at various mixed liquor levels are
shown in Table 12. An average uptake rate in the range of 30 to
40 mg/l/hr can be used for design purposes and these should be easily
attainable with existing aeration equipment.
As discussed earlier, the solids liquid separation step imposed the
limiting restraint towards the maximum level of mixed liquor solids
that could be utilized. It was found that the settling velocities
at 7000 and 10,000 rag/1 solid levels were extremely low at 0.35 and
0.13 ft per hour, respectively as compared to the generally acceptable
settling velocity of 4 ft/hour. Settling velocities greater than
5 ft/hour were achieved in most cases at MLSS levels below 6000 mg/1.
The variation of the settling velocities with mixed liquor suspended
solids is shown in Figure 10. The settling velocities were found to
vary widely for specific MLSS levels, but a trend of decreasing
settling velocities with increasing mixed liquor solids is quite
clearly shown in this figure. Typical settling curves at various
mixed liquor solid levels are also shown in Figure 11. It can be
noted here that the settling velocity decreased as the concentration
of the mixed liquor solids increased. This effect has also been
documented elsewhere (20). The SVI index was generally good and
ranged between 23 and 102 for the recommended mixed liquor solids
range (below 6000 mg/1).
The loading rates in terms of #BOD//'MLVSS were in the range of 0.25
to 0.4. Higher loading rates could not be evaluated within the
scope of these bench scale investigations because of the limitation
on the amount of RO concentrate available for feeding purposes. The
limitation on the availability of the RO concentrate also imposed a
restraint on the evaluation of the expected sludge volume production.
The data available in this respect was found to be extremely erratic
and no definite conclusions could be drawn. Therefore, it is recom-
mended that higher loading rates as well as sludge production be
evaluated in the future based on the results of this investigation.
The settled effluent after biological oxidation had a TOC value in the
range of 60 to 150 mg/1 and a suspended solids concentration in the
range of 100 to 150 mg/1. The poorer effluent quality shown during
thpse hench scale investigations may have been a result of overaeration
of the mixed liquor in the aeration chambers, since no control was
-44-
-------
200
160
120
i
0)
4J
CO
CM
o
40
0
6 8
FIGURE 9
10
12
OXYGEN UPTAKE RATE CURVE - CHEMICALLY TREATED SEWAGE CONCENTRATE
14
16
-------
TABLE 12
BIOLOGICAL OXIDATION DATA
CHEMICALLY TREATED SEWAGE CONCENTRATEJ
Average
Effluent Sustainable
MLSS
mg/1
5850
5000
3800
4000
2500
1500
MLVSS
mg/1
3450
2900
2000
—
—
—
pH
8.0
8.0
8.0
8.1
8.1
8.2
% TOC Removal Per
24 hr aeration
91.5
92.5
91.0
87.2
84.7
71.5
S.S. '
mg/1
103
135
135
' 0- Uptake
Rate rag/l/hr
30
36
27
62
40
19
1 TOC of RO concentrate; 830 and 810 mg/1 for two samples
2 After 24 hour aeration and one hour settling
-46-
-------
30
£ 20
•H
O
O
r
-------
1000
oo
70
TYPICAL SETTLING CURVES FOR RO CONCENTRATE - CHEMICALLY TREATED SEWAGE
-------
exercised on the amount of air being supplied to the aeration units as
long as sufficient dissolved oxygen was exhibited in the mixed liquor.
The high TOG values of the settled effluent may also have been a result
of the increase in the bio-resistant fraction of the sewage due to
tenfold concentration. It is expected, however, that the suspended
solids removal in the settled effluent will improve considerably for
a larger size plant as compared to the pilot unit test results. Also,
the TOG values of the settled effluent can be expected to reduce
significantly for lower strength domestic sewages. It may also be
possible to reduce the organic quality of the biologically treated
RO concentrate by undergoing a second biological oxidation in series
in an aerated lagoon. This concept could not be evaluated within
the scope of this study but such evaluations are recommended for future
studies. The TDS content of the settled effluent ranged between 6000
to 7000 mg/1 as expected. However, the ammonia nitrogen concentration
in the treated effluent was found to be quite high at 87 mg/1. This
indicates that if these effluents are to be discharged to streams,
stripping of ammonia nitrogen will be necessary even though the
organic quality may meet the effluent discharge standards.
Permeate Investigation Results
The objective of this phase of work was to identify any major organic
compounds that could pass through the CA membranes. A series of
gas/liquid chromatography tests were performed to accomplish this
objective. A detailed description of the methods and procedures
employed, sample preparation techniques, chromatograms of various
samples and the quantitative analysis results are presented in Appendix
III. Only the highlights of this work will be discussed in this
section.
A typical chromatogram, representative of the product samples from the
reverse osmosis tests on Milwaukee Sewage is shown in Figure 12. It
consisted generally of four peaks A, B, C and D of which peak B was
the largest. The compounds whose peaks did not match peaks A, B, C
or D because of the difference in their elution times and were there-
fore concluded to be not responsible for these peaks were as follows:
Formic acid, acetic acid
Methylamine, ethylamine
Diethylamine
Triethylamine
Formamide
Ethyl acetate
1-propanol, 2-propanol
Phenol
However, it was found that the largest peak B was matched by ethanol
(C2H5OH) in all tests. Hence, the largest peak was identified as
ethanol. Quantitative analysis (by graphical measurement of the area
-4-9-
-------
Water Elution Peak
FIGURE 12
TYPICAL CHROMATOGRAM FOR RO SAMPLES OF MILWAUKEE SEWAGE
-50-
-------
under the chromatogram peaks) of these peaks indicated that the ethanol
content (peak B) was of the order of 70% of the total TOG for most
permeate samples. The concentration of the compounds producing the
other peaks was indicated to be very small (of the order of 2.0 mg/1
or less). Thus, it would appear that the major portion of the organics
in the permeate were represented by peak B or ethanol for the
Milwaukee sewage.
Chromatograms were also run on raw sewage and other samples to answer
some questions concerning the origin and occurrence of the apparent
ethanol peak in the permeates. These questions were raised in light
of the possibility that the presence of ethanol in Milwaukee sewage
may have been a result of Milwaukee's large brewing industry. Peaks A,
B, C and D were found in the Milwaukee raw sewage samples. As expected,
the portion of the TOC attributable to peak B (ethanol) was small for
the raw sewage sample, but the ethanol peak could be distinctly
identified. When chromatograms on the raw sewage samples from other
nearby cities of Kenosha and Racine were run, no significant amount of
peak B could be identified. Therefore, it was concluded that the high
concentration of ethanol was peculiar to Milwaukee sewage because of
its brewing industry. Also, it was noticed that various other peaks
representing other unidentifiable low molecular weight organics were
either smaller or nonexistent in the raw sewage samples from other
cities compared to Milwaukee sewage. This necessitated the reverse
osmosis testing of a sewage sample from a city that did not have a
brewing industry.
Therefore, a raw sewage sample from the City of Racine, Wisconsin was
subjected to RO evaluations after chemical clarification. The results
of these tests are shown in Table 13. It was found that the percent
rejection of soluble organic carbon was only 77% at a feed water
recovery of 45%. When these results were projected to the 90% recovery
level, the soluble organic carbon rejection was calculated to be only
60%. The ethanol content of the feed and permeate was less than
1 mg/1 as TOC and yet the soluble organic carbon rejections were not
significantly better than for Milwaukee sewage which had contained
much larger concentrations of ethanol. This indicates that there is
no single predominant organic compound common to various sewages which
is responsible for the poor separation performance of the cellulose
acetate membranes for soluble organic material. A variety of organics
seem to pass through these membranes in very small concentrations and
the nature of these compounds also seem to vary over a wide range in
various sewages. Identification of all the individual species was
beyond the scope of this project, but further investigations on
various sewages are recommended to confirm the finds on the Milwaukee
and Racine sewages.
Cursory activated carbon treatment tests were also conducted on the RO
permeate of the Milwaukee sewage to study the post treatability of the
product water towards making it of potable quality. The results
-51-
-------
TABLE 13
WATER QUALITY DATA FOR RACINE SEWAGE
Analysis
Total Dissolved Solids
Soluble Organic Carbon
Ethanol as C
Feed
Quality, mg/1
Permeate Quality, mg^l
45% 90%
Recovery Recovery
717
39
32
9
61
15.6
*Calculated through a computer program from the laboratory
analysis results at 45% recovery level.
-52-
-------
indicated that the Milwaukee sewage RO permeate is not amenable to
activated carbon treatment as shown by carbon isotherm tests (Table 14,
Figure 13). Only 25% of the product water TOG was adsorbed at a
Carbon/TOC ratio of 12. This indicated very poor efficiency of carbon
utilization which seems to be the result of the poor adsorption affinity
of high concentrations of ethanol in the RO permeate. However, this is
peculiar to Milwaukee sewage only and has been shown before in an
earlier study (21). The other Milwaukee area sewages could, however,
be efficiently treated with activated carbon. Therefore, it is expected
that the post treatment of RO permeates would be feasible with activated
carbon for other sewages not containing ethanol.
-53-
-------
TABLE 14
CARBON ADSORPTION ISOTHERM TEST DATA
(MILWAUKEE SEWAGE RO PERMEATE)
Carbon Dose TOC of Permeate mg TOG Adsorbed Adsorption Capacity
mg/1 mg/1 mg Carbon Used mg TOC/mg Carbon
0 26 — 0.12
125 22 0.032
250 21 0.020
500 20 0.012
1250 19 0.0056
2500 18.5* 0.0032
Contact time: 24 hours
-------
150
100
80
60
40
30
g 20
W
o
I
T3
Q>
X)
o 10
09
o
H
L«dOSAlD^«%fflm:i%l^@^a£a^G«^i^^;9t»^ it
I I !
Equilibrium TOC
Concentration, mg/
8 10
20
FIGURE 13
30
50
70
100
CARBON ADSORPTION ISOTHERM FOR MILWAUKEE SEWAGE RO PERMEATE
-55-
-------
SECTION VII
APPLICABILITY OF REVERSE OSMOSIS IN THE RENOVATION OF WASTEWATER
This study has made it possible to outline the role of reverse osmosis
in the reclamation of wastewaters. It has clearly demonstrated that
suitable pretreatment of the raw sewage will be required prior to the
RO treatment even when the tubular configuration is utilized. This
would be necessary for protecting the mechanical hardware as well as
the RO membranes. Also, it was shown that the product waters from
the RO treatment were of excellent quality as far as inorganic constit-
uents were concerned but would have to be followed up by some form of
post treatment for the removal of the permeating organics to render
these waters of potable quality. Since the technical feasibility of
utilizing the RO process for the treatment of pretreated domestic waste
waters has been proven, the other most important factors affecting the
utility of this process in the waste reclamation area are:
1. The need to demineralize wastewater.
2. The economic attractiveness of the reverse osmosis process
compared to competing processes.
