United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati OH 45268
EPA/54Q/R-96/507a
April 1998
r/EPA
Site Technology Capsule
Rochem Separation
Systems, Inc., Disc Tube™
Module Technology
Abstract
The Rochem Separation Systems, Inc. (Rochem) Disc
Tube™ Module (DIM) technology is an innovative mem-
brane separation process. It is designed to treat liquid
waste that is higher in dissolved solids content, turbidity,
and contaminant levels than waste treated by conven-
tional membrane separation processes. According to the
technology developer, Rochem, the innovative DTM de-
sign reduces the potential for membrane fouling and
scaling, which allows it to be the primary treatment for
liquid wastes such as landfill leachate.
The DTM technology was evaluated by Science Appli-
cations International Corporation (SAIC) under the
Superfund Innovative Technology Evaluation (SITE) Pro-
gram at the Central Landfill Superfund Site in Johnston,
Rhode Island. The DTM technology treated leachate
contaminated with chlorobenzene and 1,2-dichloroben-
zene at average concentrations of 21 and 16 milligrams
per liter (mg/L), respectively, and lower levels of 1,4-
dichlorobenzene at 0.7 mg/L; toluene at 1.8 mg/L; xy-
lenes at 1.3 mg/L; and ethylbenzene 0.79 mg/L. Total
organic carbon (TOG) was present in the leachate at an
average concentration of 460 mg/L, and total dissolved
solids (TDS) were present at an average concentration
of 4,900 mg/L. Metals were also present at average
concentrations such as 1.4 mg/L for barium, 130 mg/L
for calcium, 48 mg/L for iron, and 21 mg/L for manga-
nese. The purpose of this SITE Demonstration was to
assess the DTM technology's effectiveness in removing
organic and inorganic contaminants from the landfill
leachate and in resisting scaling and fouling of the mem-
branes.
Overall, the DTM technology was very effective in
removing contaminants from the landfill leachate. Mean
contaminant rejections were greater than 96.7% for TOG
and 99.4% for TDS, both exceeding the developer's
claims of 92% for TOG and 99% for TDS. The overall
mean rejection for total metals was greater than 99.2%,
exceeding the developer's claim of 99%. The overall
mean rejection for target VOCs was greater than 92.3%
which exceeded the developer's claim of 90% for VOCs.
In addition, the DTM process achieved a treated water
recovery rate of approximately 75%. The developer's
claim was 75%. DTM operational parameters, such as
permeate (treated water) flow rate and module pressure
drop, and system permeate quality, indicate that there
was a decrease in technology performance over the
course of the Demonstration.
The Rochem DTM technology was evaluated based
on seven criteria used for decision-making in the
Superfund Feasibility Study (FS) process. Results of the
evaluation are summarized in Table 1.
Introduction
This report provides information on the Rochem DTM
technology, an innovative membrane separation process
for removal of contaminants from liquid hazardous waste
streams. The Rochem DTM technology was evaluated
under the U.S. Environmental Protection Agency's (EPA)
SITE Program during August and September 1994 at the
Central Landfill Superfund Site in Johnston, Rhode Is-
land. Contamination in an area of the Central Landfill
designated as the "hot spot" resulted from the disposal
of chemical wastes in the mid-1970s. Leachate from this
INNOVATIVE
TECHNOLOGY EVALUATION
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Table 1.
Criteria Evaluation for the Rochem Disc Tube™ Module Technology
Overall
Protection of
Human Health &
the Environment
Provides both
short- and long-
term protection
by reducing
exposure to
organic and
inorganic
contaminants in
landfill leachate
(or liquid waste).
Prevents harmful
effects of liquid
waste migration
to public water
supplies.
Reduces the
volume of
contaminated
material.
Concentrated
contaminants can
be incinerated or
treated by other
methods.
Technology is
able to treat a
variety of
contaminants.
Compliance with
Federal ARARs
Requires compliance
with RCRA treatment,
storage, and land
disposal regulations
(for a hazardous
waste).
On-site treatment may
require compliance
with location-specific
ARARs.
Permeate discharge to
POTW or surface
bodies requires
compliance with the
Clean Water Act
regulations. Without
additional treatment,
the final permeate
produced during the
Demonstration met
discharge permit
requirements for
heavy metals. The
discharge requirement
for total toxic organics
(TTO) was met after
activated carbon
polishing. Limits for
biochemical oxygen
demand, chemical
oxygen demand, and
total suspended solids
were not applicable to
Central Landfill' s
Industrial Waste
Discharge Permit.
If volatile compounds
are present in the
liquid waste, emission
controls may be
needed to ensure
compliance with air
quality standards,
depending on local
ARARs.
Requires compliance
with OSHA regulations
to protect the health
and safety of workers
at hazardous waste
sites.
Long-Term
Effectiveness
Permanently
reduces the
volume of
contaminated
leachate or other
liquid waste.
Involves a
demonstrated
technique for
removal of
organic and
inorganic
contaminants.
Permeate may
require treatment
prior to disposal,
depending on
site-specific
discharge
limitations.
Removed
(concentrated)
contaminants
may require
treatment by
other methods
such as
incineration or
solidification/
stabilization prior
to disposal.
Recirculation by
surface
application to the
landfill may be
appropriate for
municipal landfill
leachate.
Membrane
cleaning is
required to
maintain system
performance and
to extend
membrane life.
Membranes are
cleaned at the
discretion of the
operator, typically
based on a
change in
module pressure,
flow rate, or
temperature
readings.
Short-Term
Effectiveness
Depending on
the application,
additional
modules may be
added to the
DTM™ system to
reduce
remediation time.
Treatment may
cause noise and
minor air
emissions,
posing short-term
risks to workers
and possibly to
the nearby
community.
Process noise
levels are not
high. Air
emissions can be
mitigated.
Some personal
protective
equipment (PPE)
may be required
for workers
during system
operation.
Reduction of
Toxicity, Mobility,
or Volume
through
Treatment
Significantly
reduces toxicity
of treated water
and volume of
contaminated
water through
treatment.
