WATER POLLUTION CONTROL RESEARCH SERIES • 12040 FUB 01/72
RECYCLE OF
PAPERMILL WASTE WATERS AND
APPLICATION OF REVERSE OSMOSIS
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, development, and demonstration
activities in the water research program of the Environmental
Protection Agency, through in-house 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
(Water}, Research Information Division, R&M, Environmental
Protection Agency, Washington, D. C. 20460
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RECYCLE OF PAPERMILL WASTE WATERS
AND APPLICATION OF REVERSE OSMOSIS
by
David C. Morris
William R. Nelson
Gerald 0. Walraven
Green Bay Packaging Inc.
Mill Division
P. 0. Box 1107
Green Bay, Wisconsin 54305
for the
Office of Research and Monitoring
ENVIRONMENTAL PROTECTION AGENCY
Program #12040 FUB
January, 1972
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00
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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 necessarily
reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names or
commercial products constitute endorsement or recommenda-
tion for use.
ri
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ABSTRACT
A program is in progress involving the closure of a pulp
and paperboard mill and includes the recycle and re-use of „
weak waste waters. These waste waters, containing dissolved
organics, occur as a consequence of normal production
methods in such a mill. A method of recycling weak waste
waters has been developed and incorporated that results in
the reduction and partial concentration of the waste stream.
Reverse osmosis is being investigated for use as a unit
operation in which clarified water is separated from the
remaining wastes for process re-use, and the organics are
concentrated for processing by more conventional techniques.
To ensure that the production reverse osmosis facility
would reflect the latest technology, the project required a
pilot phase in which reverse osmosis vendors would operate
proprietary equipment simultaneously and continuously on
the same feed. This preliminary phase allowed the develop-
ment of operating techniques applicable to this particular
feed. Criteria were determined for the design of a full-
scale production facility. The proprietary equipment de-
signs of the participating vendors were assessed.
This report is submitted in partial fulfillment of
Program No. 12040 FUB under the partial sponsorship of the
Office of Research and Monitoring, Environmental
Protection Agency.
KEY WORDS: Reverse osmosis, recycle, membrane process,
organics removal.
111
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Introduction 5
IV Recycle Development 9
V Recycle Results 13
VI Reverse Osmosis Equipment Description 17
VII Test Specifications and Procedures 25
VIII Process Investigation 33
IX Discussion of Process Investigation 69
X Special Processing—High Temperatures 73
XI Equipment Evaluation 75
XII Equipment Discussion—Mechanical Performance 81
XIII Acknowledgments 83
XIV Appendices 85
v
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FIGURES
Page
1 Process Water System--1967 H
2 Process Water System—1971 12
3 Overall Equipment Arrangement 18
4 American Standard Unit 19
5 Aqua-Chem Unit 20
6 Gulf Unit 22
7 Havens Unit 23
8 Typical Reverse Osmosis Data Sheet 31
9 Short-Term Membrane Productivity 38
10 Fouling Test at 9 Percent Feed Solids 40
11 Fouling Test at 1.5 Percent Feed Solids 41
12 Typical Individual Module Flux Rates 46
13 Waste Water vs. City Water Flux Rates 47
14 Individual Module Flux Rates at 3 fps Velocity 49
15 Individual Module Flux Rates at 4 fps Velocity 50
16 Individual Module Flux Rates at 5 fps Velocity 51
17 Pressure vs. Flux, Comparison of Two Runs 52
18 Measured Solids vs. Flux for Modules in Series 53
19 Measured Pressure vs. Flux for Modules in Series 54
20 Pressure-Solids Factor vs. Flux for Modules in
Series 55
21 Pressure vs. Flux, Comparison of Two Runs 57
22 Flux Rate vs. Concentration of Feed (Unit X) 58
VI
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FIGURES (continued)
Page
23 Flux Rate vs. Concentration of Feed (Unit Y) 59
24 Feed Soluble Solids vs. Product Water Soluble
Solids 62
25 Feed Soluble Solids vs. Product Water Sodium 63
26 Feed Soluble Solids vs. Product Water BOD5 64
27 Feed Soluble Solids vs. Product Water Color 65
28 Feed BODs vs. Product Water BOD5 67
29 Conductivity vs. Product Water BOD5 68
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TABLES
No. Page
1 Recycle Data 14
2 Tests Scheduled and Completed, Aqua-Chem Unit 26
3 Tests Scheduled and Completed, American
Standard Unit 28
4 Tests Scheduled and Completed, Gulf Unit 29
5 Tests Scheduled and Completed, Havens Unit 30
6 Membrane Productivity Changes 34
7 Percent Rejections Experienced on All Units 61
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SECTION I
CONCLUSIONS
Recycle techniques have been incorporated that substantially
reduce the volume of waste waters. Significant problems
have resulted from this extensive recycle, and further
refinements will be necessary.
The reverse osmosis process is effective in concentrating
the dilute waste water stream while producing a clarified
water flow that can be utilized for process purposes. The
process is capable of concentrating a stream containing
1 percent dissolved solids to 90 percent less volume con-
taining 10 percent dissolved solids. The product water
thus separated is of high quality and can be utilized for
stock dilution, pump shaft seal lubrication, etc. The
overall flux rate for the operating portion of a plant per-
forming to these standards is about 7 gallons/ft2/day.
Operating techniques, such as maintaining a certain
velocity, have been developed and can control the tendency
to foul the membranes with materials in the feed stream.
These techniques must be incorporated in any production
process planned. Further, the resultant production plant
would have to be constructed such that further refinement
of the flux regeneration techniques could be undertaken.
There are many portions of the process that are not
well-defined, and a production operation would initially
involve a program of continuing development.
The cellulose acetate membranes exhibited no significant
deterioration, and a conclusion that the membranes are
capable of providing a minimum of one year of continuous
service is encouraged. The limited testing at higher
temperatures indicated that the membranes do not deteriorate
as rapidly as predicted.
The reverse osmosis process equipment will perform ade-
quately with a tolerable maintenance" cost, but opportunities
for improvements to meet industrial standards are apparent.
It is concluded that further development and commercial-
ization will result in plants that approach the performance
of industrial process equipment.
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SECTION II
RECOMMENDATIONS
It is recommended that efforts continue to reduce and
eliminate the problems resulting from the high degree of
waste water recycle. Duplication of some items of
equipment, monitoring and control devices, and greater
surge capacity will be required to ensure constant and
adequate reduction of the waste water losses.
It is recommended that reverse osmosis be considered for
incorporation in the mill process if other steps taken to
reduce the waste stream are insufficient to bring the total
mill effluent within the allowable standards set by the
enforcement agencies.
Because the application of the reverse osmosis process has
not been previously demonstrated, a reverse osmosis
production plant must be compatible with main plant process
variations and equipment modifications. Hence, the prime
consideration in judging competitive designs must be
system engineering, presuming that the cost differences
among several vendors would be reasonably close. A produc-
tion plant should be considered an integral part of the
overall manufacturing facility, and its design must in-
corporate similar reliability goals.
It is recommended that very tight supervision of the entire
design, construction, and start-up be maintained by Green
Bay Packaging since the reverse osmosis equipment suppliers
do not have broad experience in the field of industrial
process plant engineering.
It is recommended that process development pilot operations
continue until the production plant is considered totally
operational. The process techniques developed during the
brief pilot phase require refinement and verification.
Also, the significant cost reductions offered by higher
temperature operational capability are important, and
pilot investigations of this aspect should continue.
Regardless of further action taken by Green Bay Packaging,
it is recommended that encouragement be given for further
development of the reverse osmosis process. The prospect
of significant advancement in the field of pollution
abatement warrants the extensive sustained development
programs that will be required to apply the process to
complex waste streams.
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SECTION III
INTRODUCTION
In June, 1970, Green Bay Packaging Inc. was awarded a
Research, Development, and Demonstration Grant by the
Office of Research and Monitoring of the Environmental
Protection Agency. The grant is in support of a project
to recycle weak waste waters in the Green Bay mill,
utilizing a reverse osmosis plant as a tool in the normal
production scheme.
The company operates a pulp and paperboard mill adjacent
to the Fox River in Green Bay, Wisconsin. The mill
utilizes the neutral sulfite semichemical process to
produce fiber pulp from hardwoods. The pulp, suspended
in water, is dispersed on a forming screen to produce
paper and the bulk of the drained water is returned to
process. These operations utilizing water as a carrier
fluid result in the dispersion of dissolved organics in
the water. The majority of the organics may be collected
in a concentrated form and are treated conventionally by
evaporation and combustion. A portion of the organics are
in a very dilute solution; the excess and loss of these
weak waste waters creates a stream pollution load.
The mill had been under state orders since 1957 to reduce
the mill effluent discharge to no more than 22,684 pounds
of biochemical oxygen demand (BODs). Soon after the
FluoSolids combustion system was constructed, this
requirement was met. Green Bay Packaging has had a long
standing goal of maximum pollution abatement and conse-
quently expected more stringent restrictions. Three
routes were taken in searching for more complete abatement--
electrodialysis, reverse osmosis, and activated sludge
sewage treatment. Electrodialysis proved impractical for
technical reasons and the investigation of it was
terminated.
The company became one of four local mills involved with
the local Metropolitan Sewerage District in research of
joint industrial-municipal sewage treatment. At the same
time, investigation of reverse osmosis was being done throug
the agency of the Institute of Paper Chemistry. Both
programs included demonstration as well as research and
development and involved industry and government, with
partial support from the Environmental Protection Agency.
These early efforts included the operation of two pilot
reverse osmosis units at the mill. The goals of this
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process investigation were two-fold: first, to concentrate
the weak wastes to the point that the existing conventional
techniques could be used for disposal; and second, to
extract a clarified stream suitable for process re-use or
simplified disposal. This earlier work demonstrated that
reverse osmosis was effective in separating wastes but
that the equipment had not been sufficiently developed to
be mechanically reliable, and that there were processing
problems which resulted in a sizable loss of membrane
productivity.
Since the trials indicated that the process might prove
feasible, an investigation was begun to determine if the
potential costs could be minimized by reducing the waste
stream volume. The entire process water system was surveyed;
it was determined that the only sizable reduction would
result if waste water could be substituted for fresh water
supplied to the paper machine showers. Since such showers
require a stream relatively free of suspended matter,
it was necessary to evaluate clarification equipment.
Various shower nozzle designs were also tested. The
investigation demonstrated that waste waters could be
recycled, although it was not possible to evaluate the
impact upon the papermaking process, maintenance costs, and
product quality. Nonetheless, it was decided to recycle
waste waters to the machine showers and several other minor
uses.
Green Bay Packaging Inc. was successful in obtaining
another reverse osmosis pilot unit in early 1970, and
several concepts of maintaining membrane productivity were
soon verified. Also, the unit demonstrated an improved
mechanical integrity.
Investigation into joint industrial-municipal sewage
treatment had proceeded at the same time as the reverse
osmosis study. It was found that joint treatment was
technically feasible for meeting the requirements of the
enforcement agencies.
The immediate goals of pollution abatement to be attained
were defined in the new State Orders received in
December, 1969. These orders required that by the end of
1972, the mill discharge could not exceed 35.0 pounds of
BOD5 per ton of pulp produced, or 6934 pounds daily,
whichever was least. The orders also set a limit of
20 pounds of suspended fiber per ton of paper produced,
or 1.0 percent of machine production, again whichever
was least.
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The success of both the recycle trials and the most recent
pilot plant led to a commitment to incorporate reverse
osmosis in the mill process, and further effort on joint
sewage treatment was terminated. Several reasons in-
fluenced the selection of the relatively unproven reverse
osmosis process. Biological treatment does not destroy
the color bodies (sulfonated lignin compounds) in the waste,
and it has been assumed that color will be part of the
defined criteria for judging effluent quality in the
future. The combustion plant was available and had been
expanded for possible disposal of wastes concentrated by
reverse osmosis.