3. The potential of using reverse osmosis as a pollution
control device with discharge to a receiving stream.
The need for demineralization of the waste water has often been emphasized
in recent literature (2,3,4,5,9). Moreover, the fact that the dissolved
solids content of domestic wastewaters ranges from 500 to 1500 mg/1 and
the USPHS standards call for a maximum TDS content of 500 mg/1 for
potable water indicates that the removal of dissolved solids from the
wastewaters would be essential in its renovation towards potable use.
Furthermore, each domestic use of water supply adds from 300 to 800 mg/1
of TDS to the original dissolved solids content of the fresh water.
With the impending legislation being sought in several states towards
limiting the TDS content of the effluent discharges, it is imperative
that the demineralization of the wastewaters be required in the future.
Thus, with the establishment of the need for demineralization, the
following treatment scheme utilizing reverse osmosis was developed that
would not only provide potable quality water at economically attractive
costs for domestic wastewaters but also would reduce pollution to
discharging streams:
Proposed Treatment Scheme
Figure 14 shows a schematic of the recommended flow scheme comprised
of various treatment processes. This scheme is designed for a medium
strength domestic waste having a TOG content of approximately 100 mg/1
and TDS concentration of approximately 800 mg/1. The schematic layout
-57-
-------
Water Supply
Source
TDS: 250-400
Backwash 0.05 MGD
3 Q
O
o- x:
0)
.*
(0
Split Flow 4.8 MDD
Raw Waste
10 MGD
IDS:800
TOC:100
Chemical
Clarification
9.8 MGD
IDS:800
TOC:40-50
Turb:l-5
Sand
Filtration
Reverse
Osmosis
TOC:40-50
Turb: 1
4.5 MGD
TDS:50-75
TOC: 20-25
oncentrate
0.5 MGD
TDS:7500
TOC:200-300
Water Use
13. 3 MGD
00
i
Incineration
Sludge
0.05 MGD
Activated
Sludge
9.3 MGD
TDS:400
TOC:0
Ozone
Regeneration
Ammonia
Stripping
'iltration
Discharge
to Water
Source
0.45 MGD
TDS:7500
TOC:20-40
9.3
MGD
IDS:400
TOC:1-5
Activated
Carbon
9.3 MGD
TDS:425
TOC:35
FIGURE 14
TDS and TOC Values in mg/1
RECOMMENDED TREATMENT SCHEME
-------
has been described for a plant capacity of 10 mgd and economic projections
have been drawn for the same. The flows handled by each subprocess and
the expected water qualities before and after treatment are also shown
on the flow diagram. Other assumptions, logistics and the general rules
laid in the development of the above schematic are as follows:
1. The effluent after chemical clarification is free of most
suspended material. The recommended chemicals are ferric
chloride and alum as discussed earlier in the report. No
extra pH adjustment is needed for this water before RO
treatment.
2. Sand filtration of the chemically treated effluent is to
be provided for reducing the membrane fouling by any
residual suspended solids.
3. The sand filtered effluent will be split for RO treatment
in such a proportion so as to produce less than 500 mg/1
TDS in the combined effluent in accordance with USPHS
standards.
4. A 90% recovery of the feed flow to RO was considered
feasible based on the present study.
5. Only 50 to 60% removal of soluble organic carbon is
expected through the RO treatment at a feed water recovery
of 90%. However, the TDS removals can be expected to be
in the range of 93 to 95%.
6. The concentrate from the RO treatment will be biologically
oxidized and a minimum of 90% reduction in the total organic
carbon can be achieved. The biologically treated effluent
would remain concentrated in the total dissolved solids
but would be rendered of such quality that is comparable
to conventional secondary effluents in organic content.
This effluent may have to be stripped of ammonia nitrogen
and then can be discharged to the downstream end of the
fresh water source under consideration.
7. The split flow when combined with the RO effluent will
produce a water quality of less than 500 mg/1 TDS and 30
to 40 mg/1 TOG. This water will then be treated with
activated carbon to reduce the dissolved organic matter.
8. Incineration facilities required for the regeneration of
activated carbon will also serve the purpose of sludge
disposal from chemical clarification, and wasted activated
sludges.
9. The activated carbon treated effluent will have a TOC
-59-
-------
value in the range of 1 to 5 mg/1. This remaining
organic carbon will then be oxidized with ozone. The
effluent water is not only expected to be free of organic
matter but also will be rendered sterile because of
ozone use and hence will be of potable quality.
From the above recommended flow scheme, a 93% overall recovery of
reusable and potable water would be achieved. The additional make
up water in each cycle of water use will be approximately 7%. The
increase in dissolved solids in the treated water as compared to the
original fresh water dissolved solids level may slightly increase
the percentage of split flow treatment by reverse osmosis in the
subsequent cycles. These considerations however will vary in
specific situations and may be controlled as necessary. The above
scheme would reduce the organic pollutant discharge to streams by
almost eight-fold compared to the conventional secondary treatment
discharges. The above claim can be verified as follows:
Assuming a TOG value of 15 mg/1 for conventional secondary effluents,
the Ibs TOC discharge to streams from a 10 mgd plant =
15 x 8.34 x 10
- 1250 Ibs TOC/day,
while only 4.5% of raw flow will be discharged to streams after the
biological treatment of RO concentrates. Assuming a maximum TOC value
of 40 mg/1 for this effluent, the maximum Ibs TOC discharged to streams
from the proposed treatment scheme =
40 x 8.34 x 0.45
= 150 Ibs TOC/day
which is less than 15% of the Ibs discharged from the conventional
secondary effluent and is comparable to the tertiary treatment discharges.
Alternatively, it may also be possible to utilize the concentrated
RO brines for the recovery of fertilizer products or may directly be
able to apply to soil because of its rich mixture of nutrients. A
feasibility study in this regard is recommended for future studies.
Economics of the Proposed Treatment Scheme
The economic attractiveness of the proposed treatment schematic will
be analyzed by comparing its cost with the cost of water use and its
treatment by conventional methods. These costs have been developed
for a 10 mgd sewage handling facility. The total treatment costs for
conventional and advanced methods have been utilized from published
literature (9,22,23,24). The total operating cost of RO treatment
alone has been assumed as 35C/1000 gal. based on spiral wound RO
membranes for a five mgd capacity RO plant (25). Sludge disposal costs
-60-
-------
were not included in these comparisons as these are expected to be
similar in both cases.
(A) Total Costs Without the Reuse of Water
Cost Item
Fresh water use (based on
75% conversion of fresh
water used to sewage)
Conventional primary and
secondary treatment
Chlorination before
discharge
Therefore, the present cost of water
Flow
mgd
13.33
10.0
10.0
use and
Unit Cost
C/1000 gal
10
12
1.0
treatment = $2
$/day
1,333
1,200
100
2,633
,633/day
or 26.3 C/1000 gal
(B) Total Costs with the Reuse
Cost Item
Fresh water use after first
cycle (based on 93% conversion
of sewage to reusable water
and 75% conversion of fresh
water used to sewage)
Chemical clarification
Sand Filtration
Reverse Osmosis
Activated Carbon
Activated Sludge
Ammonia Stripping
Ozonation
and Treatment of Water
Flow
mgd
4
10
10
5
9.3
0.5
0.5
9.8
Unit Cost
c/1000 gal
10
7.5
3.0
35.0
8.5
12.0
10.0
5.0
$/day
400
750
300
1,750
790
60
50
490
4,590
Hence, the proposed treatment costs « $4,590/day or 45.9 C/1000 gal
-61-
-------
Therefore,-comparing the costs in (A) and (B) Sections, it is evident
that for only an additional 20C/1000 gallons cost, it would be
possible to convert our domestic wastes into reusable potable water
supplies and also reduce the pollutant discharges by nearly eight-fold
to the fresh water supplies as compared to the present conventional
practices. Apart from the tangible benefits, there would emerge a
large number of intangible benefits by implementing the above
recommended scheme. These indirect benefits may be in the form of
improved environment, availability of clean water for recreational
activities, meeting of large demands of water supplies from the
continued industrial growth. The intangible effects of these
improvements on communities would be widely varied and a great
stimulant to the general economy.
The economics for this treatment scheme can be looked at in another
way. The complete cost of treatment alone with the recommended
scheme is 45.9C/1000 gallons, and when a cost recovery value because
of the 93% water reuse is applied, the net treatment cost is only
32.6C/1000 gallons. These treatment costs would further reduce with
increase in plant size as well as the improvements in equipment and
hardware to make this treatment scheme even more attractive.
However, it should be pointed out here that the above schematic
will be most applicable for those domestic wastes that are amenable
to efficient treatment via activated carbon. In the case of a
domestic waste, such as for Milwaukee, which contains a large amount of
ethanol that is not efficiently treatable by activated carbon, con-
ventional primary and secondary treatment would be required prior to
the upgrading of the secondary effluents by reverse osmosis, activated
carbon and ozonation on a split flow basis. The cost of treatment
n such cases would be higher than for the recommended flow scheme
•i would have to be evaluated for specific situations.
-62-
-------
SECTION VIII
ACKNOWLEDGMENTS
This twelve-month study was conducted by the Ecology Division of
Rex Chainbelt Inc. Many people contributed to the success of this
project. The Bench Scale tests were conducted by Messrs. Charles
Hansen, Frank Toman, Donald Murray and Mahendra Gupta. The
analytical determinations were performed in the process equipment
laboratory of Rex Ecology Division under the direction of Richard E.
Wullschleger. The gas chromatography work was also conducted by
Richard E. Wullschleger and his report of the results obtained is
located in Appendix III.
The principal author of the report is M.K. Gupta. Acknowledgment
with sincere thanks is extended to Donald G. Mason whose helpful
advice and guidance was a source of inspiration throughout the
conduct of this study.
Encouragement and assistance from EPA personnel, Messrs. Walter
Feige, Project Officer, and J.M. Smith and the cooperation of the
staffs of the sewage treatment plants of Milwaukee, South Milwaukee,
Brookfield, Racine, Kenosha and Waukesha is deeply appreciated.
-63-
-------
SECTION IX
REFERENCES
1. Mason D.G., The Reverse Osmosis Process and its Potential for
Application in Water and Waste Treatment, Research and Development
project report, Rex Chainbelt Inc., Nov. 1968.