Permeate water
quality is
dependent on
waste
characteristics.
During the
Demonstration,
contaminant
levels were
reduced 90% or
greater on
average (99.4%
for TDS, 99.2%
for target metals,
96.7% for TOC,
and 92.3% for
VOCs).
Waste volume
reduction is
dependent on
waste
characteristics
and the required
system water
recovery rate.
Waste volume
reduction for the
Demonstration
was
approximately
75%.
Implementability
Utility requirements
are minimal and
include water and
electricity.
Equipment is skid-
mounted or
containerized and
easily transportable
by a tractor trailer.
Support equipment
includes a heavy
duty forklift or crane
for loading/
unloading and
arranging the units,
and tanks for
process stream
storage.
Treatability testing
with the selected
waste is
recommended prior
to field installation.
If the necessary
facilities and
utilities are
available, the
system can be set
up and operational
in three to five
days. Initial testing
(shakedown) of the
equipment prior to
going on-line
normally takes two
to five days. After
treatment, the
entire system can
be demobilized
within two to three
days.
The concentrations
and types of
scaling ions can
limit the treated
water recovery rate
or cause
membrane fouling
and scaling,
thereby limiting the
use of the DTM
technology.
Cost
The estimated costs
for treating leachate
at 3 and 21 gpm at
a fixed facility and
with a treated water
recovery rate of
75% are $0.1 61
permeate-gal and
$0.06/permeate-gal,
respectively. These
costs do not include
a waste disposal
fee for the
concentrate since
this cost is site- and
concentrate-
specific. Costs are
based on data
gathered from the
Demonstration and
on treating a
leachate with
characteristics
similar to the
Central Landfill
leachate. Estimated
costs are highly
leachate-specific.
Treatment costs are
higher for liquid
wastes that have a
high potential for
membrane scaling
and thus require
increased use of
chemical cleaners
and pH adjustment
chemicals.
Operating the
technology at a
higher on-line factor
and treated water
recovery rate (both
dependent on
system design and
leachate
characteristics) will
result in a lower
overall cost.
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hot spot was pumped from an existing well for treatment
by a Rochem Model 9122 DIM system operating at a
feed flow rate of about 4 gallons per minute. Approxi-
mately 33,000 gallons of leachate were treated during
the Demonstration at the Central Landfill. The leachate
contained VOCs, metals, and high dissolved solids.
Information in this Capsule details the specific site
characteristics and results of the SITE technology Dem-
onstration at the Central Landfill. This Capsule presents
the following information:
Technology Description
Technology Applicability
Technology Limitations
Process Residuals
Site Requirements
Performance Data
Economic Analysis
Technology Status
SITE Program Description
Sources of Further Information
Technology Description
The DTM technology can utilize reverse osmosis (RO),
ultrafiltration (UF), or microfiltration (MF) membrane ma-
terials, depending on the application. The membranes
are generally more permeable to water than to contami-
nants or impurities. RO membranes are most commonly
used with this technology. They can reject dissolved and
suspended solids, dissolved salts and ions, and many
low and most high molecular weight organic compounds
(1). In RO, water in the feed is forced through a mem-
brane by applied pressure which exceeds the osmotic
pressure of the feed. This water, called permeate, has a
lower concentration of contaminants. The impurities are
selectively rejected by the membranes and are thus
concentrated in the concentrate left behind. The percent-
age of water that passes through the membranes is a
function of operating pressure, membrane type, and con-
centration and chemical characteristics of the contami-
nants. The DTM technology utilized thin-film composite
(TFC) RO membranes during the Demonstration at the
Central Landfill.
The patented membrane module features larger feed
flow channels and a higher feed flow velocity than con-
ventional membrane separation systems. According to
the technology developer, these characteristics allow the
DTM greater tolerance for dissolved solids and turbidity,
and a greater resistance to membrane fouling and scal-
ing. Suspended particulat.es are readily flushed away
from the membrane during operation. The high flow
velocity, short feed water path across each membrane,
and the circuitous flow path create turbulent mixing to
reduce boundary layer effects and minimize membrane
fouling and scaling. In addition, the developer claims that
the design of the DTM allows easy cleaning and mainte-
nance of the membranes—the open channels facilitate
rinsing and cleansing of particulate matter, and mem-
branes can be removed as needed from modules for
replacement.
Figure 1 details a cutaway diagram of the Disc Tube™
Module. Membrane material for the DTM is formed into a
cushion surrounding a porous spacer material. The mem-
Feed water
Permeate Concentrate
(product) (reject)
Pressure vessel
End flange Tension rod
Membrane Hydraulic
/ cushion djsc
Figure 1. Cutaway diagram of the Disc Tube™ module.
brane cushions are alternately stacked with hydraulic
discs on a tension rod. The hydraulic discs support the
membranes and provide the flow channels for the feed
liquid to pass over the membranes. After passing through
the membrane material, permeate flows through collec-
tion channels out of the module to a product recovery
tank. A stack of cushions and discs is housed in a
pressure vessel. Flanges seal the ends of the module in
the pressure vessel and provide the feed water input and
the product (permeate) and reject (concentrate) output
connections. The number of discs per module, number
of modules, and the membrane materials can be cus-
tom-designed to suit the application.
Modules are typically combined in a treatment unit.
The DTM system design includes built-in multimedia and
cartridge filters to remove suspended particulates from
the input feed and to protect pumps and membranes
from physical damage. The multimedia filters are cleaned
by backwashing; cartridge filters are manually replaced
as needed. To monitor the operation of the modules, the
system is equipped with pressure and flow meters.
A three-stage DTM process was used to treat the
leachate at the Central Landfill site. Each stage was a
separate DTM unit interconnected with piping and tank-
age. Two DTM stages were used in series to produce
the final permeate. The third DTM stage was a high-
pressure unit (HPU) which further treated the concen-
trate from the first-stage to increase system water
recovery. A schematic of the multistage DTM process
utilized during the Demonstration is presented in Figure
2. The system operated up to eight hours a day for 19
days at a feed flow rate of 3 to 4.5 gallons per minute
(gpm).