The company has had a long-standing policy of doing the
best possible pollution abatement at the present and
in the future. It was felt that a higher level of abate-
ment could be accomplished by incorporating reverse osmosis.
With a self-contained process independent of an outside
agency, it would be possible to freely develop improve-
ments. Also, water quality criteria may become more
stringent and alternate processes might not be adequate.
The modular reverse osmosis concept is flexible and can be
modified or varied as mill conditions change. Substantial
improvements in equipment reliability, membrane performance,
etc., are expected in the future. Finally, the estimated
costs—capital, operating, etc.—for sewage treatment of
this particular waste stream seem fairly close to those
for reverse osmosis.
Having made the commitment to reverse osmosis, an
application was made to the Environmental Protection Agency
for the support of further development and the construction
of a production unit. The grant was made June, 1970; and
the project began employing a formal schedule of
investigation.
To ensure that the production reverse osmosis facility
would reflect the latest proven technology, the project
required a pilot phase in which reverse osmosis vendors
would operate proprietary equipment simultaneously on the
same feed, on a continuous basis. This phase provided
information for three requirements:
a. To develop operating techniques applicable to
this particular feed.
b. To provide criteria for. the design of a full-scale
production facility.
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c. To permit assessment of the proprietary designs
of the participating vendors.
Contact had been made with several vendors prior to the
grant; ultimately, four vendors elected to participate in
the pilot phase of the program. They were:
a. American Standard, Hightstown, New Jersey.
(Note - After entry into the program, the ConSeps
Division of American Standard was purchased by
Abcor, Inc., Cambridge, Massachusetts.)
b. Aqua-Chem, Inc., Waukesha, Wisconsin,
c. Gulf Environmental Systems, San Diego, California.
d. Havens International, San Diego, California.
(Note - Havens was acquired by the Calgon
Corporation, a subsidiary of Merck, and is now
known as Calgon-Havens.)
The pilot phase was split into two segments. The first,
from September 1 through November 30, 1970, was a trial
period during which the vendors were free to gain experience
and make modifications, improvements, substitutions, etc.
The second segment ran from December 1, 1970, through
February 28, 1971, and was designated the "frozen design"
period because no improvements, modifications, or sub-
stitutions were permitted on the proprietary equipment.
Maintenance was permitted, but records were kept for
comparative evaluation. The vendors specified the test
requirements—samples, pressures, etc.; data were collected
and samples analyzed under the supervision of Green Bay
Packaging. The data on each unit were made available to
the specific vendor. The vendors were permitted to collect
extra data and perform special tests with the approval of
Green Bay Packaging.
The quantity of reverse osmosis data acquired by Green Bay
Packaging personnel is too great for complete inclusion in
this report. Summaries of data will be presented as well
as specific examples to illustrate the observed performance.
•The process data cited should not be used for evaluation
of a vendor except where noted. Most of the tests resulted
in conclusions on principles that would apply to any
reverse osmosis unit.
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SECTION IV
RECYCLE DEVELOPMENT
Reverse osmosis trials performed in 1969 indicated that
the process could be applied to the weak waste waters/
although it would require further development. The process
was also expensive, and a reduction in the volume of wastes
offered obvious advantages. Thus, all the mill process
streams were surveyed. Much of the waste water was already
being recycled for repulping, stock dilution, and similar
operations. It was determined that the only substantial
volume reduction possible was the substitution of waste
water for fresh water fed to the wire cleaning showers
on the paper machine.
These showers are utilized for cleaning the wire on its
return path; the high pressure stream removes any entrapped
debris to ensure proper drainage of the pulp slurry in the
sheet-forming section. The showers have very small
openings; waste waters containing fibrous matter plug the
nozzles quickly. Also, the fibrous matter that passes
through the nozzle tends to accumulate on machine
components.
Originally, a portion of the waste water had been partially
clarified using a flotation technique. The gradual closure
of the mill water loop over several years had resulted in
increased water temperatures. The flotation process became
less effective, and a new clarification step was devised
in 1968. The waste stream containing large quantities of
fine fiber was utilized as dilution water for repulping
kraft (corrugated) clippings. The repulped stock was
supplied to the vacuumless (seal leg type) pulp thickener.
The thickened fibrous mat formed on the thickener drum
proved effective in removing a high percentage of the fine
suspended matter.
The filtered waste stream coming from the pulp thickener
required further reduction of the fiber rubble and
virtually complete removal of the remaining long fiber
if it was to be used for showers. A program was initiated
late in 1969 to find a method for additional fiber
elimination and to determine if there were shower nozzles
available that would resist plugging or were simple to
clean.
By mid-1970, many types of conventional devices for the
removal of suspended matter—screens, filters, strainers,
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etc.—had been tested at the mill. It was determined
that a slotted screen (DSM, marketed by Dorr-Oliver, Inc.)
removed almost all remaining long fiber. Several shower
nozzle designs were evaluated. The Bird Aqua-Purge nozzle
was found to remain open for long periods and to be
easily cleaned.
These two items were incorporated in a major redesign of
the mill water system to permit recycling of waste water
to the paper machine showers. Figure 1 shows the key
waste water flows before the revisions, and Figure 2
indicates the system presently in use. The design effort
and modifications included far more than the incorporation
of new screens and nozzles. The entire water system was
overhauled. Sewers were re-routed to prevent losses,
new tanks were required for surges, and extensive controls
were installed to ensure a constant supply to the showers
as well as to reduce the possibility of accidental losses.
10
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Pulp
Thickener
Sewer
Sewer
Flotation
Unit
Recycle
Seal
Water
Vacuum
Pumps
Paper Machine
Misc.
Sewers
Screen
Machine
Sewer
Process Waters
Kraft
Clippings
Repulping
Refining
Heat
(Recovery
Plant
Scrubber)
(Machine Waste
Repulping
^Digester
Wash
->Dilutions
Figure 1. PROCESS WATER SYSTEM—1967
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to
Loss
(Reverse <~
Osmosis)
Seal
Water"
Vacuum
Pumps
O
Sewer
Pulp
Thickener
r
A
DSM
Screen
Machine
Showers
Paper Machine
Machine
Process Waters
Misc.
Kraft
Clippings
Repulping
> Pul?
Refining
Heat
(Recovery
Plant
Scrubber)
.Machine Waste
Repulping
Digester
Wash
Dilutions
Sewers
Figure 2. PROCESS WATER SYSTEM--1971
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SECTION V
RECYCLE RESULTS
Waste water was first substituted for fresh water supplied
to the machine showers in February, 1971, when the reverse
osmosis "frozen design" period was almost complete. Several
problems were encountered, including accumulations of fines
in unagitated areas, cool spots'" promoting the growth of
slime, mechanical breakdowns, and so forth. These were
solved, and the shower water recycle program has been
essentially continuous since April, 1971. In addition
to the substitution at the showers, several other low-
volume fresh water uses became 'evident and further
recycling was accomplished. The characteristics of the
waste water and the impact of recycle are indicated in
Table 1.
After the initial difficulty with slime formation, routine
addition of slimicide to the recirculating waters was-begun.
The quantity of slimicide has been substantially reduced.
It is maintained primarily as insurance against the
occurrence of unusual conditions that would promote slime
growth. No change has been necessary in the defoamer
agents added routinely at certain points in the process.
An increase has been noted in the consumption of wet-
strength resins required for certain grades of paperboard. :
The quality of paperboard has remained satisfactory in the
relatively brief time in which extensive recycle has been
practiced. Long-term effects and the impact of seasonal
variations in the fiber supply have not been determined.
Clouds of vapor and mist are characteristic around a paper
machine wire section. These waters of varying solids
content collect and fall at different points—above the
machine, on catwalks, shower pipes, etc. After waste
water re-use began on the showers, the combination of
higher temperatures, more vapor, mist with a high solids
content, and inadequate air flow resulted in many operating
problems. The primary problems were breaks in the machine
wires, shortened wire life (number of days in service),
more frequent breaks of the paper web, and discomforting
working conditions. Many corrective actions were taken—
shower pipes relocated, exhaust air system modified, and
so forth. Most of the problems have been alleviated, but
the wire life has been only partially improved. Further
work is planned for modifications around the machine and
to evaluate other "wire" fabrics which will tolerate the
new conditions.
13
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Table 1
RECYCLE DATA
Before After
Recycle Recycle
Waste Water Loss, gpm 650 25
Additional Recycle, gpm 625
Process Water
Dissolved Solids Content 0.9% 3.5%
Fresh Water Consumption, gpm
(Including Boilers) 970 610
Process Water Temperature 130°F 155°F
14
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The other problem area that has become apparent is the
necessity for better control of the entire recirculating
water system. The impact of a human error or a pump
failure, for example, was often minimal with the old system.
With a high re-use rate, the water system is so tightly
closed that a failure or error can cause serious imbalances
rapidly. Closer monitoring, control, and automation of
the water system will be necessary. Greater surge capacity
will also be required.
In addition to close control of the water volumes, it may
be necessary to regulate the quality of the water.
Stability of the machine water characteristics, such as
dissolved solids content, may be mandatory. Thus, there
are indications that reverse osmosis might fulfill a
control function. It would permit the removal and clari-
fication of some water for stabilization of the main
process stream.
15
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SECTION VI
REVERSE OSMOSIS EQUIPMENT DESCRIPTION
The general arrangement of the major pilot equipment is
shown in Figure 3. In addition, two small pilot units were
fed an uncooled waste water in a program which is described
separately in this report. The four main pilot plants were
all fed from a common line.
The American Standard unit, illustrated in Figure 4, was
supplied with 84 modules (approximately 798 ft2 of membrane
surface). Each module contained 18 tubes in series, bonded
into stainless heads. The tubes contained turbulence
promoters. The modules were arranged in fourteen parallel
rows containing six modules in series, all fed from a
common manifold and returned to a common manifold. The
feed was pumped with a three-section plunger pump with a
variable-speed drive; a bladder accumulator on the down-
stream side reduced pulsations. Following the backpressure
valve, the concentrate flowed to the sewer or to a
concentrate tank. During recycle operations for tests at
high feed solids, the majority of the concentrate overflowed
into the feed tank, and the remainder was metered from the
bottom of the tank with a variable-speed pump. The
product water (permeate) was initially collected in a low
header; later in the program, a second elevated header
was used for some modules while demonstrating the effect
of flooded shrouds. The unit was originally provided
for continuous operation and was later modified for a
depressurization cycle.
The Aqua-Chem unit, illustrated in Figure 5, had 24 modules
(864 ft2); each module consisted of 36 eight-foot tubes,
all in series. The modules were arranged in four parallel
rows of six modules in series; the four rows were connected
to common inlet and outlet manifolds. The feed was pumped
by a three-section plunger pump with a variable-speed
drive; a sleeve-type accumulator was used on the downstream
side. Following the backpressure valve, the concentrate
was led to the sewer or to a recycle receiver fitted with
an adjustable weir which served as a splitting device
allowing recycle of some concentrate into the feed tank
during runs at higher concentration. The product water
was initially collected from the main heads only; this was
later modified for discharge from both ends of the modules
in two rows (12 modules). The unit had a timing device
that provided a depressurization period followed by
flushing.
17
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Cooling
Water In
CO
Temperature
Controller
Temperature
Sensor
Heat Exchanger
Reverse
Osmosis
Unit
_^ Cooling
Water Out
Reverse
Osmosis
Unit
Reverse
Osmosis
Unit
Reverse
Osmosis
Unit
Slotted
Screen
Unscreened
Feed
c \
_J
' N
Reverse
Osmosis
Hot Unit
f
Reverse
Osmosis
Hot Unit
Figure 3. OVERALL EQUIPMENT ARRANGEMENT
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Figure 4. AMERICAN STANDARD UNIT
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to
o
Figure 5. AQUA-CHEM UNIT
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Gulf provided two main units. The first was operated during
September through November, 1970, and consisted of three
spiral-wound modules in series (about 150 ft2). The
unit was fed by a plunger pump. Considerable experimen-
tation was done with this unit, resulting in a major
alteration of the proprietary module design.