2. Channabasappa, K.C., "Reverse Osmosis Process for Water Reuse
Application, Water - 1969", Chemical Engineering Progress Symposium
Series, Vol. 65, No. 97, 140-147, 1969.
3. Bregman, J.I., "Membrane Processes Gain Favor for Water Reuse",
Environmental Science and Technology, Vol. 4, No. 4, Aoril 1970.
4. Kline, G.M. "Cellulose Acetate Membranes for Waste Water
Purification", Modern Plastics, 141-148, May 1968.
5. "Membrane Science and Technology - Industrial, Biological and Waste
Treatment Processes", Proceedings of Battelle Memorial Institute
Conference held at Columbus, Ohio, October 1969, Plenum Press, New
York, 1970.
6. Reverse Osmosis as a Treatment for Wastewater, A final report to
U.S. Public Health Service, Contract No. 86-63-227, Report No. 2962,
January 1965.
7. Study and Experiments in Waste Water Reclamation by Reverse Osmosis,
by Gulf Environmental Systems, for EPA, Contract No. 14-12-181, May,
1970.
8. Reverse Osmosis Renovation of Municipal Waste Water, by Aerojet
General Corporation for EPA, Contract No. 14-12-184, Dec. 1969.
9. Smith, J.M. ejt al, Renovation of Municipal Waste Water by Reverse
Cosmosis, Municipal Treatment Research Program Report draft, EPA,
May 1970, (Report to be published).
10. Standard Methods for the Examination of Water and Wastewater, 12th
Edition, American Public Health Assn., New York, New York, 1965.
11. Methods for Chemical Analysis of Water and Wastes, WQO, EPA Analytical
Quality Control Laboratory. Cincinnati, Ohio, July 1971.
12. Beckman Instrument Bulletin 81706-B, TOC Analyser model 915, Beckman
Instruments Inc., Process Instruments Division, Fullerton, Calif.
Aug. 1969.
13. Analytical Methods for Atomic Absorption Spectrophotometry, Instructions
Manual by Perkin-Elmer, Norwalk, Conn., March 1971.
~65~
AWBERC UBRA.xY U.
..
-------
14. Engineering and Economic Evaluation Study of Reverse Osmosis,
Research and Development Progress Report No. 509, Office of
Saline Water, December 1969.
15. Eckenfelder, W. W. and Ford, D. L. Laboratory and Design Procedures
for Wastewater Treatment Processes, The Center for Research in
Water Resources, The University of Texas at Austin, December 1968.
16. Boyle, W.C. and Polkowski, L.B., Sanitary Engineering Institute -
Biological Treatment and Design. Short course sponsored bv the
Department of Engineering, Universitv Extension, The University of
Wisconsin, March 1967-
17. McKinney, R.E., Microbiology for Sanitary Engineers, McGraw-Hill
Book Co., Inc., 1962.
18. Eckenfelder, W.W. and O'Connor, D.J., Biological Waste Treatment,
Pergamon Press, 1961.
19. Gupta, M.K., An Investigation of the Application Feasibility and
Economic Analyses of Reverse Osmosis Process in the Field of
Demineralization, R&D Project Report, Rex Chainbelt Inc.,
March 1970.
20. Katz, W.J., et_ a±, "Concepts of Sedimentation Applied to Design",
Water and Sewage Works, Aoril 1962 and July 1962.
21. Douglas, G., Physical/Chemical Treatment of Raw Sewage, R&D
Project Report, Rex Chainbelt Inc., June 1970.
22. Smith, Robert, "Cost of Conventional and Advanced Treatment of
Wastewater", Journal WPCF, 40:1547, September 1968.
23. Weber, W., Bloom, R., and Hopkinds, C., "Physicochemical Treatment
of Waste Water", Journal WPCF, 42:83, Januarv 1970.
24. Middleton, F.M., Advanced Treatment of Municipal Wastewaters in
the United States of America, presented at the Biennial Conference
of the South African Branch of the Institute of Water Pollution
Control, Capetown, South Africa, March 9, 1970.
25• American Petroleum Institute Water and Wastewater Management Research
Study - Phase I, bv Ecologv Division, Rex Chainbelt Inc., March 1971.
-66-
-------
SECTION X
APPENDICES
APPENDIX I
PRETREATMENT INVESTIGATION DATA
-67-
-------
TABLE 1-1
WASTE CHARACTERISTICS FOR VARIOUS TREATMENT
PLANTS FOR MAY, 1970
Plant Analysis
Brookfield Jones Island
Kenosha Puetz Road Racine Waukesha
oo
I
Flow
MGD
pH
Total Solids
mg/1
Suspended Solids
mg/1
BOD
mg/1
COD
mg/1
Avg
Range
Avg.
Range
Avg
Range
Avg
Range
Avg
Range
Avg
Range
2.96
1.99-6.27
7.3
7.2-7.4
—
12C
38-240
75
32-110
-
172.6
126.6-205.2
7.7
7.3-8.1
944
719-1155
193
109-272
192
80-295
420
197-606
20.7
15.^-29.1
7.8
7.7-8.0
—
120
51-300
71
36-158
—
23.25
15.9-42.9
7.5
7.3-7.6
1185
891-1862
371
123-1092
296
166-491
—
23.7
170-30.7
7.7
7.5-7.9
672
606-727
125
68-209
64
39-115
—
9.72
7.15-11.2
7.6
7.4-8.2
—
174
85-370
140
64-228
—
-------
TABLE 1-2
WASTE CHARACTERISTICS OF THE SAMPLES UTILIZED IN JAR TESTS
Plant Analysis
Brookfield Jones Island Kenosha Puetz Road Racine Waukesha
pH range
Total Solids Range
mg/1
Suspended Solids Range
mg/1
BOD Range
mg/1
COD Range
mg/1
TOC Range
mg/1
TIC Range
mg/1
7.7-7.8
989-1363
99-219
97-115
187-275
^60
^90
7.0-7.2
855-1312
152-435
190-267
470-661
192-225
46-50
7.3
696-1654
135-900
63-300
199-1237
^75
^56
7.3-8.1
1070-1798
244-691
110-315
349-1421
110-408
64-70
6.8-7.4
614-829
87-203
110-113
247-312
VL13
Vjl
7.45-7.6.
1037-130.
110-138
127-175
266-311
^104
^76
-------
TABLE 1-3
JAR TESTS WITH FeCl.
Waukesha
Dose
mg/1
Raw
50
75
100
125
150
Dose
mg/1
Raw
75
100
125
150
175
200
Dose
mg/1
0
50
75
100
125
150
Turbidity
72 JTU
37 JTU
35 JTU
23 JTU
13 JTU
10 JTU
Turbidity
70 JTU
28 JTU
22 JTU
21 JTU
10 JTU
8 JTU
7 JTU
Turbidity
58 JTU
45 JTU
38 JTU
22 JTU
17 JTU
6 JTU
PH
7.45
—
—
—
—
•• ™
Waukesha
pj_
7.6
6.75
6.7
6.6
6.5
6.4
6.3
Waukesha
ElL
7.2
7.0
6.8
6.8
6.5
6.6
Remarks
Extreme
Clarity
2
Remarks
Clear
Extreme
Clarity
3
Remarks
Extreme
Clarity
Achieved
Brookfield
Turbidity
49 JTU
30 JTU
26 JTU
20 JTU
13 JTU
8 JTU
£H_
7.7
—
—
—
—
— —
Brookfield
Turbidity
65 JTU
32 JTU
28 JTU
16 JTU
14 JTU
11 JTU
11 JTU
£H_
7.8
6.9
6.9
6.8
6.75
6.65
6.50
Brookfield
Turbidity
54 JTU
28 JTU
20 JTU
21 JTU
15 JTU
10 JTU
£H_
7.7
7.2
7.0
6.9
6.8
6.6
Remarks
Extreme
Clarity
2
Remarks
Clear
Extreme
Clarity
3
Remarks
Extreme
Clarity
Achieved
1. Samples obtained on a Friday at 9:45 am for Waukesha and
10:15 am for Brookfield.
2. Samples obtained on a Monday at 12:30 pm for Waukesha and at
1:00 pm for Brookfield.
3. Samples obtained on a Thursday at 11:30 am for Waukesha and
at 12:00 noon for Brookfield.
-70-
-------
TABLE 1-3 (cont.)
JAR TESTS WITH Fed,
Jones Island
Puetz RoadJ
Dose
mg/1
Raw
50
75
100
125
150
Turbidity
64 JTU
35 JTU
28 JTU
20 JTU
15 JTU
8 JTU
£H
7.0
7.0
6.5
6.6
6.6
6.2
Remarks
Clarity
Achieved
Jones Island
Dose
mg/1
Raw
50
75
100
125
150
Turbidity
72 JTU
32 JTU
23 JTU
13 JTU
11 JTU
8 JTU
2H
6.8
6.5
6.4
6.3
6.1
6.0
Remarks
Clarity
Achieved
Turbidity
72 JTU
55 JTU
35 JTU
31 JTU
28 JTU
15 JTU
jjH
8.1
7.4
7.2
7.0
7.0
6.2
Puetz Road
Turbidity
82 JTU
55 JTU
35 JTU
28 JTU
20 JTU
11 JTU
£H
7.0
6.8
6.7
6.6
6.5
6.4
Remarks
Clarity
Achieved
2
Remarks
Clarity
Achieved
1. Samples obtained on a Monday at 10:30 am for Jones Island and
11:15 am for Puetz Road.
2. Samples obtained on a Tuesday at 11:30 am for Jones Island and
12:45 pm for Puetz Road.
-71-
-------
TABLE 1-3 (cont.)
JAR TESTS WITH FeCl-j
Kenosha
Racine
Dose
mg/1
Raw
25
50
75
100
125
Dose
mg/1
Raw
25
50
75
100
125
Turbidity
55 JTU
45 JTU
42 JTU
35 JTU
15 JTU
11 JTU
Turbidity
unreadable
-v-100 JTU
80 JTU
41 JTU
25 JTU
15 JTU
PH
7.3
7.2
7.0
6.8
6.6
6.5
2
Kenosha
£H_
7.3
7.1
6.9
6.7
6.7
6.5
Remarks
Extreme
Clarity
Remarks
Clarity
Turbidity
78 JTU
50 JTU
43 JTU
28 JTU
25 JTU
11 JTU
£i_
7.4
7.1
6.9
6.6
6.5
6.4
Remarks
Clarity
2
Racine
Turbidity
50 JTU
48 JTU
34 JTU
25 JTU
19 JTU
14 JTU
DH_
6.9
6.9
6.7
6.6
6.4
6.2
Remarks
Clarity
Samples obtained on a Monday at 9:45 am for Kenosha and at
10:30 am for Racine.