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Acid
feed
First stage
DIM unit
Leachate
tank
Feed tank
Media
filter
Hi-pres. Booster
pump pump
A 6^
ft
Second
stage
DIM unit
'-fi*
Cartridge
filter
Acid
feed
tfl
First
stage
permeate
tank
First
stage
cone.
tank
Feed stream
Concentrate stream
Permeate stream
Hi-pres.
DIM unit
I
Second
stage
(final)
permeate
tank
To municipal
sewer
Figure 2. Schematic of the DIM process.
Two 5,000-gallon tanks stored leachate that was
pumped continuously from well MW91ML7. This leachate
was then pumped to a 100-gallon feed tank for the first-
stage unit. After filtration, contaminated leachate was
pumped into the first-stage unit at pressures which ranged
from 600 to 1,000 pounds per square inch gauge (psig).
The first-stage unit had eight modules which utilized
standard TFC membranes. The permeate produced from
this unit was directed to a holding tank designated for
first-stage permeate, and was then fed at 700 to 1,000
psig to the second-stage unit for further treatment.
The second-stage unit, which had 2 modules that
utilized standard TFC membranes, was not brought on-
line until enough first-stage permeate accumulated in its
feed holding tank. The second-stage permeate was the
system's final permeate, while the second-stage concen-
trate was recycled into the first-stage feed line. Rochem
had originally planned to use a different DTM system for
the Demonstration in which the first-stage unit and the
second-stage unit were combined in a single prefabri-
cated container and the HPU housed in a separate
container. With this type of system, the second-stage
unit is not operated in a semi-batch mode, but is continu-
ously fed permeate from the first-stage unit.
The concentrate from the first-stage unit was routed to
a 300-gallon holding tank. This concentrate was fed into
the HPU at 1 to 3.5 gpm and 900 to 1,800 psig. Use of
the HPU was initiated later than the first two stages after
accumulation of first-stage concentrate; the HPU oper-
ated in a batch mode. The HPU had two stainless steel
modules which utilized TFC membranes specially modi-
fied for high pressure. The purpose of the HPU was to
reduce the volume of the first-stage concentrate, thereby
reducing the final waste volume and increasing the sys-
tem water recovery rate. High pressure was needed to
overcome the osmotic pressure of the first-stage con-
centrate. HPU permeate was recycled into the first-stage
permeate tank (feed for the second-stage). The HPU
produced the system's final concentrate. Initially, the
HPU was operated in a recycle mode to allow the HPU
concentrate to reach an optimal concentration and fur-
ther increase the system's water recovery rate. This
mode of operation was discontinued after the first two
days of the test. It was determined by Rochem that the
desired system water recovery rate could be achieved
without the concentrate recycle mode; recycling the con-
centrate increased the chance of HPU membrane fouling
and scaling.
Permeate was used to rinse and clean the DTMs.
Rinsing was performed on the HPU and second-stage
unit in between batch treatment cycles each day to
displace any leachate from membrane surfaces. In addi-
tion, all stages were rinsed at the end of the day to flush
the system prior to shutdown overnight. Cleaning was
accomplished by adding cleaning agents—either alkaline
for fouling, acidic for membrane scale, or detergent for
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both—to the rinse tank for each unit. The cleaning solu-
tion was then cycled through the unit. Membranes were
cleaned at the discretion of the Rochem system operator
based on an increase in module pressure readings or
changes in operating temperature or flow rate.
Hydrochloric (HCI) acid was added to the first-stage
feed and the HPU feed at dosing rates of 1.6 to 2.8 liters
per hour (L/hr) and 0.53 to 1.6 L/hr, respectively. The
addition of HCI, which facilitated pH adjustment, was not
started until the third day of leachate treatment. Rochem's
target system feed pH for the Demonstration was be-
tween 5 to 6.
As a precautionary measure, the final permeate was
run through activated carbon canisters to ensure compli-
ance with discharge requirements. After treatment by
activated carbon, it was stored and batch discharged to
the sanitary sewer.
Technology Applicability
Rochem claims that the DTM technology can treat
liquid waste streams containing volatile and semivolatile
organics, metals and other inorganic ions or compounds,
and radioactive wastes. The DTM technology has been
used to treat landfill leachate, water soluble oil coolants,
oil/water mixtures, and solvent/water mixtures (2). The
DTM technology was used in the United States to treat
lagoon water contaminated by petrochemical wastes
(volatile organics, phenols, heavy metals, and polychlori-
nated biphenyls). In addition, the technology is treating
municipal landfill leachate in the U.S. and municipal and
hazardous landfill leachate in Europe. (See "Technology
Status" for further details).
The DTM technology is capable of treating liquid waste
with wider ranges and higher levels of contaminants than
conventional membrane separation technologies using
RO membranes. A high-pressure unit can be used to
increase the treated water recovery rate for liquid wastes
that have a higher level of TDS or scaling ions. Results
from the Demonstration show that the DTM technology
achieved excellent removals of metals, TDS, and TOG.
VOC removals were also very good (approximately 90%
or greater). The VOC removals are notable because
membrane separation technologies typically do not ef-
fectively separate lower molecular weight organic com-
pounds, particularly VOCs; these compounds tend to
pass through the membranes (3).
The suitability of the DTM process is dependent on the
characteristics of the feed liquid. Rochem claims that for
many liquid wastes, the DTM system's hydraulic design
allows it to operate with minimal or no pretreatment.
However, chemical or physical pretreatment may be
needed to reduce the potential for membrane scaling or
fouling for liquid wastes such as the Demonstration
leachate. This may add to the cost of using the technol-
ogy. Pretreatment may include equalization, aeration to
remove carbon dioxide generated from acid addition (for
pH adjustment), and other processes (4). The user of the
technology will be responsible for arranging for treatment
and disposal of the final concentrate and disposal of the
final permeate.