The second Gulf unit provided for the "frozen design"
trial, illustrated in Figure 6, consisted of 18 modules,
3" diameter, and three feet long. It contained about
900 ft2 of membrane surface. Late in the period, three
of the original modules were replaced with modules of
smaller diameter in a smaller pressure tube. The feed
pump was a multistage centrifugal with a fixed speed;
volume adjustment and pressure control were obtained with
valves. Following the backpressure regulator, the concen-
trate was split into two streams (recycle and sewered
concentrate) utilizing ball valves. The system had a
timing mechanism to control a pause cycle and a backflush
cycle; a small pump was utilized for the latter. Product
water was collected from groups of three modules.
o
The Havens unit contained 24 modules (432 ft'') in six
parallel rows with four modules in series, and it is
shown in Figure 7. The modules contained 18 eight-foot
tubes in series. The six rows were connected to common
inlet and outlet manifolds. The feed was pumped with a
three-section plunger pump with a variable-speed drive;
a bladder accumulator was utilized on the discharge.
Following the backpressure valve, the concentrate was led
to either the sewer or a weir pot for splitting off a
portion for recycle during runs at higher concentration.
The product water from each row of four modules was passed
to a common collector. The unit had a timing device for
the depressurization cycle.
21
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Figure 6. GULF UNIT
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' •
Figure 7. HAVENS UNIT
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SECTION VII
TEST SPECIFICATIONS AND PROCEDURES
Each vendor originally submitted a specific test plan of
the test conditions for the unit, analytical samples
required, etc., to be followed during the second segment
of the pilot phase. These scheduled tests are summarized
in Tables 2 through 5, together with the tests actually
accomplished.
The measurement of operating characteristics for each unit
was done with the standard devices of process development--
stopwatches, thermometers, etc. Measurements were taken
frequently, averaging about five times daily per unit and
included readings at various intervals between pause
(depressurization) cycles. When analytical samples were
not required, grab samples were frequently taken of feed
and concentrate to ensure good correlation with observed
data (see Figure 8, for example). Measurements were made
every day including weekends. To ensure maximum running
time, a qualified technical representative was on call
during the night hours to respond to any problem or
unusual condition reported by the mill operating super-
vision, who made periodic observations.
The analytical samples were composite or grab, depending
upon the requirements of the vendors. Each was taken to
coincide with the measurement of the unit characteristics.
The analytical techniques are summarized in Appendix 1.
25
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Table 2
TESTS SCHEDULED AND COMPLETED
Aqua-Chem Unit
Specified Conditions
Actual Test
Feed
% Total
Solids
City Water
City Water
City Water
1.0
1.0
2.5
2.5
5.0
5.0
7.0
7.0
9.0
9.0
1.0
1.0
2.5
2.5
5.0
5.0
Inlet
Pressure
psi
500
500
500
500
650
500
650
500
650
500
650
500
6"50
500
650
500
650
500
650
Feed
Rate
4
8
12
12
12
14
14
14
14
13
13
13
13
10
10
10
10
10
10
Feed
% Total
Solids
City Water
City Water
City Water
0.65
1.22
2.27
2.34
4.11
3.59
4.85
6.12
5.61
Unit Unable
13 gpm.
6.71
0.85
1.02
1.71
2.96
4.61
3.79
Inlet
Pressure
psi
500
500
500
500
650
505
650
500
650
650
550
650
to Meet 9%
650
500
650
500
650
505
650
Feed
Rate
4.0
8.0
12.0
11.8
12.2
11.6
11.9
11.7
14.0*
12.0**
12.1
12.9
at 500 psi,
13.0
10.1
10.6**
9.7
9.8
10.4
10.2
-------
to
-J
Table 2 (continued)
TESTS SCHEDULED AND COMPLETED
Aqua-Chem Unit
Specified Conditions
Feed
% Total
Solids
7.0
7.0
9.0
9.0
1.0
1.0
2.5
2.5
5.0
5.0
7.0
7.0
9.0
9.0
9.0
1.0
Inlet
Pressure
psi
500
650
500
650
500
650
500
650
500
650
500
650
500
650
600
650
Feed
Rate
gpm
10
10
10
10
7
7
7
7
7
7
7
7
7
7
Vary
Vary
Actual Test
Feed
% Total
Solids
5.40
4.90
8.10
8.14
0.81
0.66
2.30
2.92
2.56
4.86
3.72
6.84
4.23
6.78
7.76
6.40
8.32
Velocity and
Velocity and
Inlet
Pressure
psi
500
655
500
650
500
650
500
650
650
500
650
500
645
650
500
650
650
Pause Test
Pause Test
Feed
Rate
£EHL-
10.5
10.4
10.2**
9.9
7.2
6.8
7.2
7.0*
7.3
7.0
7.0
7.3
7.0*
8.0
7.0
6.7*
8.1
*Results Questionable—Test Repeated
**City Water Flux Measured After This Test
-------
Table 3
TESTS SCHEDULED AND COMPLETED
American Standard Unit
Specified Test
Actual Test
NJ
CO
Total
Solids
Content
1.0%
Feed
5.0%
Concentrate
9.0%
Concentrate
Pressure
psi
600
Exit
600
Exit
500
Exit
Flow
gpm Duration
4.2 3 Weeks
Exit
4.2 3 Weeks
Exit
4.2 3 Weeks
Exit
Total
Solids Pressure Flow
Content psi gpm
0.73% 600 4.2
Feed
5.43% 600 4.1
Concentrate
Not Performed
Duration
5 Weeks
5 Days
Unscheduled
9.00%
Concentrate
4.42%
Concentrate
920
Inlet
920
Inlet
7.6
Inlet
7.6
Inlet
4 Days
1 Day
-------
Table 4
TESTS SCHEDULED AND COMPLETED
Gulf Unit
Specified Test
Actual 'Test
to
vo
% Recovery
50
75
83
90
Duration
7 Days
7 Days
7 Days
7 Days
Pressure
% Recovery* psi
51 400
77 460
Not Performed
87 600
96
Unscheduled
600, 800
Duration
8 Days
23 Days
7 Days
5 Days
*% Recovery Equals Permeate Volume (100)
Raw Feed Volume
-------
o
Table 5
TESTS SCHEDULED AND COMPLETED*
Havens Unit
Specified Conditions
Feed
% Total
Solids
1.0
1.0
1.0
1.6
1.6
1.6
3. 0
3.0
3.0
4.1
4.1
4.1
6.5
6.5
6.5
9.0
9.0
9.0
Velocity
fpm
4.0
4.5
5.0
4.0
- 4.5
5.0
4.0
4.5
5.0
4.0
4.5
5.0
4.0
4.5
5.0
4.0
4.5.
5.0
Actual Conditions
Feed
% Total
Solids
0.7
0.7
0.8
1.2
1.0
1.4
2.8
2.2
3.4
3.8
"3.3
3.6
5.3
4.4
4.9
7.9
8.6
7.7
Velocity
- f pm
3.9
4.5
5.0
4.1-
4.5
5.0
4.0
4.4
4.9
4,0
4.5
4.8
4.0
4.3
4.9
4.0
4.5
5.0
*A11 Tests 48-72 Hours Duration, at 800 psi.
-------
XXX Unit
Pause Cycle 14 Min./2 Hr.
Date
Time
Clock Hours
Run Hours
Reference
to Pause
t~ ^n
Pressure |_ Qut
Temperature
°C
Concentrate
to Sewer
Total
Concentrate
h Feed
- Cone.
- Avg.
- Ml/Sec.
- Flow--gpm
- (2 Gal.) - Sec.
- Flow--gpm
Recycled Concentrate--gpm
j- (2 Gal.)
- Sec.
Product - Flow--gpm
Water - Flux As Is
- Flux @ 35
°C
Calculated Feed — gpm
Inlet Velocity — Feet/Sec.
Conductivity
(Dis. Solids--ppm)
Oven Solids
Sample - %
- Hand Meter
- Unit Meter
- Feed
- Cone.
Analytical Sample
12/17
1:00 p.m.
2981.1
370.4
10 Min.
After
550
300
33.8
34.0
33.9
718/59.6
0.191
11.5
10.417
10.226
64.0
1.875
3.125
3.204
12.292
5.122
109
176
-
-
—
12/17
1:25 p.m.
2981.7
371.0
Mid
Cycle
550
300
34.0
34.6
34.3
800/60.1
0.211
11.8
10.152
9.941
62.9
1.908
3.182
3.233
12.060
5.025
98
160
6.12
7.02
—
12/18
9:40 a.m.
3001.8
391.1
20 Min.
Before
650
330
35.2
36.2
35.7
646/59.2
0.173
10.5
11.429
11.256
54.9
2.186
3.645
3.586
13.615
5.673
111
156
-
-
—
12/18
10:30 a.m.
3002.6
391.9
10 Min.
After
650
335
34.6
35.6
35.1
767/59.9
0.203
10.2
11.765
11.562
53.3
2.251
3.753
3.744
14.016
5.840
108 "
158
-
-
-
12/18
1:12 p.m.
3005.3
394.6
Ylid
Cycle
650
365
35.8
36.4
36.1
536/58.6
0.145
11.6
10.363
10.218
47.8
2.510
4.187
4.081
12. 873
5.364
89
130
-
-
XXX- 6
Figure 8. TYPICAL REVERSE OSMOSIS DATA SHEET
-------
SECTION VIII
PROCESS INVESTIGATION
Feed Characteristics
The feed stream may be described as a solution of wood
extractives and sodium lignosulfonates characteristic of
the NSSC hardwood pulping process. During the frozen
design phase, the stream as received at each reverse
osmosis unit contained 0.6 - 1.9 percent total dissolved
solids and an average of 280 ppm suspended solids. The
suspended solids are colloidal and suspended fiber debris
as well as very short hardwood fibers.
The temperature of the feed supply line common to all
units was normally 35-38°C. When a portion of the concen-
trate from a unit was recycled to increase the feed
solids, the several characteristics of the total feed
stream changed proportionately with one exception; since
the concentrate is depleted of those low molecular weight
organic compounds (primarily acetic acid) which pass the
membrane, the average molecular weight of the total feed
is increased.
Initial Membrane Flux Loss
During early experience, it had been noted that the membranes
would lose some productivity rapidly when first exposed to
the waste stream. At one time it had been speculated that
this was a result of fouling or concentration polarization;
however, the loss still occurred after development of
processing techniques which precluded these causes.
Membrane productivity was measured before exposure to
waste water and after several time intervals to determine
if there was a permanent loss unrelated to processing
problems. These tests were performed on both city water
and waste water, with a preference for the former since
the composition changes little. The tests were all
performed at 600 psi inlet pressure and at constant
velocity. Those tests performed with waste water were
all about 0.9 percent dissolved solids. Conductivity
of the product water was checked with a dissolved solids
hand meter. Continued exposure to waste water resulted
in a reduction in conductivity, indicating a tightening
of the membrane and greater rejection of dissolved solids.
The results on three sets of membranes are shown in
Table 6.