Samples obtained on a Thursday at 11:45 am for Kenosha and at
1:00 pm for Racine.
-72-
-------
TABLE 1-4
JAR TESTS WITH ALUM
Waukesha
Dose
mg/1
Raw
75
100
150
200
250
Dose
mg/1
Raw
200
205
250
275
300
400
Turbidity
75 JTU
70 JTU
65 JTU
52 TJU
17 JTU
21 JTU
Turbidity
75 JTU
44 JTU
23 JTU
32 JTU
33 JTU
20 JTU
11 JTU
pH
7.45
—
__
__
—
—
Waukesha
pH
7.6
6.5
6.5
6.5
6.5
6.4
6.2
Remarks
Clarity
Achieved
2
Remarks
Clarity
Achieved
Waukesha
Dose
mg/1
Raw
200
225
250
275
300
Turbidity
65 JTU
35 JTU
23 JTU
23 JTU
13 JTU
11 JTU
£H
7.2
6.7
6.6
6.6
6.5
6.3
Remarks
Clarity
Achieved
Brookfield
Turbidity gH
41 JTU 7.7
38 JTU
40 JTU
42 JTU
36 JTU
17 JTU
Brookfield
Turbidity ]>H
65 JTU 7.8
40 JTU 6.8
45 JTU 6.8
40 JTU 6.75
35 JTU 6.70
27 JTU 6.65
12 JTU 6.5
Brookfield
Turbidity £H
55 JTU 7.4
30 JTU 6.9
28 JTU 6.7
15 JTU 6.7
8 JTU 6.6
8 6.7
Remarks
Clarity
2
Remarks
Very Clear
3
Remarks
Clarity
Achieved
Samples obtained on a Friday at 9:45 am for Waukesha and
10:15 am for Brookfield.
Samples obtained on a Monday at 12:30 pm for Waukesha and
1:00 pm for Brookfield.
Samples obtained on a Thursday at 11:30 am for Waukesha and
12:00 noon for Brookfield.
-73-
-------
TABLE 1-4 (cont.)
JAR TESTS WITH ALUM
Kenosha
Dose
mg/1 Turbidity p_H Remarks
Raw
200
225
250
275
300
46
20
18
12
11
10
JTU
JTU
JTU
JTU
JTU
JTU
7.3
6.6
6.5
6.4
6.3
6.3
Clarity
Achieved
Racine
Turbidity pH Remarks
70 JTU
20 JTU
14 JTU
12 JTU
12 JTU
13 JTU
7.4
6.7
6.6
6.5
6.4
6.4
Clarity
Achieved
Kenosha
Racine
Dose
mg/1 Turbidity
pH Remarks
Raw
200
225
250
275
300
unreadable
29 JTU
21 JTU
19 JTU
11 JTU
7 JTU
7.3
6.7
6.7
6.6
6.5
6.5
Clarity
Achieved
Turbidity pH Remarks
50 JTU
21 JTU
18 JTU
17 JTU
17 JTU
13 JTU
7.2
6.5
6.4
6.3
6.2
6.2
Clarity
Achieved
1.
2.
Samples obtained on a Monday at 9:45 am for Kenosha and
at 10:30 am for Racine.
Samples obtained on a Thursday at 11:45 am for Kenosha
and at 1:00 pm for Racine.
-74-
-------
TABLE 1-4 (cont.)
JAR TESTS WITH ALUM
Jones Island
Dose
Raw
200
225
250
275
300
Turbidity
65 JTU
23 JTU
20 JTU
15 JTU
13 JTU
11 JTU
£S
7.0
6.7
6.5
6.5
6.4
6.3
Remarks
Clarity
Achieved
Puetz Road
Turbidity
65 JTU
28 JTU
21 JTU
20 JTU
13 JTU
11 JTU
2»
7.9
7.2
6.9
6.9
6.8
6.8
Remarks
Clarity
Achieved
Jones Island
Puetz Road
Dose
Raw
200
225
250
275
300
Turbidity
64 JTU
21 JTU
25 JTU
19 JTU
16 JTU
15 JTU
£H
6.8
6.5
6.4
6.3
6.2
6.1
Remarks
Clarity
Achieved
Turbidity £H
Remarks
80 JTU
35 JTU
22 JTU
19 JTU
20 JTU
17 JTU
6.9
6.6
6.6
6.5
6.5
6.5
Clarity
Achieved
1. Samples obtained on a Monday at 10:30 am for Jones Island
and 11:15 am for Puetz Road.
2. Samples obtained on a Tuesday at 11:30 am for Jones Island
and 12:45 pm for Puetz Road.
-75-
-------
TABLE 1-5
JAR TESTS WITH LIME (CaO)
Waukesha
Brookfield
Dose
mg/1 Turbidity £H Remarks
0
100
200
300
400
450
500
500*
600
700
800
900
1000
70 JTU
55 JTU
45 JTU
45 JTU
50 JTU
35 JTU
32 JTU
8 JTU
7 JTU
6 JTU
8 JTU
18 JTU
40 JTU
7.6
8.9
9.4
9.4
—
9.4
10.2
9.1
9.3
9.5
11.6
12.0
12.0
No acceptable
clarity was
achieved
Good
clarity
achieved up to
800 mg/1 CaO
Turbidity £H Remarks
65 JTU
65 JTU
52 JTU
45 JTU
44 JTU
70 JTU
35 JTU
>35 JTU
" JTU
" JTU
" JTU
" JTU
7.8
9.0
9.3
9.4
9.5
—
9.6
>9
Tt
tl
U
fl
No acceptable
clarity was
achieved
All effluent
samples
extremely
turbid.
JTU
* Samples were first run at concentrations between 500 mg/1 and
1000 mg/1, and one day later were run at concentrations between
100 mg/1 and 500 mg/1.
1. Samples obtained on a Monday at 12:30 pm for Waukesha and
1:00 pm for Brookfield.
-76-
-------
TABLE 1-6
JAR TESTS WITH PRIMAFLOC A-23
Waukesha
Brookfield
Dose
mg/1
Raw
.15
.20
.25
.30
.40
.50
.60
.70
1.00
1.10
1.20
1.30
Turbidity
70 JTU
100 JTU
80 JTU
96 JTU
80 JTU
82 JTU
62 JTU
60 JTU
60 JTU
57 JTU
60 JTU
58 JTU
60 JTU
2
Waukesha
Turbidity
65 JTU
38 JTU
41 JTU
43 JTU
40 JTU
39 JTU
£H
7.6
7.4
7.5
7.5
7.5
7.5
7.5
7.4
7.5
7.5
7.4
7.5
7.4
£H
7.6
7.6
7.6
7.5
7.5
7.1
Turbidity
65 JTU
56 JTU
60 JTU
65 JTU
62 JTU
28 JTU
28 JTU
40 JTU
40 JTU
35 JTU
32 JTU
30 JTU
30 JTU
2
Brookfield
Turbidity
48 JTU
35 JTU
35 JTU
35 JTU
35 JTU
30 JTU
£H
7.8
7.5
7.5
7.7
7.7
7.7
7.7
7.6
7.6
7.6
7.6
7.6
7.6
£H
7.6
1. Samples obtained on a Monday at 12:30 pm for Waukesha
and at 1:00 pm for Brookfield.
2. Samples obtained on a Thursday at 11:30 am for Waukesha
and at 12:00 noon for Brookfield.
-77-
-------
TABLE 1-7
JAR TESTS WITH ALUM & A23
Puetz Road
Turbidity
65 JTU
36 JTU
38 JTU
33 JTU
28 JTU
40 JTU
19 JTU
7.9
6.8
6.9
7.1
7.0
7.1
7.1
Puetz Road
Jones Island'
Turbidity pH
175
175
175
200
200
200
.5
1.0
2.0
.5
1.0
2.0
29 JTU
21 JTU
20 JTU
18 JTU
20 JTU
19 JTU
6.4
6.6
6.7
6.6
6.6
6.7
Remarks
Clarity
Achieved
Turbidity pH Remarks
22 JTU
20 JTU
18 JTU
20 JTU
20 JTU
12 JTU
6.2
6.4
6.4
6.5
6.5
6.5
Clarity
Achieved
1. Sample obtained on a Monday at 11:45 am.
2. Samples obtained on Tuesday at 11:30 am for Jones Island and
12:45 pm for Puetz Road.
-78-
-------
TABLE 1-8
JAR TESTS WITH ALUM & C31
200
200
200
C31
Dose
.5
1.0
2.0
Jones Island
Turbidity
18 JTU
18 JTU
12 JTU
£H
6.9
6.9
6.8
Remarks
Clarity
Alum
Dose
mg/1
100
100
125
125
150
150
Jones Island
Turbidity
.5
1.0
.5
1.0
.5
1.0
34 JTU
29 JTU
22 JTU
30 JTU
19 JTU
20 JTU
6.5
6.7
6.7
6.7
6.6
6.6
Remarks
Clarity
Puetz Road
Turbidity pH Remarks
35 JTU
35 JTU
32 JTU
33 JTU
20 JTU
20 JTU
6.7
6.7
6.8
6.8
6.7
6.7
Clarity
1. Sample obtained on a Monday from Jones Island at 10:30 am.
2. Samples obtained on a Tuesday from Jones Island at 11:30 am
and at Puetz Road at 12:45 pm.
-79-
-------
TABLE 1-9
JAR TESTS WITH FeCl3 & A23
FeCl0
3
Dose
mg/1
50
50
50
75
75
75
A23
Dose
mg/1
.5
1.0
2.0
.5
1.0
2.0
Jones Island
Puetz Road
FeCl3
Dose
mg/1
25
25
25
50
50
50
A23
Dose
mg/1
.25
.5
1.0
.25
.5
1.0
Turbidity
29 JTU
25 JTU
30 JTU
21 JTU
18 JTU
22 JTU
£H
6.4
6.6
6.7
6.7
6.6
6.6
Kenosha
Turbidity
43 JTU
35 JTU
35 JTU
25 JTU
27 JTU
22 JTU
2H
7.1
7.1
7.1
6.9
6.9
6.9
Turbidity
51 JTU
52 JTU
54 JTU
42 JTU
34 JTU
42 JTU
Racine2
Turbidity
61 JTU
50 JTU
52 JTU
25 JTU
23 JTU
30 JTU
£H
6.6
6.7
6.8
6.7
6.7
6.6
£H
7.1
7.1
7.1
6.9
6.9
6.9
1. Samples obtained on a Tuesday at 11:30 am for Jones Island and
at 12:45 pm for Puetz Road.