The Rochem DTM technology is transportable on trac-
tor trailers and can be installed by Rochem personnel
within three to five days, if power and auxiliary tankage
and piping are available. Multiple DTM systems can be
used to increase treatment capacity.
Technology Limitations
The composition of the feed waste may limit the appli-
cability of the DTM technology. In RO, inorganic salt
percent rejections are usually high (ninety to ninety-nine
percent). Some constituents (barium, calcium, fluoride,
iron, silica, strontium, sulfate, etc.) may cause scaling on
membranes, depending on the water recovery rate. Higher
water recovery rates increase the potential for scaling
and fouling because of potential for precipitation of spar-
ingly soluble salts such as calcium carbonate (CaCO3)
and calcium sulfate (CaSO4). Deposits of metal oxides
(formed from metals such as iron or manganese), col-
loids, organic compounds, or oil and grease can also
contribute to scaling and fouling as will biological activity.
This, in turn, may limit membrane life and treatment
effectiveness (5).
The maximum treated water recovery rate is depen-
dent on the TDS concentration in the liquid waste. For
treatment of landfill leachate with high scaling potential,
the use of acid dosing for pH control is necessary to
achieve a high water recovery rate. A water recovery
rate of 75 to 80% is achievable for leachate similar in
composition to the Central Landfill leachate while still
maintaining acceptable membrane life and permeate wa-
ter quality. Higher recovery rates may be possible but
may require the use of additional equipment and sup-
plies. Any increased operating costs may be offset by
cost savings for treatment and disposal of a smaller
volume of concentrate.
Process Residuals
The DTM process separates contaminants from liquid
waste generating two process streams: permeate (treated
water) and concentrate (waste). If appropriate discharge
limitations are met and the proper permits are obtained,
the permeate can be discharged to the local publicly
owned treatment works (POTW), into surface waters, or
reinjected through underground injection wells. When
discharge requirements are not met, polishing treatment
is required. Depending on its composition and classifica-
tion, the concentrate may be a hazardous waste and
may require further treatment and disposal.
The approximate volume ratio of permeate to concen-
trate (including used cleaning solutions and unused
samples) produced during the Demonstration was 3:1.
Permeate generated was discharged to a municipal
sewer. Although not classified as a RCRA waste, the
concentrate required off-site treatment prior to land dis-
posal due to its elevated levels of hazardous constitu-
ents. Concentrating the liquid waste volume reduced
transportation and treatment costs. Options for concen-
trate treatment or disposal include solidification/ stabili-
zation, evaporation, and recirculation into the landfill by
surface application in the case of municipal landfill
leachate (4).
During treatment of waste containing VOCs, there may
be minor releases of volatile contaminants to the atmo-
sphere from intermediate process holding tanks. Such
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losses were measured during the technology Demon-
stration at the Central Landfill. These losses did not
significantly influence system performance results, but
may require mitigation to reduce air emissions in some
cases. Emissions from auxiliary storage tanks may also
need to be controlled.
Site Requirements
Each DIM unit or stage is comprised of a control unit
and membrane modules. The control unit consists of
electronic controls, pumps, filters, pressure gauges, and
valves. During the Demonstration the control units and
corresponding modules were separate and mounted on
skids with a maximum weight of one ton each. The skid-
mounted units were transported by tractor trailer and
could be moved with a heavy-duty forklift. In most cases,
the units are built into cargo containers for easier trans-
portation and installation and to prevent leaks and spills
during operation. For loading and unloading, container-
ized units require a crane capable of lifting 15,000 pounds.
The containerized units may be placed on wheels for
indoor mobility. Additional equipment necessary for sys-
tem operation includes auxiliary tanks for process stream
storage and interconnecting piping.
Utilities requirements are limited to electricity and wa-
ter. The DTM system used for the Demonstration (Model
9122) required a three-phase, 440/480-volt, 60-hertz elec-
trical circuit to power the pumps and control equipment.
The 9122 DTM system requires a maximum power sup-
ply of 21 kilowatts (kW). A direct on-site hookup is
preferred, but if this is not available, a generator may be
used (4). The use of a generator is not cost effective for
long-term applications. DTM systems larger than the one
utilized for the Demonstration have higher power re-
quirements than Model 9122. For example, Model 9142
requires a maximum power supply of 50 kW. Additional
power is needed for on-site office trailers (if present),
any ancillary pumps, and outdoor lighting. Water is re-
quired to perform system leak-testing, and to shakedown
and calibrate the equipment. Water is also needed for
cleanup and decontamination.
Support facilities include shelter to protect equipment
and personnel from weather extremes and level equip-
ment staging areas. At locations with colder climates, an
indoor installation with heating would be preferred. Dur-
ing the Demonstration, the treatment units were arranged
under a tent. A more permanent shelter including office
space is desirable for long-term treatment projects. The
technology requires a flat site in order to control liquid
levels and provide optimum operation. A 500-square-foot
equipment staging area with additional storage space for
auxiliary system tanks was adequate for the three-stage
Demonstration system.
Storage of raw feed and final concentrate is required,
and storage of final permeate may be required. Storage
tank sizing and design are dependent on site-specific
applications. The user of the technology may be respon-
sible for providing storage tanks. In addition, an area
constructed to contain potential spills is required to hold
containers for process stream storage, chemicals, and
process wastes.
Performance Data
The DTM technology was evaluated on its effective-
ness in removing organic and inorganic contaminants
from leachate and the extent, if any, of membrane foul-
ing and scaling observed when treating landfill leachate
containing hazardous constituents.
Prior to the SITE Demonstration, bench-scale treat-
ability tests were conducted on hazardous leachate from
a landfill in the western U.S. This leachate was contami-
nated with many of the same constituents as the Central
Landfill leachate, including VOCs, heavy metals, and
high dissolved solids. The purpose of the treatability
tests was to determine how effectively the technology
could treat hazardous leachate. Data were also obtained
so Rochem could establish the type of DTM system to
be used, the order of system units, and the type of
membranes to be used for a demonstration at that site.