33
-------
Table 6
MEMBRANE PRODUCTIVITY CHANGES
u>
% Flux Change
Membrane Test
Vendor Set Fluid
A 1 City
Water
A 1 Waste
Water
A 2 City
Water
A 2 Waste
Water
B 1 City
Water
B 1 Waste
Water
Hours
Exposure
To Waste Other Conditions
0
15.3
63.6
280.0
0.2
15.3
58.0
59.0 Immediately After 5 Days Rest
0
285.0
443.0
600.0 Immediately After 4 Days Rest
911.0
1288.0
1724.0 After Deliberate Fouling
0.4
42.0
0
270.0 After 24 Hour Rest
0.5
49.0
183.0
270.0 After 24 Hour Rest
560.0
Flux
gfd
@ 35°C
17.92
15.58
12.85
11.59
11.90
10.68
9.90
10.33
10.03
5.78
6.25
7.05
6.30
6.84
4.76
11.93
10.68
12.99
9.59
10.82
8.54
8.56
9.47
8.67
From
Last
Test
-18
-10
-7
+ 4
+ 8
4-13
-11
+ 9
-30
+ 11
-8
From
Original
-13
-28
-35
-10
-17
-13
-42
-38
-30
-37
-32
-10
-26
-21
No Change
-12
-20
-------
Even these measurements are not ideal since some were made
after extensive process manipulation. However, it is
evident that the membranes undergo a considerable tightening
resulting in the reduction of the flux rate as a consequence
of exposure to the waste water. Since part of the lost
productivity is recovered after a rest period, it appears
that there is a loss caused by compaction in addition to a
permanent loss. For example, the membranes from Vendor B
indicated a permanent loss of nine or ten percent when
exposed to waste water and a further loss of about 10
percent when exposed to pressure with this latter loss
recovered after resting.
The data also reflect an inconsistency in that the measure-
ments made with both feeds—city water and waste water—do
not always reflect the same amount of loss for the same
amount of exposure.
Membrane Fouling
During the 1968-1969 investigative work at Green Bay
Packaging, physical fouling of membranes had been observed;
this fouling consists of colloidal and suspended fiber
material which deposits on the membrane surface. This early
experience indicated but did not prove that .the minimum
velocity was higher than expected; that some fouling was
inevitable at any practical operating condition; that
pausing (depressurizing) caused a restoration of the loss
of productivity; and that permitting fouling to continue
beyond some limit would result in a substantial permanent
loss of productivity.
A primary purpose of the pilot phase was to better define
the processing techniques which would permit control, if
not elimination, of the fouling. Complete removal of the
fiber rubble to preclude fouling is well recognized as a
very costly operation and could not be considered if
costs were to be minimized.
Prior to the pilot phase, all vendors were informed of our
general experience with fouling and the partially-proven
techniques which apparently could control it. It should
be noted that this form of fouling is not necessarily
unique to our feed, but the techniques evolved for
prevention and control may be unique to the characteristics
of our waste. The following control techniques and
requirements were defined as a result of the pilot phase:
a. Pause Requirement
There is a distinction between a rest period and a
35
-------
pause. The rest period lasts several hours, during
which membrane compaction may lessen. The pause
(depressurization) cycle is brief but sufficient for
osmotic flow to take place.
The absolute necessity for a pause was illustrated
on two units. The first unit was initially operated
with an adequate velocity but a very short pause
(depressurization) cycle—2.5 minutes down after
90 minutes running. After forty-five hours operation,
the flux rate had dropped 49 percent. The pause
duration was then changed to 8.25 minutes for the
same run time; within four hours, the flux rate
recovered 55 percent for a net loss of 20 percent
from the original (new) productivity.
The second unit utilized turbulence promoters which,
it was claimed, eliminated any tendency to foul.
This pilot plant had no timing control or depres-
surization mechanism. Upon being exposed to sustained
running, the unit lost flux rapidly. Manually
pausing (shutting down) one to four times daily
helped reduce the overall rate of decay; but after
563 hours, the unit lost 65 percent of the original
productivity and after 760 hours, 78 percent.
b. Complete Depressurization
The pause cycle that has evolved during these
studies has required full depressurization of the
unit. It was demonstrated that a positive bleed
was required. If the system remained closed between
a backpressure valve and a plunger pump, for example,
the unit pressure would rise to the osmotic pressure
and then the "lifting" of fouling would cease. It
was necessary to eliminate flushing cycles or to
ensure that there was a period of depressurization
before flushing since even low pressures reduced the
effective osmotic flow. [It is worth noting also
that flushing after a pause had no effect on
membrane restoration or in inhibiting the resumption
of fouling upon repressurization.]
Booster pumps utilized on the suction side of
positive displacement pumps also had to be inter-
rupted during the pause.
c. Pause Frequency
The pausing frequency was found to be once every
60 to 120 minutes, depending upon the preference
36
-------
of the vendor, the velocity past the membrane
surface, the amount of pause time, etc. A typical
plot of water productivity through an entire time
cycle on a unit being properly paused is shown in
Figure 9. As time progresses after depressurization
(pause), the flux rate drops for about ten minutes
and then levels off and remains relatively constant
for thirty to ninety minutes (the duration depending
upon conditions and configuration). The flux rate
then begins to drop, and the unit again requires
depressurization.
The velocity and turbulence at the membrane surface
obviously influence the accumulation of fouling. The
average velocity through all tubes employed on one
tubular unit exceeded 5.1 feet per second. None-
theless, sufficient fouling occurred to produce a
7 percent loss in flux rate over a ninety-minute
period. On a second tubular unit operating at 4.8 feet
.per second average velocity, fouling caused a 4 percent
loss over a seventy-minute period. None of the four
pilot plants was operated at higher velocities
because of equipment limitations and also because the
pressure drops can become excessive.
Upon repressurization after a pause, the loosened
fouling does not immediately and completely migrate
to the membrane surface. If such were the case, the
flux would rapidly drop to the value that existed
before pausing. As illustrated in Figure 9, the
flux degradation occurs over several minutes until
the normal productivity level is reached.
Flushing after pausing might be expected to sweep
away fouling that was loosened by osmotic action
during the pause. As part of the investigation of
the operating cycle, a unit was operated with and
without flushing between the end of pause and begin-
ning of repressurization. The characteristic curve
shown in Figure 9 was unchanged by the inclusion of
a flushing step.
It was observed that membranes which became somewhat
permanently fouled required the shorter total running
cycles (60 minutes vs. two hours).
Pause Duration
The duration of the pause cycle is dependent upon the
other processing variables, such as velocity. None-
theless, the vast quantity of data taken under
37
-------
Pause
Pause
X
ID
OJ
00
X
EH
H
>
H
D
Q
§
TIME
Figure 9. SHORT-TERM MEMBRANE PRODUCTIVITY VS. TIME
-------
numerous conditions on four units has indicated
similar minimum pause time requirements.
Several attempts were made to define the minimum
pause time as well as the minimum velocity. As noted
in the subsection "Pause Requirement", one unit was
started with a very inadequate 2 1/2 minute pause
time. The flux began to recover when the time was
adjusted to 8.25 minutes. The optimum time
eventually proved to be twelve minutes on this unit.
Two sustained runs were made on one unit. The first
was performed with a feed of about 9 percent solids
over fifteen days (see Figure 10). After several
days of erratic performance, a base line was estab-
lished using a fourteen-minute pause (two-hour total
cycle). The pause time was then reduced to twelve
minutes and the flux began to decline. The velocity
was then increased to 4 feet per second and the flux
rate improved.
The second test (Figure 11) was performed with a feed
of about 1.5 percent splids. After two days of
irregular performance, the unit stabilized. The
flux rate was normal compared to previous runs at the
same conditions. The velocity was relatively low
at 3 feet per second, and the pause was set at
14 minutes (two-hour total cycle). The pause was
changed to twelve minutes, and some loss of
productivity was noted. A further reduction to ten
minutes was made with flux deterioration becoming
quite evident after about three days. The velocity
was then increased, and the flux rate improved
noticeably. Soon after, the high pressure pump
began to perform erratically. The feed rate (and
thus the velocity) would drop off sharply and later
return to normal. During the night hours, this would
go undetected when it did not coincide with the
periodic observations by the mill supervisory
personnel. Permanent or stable fouling evidently
occurred at this time, and a final adjustment of the
pause to fourteen minutes was ineffective.
We have observed in these runs that the effect of
revising an operating limit is often not evident for
two or three days. The tests are difficult to perform
since many variables—pump speed, feed solids, etc.—
are constantly changing; and even when several points
of data are taken under apparently identical conditions
in a short time, there will be a wide variation in
results.
39
-------
Pause 14'
12'
Velocity 3 fps
4 fps
60
40
20
w
C»P
U
^5.0
Ti
m
Cn
X
D
.-4.0
3.0
Q Pause
1 | 2 I3l 4 I 5 I 6 I 7 I 8 | 9 llOl 11 I 12
TIME (days) - no scale
13 I 14
Il5tl6
Figure 10. FOULING TEST AT 9 PERCENT FEED SOLIDS
-------
ifc.
Velocity 3 fps
QPause
OMidcycle
1 I
2 I 3 I 4 I 5 I 6 I 71 8 19 110|ll| 12 Il3|l4|l5| 16 I 17 |18|l9|20
TIME (days) - no scale
Figure 11. FOULING TEST AT 1.5 PERCENT FEED SOLIDS
-------
Both figures include a plot of the percent flux
recovery, which is defined as the percentage by which
the flux rate recovers over a pause cycle. It had
long been observed that this percentage was greater
as fouling proceeded. During the pause trials, this
factor became useful in judging the degree of
temporary fouling that occurred in each cycle..
It has been observed that the optimum duration of
the pause cycle varies little, if any, with the
concentration of dissolved solids and suspended
solids. A correlative observation is that percentage
flux decay over a cycle varies little with concen-
tration.
The experience with the pilot plants has indicated
that the minimum pause cycle is eight minutes for
total cycles of one hour, ten minutes for an hour-
and-a-half, and twelve minutes for,two hours. This
corresponds to 13, 11, and 10 percent of the total
operating time. :
: i
e. Minimum Velocity
Several brief tests were made to ascertain the
minimum velocity required. In addition, three long
runs were made in which,velocity was one of the
variable conditions. The two open half-inch
tubular units were utilized in these tests. The
minimum velocity in one unit was evidently about
4 feet per second, and in the other about 3.5 feet
per second. Since these units were run under virtually
identical, conditions, the difference was attributed
to turbulence; the unit tolerating a lower velocity
contained a significant constriction at each 180° turn.
One unit was utilized for minimum velocity tests (in
conjunction with the above pause tests) at both high
and low feed concentrations. The minimum velocity
was not significantly greater for higher concentrations.
In performing the pause and velocity tests, it was
noticed that the pressure drop across the modules
increased slightly (approximately 5 percent) as
the unit became fouled. Apparently the reduced water
removal in the initial modules resulted in a greater
volume through the terminal modules, thus increasing
the pressure drop.
42
-------
Velocity tests per se were not performed with the
tubular unit which contained turbulence promoters.
Some velocity testing was performed on the unit with
spiral-wound modules, but the results were incon-
clusive because of many processing problems. Toward
the completion of testing on,the latter unit, a
modification in one section resulted in a velocity
of about 5.0 feet per second as opposed to approxi-
mately 2.5 feet per second in the remainder of the
sections. The absence of fouling in the higher velocity
modules was evident.
f. Osmotic Water Requirements
The requirement for available water to be drawn back
by osmosis during a pause cycle was not evident in our
early experience with reverse osmosis tubes in a
shroud. As we experimented with a unit which had no
reservoir of product water adjacent to the membrane
but did have transparent discharge lines, we observed
the rapid drawback of air during the pause cycle.
Theorizing that the evident osmotic driving force
would be effective in lifting fouling from the membrane
surface, the product water discharge line was submerged
in a bucket. This permitted the return of permeate
to the membrane. It resulted in a recovery in flux
rate over a pause that was double the amount of
recovery before the water was available. At that
time these membranes had several hundred hours ex-
posure. When the same unit was refitted with new
membranes, it was found that more than four times
as much water was returned. Evidently, the membrane
backing remained more elastic and open to flow. The
water availability also resulted in a reduction of
the initial flux loss that occurs when new membranes
are first exposed to the waste waters.
These results encouraged the vendor to modify half
the modules to discharge at both ends, thu's reducing
the path both for permeate discharge and for the
return of permeate during the pause. These double-
ended modules, which had been exposed to our feed for
over three hundred hours, immediately demonstrated
a 20 percent increase in flux rate over the unmodified
modules. This regained productivity continued in
the ensuing months regardless of process variations.