2. Samples obtained on a Monday at 9:45 am for Kenosha and at
10:30 am for Racine.
-80-
-------
TABLE 1-10
JAR TESTS WITH FeCl, & C31
FeCl
Dose
mg/1
50
50
50
FeCl3
Dose
mg/1
25
25
25
25
25
25
FeCl3
Dose
mg/1
25
25
25
50
50
50
Jones
C31
Dose
mg/1
.5
1.0
2.0
C31
Dose
mg/1
.5
1.0
1.5
2.0
3.0
4.0
C31
Dose
mg/1
.5
1.0
2.0
.5
1.0
2.0
Island
Turbidity
39 JTU
35 JTU
34 JTU
£H
6.9
7.0
7.0
Jones Island
Turbidity
35 JTU
35 JTU
33 JTU
35 JTU
25 JTU
26 JTU
£«_
6.6
6.9
6.9
6.9
6.9
6.9
3
2
Remarks
Kenosha'
Turbidity
35 JTU
24 JTU
28 JTU
16 JTU
15 JTU
11 JTU
M
7.1
7.1
7.0
6.8
6.8
6.8
Remarks
clarity
achieved
Puetz Road2
Turbidity
52 JTU
60 JTU
60 JTU
60 JTU
46 JTU
45 JTU
pH Remarks
6.7
6.9
7.0
6.9
7.0
7.0
3
Racine
Turbidity
53 JTU
50 JTU
45 JTU
38 JTU
31 JTU
21 JTU
pH Remarks
7.2
7.2
7.2
7.0
7.0
6.9
1. Sample obtained on a Monday from Jones Island at 10:30 am.
2. Samples obtained on a Tuesday from Jones Island at 11:30 am
and Puetz Road at 12:45 pm.
3. Samples obtained on a Monday from Kenosha at 9:45 am and
Racine at 10:30 am.
-81-
-------
TABLE 1-11
JAR TESTS WITH FeCl-j AND HERCOFLOC 822A
Fed
822A
Kenosha
Racine
J
Dose
mg/1
n_
Raw
25
25
25
25
25
FeCl3
Dose
mg/1
25
25
25
25
FeC I3
Dose
mg/1
25
25
25
50
50
50
Dose
mg/1
. ..ha.'
Raw
.25
.50
.75
1.00
2.00
810-C
Dose
mg/1
.5
1.0
2.0
3.0
810-C
Dose
mg/1
.5
1.0
1.0
.5
1.0
2.0
Turbidity
41 JTU
31 JTU
31 JTU
30 JTU
31 JTU
31 JTU
JAR TESTS WITH
Kenosha
Turbidity _
30 JTU
25 JTU
27 JTU
24 JTU
pH
7.3
7.1
7.0
7.1
7.0
7.0
FeCl3
pH
7.2
7.2
7.2
7.2
2
Kenosha
Turbidity
86 JTU
79 JTU
64 JTU
46 JTU
34 JTU
35 JTU
p_H
6.9
7.0
7.0
6.9
6.9
6.9
Remarks Turbidity
65 JTU
46 JTU
46 JTU
47 JTU
48 JTU
48 JTU
AND HERCOFLOC 810-C
pH Remarks
7.4
7.1
7.1
7.0
7.1
7.1
Racine
Remarks Turbidity
35 JTU
35 JTU
40 JTU
30 JTU
24 JTU
24 JTU
pH Remarks
6.9
6.7
6.8
6.6
6.6
6.6
1.
2.
Samples obtained on a Monday at 9:45 am for Kenosha and
and 10:30 am for Racine.
Samples obtained on a Thursday at 11:45 am for Kenosha
and 1:00 pm for Racine.
-82-
-------
TABLE 1-12
JAR TESTS WITH FeCl-j AND 675A
FeCl
Kenosha
25
25
25
50
50
50
.25
.50
1.00
.25
.50
1.00
Turbidity
35 JTU
26 JTU
25 JTU
24. JTU
22 JTU
22 JTU
£l
7.1
7.1
7.1
6.9
6.8
6.8
Remarks
Racine
Turbidity pH
48 JTU 7.0
44 JTU 7.0
42 JTU 7.0
36 JTU 6.8
39 JTU 6.8
38 JT$ 6.8
Remarks
JAR TESTS WITH FeCl3 and MAGNIFLOC 905-N
FeCl3 905N
Kenosha
Racine
Dose
mg/1
25
25
25
25
25
25
Dose
mg/1
.5
.75
1.00
1.25
1.50
2.00
Turbidity pJH
79 JTU
70 JTU
72 JTU
68 JTU
70 JTU
62 JTU
6.9
Remarks
Turbidity pH Remarks
7.0
41 JTU
38 JTU
42 JTU
41 JTU
37 JTU
38 JTU
6.8
6.9
6.9
6.9
6.9
6.9
1. Samples obtained on a Monday from Kenosha at 9:45 am and
at Racine at 10:30 am.
2. Samples obtained on a Thursday from Kenosha at 11:45 am
and at Racine at 1:00 pm.
-83-
-------
TABLE 1-13
JAR TESTS WITH FeCl3 AND ALUM
FeCl
Kenosha
Racine
25
25
25
50
50
50
Turbidity
50
100
125
25
50
100
65 JTU
24 JTU
20 JTU
35 JTU
28 JTU
11 JTU
6.9
6.8
6.8
6.8
6.8
6.7
Remarks
Clarity
Clarity
Turbidity pH Remarks
48 JTU
25 JTU
21 JTU
32 JTU
26 JTU
11 JTU
6.7
6.6
6.5
6.6
6.6
6.6
Clear
Fed Alum
Dose Dose
mg/1 mg/1
10
10
10
15
15
15
Racine
Turbidity p_H
75
100
125
75
100
125
49 JTU
36 JTU
28 JTU
44 JTU
25 JTU
11 JTU
6.8
6.7
6.6
6.7
6.7
6.6
Remarks
Clarity
1.
Samples obtained on a Thursday at 11:45 am for Kenosha and
at 1:00 pm for Racine.
-84-
-------
TABLE 1-14
JAR TESTS WITH Fed & PRIMAFLOC C7
FeCl
C7
Dose
Kenosha
Dose"
mg/1 mg/1 Turbidity
25
25
25
25
25
25
.25
.50
.75
1.00
1.25
1.50
90 JTU
65 JTU
61 JTU
60 JTU
62 JTU
48 JTU
7.0
7.0
7.0
7.0
7.0
7.0
Remarks
Racine
Turbidity pH Remarks
35 JTU
35 JTU
35 JTU
34 JTU
36 JTU
36 JTU
7.0
7.0
7.0
7.0
7.0
7.0
1. Samples obtained on a Thursday at 11:45 am for Kenosha and
at 1:00 pm for Racine.
-85-
-------
APPENDIX II
BIOLOGICAL OXIDATION DATA
-86-
-------
Bio-Treatment of the Settled Sewage RO Concentrate
The ten-fold concentrate obtained from the RO experiments utilizing
the tubular system as discussed earlier was subjected to biological
oxidation in the pilot activated sludge units. The units were
seeded with returned sludge from the Milwaukee Sewage Treatment
Plant and an aeration time of 24 hours was provided. The units were
fed once a day in the mornings. In an effort to collect the maximum
amount of acclimated sludge from this study for setting up a batch-
kinetic study at high mixed liquor solid levels, little or no sludge
volume was wasted from the aeration units and only the settled
supernatant after one hour sedimentation was wasted at the feeding
time. However, attempts to collect a second batch of RO brine from
the settled sewage failed due to module plugging problems (as
described in the main body of this report), and therefore the biological
treatment feasibility data for settled sewage was limited to only
one experiment. Also, no further attempts were made to collect
more brine from settled sewage as it had already been indicated
that prior chemical treatment of the raw sewage would be necessary
even when tubular RO systems were utilized. Hence, future experiment
program priorities were shifted towards obtaining data on concentrates
obtained from the RO treatment of chemically treated and settled
sewages.
However, significant amounts of data had emerged from the above
described experiment, and it was shown that it was feasible to
biologically oxidize the RO concentrate stream. TOC removals of
the order of 85 to 90% were achieved in the biologically oxidized
and settled effluent (Table II-l). No acclimitization of the activated
sludge biota was needed for the concentrate stream and the returned
sludge from the Milwaukee Sewage Treatment Plant was found to be
suitable for the system start-up.
A typical oxygen uptake curve is shown in Figure II-l. Immediately
after feeding, the oxygen uptake rate would increase markedly as
expected. An oxygen uptake rate as high as 187 mg/l/hr occurred
immediately after feeding and decreased to approximately 30/mg/l/hr
after the 24 hour aeration period. The mixed liquor suspended
solid concentrations utilized in the aeration units ranged between
2800 and 4700 mg/1 (Table II-l). The loading rates in terms of
#TOC/#MLVSS/day varied between 0.21 and 0.37.
The settling characteristics of the activated sludge were found
to be quite good and the SVI index ranged between 39 and 104. A
typical settling curve is shown in Figure II-2, and the settling
data is presented in Table II-2. Settling velocities of the sludge
were good and ranged between 6 to 15 ft/hr. The suspended solids
content of the settled effluent ranged between 48 and 96 mg/1 in
the pilot units but this is expected to improve significantly in
large size plant operation.
-87-
-------
TABLE II-l
BIOLOGICAL OXIDATION DATA - SETTLED SEWAGE CONCENTRATE
MLSS
mg/1
2790
3590
4700
3600
MLVSS
mg/1
2010
2440
3200
2310
TOC
Loading
pH //TOC/ffMLVSS/day
8.0 0.37
8.3 0.31
8.3 0.25
8.3 0.21
% TOC
Removal
per 24 hr
Aeration
85.0
89.5
90.0
87.5
Effluent
S.S.
mg/1
90
96
86
48
02 Uptake
Rate after
24 hr aeration
Period
mg/l/hr
29
26
—
32
1 TOC of RO concentrate : 710 mg/1
2 After 24 hour aeration and one hour settling
-88-
-------
200
160
VO
I
00
6
0)
4J
(0
Q>
rt
4J
0.
c
(U
M
120
80
40
MLSS: 3590 mg/1
Aeration Time, hrs.
16
20
12
FIGURE II-l
TYPICAL OXYGEN UPTAKE CURVE FOR RO CONCENTRATE - SETTLED SEWAGE
24
-------
1000
900
700
w
E
C
C
•H
•O
(B
Di
PK "°
O 5
2 ?
O
10
o
CL,
u
10
3
•o
n
t-l
o
500
MLSS: 4700 mg/1
Timej.Min.