The treatability tests aided Rochem in developing claims
for the quality and quantity of water that the DTM system
could produce when treating hazardous landfill leachate.
Treatability testing was not conducted by Rochem on
the Central Landfill leachate. Shakedown testing with the
Central Landfill leachate was performed by Rochem for
about one day prior to the Demonstration.
Based on prior treatability testing and other Rochem
applications, the following critical objectives were devel-
oped for the Demonstration:
determine if the technology could meet the
developer's claims for contaminant rejections of
greater than 90% for VOCs, greater than 92% for
TOG, and greater than 99% for TDS and metals;
determine if the technology could achieve and
maintain a system treated water recovery rate of
75% or greater; and
evaluate the DTM technology's resistance to mem-
brane fouling and scaling.
Other noncritical objectives for this Demonstration were
to
develop capital and operating costs for the DTM
system;
determine whether the DTM system could meet
applicable or relevant regulatory criteria for dis-
charge of the permeate;
evaluate the ease of use, reliability, and mainte-
nance requirements of the DTM system;
calculate a material balance for the overall pro-
cess for water and target contaminants; and
estimate the potential fugitive emissions from the
system during use.
During the Demonstration, samples were collected from
sample taps on 11 process streams throughout the sys-
tem. The process streams considered critical in evaluat-
ing the technology were the raw feed, the final permeate,
and the final concentrate. Samples for off-site laboratory
analysis were collected at a frequency of once per day
(three times per day on two selected days). Samples for
field analyses were collected once or twice per day,
depending on the analysis. Off-site laboratory analyses
included TDS, total solids (TS), TOG, VOCs, total met-
als, ammonia, and anions. Field parameters that were
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measured included turbidity, pH, temperature, conductiv-
ity, silica, alkalinity, chemical oxygen demand (COD),
calcium, and hardness. Table 2 presents the average
concentrations of contaminants measured in the system
feed, permeate, and concentrate process streams during
the Demonstration.
Percent rejections of contaminants were calculated
from daily raw feed and final permeate concentrations.
Table 3 summarizes the calculated mean percent rejec-
tions achieved for the target contaminants considered
critical for this Demonstration. Mean contaminant rejec-
tions were greater than 96.7% for TOG and 99.4% for
TDS, both exceeding the developer's claim. All target
metals except potassium showed mean rejections greater
than the developer's claim of 99%. The overall mean
rejection for total metals was greater than 99.2%. The
mean rejection for potassium was greater than 98.7%
and the 95% confidence interval around this mean was
98.0 to 99.4%. The calculated mean percent rejections
of 1,2-dichlorobenzene; ethylbenzene; toluene; and xy-
lenes were greater than the developer's claim of 90% for
VOCs. The overall mean rejection for total VOCs was
greater than 92.3%. However, the calculated mean re-
jection for chlorobenzene was 86.8% with a confidence
Table 2. Average Concentration for the System Feed, Permeate and
Concentrate Streams
Average Concentration (Mg/L)
Table 3. Target Contaminants Average Percent Rejection
System
Contaminant Feed
Target VOCs
1,2-Dichlorobenzene 16
1,4-Dichlorobenzene 0.70
Chlorobenzene 21
Ethylbenzene 0.79
Toluene 1.8
Xylenes 1 .3
Target Metals
Barium 1.4
Calcium 130
Iron 48
Magnesium 250
Manganese 21
Potassium 150
Sodium 710
Strontium 0.89
Anions
Chloride 2,500
Fluoride <2.7
Nitrate <12
Sulfate 81
Other Parameters
Total Alkalinity (as CaCO3)1 ,600
Ammonia 650
Silica 15
Total Dissolved Solids 4,900
Total Solids 5,800
Total Organic Carbon 460
* = Permeate concentration is based
Final
Permeate
.76
<0.081
2.7
<0.031
0.083
<0.039
<0.014
<1.1
<0.38
<1.6
<0.14
<1.8
<5.7
<0.0068
<13.
<0.10
<0.40
<1.8
<1.0*
5.3
<0.63*
<32
<100
<15
on 6 sampling days.
Final
Concentrate
23
<0.80
36
1.1
3.4
<1.7
4.3
410
140
850
70
550
2,500
2.9
1 1 ,000
11
<26.
300
4,100
2,300
86
17,000
21 ,000
1,600
Developer's
Claims
Percent
Rejection
Contaminant (%)
Target VOCs
1 ,2-Dichlorobenzene
1,4-Dichlorobenzene
Chlorobenzene
Ethylbenzene
Toluene
Xylenes
Target Metals
Barium
Calcium
Iron
Magnesium
Manganese
Potassium
Sodium
Strontium
Total Dissolved Solids
Total Organic Carbon
>90
>90
>90
>90
>90
>90
>99
>99
>99
>99
>99
>99
>99
>99
>99
>92
Average
Percent
Rejection
Achieved*
(%)
94.9
>87.6
86.8
>95.6
93.8
>95.0
>99.0
>99.2
>99.2
>99.3
>99.4
>98.7
>99.2
>99.2
>99.4
>96.7
95%
Confidence
Interval
(%)
92.7-97.1
83.5-91 .7
83.1-90.5
94.1-97.1
90.5-97.1
92.3-97.7
98.3-99.7
98.5-99.9
98.6-99.8
98.6-99.9
98.7-100.0
98.0-99.4
98.5-99.9
98.5-99.9
98.9-99.9
95.6-97.8
Greater than symbol indicates that at least one measured value was
below the method detection limit.
interval of 83.1 to 90.5%; the calculated mean rejection
for 1,4-dichlorobenzene was 87.6% with a 95% confi-
dence interval of 83.5 to 91.7%. These rejections were
less than the specified criteria of 90%, but the 90%
rejection criteria fell within the 95% confidence intervals
for both compounds. These results indicate that the DTM
system was very effective in removing all classes of
contaminants in the Central Landfill leachate.