The volumes of water drawn back during a pause cycle
were measured and reflected the improved return path
developed by providing permeate connections at both
ends of the module. It was also observed that the
effect of water availability was more noticeable
43
-------
during low-velocity trials when conditions for
increased fouling were optimum.
Approximately 1700 hours later, the remaining modules
on this unit were modified to discharge on both ends.
The productivity of these modules slowly improved to
within five percent of the flux rate of the modules
that were earlier modified.
Since this one particular unit had little water
adjacent to the membranes and had to draw it from the
reservoir, it was possible to measure the quantities
under varying conditions. During a fourteen-minute
pause while running at low concentration (about 1
percent dissolved solids), the unit drew back about
10 cc per square foot of membrane surface. At high
concentration (about 9 percent), the drawback was
about 70 cc per square foot, approximately reflecting
the ninefold increase in osmotic pressure. The rate
of drawback was high immediately upon depressurizing
and tapered off during the total pause time. The
total volume increased slightly when the unit was
being deliberately fouled. The operating velocity
seemed to have no effect on the volume drawn back
unless the velocity bordered the limit for fouling.
Tests were made with a dye in the product water which
showed that the configuration of the piping is
important; the returning water preferentially takes
the least constricted route.
i
Some brief tests early in the program with the
spiral-wound modules indicated that they drew back
about 7 cc per square foot of membrane surface when
the feed contained 1 percent dissolved solids.
Some volume return measurements were attempted with
the second tubular unit (without turbulence promoters)
but poor product water connections resulted in air
being drawn into the piping. This unit had no flux
difficulty, however, because the pressure tubes were
within a flooded shroud.
One tubular unit, provided with turbulence promoters,
was not flooded initially. A few modules were
modified to flood the shroud. This resulted in a
7 percent improvement in the flux recovery during a
manual pause, as opposed to nonflooded modules. This
unit had no regular pause cycle and the flux rate
deteriorated greatly. After 467 hours of operation,
the entire unit (including flooded modules) had lost
44
-------
36 percent of the flux rate while the flooded modules
lost less than 5 percent. Later this unit was
modified to have about 40 percent of the modules
flooded. After further operation, the flux rate of
the flooded modules was 18 percent greater than those
not flooded.
This unit was then modified to incorporate a regular
pause cycle, and the effect of flooding was less
noticeable.- After stabilized operations with proper
depressurization, the productivity of the flooded
modules was 8 percent greater than that of the non-
flooded modules.
Number of Modules in Series
The measurement of the flux rate of the individual
modules comprising a unit can determine variability,
fouling, etc. During the pilot phase of this program,
one vendor requested the measurement of individual
modules during each of the many specific trials.
Also, since the tests included trials on city water
of low dissolved solids, there was an opportunity to
compare modules with a standard fluid.
Each module in a group connected in series will per-
form differently from the previous module in the series
since the pressure will be lower and the feed stream
will contain a higher concentration of solids; thus,
the flux rate of successive modules will drop. As
large quantities of individual module data were
acquired, it was realized that flux losses were
disproportionate to any change in pressure or
dissolved solids. This was noted even where the pause
cycle was adequate and the velocity was high (see
Figure 12).
The manufacture of membranes is known to result in
variable performance from module to module; hence,
the measurement of each module using city water
produces a standard by which to reference later per-
formance. These standard tests were performed at
500 psi inlet pressure and 3.3 feet per second
velocity. Under the same conditions, the measurement
of individual modules while operating with waste
water feed showed a characteristic break in the flux
plot. Figure 13 illustrates the variation in flux
rate'with reference to the module position on the
same modules operating with both feeds.
45
-------
9.0
CTi
o
in
ro
8.0
7.0
X
D
t-q
w
H 6.0
EH
U
D
Q
O
n^ 5.0
4.0
O
INLET
Run Data:
Pressure, psi
Velocity, fps
Percent Solid
I
Out
4.4
4.42
idual
ge of 4
Mocules
Modules
345
MODULE POSITION
OUTLET
Figure 12. TYPICAL INDIVIDUAL MODULE FLUX RATES
-------
o
LO
n
X
O
D
Q
s
City
Water
Waste
Water
Run Data:
Inlet
Inlet
Average
elocity,
Pressure,
Feed Sol
City W
@ 35°d
ndual Mo
AAverlage of 4
ules
odules
Waste W
§ 35°
INLET
345
MODULE POSITION
OUTLET
Figure 13. WASTE WATER VS. CITY WATER FLUX RATES
-------
The tests on this particular unit included three
major variables—pressure at two levels, three
different inlet velocities, and five feed concen-
trations. The latter were very difficult to control,
and any analysis of data requires grouping of con-
centration ranges. To simplify plotting, thirty
tests were grouped by velocity and pressure; the
feed solids concentration of individual runs was
disregarded. A flux rate for each module position
was computed by averaging the several results for the
particular module. These six charts are illustrated
in Figures 14, 15, and 16. Generally, the contour
of these plots indicates that after about the third
or fourth module in series, the flux rate shows
more decay. One unusual feature noted in the indi-
vidual tests as well as Figure 14 was that the first
module in series when operating at 650 psi and 3 fps
had a lower flux rate than the second module.
The unusual "S" curve often noted led to a comparison
of two runs, utilizing the discharge conditions of
one run as the inlet conditions for a second run.
Figure 17 illustrates the inconsistency; the two
plots could be expected to align reasonably well.
To produce more information, one of the rows
(of six modules in series) in the unit was modified
to permit the measurement of pressure as well as
feed solids at each module. Figures 18 and 19
illustrate the change in performance with position.
It was theorized that the plot of flux vs. average
solids could be deceptive if the lower pressure in
modules 5 and 6 resulted in a lower flux. Similarly,
the increasing solids effect in modules 5 and 6 could
be influencing a plot of flux vs. average pressure.
Hence, an empirical number was derived by multiplying
the average pressure and average solids content for
each module, and this product was plotted versus the
flux (see Figure 20). Again, it may be seen that the
last two modules perform quite differently.
The many test results implied both that fewer modules
in series was desirable and that the pilot data could
not be merely applied to a production plant design
without some verification that fewer modules in a
short series behaved in the same manner as the first
few modules in a longer series. Thus a brief test
was made in which the unit was operated with only
three modules in series. After an initial set of
data was obtained, the feed conditions for the second
run were modified to simulate the discharge conditions
48
-------
9.0
Pressure
Pressur
Pressure -
Pressur
INLET
345
MODULE POSITION
OUTLET
Figure 14. INDIVIDUAL MODULE FLUX RATES AT 3 FPS VELOCITY
-------
8.0
Ul
o
u
o
in
n
M-l
tr>
X
I
EH
U
CD
Q
s
CM
7.0
6.0
5.0
4.0
3.0
650 psig
- 519 pslig
A Inlet Pressure -
Outlet Pressurd
500 psig
- 355 ps
OInlet Pressure -
Outlet Pressure
INLET
345
MODULE POSITION
OUTLET
Figure 15. INDIVIDUAL MODULE FLUX RATES AT 4 FPS VELOCITY
-------
en
9.0
CJ
o
m
ro
8.0
7.0
X
w
EJ 6.0
u
Q
g 5.0
4.0
INLET
I
A Inlet
Outlet
Pressure
Pressur
D Inlet
Outlet
Plressure
Pressur
650 psig
; - 422 p
500 psig
> - 303 p
ig
345
MODULE POSITION
OUTLET
Figure 16. INDIVIDUAL MODULE FLUX RATES AT 5 FPS VELOCITY
-------
U1
K>
Exit Conditions, Run A
Inleti Conditions, Run B
400
440 480 520 560
AVERAGE MODULE PRESSURE, psig
600
640
Figure 17. PRESSURE VS. FLUX, COMPARISON OF TWO RUNS
-------
11.0
UT
UJ
U
o
m
(SJ
10.0
D
J
Cn
W
1
EH
U
D
Q
§
7.0
6.0
1.6
1.8 2.0 2.2
AVERAGE PERCENT SOLIDS
2.4
2.6
Figure 18. MEASURED SOLIDS VS. FLUX FOR MODULES IN SERIES
-------
11.0
650
630 610 590 570
AVERAGE PRESSURE, psig
550
530
Figure 19. MEASURED PRESSURE VS. FLUX FOR MODULES IN SERIES
-------
11.0
Ul
Inlet
Module /
900 1000 1100 1200 1300 1400 1500
AVERAGE PRESSURE x AVERAGE SOLIDS (psig - percent solids)
Figure 20. PRESSURE-SOLIDS FACTOR VS. FLUX FOR MODULES IN SERIES
-------
of the previous run. The results, shown in Figure 21,
may be compared with Figure 17.
h. Removal of Fouling
During our early experience with reverse osmosis, the
processing techniques for preventing fouling were not
understood; later, heavy fouling occurred because of
equipment limitations. It has been our general
experience that after an extended period, fouling is
very difficult to remove. The mill practice for
removing fines accumulations from process equipment
such as heat exchangers is to wash with a strong
caustic solution, which is, of course, not compatible
with cellulose acetate membranes. Several attempts
were made to remove fouling using neutralized
solutions of enzyme detergent, which had only a
limited effect. Allowing bacterial action to take
place by shutting a unit down for extended periods
with feed against the membrane also resulted in only
limited improvement. Reversing the flow past the
membranes for short periods had little effect. . Back-
flushing with feed, clear water, etc., did not improve
the membrane productivity appreciably, although it
helped remove accumulations at sites other than the
membrane. Long shutdowns with clean water did not
produce much improvement.
The one technique that has proven effective although
slow is to operate with adequate depressurization
cycles and during the operating cycle to increase
the velocity 10-15 percent above normal. It is sus-
pected that the heavy, stable fouling is eroded away
with time.
Occasionally, light fouling has been both physically
observed as well as reflected in the operating results.
This has occurred despite operating with an adequate
velocity, pause cycle, etc., that previously had
effectively controlled the fouling. After a period
of time, the fouling would disappear. No explanation
has been found for this.
Process Results
The productivity of the membrane (flux rate) was similar
to that experienced previously on our feed. Typical curves
of flux vs. average feed concentration from two different
units are illustrated in Figures 22 and 23. The curves
are not identical, of course, because of different pressure
ranges, equipment configuration, etc.
56
-------
8.0
Ul
u
o
in
CO
cs>
U-t
Cn
X
H
1
EH
O
D
Q
§
7.0
6.0
5.0
4.0
3.0
1
^
1
1
Exit
Inlet
Run B
^
XI
\s—
I
Condition
Conditio
V
a
a
^ Inlet
Module
1
s , Run A
is , Run B
Run A^
S
"^-Outlet
Module
!
Pressure
psig
560
560
A
S
1
Percent
Solids
7.19
7.14
1
Velocity
fps
3.37
3.52
I
460
500 540 580 620 660
AVERAGE MODULE PRESSURE, psig
700
Figure 21. PRESSURE VS. FLUX, COMPARISON OF TWO RUNS
-------
ui
00
13. 0
12.0
U 11.0
o
IT)
n
ca> 10. 0
9.0
M-l
tn
X
w
I
E-i
u
3
Q
§
8.0
7.0
6.0
5.0
4.0
3.0
J_
I
I
2.0
4.0 6.0 8.0 10.0
AVERAGE FEED PERCENT SOLIDS
12.0
14.0
Figure 22. FLUX RATE VS. CONCENTRATION OF FEED (UNIT X)
-------
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
U
o
in
ro
M-i
X
D
Cti
M
1
E-i
U
D
Q
s
fit
\
2.0
tt
0
4.0 6.0 8.0 10.0
AVERAGE FEED PERCENT SOLIDS
12.0
14.0
Figure 23. FLUX RATE VS. CONCENTRATION OF FEED (UNIT Y)
-------
The osmotic pressure of the waste stream was measured
using one of the pilot plants. The technique involved
blocking the product water channels and measuring the pres-
sure on the back side of the membrane. This pressure
subtracted from the operating (feed) pressure yielded the
osmotic pressure. In this test, the osmotic pressure
averaged about 31 psi for each percent soluble solids
in the feed.