50
20 ~36" 40
FIGURE II-2
TYPICAL SETTLING CURVE FOR RO CONCENTRATE - SETTLED SEWAGE
60
-90-
-------
TABLE I1-2
SETTLING TEST DATA - SETTLED SEWAGE CONCENTRATE
MLSS
mg/1
2790
3590
4700
3600
Aeration
Time
hours
24
24
24
24
SVI
104
72
57
39
Settling
Velocity
ft/hr
9.3
8.5
6.2
15.0
-91-
-------
TABLE II-3
CHEMICALLY TREATED SEWAGE CONCENTRATE1 - BATCH KINETIC RUN //I
BIO-OXIDATION DATA
Effluent Quality at Various MLSS Levels & Aeration Periods
N>
Aera-
tion
Time
hrs.
0.25
0.50
1.5
3.0
6.0
8.0
15.0
24.0
pH
Units
8.3
8.2
8.2
8.2
8.2
8.25
8.25
8.3
1500
Fil?
TOC
mg/1
667
639
485
455
350
361
260
218
02 Up-
take
Rate
mg/1
39.4
31.9
22.7
18.8
10.1
11.2
7.1
11.2
pH
Units
8.05
8.15
8.2
8.25
8.3
8.4
8.4
8.4
2500
Fil?
TOC
mg/1
606
648
456
307
240
150
110
104
3000
02 Up-
take
Rate
mg/l/hr
105.5
79.7
62.8
39.5
35.1
24.5
9.0
5.8
pH
Units
8.2
8.1
8.0
8.2
8.2
8.25
8.25
8.3
Fil?
TOC
mg/1
553
425
321
210
111
100
85
133
02 Up-
take
Rate
mg/l/hr
103.0
98.5
36.0
36.6
19.1
20.9
9.4
6.7
pH
Units
8.2
8.1
8.3
8.2
8.2
8.25
8.25
8.3
4000
Fil?
TOC
mg/1
700
608
500
317
170
133
120
90
02 Up-
take
Rate
mg/l/hr
35.1
111.4
75.0
65.5
60.5
26.7
19.0
6.0
1. TOC of RO concentrate: 710 mg/1.
2. Samples filtered through //I Whatman filter paper,
-------
TABLE II-4
CHEMICALLY TREATED SEWAGE CONCENTRATE1 - BATCH KINETIC RUN NO. 2
BIO-OXIDATION DATA, UNIT 1
I
?
Day &
After
I
II
III
IV
V
Time
Feeding
2 hr
6 hr
24 hr
1.5 hr
4.0 hr
16 hr
1.25 hr
5.0 hr
16 hr
15.0 hr
15.0 hr
pH
Units
8.45
8.25
8.05
8.05
8.0
8.05
8.0
7.85
7.9
7.9
7.8
MLSS
mg/1
3700
4125
3200
3600
4080
4530
4230
4270
3310
3080
3370
MLVSS
mg/1
2800
2750
2040
2630
2860
2000
1810
1880
Filtered
TOC
mg/1
166
112
89
115
87
69
101
83
64
64
64
Unfll-
0 Uptake tared Effluent3
2 Rate Effluent3 Suspended
mg/l/hr TOC.mg/1 Solids mg/1
90.0
63.5
25.7
57.6
41.1
19.5
69.0
34.7
16.7
15.2
27.0
249
130
133
127
162
440
162
210
234
Sludge
Concentration
% Total
Solids
1.72
2.80
3.39
2.56
3.58
3.32
3.50
1. TOC of the RO concentrate 710 mg/1 on 1st day and 810-830 mg/1 thereafter.
2. TOC of the mixed liquor sample after filtration through #1 Whatman filter paper.
3. Effluent after one hour settling.
-------
TABLE II-5
CHEMICALLY TREATED SEWAGE CONCENTRATE1 - BATCH KINETIC RUN //2
BIO-OXIDATION DATA, UNIT 2
Day &
After
I
II
III
IV
V
Time
Feeding
2 hr
6 hr
24 hr
1.5 hr
6 hr
16 hr
1.25 hr
5 hr
16 hr
15 hr
15 hr
PH
Units
8.25
8.2
8.2
8.05
8.2
8.1
7.9
7.9
7.8
7.7
7.8
MLSS
mg/1
7150
7417
7420
4460
4760
4730
4920
4540
5350
3860
4770
MLVSS
mg/1
5317
5400
5140
3460
3270
3470
2380
2980
Filtered
TOC
mg/1
154
102
88
99
80
67
82
75
71
67
58
0 Uptake
Rate
mg/l/hr
90.8
69.6
26.6
50.1
34.5
24.6
64.0
45.7
26.1
31.5
23.0
Unfil-
tered
Effluent3
TOC, mg/1
—
117
114
103
117
125
105
Effluent3
Suspended
Solids mg/1
—
150
102
100
147
136
123
Sludge
Concentration
% Total
Solids
2.23
2.41
2.77
2.91
3.64
3.67
1. TOC of the RO concentrate 710 mg/1 on 1st day and 810-830 mg/1 thereafter.
2. TOC of the mixed liquor sample after filtration through //I Whatman filter paper.
3. Effluent after one hour settling.
-------
TABLE II-6
CHEMICALLY TREATED SEWAGE CONCENTRATE1 - BATCH KINETIC RUN #2
BIO-OXIDATION DATA, UNIT 3
Unfil-
Sludge
i
VO
Day & Time
After Feeding
I
II
III
TV
V
2 hr
6 hr
24 hr
1.5 hr
6 hr
16 hr
1.25 hr
5 hr
16 hr
15 hr
15 hr
pH
Units
8.15
8.25
8.10
8.15
8.05
7.9
7.95
7.9
7.8
7.7
7.8
MLSS
mg/1
10317
10250
9710
5840
5880
5440
5160
5480
6320
5620
5760
MLVSS
mg/1
7800
7580
7160
3750
2050
3610
3590
Filtered
TOC
mg/1
192
141
109
117
100
73
86
73
79
75
58
0_ Uptake
Rate
mg/l/hr
102.0
87.4
33.4
48.9
36.0
39.0
65.0
52.8
45.4
56.1
28.0
tered
Effluent 3
TOC, mg/1
132
108
118
128
146
101
Effluent
Suspended
Solids mg/1
94
127
135
147
160
110
Concentration
% Total
Solids
2.39
3.40
4.54
3.00
3.38
2.67
1. TOC of the RO concentrate 710 mg/1 on 1st day and 810-830 mg/1 thereafter.
2. TOC of the mixed liquor sample after filtration through #1 Whatman filter paper.
3. Effluent after one hour settling.
-------
TABLE II-7
CHEMICALLY TREATED SEWAGE CONCENTRATE1 - BATCH KINETIC RUN 92
BIO-OXIDATION DATA, UNIT 4
Day
After
I
II
III
IV
V
& Time
Feeding
2 hr
6 hr
24 hr
1.5 hr
6 hr
16 hr
1.25 hr
5 hr
16 hr
15 hr
15 hr
PH
Units
8.3
8.35
8.2
8.1
8.0
8.0
8.05
7.9
7.85
7.7
7.8
MLSS
mg/1
7200
6833
6830
3850
4790
4370
4860
5010
4640
4300
5890
MLVSS
mg/1
5800
4900
5190
3010
3000
2700
3620
Filtered
TOC
mg/1
114
84
83
106
90
73
117
70
72
70
63
2 Uptake
Rate
mg/l/hr
Unfil-
tered
Effluent"^
TOC. mg/1
Effluent
Suspended
Solids mg/1
Sludge
Concentration
% Total
Solids
78.0
60.0
30.0
51.0
42.0
32.0
52.5
29.0
30.2
20.7
25.7
—
138
113
123
125
141
111
—
155
115
132
153
154
113
2.36
2.72
2.88
3.10
3.80
3.67
1. TOC of the RO concentrate 710 mg/1 on 1st day & 810-830 thereafter.
2. TOC of the mixed liquor sample after filtration through //I Whatman filter paper.
3. Effluent after one hour settling.
-------
TABLE II-8
CHEMICALLY TREATED SEWAGE CONCENTRATE1 - BATCH KINETIC RUN #3
BIO-OXIDATION DATA
Effluent Quality at Various Mixed Liquor Levels and Aeration Periods
MLSS 4000 mg/1
MLVSS 2100 mg/1
i
VO
•vl
Aera-
tion
Time
hrs
0.5
1.5
3.5
5.5
7.5
15.0
23.0
pH
Units
7.8
7.85
7.95
8.0
8.0
8.0
8.1
Fil?
TOC
297
195
115
85
83
64
71
02 Up-
take
Rate
mg/1
114.0
71.4
40.2
32.4
23.0
21.3
18.6
MLSS 5000 mg/1
MLVSS 2900 mg/1
pH
Units
7.9
7.9
8.0
8.05
8.0
8.0
8.1
Fil?
TOC
mg/1
201
92
77
72
70
72
65
02 Up-
take
Rate
mg/l/hr
164.0
65.4
35.5
30.0
31.3
25.1
9.4
MLSS 5500 mg/1
MLVSS 3200 mg/1
PH
Units
7.8
7.8
7.95
8.0
8.0
8.05
8.1
Fil?
TOC
mg/1
98
79
84
65
68
79
71
02 Up-
take
Rate
mg/l/hr
111.3
52.6
34.7
28.6
26.8
24.9
9.7
MLSS 6000 mg/1
MLVSS 3450 mg/1
PH
Units
7.9
7.85
8.1
8.0
8.1
8.05
8.15
Fil?
TOC
mg/1
165
83
80
67
69
67
67
02 Up-
take
Rate
mg/l/hr
127.0
58.3
37.7
30.0
24.4
23.6
7.4
1. TOC of the RO concentrate: 810-830 mg/1
2. Samples filtered through #1 Whatman filter paper
-------
APPENDIX III
PERMEATE INVESTIGATION DATA
-98-
-------
Gas Chromatograph Investigations
A series of gas chromatographic tests were performed on samples from
tests where raw sewage was treated by reverse osmosis. The initial
intention of the gas chromatography was to identify the major organic
component(s) in the permeate water and measure the amount present. When
the nature and amount of the major component was recognized, additional
gas chromatographic work was done on feed and brine samples from the
reverse osmosis tests and on several samples of raw sewage from the
Milwaukee sewage plant and other local sewage plants.