Vent emissions were measured during the Demonstra-
tion from an intermediate concentrate holding tank in the
system. VOC losses were calculated from these mea-
surements. Comparing these results on a mass basis to
the system VOC mass shows the vent losses to be no
more than 0.5% of the total mass of any given com-
pound. Therefore, these losses did not significantly af-
fect the calculated percent rejections of VOC
contaminants.
Flow rates, totalized flows, pressures, and electricity
usage were recorded on field log sheets at hourly inter-
vals during system operation. Totalized flows were used
in the calculation of system water recovery rates. Sys-
tem water recovery is defined as the volume of final
permeate divided by the volume of feed, times 100%.
Figure 3 illustrates the daily percent system water recov-
eries. Breaks in the data represent periods when the
system was off-line due to weather, maintenance, or
temporary mechanical problems. The average system
water recovery rate for the Demonstration was 73.3%
with a 95% confidence interval of 70.7% to 75.9%. The
developer's claim of 75% water recovery falls within this
confidence interval. The calculated daily water recovery
rates ranged from 66.4 to 84.4%. The system recovery
-------
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8/11 8/12 8/13 8/14 8/15 8/16 8/17 8/18 8/19 8/20 8/21 8/22 8/23 8/24 8/25 8/26 8/27 8/28 8/29 8/30 8/31 9/1 9/2
Date (1994)
Figure 3. Rochem DIM system daily percent water recovery.
rate was equal to or greater than the claim of 75% on
eight days of treatment. These daily recovery rates were
reduced by the use of first-stage and final permeate for
rinsing of the second-stage and the HPU modules be-
tween batch treatment cycles each day to displace re-
sidual leachate from the membrane surfaces. An
allowance was not made for permeate lost to these
rinses because they were part of normal operation for
the system used for the Demonstration. According to
Rochem, for other DIM system designs that are better
integrated and typically require less module rinsing than
the system demonstrated at the Central Landfill, achiev-
able recovery rates may be higher (75 to 80%) when
treating a similar liquid waste.
System operating data was evaluated to determine the
performance of membranes which received the bulk of
waste loading during the Demonstration. Figures 4 and 5
depict pressure and flow rate trends for the first-stage
and the high-pressure units. The flow rate data were
standardized for pressure, temperature, and waste con-
centration using ASTM Standard D4516-85, Standard
Practice for Standardizing RO Performance Data. The
standardized data are also presented on the graphs.
Breaks in the data represent periods when the system
was off-line due to weather, maintenance, or temporary
mechanical problems. Standardized flow rates were simi-
lar to the actual flow rates.
In general, the data presented in these figures show
an increase in operating pressures and a decrease in
flow rates over time, indicating a slight decrease in
performance for the units receiving the bulk of waste
loading during treatment. A sharp decrease in perfor-
mance is seen during the first two days of treatment
(pressure increasing and flow rate decreasing). After this
point, the system was shut down for thorough membrane
cleaning. This performance decrease was probably a
result of the lack of pH adjustment to control precipitation
and membrane scaling. HCI acid addition for pH adjust-
ment was initiated after this time and seemed to help
maintain membrane performance; membrane cleaning
was not required for the next ten days of treatment. The
feed pressure in the first-stage unit began increasing on
about August 22, 1994. The system recovery rate setting
was increased on August 24 by Rochem, and this was
followed by additional pressure increases as well as a
decrease in flow rate until the end of the leachate test.
During this period, routine membrane cleaning was con-
ducted for short periods of time almost every day of
operation. Apparently, the first-stage membranes were
beginning to foul or scale, and increasing the recovery
rate compounded this problem. As a result, the system
experienced a reduction in flow rate and reduction in
permeate quality for some contaminants. Figure 6 illus-
trates a trend in the reduction of permeate quality (most
notable near the end of the Demonstration) for TDS,
TOG, and total VOCs. Membrane cleanings were helpful
in maintaining system performance, but the leachate did
appear to have an impact on membrane performance
over the course of the Demonstration. However, due to
the short duration of system shakedown and of the
Demonstration, it was not possible for Rochem to fully
optimize the membrane cleaning procedures for this
leachate. The developer felt that better performance may
have been achieved if a more thorough process shake-
down had been performed and more sophisticated pre-
treatment for pH control had been used. Baseline testing
also indicated a decrease in membrane performance
over the course of the Demonstration. Baseline testing
-------
1000
900 -
4
800 -
700 -
600 j
§ 500 -
8
o>
ol 400 -
300 -
200 -
100 -
System
off-line
-»- Average feed pressure
-O- Average permeate flow rate
-4- Average standardized permeate flow rate
4.5
- 4
- 3.5
- 3
- - 2.5 |
S
o>
+ 2 |
o
O <
System
off-line
-\ h
-\ 1 1 1 1 1 1 h
-1 1 1 1 1 1-
-1 1-
-- 1.5
-- 1
-- 0.5
8/11 8/12 8/13 8/14 8/15 8/16 8/17 8/18 8/19 8/20 8/218/22 8/23 8/24 8/25 8/26 8/27 8/28 8/29 8/30 8/31 9/1 9/2
Date (1994)
Figure 4. First-stage unit: feed pressure and permeate flow rate vs. time.
1800
1 600 - -
1400 --
1200 --
System
off-line
-»- Average feed pressure
-O- Average permeate flow rate
-^- Average standardized permeate flow rate
-1 h
-1 1-
System
off-line
-1.2
-- 1
-0.4
0.2
8/11
8/12 8/13 8/14 8/15 8/16 8/17 8/18 8/19 8/20 8/218/22 8/23 8/24 8/25 8/26 8/27 8/28 8/29 8/30 8/31 9/1 9/2
Date (1994)
Figure 5. High pressure unit: feed pressure and permeate flow rate vs. time.
-------
160
0
8/11 8/12 8/13 8/14 8/15 8/16 8/178/18 8/19 8/20 8/218/22 8/23 8/24 8/25 8/26 8/278/28 8/298/30 8/31 9/1
Date (1994)
Figure 6. Final permeate stream: IDS, TOC, and total VOCs vs. time.
involves determining the change in flux (flow rate per
unit membrane area) as a result of liquid waste (leachate)
treatment. Baseline testing results can be found in the
Innovative Technology Evaluation Report (ITER).