The effect of temperature on membrane productivity
(flux rate) was found to be 3.0 percent per °C in the range
of 5-25°C, and 2.3 percent in the range of 25-40°C
(using city water as the test fluid). These corrections
were applied to all the data taken during the trial period.
The ability of the membranes to reject dissolved solids
was found to be excellent. Rejection has been calculated
on total quantities and not on concentration. The lowest
rejection of soluble solids from all samples was 99.37
percent; the lowest sodium rejection was 99.48 percent.
One sample for BOD5 resulted in a rejection of 97.44
percent; all other BOD5 samples were greater than
98.25 percent.
The rejection of color as determined by a subjective
optical comparison device is imprecise, but the lowest
rejection encountered was 99.92 percent. The measurement
of color using a spectrophotometer operating at the nominal
wavelength of lignin yielded a lowest rejection of
99.67 percent.
The average rejections with highest and lowest readings
experienced on each unit in these trials are listed in
Table 7.
The percent rejection increased slightly with an increase
in feed concentration, as would be expected in a recycle
system. There was no evidence that the membrane perfor-
mance declined with continued exposure. This is discussed
later in the report.
The product water quality, as judged by the percent
rejection, was excellent over the entire range of feed
concentrations. Figure 24 illustrates the change in
product water soluble solids as the average feed solids
is increased. The average feed solids for each run is an
average of the concentration in the feed and concentrate
streams. Similarly, Figures 25, 26, and 27 illustrate
the variation of product water sodium, biochemical oxygen
demand (6005), and color over the range of average feed
concentrations.
60
-------
Table 7
PERCENT REJECTIONS EXPERIENCED ON ALL UNITS
Units
CTi
Parameter
Soluble Solids
High
Average
Low
Sodium
High
Average
Low
BOD5
High
Average
Low
Color - Optical Comparator
.High
Average
Low
Color - Spectrophotometer
High
Average
Low
American
Standard
99.86
99.71
99.37
99.70
99.54
99.48
99.03
98.64
98.26
100.00
99.99
99.94
99.94
99.85
99.77
Aqua-Chem
99.92
99.80
99.45
99.89
99.66
99.13 -
99.82
99.20
97.44
100.00
99.99
99.92
99.99
99.91
99.67
Gulf
99.99
99.97
99.92
99.99
99.95
99.85
99.97
99.85
99.64
100.00
100.00
99.99
100.00
99.98
99.95
Havens
99.93
99.92
99.71
99.89
99.79
99.64
99.77
99.56
99.12
100.00
100.00
99.98
99.98
99.94
99.79
-------
I\J
1UUU
900
g
a
^ 800
w
H 700
J
O
en
H 600
J
«
g 500
0)
«
W 400
1
H 300
u
0
Q
C3 o /"\ rt
c^ 200
A<
100
0^
1
>*
^
\
KO
1
/
/
r
\
o
1
7
7
f
\
1
1
1
0
2.0
4.0 ,6.0 8.0 10.0 12.0
AVERAGE FEED PERCENT SOLIDS
14.0
Figure 24. FEED SOLIDS VS. PRODUCT WATER SOLUBLE SOLIDS
-------
CTi
U)
g
ft
o.
M
Q
O
Cfl
I
EH
U
D
Q
O
200
180
160
140
120
100
80
60
40
20
I
I
I
I
2.0
4.0 6.0 8.0 10. 0 12.0
AVERAGE FEED PERCENT SOLIDS
14.0
Figure 25. FEED SOLIDS VS. PRODUCT WATER SODIUM
-------
CTl
1UUU
900
800
e
Qb
ft 700
<*»
m
0 600
«
A
g 500
1
g 400
D
Q
§ 300
CM
*"^ f\ f\
200
i A n
lUU
n
qx
in ^^
^^
1
o o
^^ °
^6
i
o^
Q >X^
V^o
x^O
1
/
/
1
°/°
/
1
I
1
1
2.0
4.0 6.0 8.0 10.0 12.0
AVERAGE FEED PERCENT SOLIDS
14.0
Figure 26. FEED SOLIDS VS. PRODUCT WATER BOD5
-------
4J1
1.0
CO
O - _
n 0.9
U
-H
• ^4 f\ rt
Jj 0-8
r~1
H
•H
g
H °-7
00
O)
© 0.6
•
6 °-5
«k
0 0.4
O
U
tf 0.3
w
12 0.2
o
Q 0.1
O
0
l^
B
i
o
C^x
.^^^3
0
1
o
/
^ 0
o
1
/
^
1
0
7
\
i
i
i
2.0 4.0 6.0 8.0 10.0 12.0
AVERAGE FEED PERCENT SOLIDS
Figure 27. FEED SOLIDS VS. PRODUCT WATER COLOR
14.0
-------
The criterion by which the total plant discharge is judged
is the reduction of BOD$. The efficacy of reverse osmosis
in separating BODs may be seen in Figure 28, which
illustrates the variation in product water BODs with the
feed BOD5 content.
The conductivity of the product water was measured
throughout the trial runs in order to determine the
relationship with BODs content. Figure 29 shows this
relationship determined from a total of 34 runs on two
units.
It has been known from earlier studies that the primary
constituent in the product water was sodium acetate;
however, the nature and proportions of the several com-
ponents had not been determined on samples taken from
field units. Hence, samples were obtained from two runs--
one in which the feed contained 3.02 percent solids,
and the other 10.02 percent solids. The tests, performed
by outside agencies, disclosed that there was little
significant difference in the constituents dissolved in
the product water. The solids in both product waters
consisted of about 80 percent sodium acetate; and the total
organic carbon was proportionate to the difference in
dissolved solids.
66
-------
CTi
JLUUU
900
800
g
a 700
in
g 600
CQ
w 500
EH
EH 400
O
Q
§ 300
?f)fl
~\ f\ f\
100
o^
1
o
^-
1
Qr^***^
0
1
o
.^
_^^
^^ o
0
1
^/"^
^^^
^
t
o /
y
/
^
/
1
o
1
1
12 16 20
AVERAGE FEED BOD5, 103 ppm
24
28
Figure 28. FEED BOD5 VS. PRODUCT WATER BOD5
-------
a
in
Q
O
ffl
M
I
EH
U
D
Q
O
OS
100
20
60
100
140 180 220
CONDUCTIVITY, ppra
260
300
340
Figure 29. CONDUCTIVITY VS. PRODUCT WATER BOD5
-------
SECTION IX
DISCUSSION OP PROCESS INVESTIGATION
Three factors detracted from obtaining the maximum amount
of information during these trials. First, the scope of
the tests and intensive effort in a relatively short time
interfered with the orderly development of the investigation,
Second, mechanical difficulties with the pilot plant
equipment interfered with the completion of tests.
Third, the variability of the feed supply and the dynamic
nature of the membrane process made precise control and
experimentation difficult. Nonetheless, a large quantity
of data was obtained from which many conclusions may be
made.
The quantitative data, such as flux rate vs. feed solids,
was sufficient for estimating the criteria for a production
facility. The data were statistically analyzed, but it was
found that there was no simple equation for most relation-
ships.
It is concluded that allowance must be made in designing
a production facility for loss of membrane productivity.
The apparent permanent loss is approximately 20 percent.
Ten percent is presumed to be caused by a reaction of the
membrane to one or more constituents in the waste water
feed. There is an additional 10 percent loss of produc-
tivity that is assumed to be the result of membrane
compaction. This also must be considered a permanent loss
since a production unit is expected to remain in operation
virtually continuously.
It was determined that the process can easily produce a
concentrated waste stream containing 10 percent dissolved
solids, at which point conventional evaporation and com-
bustion processes are feasible. The product water
recovered was of excellent quality and is suitable for
many process operations requiring clear water. All_
analyses on the product water indicated that there is
little or no change in the proportion between the various
dissolved constituents at different levels of concentration.
The data for product water BODs and conductivity were
statistically analyzed, and there is a strong correlation
(r = 0.96) between these two properties. The use of
conductivity for monitoring plant performance in terms of
product water quality is warranted.
69
-------
All evidence in the trials indicated that the number of
modules in .series is critical. There were indications
of poor performance even,when the discharge velocity from
the last module in a long series was above what is con-
sidered to be the minimum velocity. It is concluded that
the number of modules in series should be less than was
utilized in the pilot phase. Such a reduction would
require more staging;and "pyramiding" to effect the
necessary concentration, but the expense, would be warranted.
Performance variation between,modules, which is charac-
teristic in the membrane processing field, will result
in irregular series flow conditions. The effect of such
performance variations would be minimized by reducing
the length of the fluid path before the flows are combined
and redistributed for another stage.
? *"
One unexplained inconsistency noted in performing the tests
was the lower flux rate that often occurred in the first
module in series.
The major effort to define the techniques to prevent
membrane fouling resulted in certain firm conclusions.
The mechanical construction of the module must be such that
there will be no membrane areas unexposed to high velocity.
The minimum velocity identified for the waste water feed
investigated is higher than previously reported and must
be about four feet per second. Since the fouling is not
primarily caused by concentration polarization, turbulence
promoters are of little value.
Unless some preventive technique or better flux regenerative
technique can be developed, a pausing cycle is required
together with an opportunity for the return flow of
product water. This cycle will result in an effective
loss of 10 percent of the plant capacity at any given
time. The requirement for routine depressurization will
result in higher costs, not only for extra membrane surface
area, but also for reliable control of the cycle. The
pausing cycle determined by the trials is quite uniform
over the range of concentrations. It is theorized that
at higher concentrations the more dense fouling is lifted
by the higher osmotic flow, and thus the same cycle may be
used for all stages.
There must be an unobstructed path for the return of product
water during the pause cycle. This path must extend to
within the module structure up to the back side of the
membrane support structure.
The fouling accumulates in a definite pattern that does not
seem to be influenced by the concentration of the feed.
70
-------
Fouling is not easily detected by one or two measurements
of the flux rate since the membrane productivity is so
sensitive to influences such as momentary changes in the
feed concentration. The amount of flux recovered after
a pause (percent flux recovery) is the most sensitive
indication that fouling is occurring.
Fouling of the type experienced is not easily removed,
particularly if allowed to continue. No special technique
was found which readily removed accumulated fouling.
A final comment is necessary about the results of this
investigation. It was found that there is an inter-
dependency between the processing variables that has made
it difficult to reach firm conclusions about any one
variable. Better process definition will require
extensive experience at steady conditions with a large,
reliable unit. >
71
-------
SECTION X
SPECIAL PROCESSING - HIGH TEMPERATURES
During past investigations of reverse osmosis, it had been
understood that the maximum temperature to which cellulose
acetate membrane could be exposed was about 95°F (35°C).
Reputedly, the membranes hydrolyze rapidly at higher
temperature. However, operation at elevated temperature
not only would result in greater flux rates, but also
would reduce or eliminate the expensive preparatory
operation of cooling. Hence, the vendors were invited to
provide small pilot units for operation on uncooled feed
at a temperature of approximately 50°C.
The first unit operated was a single tubular module
(36 ft2) fed by a separate pump. It was operated for
694 hours; the flux rate did not decay greatly and the
product water quality remained good. This success led
to the installation of a second unit, again tubular, with
72 ft2 of membrane surface.
This unit operated for a total 2048 hours on feed that
averaged about 122QF (50°C). There were many mechanical
problems, such as excessive wear on the small pump and
distortion of plastic components. The flux rate declined
gradually until 40 percent was lost in the first 1000 hours
of operation. During the second 1000 hours, the decline
was only 10 percent more.
It was found that the flux rate varied more widely than
with the cooled unit. Physically, a very dense fouling
was observed that accumulated and sloughed off in a
different manner from the fouling in the cooled unit.