The paper "Removal of Organics from Wastewater by Reverse Osmosis" by
W.A. Davel, Jr., T. Helfgott, and E.J. Genetelli presented at the
American Chemical Society Meeting held in Chicago, Illinois on September
13-18, 1970 was utilized in this work. This paper presents data on the
permeability of various classes of compounds and presents three general
properties that enhance the permeability of organic molecules: low
molecular weight, small molecular size as determined by steric geometry,
and the ability to form hydrogen bonds. The data indicated that compounds
in the permeate would probably not contain more than four carbons (if an
aliphatic), would probably be a linear molecule rather than branched and
would probably be polar. Specific classes of compounds that might be
present are carboxylic acids, alcohols, amines and amides. Aldehydes,
ketones, sulfones and esters are expected to be less permeable. Phenol
forms hydrogen bonds so strongly that it is very permeable in spite of its
molecular weight and size. The classes of compounds most likely to be
found in the permeate can be readily separated and measured in mg/1
quantities by gas chromatography.
Instrumentation and Columns; the gas chromatography work was done with
a Barber-Colman Series 5000 gas chromatograph. This is a dual column
instrument equipped with two flame ionization detectors and a single
six-port thermal conductivity detector. Helium was used as the carrier gas.
The injector and detector temperatures were maintained at 225°C for most
tests (a malfunctioning voltage controller caused the detector temperature
to vary at times). Instrument conditions are listed on each chromatogram
in the appendix. A Barber-Colman recorder equipped with a disc integrator
was used to record the chromatograms.
Three packings were used in these tests: Porapak Q, Porapak S, and
Porapak Q-S; all 60/80 mesh. The Q and the S columns were made of 6 foot x
1/4 inch O.D. stainless steel tubing. The Porapak Q-S column was made of
3 foot x 1/8 inch O.D. stainless steel tubing. The columns were
conditioned at 210°C before use and occasionally during the series of
tests. Porapak Q is well suited for the separation of low molecular weight
organics. Porapak Q-S is a silanized form of Porapak Q; retention times
are about the same for both Q and Q-S packings. Porapak S is a more
polar type of Porapak; polar compounds, such as alcohols and organic acids,
elute later from Porapak S than from Porapak Q. The retention time for
non-polar compounds is about the same for all three packings used.
-99-
-------
Sample Preparation: The samples which were chromatographed were stored
under refrigeration. The reverse osmosis feed, brine, and permeate
samples and the sewage plant effluent samples were stored and tested as
received. The raw sewage samples were clarified hy centrifugation as
soon as they were received and were chromatographed immediatelv or
refrigerated until the tests could be run.
Before it was determined that direct aqueous inaction of the samples
was possible, large samples of permeate were saved for future con-
centration of the organic fraction. Two five gallon samples of the
1/13/71 permeate and one five gallon sample of the 1/20/71 permeate
were stored in glass carboys at room temperature. One of the five
gallon samples from each test date was treated with mercuric chloride
to inhibit bacterial growth. The untreated 1/13/71 sample became hazy
within one day of sampling and eventuallv formed a precipitate. The
treated samples also became hazy, but at a much slower rate. (The
refrigerated permeate samples remained clear for weeks after sampling.)
The contents of the carbovs were used only in the initial chromatographic
work to determine the optimum instrument settings and in the preliminary
qualitative work. The chromatograms obtained with the treated, untreated
and refrigerated samples were similar. Only the refrigerated samples
were used for the quantitative work.
An attempt was made to concentrate the organics in the permeate water by
carbon adsorption. A bulk volume of 100 cc Cliffs-Dow (8x32) activated
carbon was placed in a 7/8 inch I.D. column. A total of 27 gallons of
the 1/13/71 permeate water was passed through the column over a 29.5 hour
period. The carbon was drained and dried on a steam bath. A stream of
air was used to sweep the evaporated water and volatile organics through
a trap maintained at -18°C for recovery of the volatiles. The drv carbon
was extracted with chloroform in a soxhlet extractor. Because the samples
could be iniected directlv, further work on the carbon adsorption samples
was abandoned. The limitations of the concentrations of low molecular
weight organics by carbon adsorption became apparent, however. The
uncertainty about the completeness of adsorption of the organics on the
carbon and the completeness of extraction from the carbon by the solvent
can severely limit the usefulness of any quantitative data obtained. At
a later date, carbon isotherm tests performed on a sample of permeate
water showed that only 25% of the organic matter (as TOC) was adsorbed
by activated carbon. If it is necessary to concentrate low molecular
weight organics in the future, it is recomnended that a different procedure,
such as freeze concentration, be used.
Qualitative Analyses: Chromatograms of the permeate water from the
reverse osmosis tests performed on 1/13/71 and 1/20/71 are shown in
Figures 1 and 2. For comparison, a chromatogram of distilled water is
shown in Figure 3. In each figure, the vertical axis represents the
change in detector signal due to the elution of material from the column
and the horizontal axis represents time. The arrow indicates the point
at which the sample was injected. Comparison of the peaks in Figure 3
with those in the other figures show that the initial peaks are due to the
-100-
-------
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.:
DETECTOR TEMP.:
ATTENUATION:
Porapak Q
5 yi
140° C
230° C
260° C
10
CHROMATOGRAM -
FIGURE III-l
RO PERMEATE OF 1/13/71, MILWAUKEE STP
-101-
-------
20
50
30
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
FIGURE IH-2
CHROMATOGRAM - RO PERMEATE OF 1/20/71, MILWAUKEE STP
Porapak Q
8 Ml
140* C
230° C
260° C
10
-102-
-------
60
20
50
40
30
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
5 yl
140° C
230° C
260° C
10
FIGURE III-3
CHROMATOGRAM - DISTILLED WATER
-1,03-
-------
elution of water from the column. The general appearance of the water
peaks was similar to Figure 3 for all tests on the Poranak 0 column.
Because these peaks are partially due to a sudden pressure change and
disruption of the flame rather than to ionization, minor variations in
the water peaks occur. For this reason, distilled water was in-jected
periodicallv during these tests for comparison to the sample peaks.
Comparison of Figures 1 and 3 show that there are three peaks present in
Figure 1 not present in Figure 3. These peaks are laheled A, B, and D.
There are also three Deaks in Figure 2 not present in Figure 3. They are
labeled A, B, and C. The peaks labeled A and B in both figures have the
same retention time (elute from the column at the same time) and are
probably due to the same conroounds. Peaks C and D, however, have different
retention times, are due to different comoounds and are therefore labeled
differently. Because of the large size of peak B, the primarv oblective
of the qualitative tests was to identifv the compound producing this peak.
The peaks produced by known compounds were compared to the peaks produced
by the two permeate samples on both the Porapak Q and the Porapak S columns.
On both columns, the ethanol peak matched peak B. An example of the
chromatogram produced by injecting a sample of 1/20/71 permeate water on
the Porapak S column is shown in Figure 4. In this figure, peak A was
obscured by the large water peak and peak C appeared as a shoulder of peak B.
Although the matching of the ethanol peak with peak B does not prove the
identity of peak B, some observations can be made that support the conclu-
sion that peak B is probably due to the presence of ethanol:
1. Peak B eluted later on the Porapak S column than on the Porapak
Q column. Non-polar compounds elute at about the same time from
both the Q and the S columns. As compound polarity increases,
the elution time increases. The increase in elution time in
oeak B indicates that the compound producing peak B has a
polarity similar to that of alcohols. The compound producing
peak C, however, is less polar than peak B.
2. Certain classes of compounds that might be expected to be
present in permeate water can be disregarded as possible sources
of peak B, because the peaks of certain chemicals belonging to
these classes of compounds do not match peak B.
a. Peak B is not a carboxylic acid. Both formic and acetic acid
elute after peak B on Porapak S.
b. Peak B is probablv not an ester. Both methyl acetate and
ethvl acetate elute after peak B. The change in elution
time between packings Q and S indicate the neak B has a
greater polarity than esters.
c. Peak B is probably not an amine. The secondard and tertiarv
amines produce peaks that tail badly on Porapak Q. These
peaks do not resemble peak B in shape. Bot'i methvlamine and
ethvlamine elute before peak B. Propvlamine was not available
-104-
-------
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak S
5 Ml
175° C
228° C
218° C
10
FIGURE II1-4
CHROMATOGRAM - RO PERMEATE OF 1/20/71, MILWAUKEE STP
-105-
-------
for testing. A Kjeldahl organic nitrogen test showed that a
sample of 1/13/71 permeate water contained 3 rag/1 organic
nitrogen. This amount of organic nitrogen as propylamine
would produce a much smaller peak than peak B.
The known compounds that were tested and their liklihood of being present
In the permeate waters tested are listed in Table 1.
Although the evidence is strong that peak B was caused by ethanol, further
work is recommended to verify this identification. The matching of peak B
with the ethanol peak on columns having properties much different than
the two Porapak columns used should be sufficient. Columns containing
Apiezon L (non-polar) or Carbowax (more polar than the Porapaks) might
be used. Material for the preparation of these columns had just been
received by the laboratory when the available time for testing ended.
Other means of verifying the identity of peak B might be used. The
compound producing peak B might be separated by preparative gas chromato-
graphy and then identified by colorimetric means (e.g. spot test for
alcohols using eerie nitrate) or by other instrumental methods. Such
equipment is not available in our laboratory, however.
Some tests were performed on the three foot Porapak Q-S column at
temperatures up to 210°C in an effort to detect higher molecular weight
materials in the 1/20/71 permeate water. No other peaks of significance
were found. Tests were also conducted using the thermal conductivity
detector to look for non-organic materials not detected by the flame
ionization detector. None were found. It should be pointed out, however,
that the conductivity detector is much less sensitive than the ionization
detector.
When the qualitative work on the 1/13/71 and 1/20/71 permeate samples
was completed, chromatograms of other samples were run to answer some
questions concerning the origin and occurrence of the apparent ethanol
peak. These chromatograms were run on the Porapak Q column at 140°C to
facilitate comparisons and quantitative analysis. Peaks A, B, and C were
found In both the feed sample (Figure 5) and the brine sample (Figure 6)
from the 1/20/71 reverse osmosis tests. Peak D also appeared in the
brine sample. None of these peaks were found however, in the effluent
from pilot activated sludge units fed with the brine from the 1/20/71
tests (Figure 7). The possibility that the sewage used in the 1/13/71
and 1/20/71 tests mav have been contaminated by the tank truck in which
the sewage was brought to the laboratory was considered. Three samples
of sewage were obtained from the fine screen house at the Milwaukee
sewage plant. A typical chromatogram of these samples is shown In
Figure 8. A sample of sewage plant effluent was also chromatographed
(Figure 8). Peaks A, B, C and D were found in the raw waste sample;
no peaks were found in the effluent sample. It appears that the presence
of the compounds producing these peaks is not uncommon in Milwaukee
sewage.
Chromatograms of raw sewage from other local sewage plants were also run.