System mass balance calculations gave good results
for metals, TOC, TDS, and TS. Totalized flow measure-
ments were used for daily mass balance calculations.
Adjustments were made to these measurements to ac-
count for rinse cycles that used permeate to perform
rinses. This permeate was lost as concentrate. The over-
all mass balance for metals was within 15 percent of
closure, which is considered good for this type of pro-
cess. The closures for TOC, TDS, and TS were within
plus or minus 5 percent. These results indicate that
analytical data and system flow measurements were of
good quality and that these contaminants were accounted
for. Mass balances for VOCs showed a typical loss of 40
to 60% of these compounds through the system, and
final concentrate levels for VOCs were lower than ex-
pected based on feed levels and the system water re-
covery rate. These differences are probably due to VOC
losses during system sampling and possibly due to VOCs
adhering to membrane surfaces. The feed and espe-
cially the final concentrate process streams were foam-
ing during sampling due to acid addition and
pressurization, making sampling for VOCs difficult and
probably resulting in VOC losses to the atmosphere.
Organic fouling of the membranes was occurring during
leachate treatment, as evidenced by the amount of mem-
brane cleaning required using an alkaline cleaner. VOCs
may have been responsible for some of the organic
fouling, possibly in combination with iron or silica, how-
ever, these foulants would have probably been removed
from the membranes during cleaning cycles and would
therefore not be accounted for in the mass balances.
During the Demonstration, final permeate was col-
lected in holding tanks and then discharged to the sani-
tary sewer under a modification to the Central Landfill's
Wastewater Discharge Permit. The measured quality of
the permeate from the DTM technology complied with
discharge permit requirements for heavy metals without
further treatment. Polishing treatment with activated car-
bon was utilized to ensure compliance with the total toxic
organics (TTO) discharge limit of 2.13 mg/L. The TTO
level of the final permeate from the DTM technology
ranged from about 1 mg/L, less than the discharge limit,
to 10 mg/L, with an average of about 3.4 mg/L for the
Demonstration. The calculated TTO for the final perme-
ate is based on VOC analytical results; other organic
compounds were not detected in the full TTO analysis
performed on the final discharge samples. Measured
COD, BOD, and TSS values were generally very low
mg/L or non-detectable. There were no discharge permit
limits for these parameters.
The primary maintenance activity for this technology is
membrane cleaning. The technology is designed to fa-
cilitate membrane cleaning to maintain performance and
extend membrane life. During the Demonstration, for
each unit, short cleaning cycles (approximately 30 to 60
minutes in duration) were used to maintain daily treat-
ment effectiveness. More thorough cleaning was occa-
sionally required to remove accumulated membrane
10
-------
deposits. This extensive cleaning was partially effective
in restoring membrane flow rates (flux). During the Dem-
onstration, membrane cleaning was performed more fre-
quently than typical due to inadequate pH control.
The reliability of the technology during the Demonstra-
tion was good. After some initial adjustments, the system
ran steadily with short breaks for routing membrane
cleaning. The feed pump for the first-stage unit was
defective and had to be replaced towards the end of the
Demonstration. As a replacement pump was not on site,
the system was down for one day while a pump was
delivered. Typically, spare pumps and components would
be on-site, and replacement could be completed in a few
hours (4).
Economic Analysis
Estimates on capital and operating costs have been
determined for treating leachate similar to the SITE Dem-
onstration leachate (hazardous landfill leachate). Two
cost estimate cases are presented for DTM systems
operating 24 hours per day (hpd) at fixed facilities. The
first case is for a 9122 DTM system treating three gal-
lons of leachate per minute. This is slightly smaller than
the 9122 Demonstration system. The second case is for
a 9142 DTM system treating 21 gallons of leachate per
minute. For both cases the DTM system includes a high
pressure unit (HPU).
The estimated costs for treating leachate similar to the
Demonstration leachate are $0.16/permeate-gallon ($0.047
permeate-liter) for the 9122 system case and $0.067
permeate-gallon ($0.01/permeate-liter) for the 9142 sys-
tem case. These costs are for operating at a fixed
facility. They include all factors except for permitting and
waste disposal costs for the concentrate stream. Costs
are highly site- and leachate-specific. If only annualized
equipment costs and consumables costs were consid-
ered, then the cost would decrease to $0.07/permeate-
gallon and $0.03/permeate-gallon for the 9122 and 9142
systems, respectively.
The cost for treatment using the Rochem DTM system
is based on, but not limited to, the following information:
Treating leachate similar to the leachate at the
Demonstration. Leachate characteristics directly
influence the treatment cost. Different leachates
may require a different: cleaning frequency, on-
line efficiency factor, pH adjustment requirement,
membrane life, and cartridge filter life.
An on-line efficiency factor of 90%. This factor
accounts for downtime due to scheduled and un-
scheduled cleanings and maintenance. It is based
on observations recorded during the SITE Demon-
stration and other data from Rochem. The approxi-
mate on-line efficiency factor during the SITE
Demonstration was 84%.
A permeate recovery factor of 75%. This is based
on data collected during the SITE Demonstration.
Cleaning frequencies and cleaning solutions re-
quirements based on observations made during
the SITE Demonstration and other data from
Rochem.
The same pH adjustment requirements that were
observed during the SITE Demonstration.
The following membrane lifetimes: five years for
the second stage permeate-membrane, three years
for the first stage leachate-membrane, and two
years for the concentrate-membrane. These life-
times are based on information from other Rochem
applications.
System operating times of 24 hpd, 7 days per
week, and 50 weeks per year.
Labor requirements of one operator on-site for four
hpd. Because these cost estimates are based on
the Demonstration leachate characteristics, they
are higher than costs estimated for treating a non-
hazardous landfill leachate. This is because the
Demonstration leachate required more frequent
cleanings and a larger volume of pH adjustment
chemicals than other types of leachates would
require. A detailed explanation of these cost esti-
mates can be found in the ITER.