The product water quality did not deteriorate in any
property and the rejection did not change. For example,
the percent rejection of BODs was 99.67 percent in the
53rd hour of operation, and 99.66 percent after 1740 hours
more exposure. Operations were terminated because of
thermal deformation of the module, but no membrane
deterioration was experienced.
The second vendor provided a small unit with spiral-wound
modules. This was operated at approximately 122°F (50°C)
for a total of 1267 hours. The flux rate declined rapidly
in the first 150 hours of operation, until about 60 percent
of the original rate was lost. The productivity then
remained essentially constant until operation was
terminated. Again, mechanical problems caused the
cessation. No membrane deterioration was experienced.
73
-------
The product water quality on this unit remained excellent
with no change in the percent rejection. After the first
800 hours of operation, the modules were visually inspected
and found to be very heavily fouled; and yet the pressure
drop had not increased nor the membrane productivity
decreased proportionately when compared to the results
of operating the cool spiral-wound unit.
Both types of hot units were operated with the same
velocities, depressurization cycles, etc., that were in
use with the main units processing cooled waste. The
excellent condition of the membranes after high temperature
exposure implies that either the commonly recognized
temperature limitation is invalid or that a property
in the feed inhibited the rate of hydrolyzation.
Regardless of the reason, any further field investigation
of reverse osmosis should include some exposure at higher
temperature if this is a normal process condition.
74
-------
SECTION XI
EQUIPMENT EVALUATION
One of the goals of the pilot phase of the project was to
evaluate proprietary reverse osmosis equipment. The
purpose of the evaluation was to assess the capabilities
of the reverse- osmosis process as applied at Green Bay
Packaging as well as to judge whether or ;not individual
vendors could meet the equipment qualification standards
established by the project. The evaluation was based
primarily on the three-month "frozen design" period; but,
to keep performance in the proper perspective, reference
will be made to operations carried out in the pretrial
period.
Comparisons among the several vendors of the membrane
productivities are not made for several reasons. The
anticipated production plant will be judged on each
vendor's total design and total cost, regardless of
membrane surface area. A flux rate was not specified to
the vendors for the trial period. They were free to set
conditions, such as operating pressure, to obtain the
best information for the purpose of production plant
design. The pilot plants were constructed for data
acquisition and did not necessarily reflect an arrangement
for optimum flux rate.
With one exception noted in the following section,
materials of construction used in all units were found
to be compatible with the cooled feed and process
conditions. Arrangement of modules, fittings, and
associated lines often fell short of standards for
industrial service. Inconvenient connections, inferior
nonproprietary equipment, inaccessible points for main-
tenance, inappropriate instrumentation, and poor clearance
for parts removal indicate a need for improvement to cope
with industrial production and maintenance demands.
The Aqua-Chem pilot plant was received in advance of the
program and had been in operation since April 2, 1970.
Therefore, entrance into the three-month pretrial test
period on September 1, 1970, was merely a continuation
of testing already in progress.
As of September 1 the modules most recently installed in
the pilot plant had been exposed to 335 hours of operation
processing white water. By the time this total reached
450 hours on September 6, however, enough failures had
been experienced to warrant refitting the unit.
75
-------
New modules were installed in the plant on September 28.
Aqua-Chem warned that these modules were of questionable
quality, but they were providing them so that investigations
could continue. Another refitting was anticipated within
30 days. The first module failure occurred after 277 hours
of operation and was attributed to a defective end seal.
Module failures became increasingly regular until the run
was terminated on October 28 after 670 hours of operation.
At this time, 13 of the 24 modules were discharging
permeate of inferior quality. Onsight inspection of the
"bad" modules showed both seal and tube failures.
Aqua-Chem stated that the tube failures might be attributed
to variations in the tube paper used in manufacture. The
pilot plant remained inoperative for the remainder of
the pretrial period.
The unit was refitted with new modules on December 1, 1970,
the first day of the "frozen design" period. The new
modules contained tubes which were approximately 1/4"
longer than those tested previously. Apparently the shorter
tubes had caused the sealing problems that had been
encountered. These new tubes also incorporated a new •
ferrule design which had been tested on several replace-
ment tubes in the pretrial period and found to perform
satisfactorily.
Operation of the unit began on December 3. After 160 hours
of operation and immediately after a pause cycle, the unit
began to intermittently discharge discolored permeate
from all modules. Investigation revealed that the heads
at the end of each module had been improperly torqued.
After they were tightened, no discoloration was visible.
The unit ran from this point to February 28, the end of
the test period, with no more difficulty. A total of
1927 hours were logged during the "frozen" period with
no module failures.
Testing continued after February 28, and the-first module
failure was encountered after 2044 hours of operation.
Inspection of the module revealed that one of its tubes
contained a manufacturing defect. The tube was replaced,
but leaking continued. The plant was finally shut down
after 12 of the modules had been run 3936 hours and 12
had been run 3533 hours. No new leaks were encountered
before the final shutdown. Inspection of the modules
revealed only a moderate amount of fouling present in the
tubes and turnarounds. Inspection of the one module which
did fail revealed that leaking had been caused by an
irregularity in the support tube. Apparently the support
tube had been damaged when the bad tube was replaced.
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Operation of the American Standard pilot plant began on
November 6, 1970. After 59 hours of operation, one of the
84 total modules developed a high pressure leak. The
bonding which held the membrane support tube in the
module head yielded, allowing the tube to back out of the
head. A second failure of this type was experienced after
78 hours. American Standard stated that the bonding problem
was suspected at time of shipment, and more failures were
to be expected. Within a short period of time, three
more bonding failures occurred. At 148 hours a sixth
module failure took place, this one a low pressure leak
caused by a loose head nut. The nut was tightened, and
the module performed satisfactorily. As of November 30
the unit had experienced seven major module failures in
a total of 450 hours of operation. Although no visual
inspection of modules was made, the large flux degeneration
experienced and the distinct H2S odor present in the
modules indicated that the unit was heavily fouled.
The unit was restarted for "frozen design" running on
December 2. Another bonding failure occurred at 219 hours
into this run (669 total hours), the seventh failure of
this type since the unit was originally started. The
unit was shut down on March 3. It had run a total of 1447
hours during the "frozen design" period and had experienced
three major module failures at the tube to module head
bond during the frozen design period. No visual inspection
was performed.
The Gulf Environmental Systems pilot plant was placed on
line August 26. Immediately the spiral-wound unit began
to experience fouling problems. After one day of operation,
fouling had become so extensive that the unit was shut
down. Inspection of the modules showed that the suspended
materials in the white water had become entrapped in the
module's process stream spacer causing excessive pressure
drop across the modules and blinding the membrane surface.
The unit remained down while Gulf investigated means to
alleviate the problem. After pursuing several alternatives,
Gulf decided to employ a new spacer design in their test
modules.
Modules incorporating this new design were installed in
the pilot plant on October 6, and operations were resumed.
The unit was shut down three days later and the modules
inspected. Fouling was significantly less than that found
in the first set of modules. Two of the five modules
were replaced with new modules, and the two removed were
shipped to San Diego for further inspection.
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The unit was restarted and ran without incident until
November 2, when it was shut down for inspection. During
this time, it had become necessary to flush the unit
with tap water periodically and to clean with an enzyme
solution occasionally to deter excessive fouling. When
the modules were inspected, they were found to contain a
great deal of internal fouling. The annular space between
modules and support pipe was filled with slime. Also, the
adhesive backing tape, used to maintain module configuration,
had deteriorated somewhat. In a test just prior to shut-
down, the unit had been exposed to a cationic polymer which
seemed to do more harm than good and probably contributed
greatly to the fouled state of the modules. The modules
were rinsed manually and placed back in the unit.
Operation was resumed and continued until November 5 when
the unit was shut down for refitting. These modules were
exposed to a total of 532 hours on white water.
New modules of the same configuration were placed in the
unit, and it was restarted on November 6. Immediate
discoloration of the permeate on restart indicated that
either a defective module had been installed or an o-ring
seal between modules had been broken on reassembly. The
situation remedied itself, so operation was not interrupted.
The problem was attributed to a seal which had slipped out
of place and then reseated itself. The unit operated
without difficulty for 391 hours and was shut down on
November 25. Throughout the last part of this run, a
distinct H2S odor had been present in the permeate
indicating sliming in the unit. Inspection of the modules
proved this to be the case.
A completely new pilot plant was received from Gulf for
the "frozen design" period. This unit was equipped with
modules which incorporated the new spacer design concept,
but with a dimensional change. Several different types
of backing tapes were also used in an effort to find one
which would not loosen after extensive running. Three of
the 18 modules were externally wrapped so as to provide
flow around the modules to eliminate accumulations in
the dead annular space. An automatic backflush was
included as standard operating procedure.
The unit was started up on November 30. After 78 hours
the modules were inspected, and both interior and annular
fouling were found to be minimal. As operations continued,
it became necessary to clean the unit with an enzyme
solution approximately every 150 hours. After 1042 hours
of trouble-free operating, the unit was shut down for
another inspection; fouling was present but was not
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extensive. Three modules were replaced at this time,
and the modules removed were sent to San Diego for testing.
When the unit reached 1132 hours of operation, it began
to intermittently discharge discolored permeate. After
1259 total hours had elapsed, it was shut down so that
the problem could be investigated. The investigation
revealed a broken o-ring seal between two modules. Gulf
stated that this problem is often encountered when modules
are_changed, but it may take time to expose itself. The
o-ring was replaced, and operation was resumed. Sixteen
hours later the same tube began to discharge discolored
permeate; the leak was traced to another bad o-ring.
The unit was restarted and run to a total of 1425 hours
before it was shut down due to excessive fouling. In-
spection of the modules showed great amounts of fouling at
the module faces and in the tube turnarounds.
The unit was completely refitted with new modules. Three
of the new modules were installed such that the velocity
through them would be double that of the others. After
several false starts (two o-rings failed and one defective
module was replaced), the unit was run for 585 hours without
incident and was shut down on March 17. Later inspection
of the modules by the vendor showed that the high velocity
modules exhibited greatly reduced fouling characteristics.
The Havens pilot unit was placed in operation for the
pretrial period on September 11. It ran without failure
until November 12, logging 1071 hours. Inlet pressure
was maintained at 600 psi. Fouling did not appear to be
a problem.
Testing in the "frozen design" period was initiated on
December 4. Inlet pressure was 800 psi. The first module
problem was encountered after 1133 total hours of operation
on these tubes. The low volume leak was attributed to a
bad tube adapter seal. Another seal leak occurred at
1333 hours, and a third such failure took place at 1650
hours. After 2014 total hours, a fourth module failed;
the failure was a high volume leak but was not a tube
rupture. This module was replaced with a module which
had failed after 7 hours of operation. Prior to shutdown
on February 10, two more modules experienced major seal
leaks and others appeared to be leaking. These modules
had been in operation 2100 total hours at shutdown.
Havens attributed the problem to swelling of the tube
adapters and decided to rebuild all the modules with
adapters of the same design but of a new material. As
agreed prior to the start of the tests, three months running
time would be required to qualify the material. The old
79
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heads and tubes were to be reused as possible. As the
rebuild progressed, it was found that many of the heads
were also swollen, so all of them were replaced with new
ones. The membranes were in excellent condition.
Operation was resumed on February 27. One hundred hours
after restarting, one of the modules developed a high
pressure leak. Twenty-six hours later, another such
failure occurred. Several more failures were encountered
before the unit was shut down. It had logged 565 hours
after rebuild and 2664 total hours of operation had been
completed on these tubes. Inspection of the later failures
by Havens showed that the adapter swelling prior to the
rebuild had apparently caused a dimensional problem.
New modules and a new, smaller pilot plant were received
so that the qualification time for the new material could
be reached; but numerous module failures have prevented
completion of the qualification.