No peaks were found in the raw sewage from Menomonee Falls (Figure 9).
Peaks A, B, and C were found in the sample from Brookfleld (Figure 10).
Note that this was run at an instrument sensitivity 3 1/3 times higher
-106-
-------
TABLE III-l
KNOWN COMPOUNDS TESTED
Compounds whose peaks do not match peaks A, B, C or D and are
therefore concluded to be not responsible for these peaks are
as follows:
Formic acid, Acetic acid
Methylamine, Ethylamine
Diethylamine
Triethylamine
Formamide
Ethyl Acetate
1-Propanol, 2-Propanol
Phenol
Compounds which elute at or near peaks A, B, C or D and may possibly
be present are:
Methanol - elutes at or near peak A.
Acetone - elutes at or near peak C.
Propionaldehyde - Published tables indicate that this
compound also elutes near peak C.
Ethanol - matches peak B in all tests.
-107-
-------
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
5 yi
140° C
225° C
212° C
10
CHROMATOGRAM - RO FEED OF 1/20/71, MILWAUKEE STP
-108-
-------
90
80
70.
60^
5C-
40'
30-
20
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
5 pi
140° C
225° C
212° C
10
FIGURE III-6
CHROMATOGRAM - RO BRINE OF 1/20/71, MILWAUKEE STP
-109-
-------
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.:
DETECTOR TEMP. :
ATTENUATION:
Porapak Q
5 yl
140° C
215° C
225° C
10
FIGURE lfP-7
CHROMATOGRAM - BIO-TREATED EFFLUENT OF 1/20/71 RO BRINE, MILWAUKEE STP
-110-
-------
Activated Sludge
Effluent
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.:
DETECTOR TEMP.:
ATTENUATION:
Porapak Q
5 yi
140* C
200° C
218° C
10
Raw Sewage
FIGURE III-8
CHROMATOGRAMS - MILWAUKEE STP SAMPLES
-111-
-------
60
50
40
30
20
10
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
5 wl
140° C
212° C
220 C
10
FIGURE III-9
CHROMATOGRAM - RAW SEWAGE, MENOMONEE FALLS STP
-112-
-------
COLUMN:
SAMPLE VOLUME:
OVEN TEMP -:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
140° C
200° C
218° C
FIGURE Ill-IP
CHROMATOGRAM - RAW SEWAGE, BROOKFIELD STP
-113-
-------
than the other chromatograms in order to show peaks B and C more clearlv.
The concentration of material producing the apparent ethanol peak and peak
C were about the same. A chromatogram of the Kenosha sample is shown in
Fieure 11. Onlv a small peak B appeared along with the large peak due to
the 1-propanol added as an internal standard. Peaks A, B, C and D were
all present in the sample from Racine (Figure 12). It appears that the
compounds producing peaks A, B, C and D are neither peculiar to Milwaukee
sewage nor are they common to all sewages.
Whereas the permeate water may be expected to contain onlv low molecular
organics, the raw sewage samples contain a much larger range of molecu-
lar weight materials. These larger compounds are retained by the Porapak
packing at 140°C. When thev slowly elute from the column, they show up
as "bleed" and produce a wavering base-line, necessitating reconditioning
of the column. The peaks in the chromatograms of the raw sewage samples
shown in various figures should not be construed to represent all the
organics in the sewage. Only the more volatile organics are represented.
Another reverse osmosis test on chemically clarified sewage from Racine,
Wisconsin was performed on 3/8/71 to eliminate the effect of high ethanol
concentrations in Milwaukee sewage which might have been a result of its
brewing industry. The chromatograms of the RO feed and pemieate at 45%
recovery are shown in Figure 13. All four peaks A, B, C and D appear
in both the chromatograms but are verv small in magnitude. No predomi-
nant peak is noticed. This clearly shows that there is no predominant
low molecular weight organic species common to domestic sewages that may
be responsible for the poor separation performance of the CA membranes
towards soluble organic material.
Quantitative Analysis
The quantitative analysis was performed on the assumption that peak B
was caused by ethanol. Both internal standardization using either
1-propanol or 2-propanol and comparison of the sample peak area with
the peak area of known amounts of ethanol or 2-propanol were used. When
the comparison method was used, standards were Injected frequently along
with the samples. A check of the two methods showed that thev produced
similar results. All the ouantitative chromatograms were run using
the Porapak Q column at 140°C. The amount of samples and standards
used varied from 2 ul to 8 wl.
The results of the quantitative analvses are listed in Table 2. Results
of the individual injections are listed as an indication of the precision
of the measurements. The feed, permeate and brine samnles from the
1/20/71 RO test<; and the 1/13/71 permeate sample were measured approx-
imatelv 10 days after sampling. All other samples were measured within
one dav of the sampling.
-114-
-------
50
40
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
8 yl
140° C
205° C
195 C
10
1-Propanol
Internal Standard
20
10
0
TlUUkE 111-11
CHROMATOGRAM - RAW SEWAGE, KENOSHA STP
-115-
-------
80
70
60
COLUMN:
SAMPLE VOLUME:
OVEN TEMP.:
INJECTOR TEMP.
DETECTOR TEMP.
ATTENUATION:
Porapak Q
8 PJ
140 C
205° C
195° C
10
1-Propanol
Internal Standard
CHROMATOGRAM - RAW SEWAGE, RACINE STP
-116-
-------
70
60
50
40
30
COLUMN: Porapak Q __
SAMPLE VOLUME: 8 yl
OVEN TEMP.:
INJECTOR TEMP-:
DETECTOR TEMP.;
ATTENUATION:
140° C
210 C
210° C
10
FIGURE 111-13
CHROMATOGRAMS - RO FEED AND PERMEATE OF 3/8/71, RACINE STP
-117-
-------
Although the quantity of material producing peaks C and D was not
measured, a visual comparison of the chromatograms In the various
figures shows that the largest of peaks C and D are ahout the size of
Kenosha peak B which measured less than 1 mg/1 as ethanol. It is clear
that the concentration of the compounds producing peaks C and D is small.
The total organic carhon (TOG) values for the samples that were chro-
matographed are included in Table 2. For comparison, the TOC values
calculated from the average apparent ethanol concentrations are also
included. As expected, the portion of the TOC attributable to peak B
is small for the raw sewage and feed samples. For the permeate samples
at high recoverv ratios, however, the TOC calculated from the apparent
ethanol concentration accounts for all but 8 to 10 mg/1 TOC. It would
appear that the major portion of the organic in the permeate are
represented by peak B.
-118-
-------
TABLE III-2
QUANTITATIVE ANALYSIS RESULTS OF THE LARGEST CHROMATOGRAM - PEAK (B)
i
H1
M
VO
Date of
Sample Description Treatment
Permeate (composite
sample @ 90% recovery) 1/13/71
Feed 1/20/71
Permeate (composite
sample @ 90% recovery) 1/20/71
Brine @ 90% recovery 1/20/71
Act. SI. Effluent -
(pilot units on RO brine) 1/20/71
Raw Sewage 2/4/71
Raw Sewage 2/9/71
Act. SI. Effluent 2/15/71
Raw Sewage 2/10/71
Raw Sewage 2/15/71
Act. SI. Effluent 2/15/71
Raw Sewage 2/17/71
Raw Sewage 2/17/71
Feed 3/8/71
Permeate - 45% recovery 3/8/71
Measured Ave. Area of Peak B - mg/1
Treatment Plant TOC-mg/1
Milwaukee 36
Milwaukee 128
Milwaukee 38
Milwaukee 830
75
Milwaukee 272
Milwaukee 108
Milwaukee 22
Menomonee Falls 41
Brookfield 78
Brookfield 19
Racine 69
Kenosha 44
Racine 39
Racine 9
As Ethanol
53
45
53
162
0
61
23
0
0
Trace
0
6
<1
<2
<2
As TOG
28
24
28
84
0
32
12
0
0
0
0
3
<0
<1
<1
.5
-------
SELECTED WATER i. Report No.
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
2. 3. Accession No.
w
4- Tit'e 5. Report Date
AMENABILITY OF REVERSE OSMOSIS CONCENTRATE TO ff
ACTIVATED SLUDGE TREATMENT,
8. Performing Organization
7. Author(s) Report No.
Gupta, M., Mason, D. G. ' 10. Project No.
9. Organization
Rex Chainbelt Inc., Milwaukee, Wisconsin
Ecology Division
11. Contract/Grant No.
17040 EUE
13. Type of Report and
Period Covered
12. Sponsoring Organization
15. Supplementary Notes
Final Report, 119 p, 29 fig, 38 tab, 25 ref, 3 append.
16. Abstract
This report documents a laboratory-scale feasibility study for the treatment of domestic
sewage. The objective of the study was to produce potable water from chemically
clarified sewage via reverse osmosis (RO) and to determine the amenability of the RO
concentrate to biological treatment.
Pilot-scale tubular and spiral wound RO units were utilized in this study. It was
determined that chemical clarification of the raw sewage was necessary even with the
tubular RO systems. The chemicals recommended for the pretreatment (based on jar tests)
were ferric chloride and alum. Reverse osmosis produced a water of excellent quality
with regard to inorganic ions. However, a significant amount of the dissolved organic
materials passed through the cellulose acetate membranes, necessitating further
upgrading of product water for potable use. Qualitative investigations on the RO
permeate indicated that 70% of the organic matter permeating through the CA membranes
from Milwaukee sewage was apparently ethanol (C2H,-OH).
Bench-scale activated sludge feasibility tests conducted on the RO concentrate indicated
that it was feasible to treat it biologically. Soluble TOG removals of 87 to 92% in
4 to 10 hours of aeration along with good settling characteristics for MLSS concentra-
tions up to 6000 mg/1 were achieved. A treatment schematic that will provide potable
water at 93% recovery and also reduce the pollutional discharge to streams was proposed.
17a. Descriptors
*Reverse Osmosis, *Reverse osmosis concentrates, *Activated sludge, *Tubular
reverse osmosis, Domestic sewage, Chemical pretreatment, Water reuse, Economics
17b. Identifiers
Sewage reuse, Reverse osmosis, Concentrate treatment
17c. COWRR Field & Group 05D
18. Availability 19. Security Class.
(Report)
20. Security Class.
(Page)
21. No. of Send To:
Pages
Pri'i-o WATER RESOURCES SCIENTIFIC INFORMATION CENTER
*f*CG | . c rirrDAD-I-K,1C-M-rr^C-TL-IP'TM"TF"RI<™)R
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
Abstractor M. K. Gupta institution Rex Chainbelt Inc.
WRSIC 102 (REV. JUNE 1971) GPO 913.26!
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