Technology Status
Rochem Separations Systems, Inc. based in Torrance,
California is licensed to supply the DTM technology in
the United States. They are a subsidiary of the Swiss-
based Rochem Group which developed and patented
the DTM technology. The DTM units and systems are
designed and fabricated in Germany. They have been
manufactured since 1988. The high-pressure unit such
as used during the Demonstration at the Central Landfill
is a new design implemented to increase treated water
recovery rates where high recovery rates are desirable
or for applications with high TDS.
Rochem has over 800 installations of the DTM tech-
nology worldwide, mostly in Europe. During the last six
years, the technology has been used to treat landfill
leachate at more than 50 landfills in Europe, according
to Rochem. Rochem has also had projects in the United
States. At the French Limited Superfund site near Crosby,
Texas, the technology treated lagoon water contami-
nated by petrochemical wastes (volatile organics, phe-
nols, heavy metals, and PCBs). Two units with 30
modules and one with 10 modules were used to treat
three million gallons of lagoon water per month at this
site. According to Rochem, nearly 40 million gallons of
water were processed at a 30 to 50 percent recovery
rate. TOG levels from 1,700 to 1,800 mg/L in the lagoon
water were reduced to 20 to 25 mg/L in the treated
water, less than the EPA discharge requirements (6). At
the Superior Landfill in Savannah, Georgia, the technol-
ogy is treating municipal landfill leachate at a flow rate of
6,000 to 7,000 gallons per day. According to Rochem,
over 200,000 gallons of leachate have been treated to
date at a 73 to 74% recovery rate (4).
Rochem has four systems available for waste treat-
ment: Model 9122 rated for 3,000 to 9,000 gallons per
day (gpd) [11,000 to 34,000 liters per day (Ipd)]; Model
9142 rated for 10,000 to 32,000 gpd (38,000 to 120,000
Ipd); Model 9152 rated for 33,000 to 79,000 gpd (125,000
to 300,000 Ipd); and Model 9532 rated for 9,000 to
133,000 gpd (34,000 to 500,000 Ipd). All are one-stage
systems containing a leachate DTM unit and a permeate
DTM unit. A high-pressure unit can be combined with
any system. The modular design and construction of the
11
-------
DIM units allows them to be combined in series (two-
stage) to increase product quality, or in parallel to in-
crease treatment capacity. The cost per permeate-gallon
for treatment with the DIM technology decreases with
increasing treatment capacity.
Based on the results of this Demonstration, waste
treatability testing is strongly recommended prior to pro-
cess design and application. On-site pilot-scale treatabil-
ity testing should be performed to determine operational
and maintenance procedures such as chemical addition
and membrane cleaning requirements. In addition, pre-
treatment requirements can be formalized. Rochem nor-
mally performs an on-site pilot-scale treatability test lasting
two to six weeks prior to process installation (4). Treat-
ment effectiveness is very waste specific, although any
significant treatment concerns can probably be identified
from preliminary waste characterization data. If needed,
bench-scale treatability testing is used to determine mem-
brane compatibility with the waste and expected perme-
ate quality. This can be performed off-site by shipping
samples of liquid waste to Rochem's laboratory facility or
on-site by Rochem using a bench-scale system. Once
installed, a few days to a week, depending on the appli-
cation, are required to properly shakedown the system.
Once on-line, the DTM technology can operate 24 hours
per day with occasional breaks for cleaning and mainte-
nance. This is the most cost-effective mode of operation.
Operator attention requirements for system monitoring
and maintenance can be as little as one to two hours per
day. For more difficult or hazardous wastes, greater
operator attention is required.
SITE Program Description
In 1980, the U.S. Congress passed the Comprehen-
sive Environmental Response, Compensation, and Li-
ability Act (CERCLA), also known as Superfund. CERCLA
was amended by the Superfund Amendments and Re-
authorization Act (SARA). The primary purpose of the
SITE Program is to maximize the use of alternatives in
cleaning up hazardous waste sites by encouraging the
development and demonstration of new, innovative treat-
ment and monitoring technologies. It consists of four
major elements: the Demonstration Program, the Emerg-
ing Technology Program, the Monitoring and Measure-
ment Technologies Program, and the Technology Transfer
Program. The Rochem DTM technology was evaluated
under the Demonstration Program. This Capsule was
published as part of the Technology Transfer Program.
Sources of Further Information
EPA Contact:
U.S. EPA Project Manager:
Douglas Grosse
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
Telephone No.: (513) 569-7844
Fax No.: (513) 569-7676
Technology Developer Contact:
David LaMonica
President
Rochem Separation Systems, Inc.
3904 Del Amo Boulevard, Suite 801
Torrance, CA 90503
Telephone No.: (310) 370-3160
Fax No.: (310)370-4988
References
1. Porter, M.C., Nucleopore Corp., Pleasanton, Cali-
fornia, "Selecting the Right Membrane," Chemical
Engineering Progress (Vol. 71, No. 12) December
1975; pp. 55-61.
2. Rochem Separation Systems, Inc. "The Use of
Membrane Systems to Treat Leachate." SITE Pro-
posal.
3. American Water Works Association. "Removal of
Low Molecular Weight Organic Contaminants from
Drinking Water Using Reverse Osmosis Mem-
branes," 1987 Annual Conference Proceedings:
Part 2 Sessions 23-28. Kansas City, MO. June 14-
18, 1987.
4. Telecommunications between Rochem and SAIC.
1994-1995.
5. Dupont Company, Plastic Products and Resins
Dept, Permasep Products, Wilmington, DE. "Pre-
treatment Considerations for Reverse Osmosis."
Technical Bulletin No. 401. September, 1977.
6. Collins, Mark and Ken Miller. "Reverse Osmosis
Reverses Conventional Wisdom with Superfund
Cleanup Success." Environmental Solutions, Sep-
tember 1994. pp 64-66.
12
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