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SECTION XII
EQUIPMENT DISCUSSION - MECHANICAL PERFORMANCE
The pilot phase of the project demonstrated that reverse
osmosis equipment is capable of processing waste water from
NSbC pulping with reasonable efficiency. Membrane integrity
proved to be acceptable; none of the failures experienced
during the test period were attributed to membrane
degradation. Analyses of membranes which had been pro-
cessing white water for nearly 4000 hours (the longest
membrane exposure time experienced during the project)
showed that although some permanent flux deterioration had
occurred, the rejection characteristics were virtually
unchanged from those displayed initially. The majority of
proprietary equipment problems occurred because of failures
in the sealing mechanisms between membrane support struc-
tures and module heads. Most of these failures could have
been eliminated had greater care been taken in module
assembly, both at initial construction and during field
maintenance. The results of the project indicate that
continuous operation can be expected from reverse osmosis
equipment if properly assembled and maintained.
During earlier pilot plant investigations, a great variation
in membrane performance was experienced from module to
module. Vendor production control of membrane performance
was found to be greatly improved during this program.
Individual modules were reasonably uniform in their
membrane characteristics.
Based on the very low failure rate experienced during the
"frozen design" period, all Aqua-Chem proprietary equipment
has been found acceptable under the standards established
by the project. The equipment was tested for 1927 hours
during this period, with the only difficulty experienced
being a slight seal leakage caused by improper torqueing
on module heads. That problem was easily resolved.
Maintenance of proprietary equipment and identification
of module failures is not difficult with this design.
Individual permeate discharges on each module allow one to
pinpoint failures easily, and tubes may be replaced without
removing the entire module from the system. However, it
is difficult to isolate a bad tube within a module? and
individual modules or clusters of modules cannot be
isolated from the total system. During these pilot tests,
it was necessary to shut down all 24 modules in order to
inspect one particular module. The module stacking
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arrangement also makes it difficult to remove a module
from the system if that module happens to be located at
the bottom of the stack.
All American Standard proprietary equipment, with the
exception of the tube to module head bonding seal, has been
found mechanically acceptable. It is felt that because of
the eight seal failures encountered in 1897 total hours of
running time, further testing would be mandatory to
establish reliability.
Identification and isolation of module failures are
accomplished easily with this design. Valves were provided
so that banks of six modules could be taken off line while
the unit remained operative. Accessibility to modules
located in the middle of the cluster was somewhat difficult,
and enough room must be left above the unit so that the
vertically mounted modules may be removed.
All Gulf equipment met the qualification standards of the
project. However, some type of periodic flushing is
necessary to keep the modules free of excessive fouling.
It also appeared that enzyme cleaning was necessary at
150 hour intervals in order to maintain reasonable flux
rates. The only maintenance difficulty seen was the
amount of care that was necessary to protect the o-ring
seals. Module replacement can be performed rather easily,
and identification of defective modules presents no problem.
It appeared that the module binding tape was undependable
after extended running time. Further demonstration of
improved binding tape performance would be desirable.
All Havens equipment, with the exception of the end seal
adapters, has proven acceptable. The adapter change did
not involve the design. However, it is considered desirable
to test the reliability of the new material, and such tests
are underway. Identification of module failures is a
problem, but isolation and removal of defective modules
can be performed relatively easily. In several instances,
difficulty was encountered in forming the 4-module clusters
which comprised the unit. Improperly sized "peg holes"
and variations in module length made it difficult to obtain
a proper seal between modules.
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SECTION XIII
ACKNOWLEDGMENTS
This project is being performed under the direction of
Messrs. Ralph H. Scott, G. R. Webster, and W. J. Lacy
of the Environmental Protection Agency. Project Director
for Green Bay Packaging is Mr. W. R. Nelson; Project
Manager is Mr. G. 0. Walraven; and Project Engineer is
Mr. D. C. Morris. Other Green Bay Packaging personnel
participating extensively in the project are Messrs.
S. L. Brown and M. J. Pollock, Project Engineers;
Mr. T. J. Fenske, Laboratory Technician; and Miss K. R.
Jackson, Secretary.
The close cooperation and assistance of the vendors is
acknowledged. Key personnel were Mr. A. C. F. Ammerlaan,
Abcor; Mr. D. B. Guy, Aqua-Chem; Mr. J. H. Sleigh, Gulf;
and Mr. K. E. Anderson, Calgon-Havens.
The long-standing support of the staff of the Institute
of Paper Chemistry is gratefully acknowledged.
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SECTION XIV
APPENDICES
Page No.
A. Analytical and Test Procedures Used in
Pilot Phase ........... 86
Bi Visitors Observing Pilot Units in Operation
Since Initiation of Project 12040 FU6 .... 88
85
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APPENDIX A
ANALYTICAL AND TEST PROCEDURES USED IN PILOT PHASE
The analytical samples were collected when the operating
conditions of the units were stable. This required that
the samples be taken at the middle of each pause-operate-
pause cycle, since the conditions close to the depresr.
surization (pause) period were not representative of the
majority of the operating period. Operating data, e.g.
pressures, were recorded at the time of taking samples.
When samples were collected at inconvenient hours, they
were refrigerated for storage and then returned to room
temperature before analysis.
Frequent measurements were made of the total solids in the
feed and concentrate. The sample is weighed in an oven-
dried tared beaker, dried overnight at 105°C, cooled in a
desiccator, and reweighed.
Soluble solids and suspended solids were determined by a
method developed at Green Bay Packaging. A sample is
filtered through a glass fiber pad (Reeve Angel 934 AH,
11 cm), and the filtrate is collected. The pad is oven-
dried, cooled in a desiccator, and reweighed for suspended
solids. The filtrate is weighed in an oven-dried tared
beaker, dried overnight at 105°C, cooled in a desiccator,
and reweighed for soluble solids. Samples of product water
from the reverse osmosis units required no filtering.
Sodium content was determined with a Model 303 Perkin-
Elmer atomic absorption spectrophotometer. The sample
is prepared to the proper working range using distilled
water for dilution. The spectrophotometer is operated
according to Perkin-Elmer's Analytical Methods Manual.
Analysis for five-day biochemical oxygen demand (6005)
was performed according to the procedures, chemical
requirements, and apparatus described in Standard Methods
for the Examination of Water and Waste Water (APHA-AWWA-
WPCF)using the Azide Modification of lodometric (Winkler)
Method. The sample is prepared per this reference with
the exception of measuring the initial dissolved oxygen.
In lieu of this measurement, a dilution water blank
containing all the nutrients, seed, and dissolved oxygen
is incubated with each set of samples to eliminate any
dilution water variables. Volumetric flasks and pipettes
are utilized for measurement and dilution. A sample two
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cubic centimeters or larger is pipetted directly into
the BOD bottle.
Color was performed using two methods by the Institute of
Paper Chemistry. 'The first measurement-was a visual
observation of the color utilizing a Hellige optical
comparator. This technique is not precise and was done .
for reference purposes only.- The second measurement was
of the optical density, utilizing a Beckman DU spectro-
photometer operated at the nominal wavelength range for
lignins (281 millimicrons).
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APPENDIX B
VISITORS OBSERVING PILOT UNITS IN OPERATION
SINCE INITIATION OF PROJECT 12040 FUB
Number Organization or Affiliation
U. S. Industrial Companies
4 American Can Company
1 Anheuser-Busch, Inc.
3 Charmin Paper Products Division,
Proctor & Gamble
2 Combined Paper Mills, Inc.
1 Corning Glass
1 Dart Industries, Inc.
2 C. H. Dexter Paper Company
6 Dorr-Oliver, Inc.
2 Eastman Chemical
5 Esso Research & Engineering Company
1 The Foxboro Company
1 Groveton Papers Company
2 Industrial Nucleonics
3 Kraftco Corporation
1 Menasha Corporation
1 Nalco Chemical Company
5 Northwest Paper Company
2 Paterson Parchment Paper Company
2 Petrolite Corporation
1 Private Consultant
2 D. E. Riley Corporation
2 St. Regis Paper Company
4 Scott Paper Company
1 Sterling Pulp & Paper Company
1 Union Carbide
3 Waldorf-Hoerner
Foreign Concerns
3 Abitibi Paper Company Ltd. (Canada)
1 E. L. Bateman, Ltd. (South Africa)
15 Canadian Pulp and Paper Association,
Technical Subcommittee
2 Central Association of Finnish Wood
Using Industries
5 Daishowa Paper Company (Japan)
1 Finnish Pulp & Paper Research Institute
88
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2
2
2
2
1
1
1
1
1
1
1
1
AB Iggesunds Bruk (Sweden)
C. Itoh & Company (America), Inc. (Japan)
Japan Organo Company, Ltd.
Kurita Water Industrial Company (Japan)
MacMillan Bloedel (Canada)
Settsu Paper Board Manufacturing Co. (Japan)
South African Pulp & Paper Industries, Ltd.
Sumitomo Paper Company (Japan)
Swedish Forest Products Research Laboratory
Twente University of Technology (Holland)
Union Corporation (South Africa)
Valmet Oy (Finland)
5
1
2
1
2
3
Government
Green Bay Metropolitan Sewerage District
Local Elected Official
State Elected Officials
Federal Elected Official
Wisconsin Department of Justice
Wisconsin Department of Natural Resources
13
1
10 (Approx.)
15 (Approx.)
15
15 (Approx.)
Education
Institute of Paper Chemistry
Staff, Wisconsin State University-
Stevens Point
Staff* University of Wisconsin-Green Bay
Miscellaneous Students, University of
Wisconsin-Green Bay
Advanced Chemistry Students, University
of Wisconsin-Green Bay
Junior & Senior High School Students
4
1
15 (Approx.)
Environmental Groups
Citizens' Natural Resource Association
National Council On Stream & Air
Improvement
Northeast Wisconsin Chapter, Trout
Unlimited
14 (Approx.)
Miscellaneous
American Institute of Plant Engineers
89
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1 American Paper Institute
5 News Media (Press & TV)
18 Wisconsin Association of Food &
Sanitation Officials
OU.S. GOVERNMENT PRINTING OFFICE: 197Z 484-485/.2Z7 1-3
90
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Accession Number
w
Organization
Subject Field St Group
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Green Bay Packaging Inc., Green Bay, Wisconsin
Mill Division
Title
RECYCLE OF PAPERMILL WASTE WATERS AND APPLICATION OF REVERSE OSMOSIS
10
22
Author(s)
Morris, David C.
Nelson, William R.
Walraven, Gerald O.
Citation
16
Project Designation
EPA, OR&M Program No. 12040 FUB
21
Note
23
Descriptors (Starred First) ~~ "
*Reverse Osmosis, *Membrane Process, *Pulp Waste, Waste Treatment
Waste Control
25
Identifiers (Starred First)
*Waste Recycle, Organic Removal, Color Removal, Membranes
Tertiary Treatment
27
Abstract
A program is in progress involving the closure of a pulp and paperboard
mill and includes the recycle and re-use of weak waste waters. These
waste waters, containing dissolved organics, occur as a consequence of
normal production methods in such a mill. A method of recycling weak
waste waters has been developed and incorporated that results in the
reduction and partial concentration of the waste stream. Reverse
osmosis is being investigated for use as a unit operation in which
clarified water is separated from the remaining wastes for process
re-use, and the organics are concentrated for processing by more
conventional techniques.
To ensure that the production reverse osmosis facility would reflect
the latest technology, the project required a pilot phase in which
reverse osmosis vendors would operate proprietary equipment simul-
taneously and continuously on the same feed. This preliminary phase
allowed the development of operating techniques applicable to this
particular feed. Criteria were determined for the design of a full-
scale production facility. The proprietary equipment designs of the
participating vendors were assessed. (Morris - Green Bay Packaging)
Abstractor
David C.
Morris
Institution ,
fireen Bay Packaging Inc.
WR:I02 (REV. JULY 1969)
WRSf C
SEND, WITH COP
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
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