&EPA
United States
Environmental Protection
Agency
EPA/540/M5-90/007
February 1991
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Membrane Microfiltration
E. I. DuPont de Nemours and Company, Inc.
Oberlin Filter Company
TECHNOLOGY DESCRIPTION: The DuPont/Oberlin
microfiltration technology is a physical separation process that
removes solid particles from liquid wastes. The process can filter
particles that are submicron or larger in diameter. Pretreatment,
such as chemical additions, will be required if dissolved contami-
nants are present in the liquid waste. The end microfiltration
products are filtered solids, called filter cake, and filtered liquids,
called filtrate.
The DuPont/Oberlin microfiltration system is transportable and
requires little or no attention during operation. The system uses
Oberlin's automatic pressure filter and DuPont's special
spunbonded olefin style filter material called Tyvek® T-980. The
automatic pressure filter has two chambers—an upper chamber
that feeds liquid waste under pressure through the Tyvek® and a
lower chamber that collects the filtrate (Figure 1).
A typical microfiltration cycle consists of four steps: (1) initial
filtration, (2) main filtration and cake forming, (3) cake drying, and
(4) cake discharge. The process begins with liquid waste being
pumped usually from a waste feed tank into the upper chamber.
During the first minute of filtration, or the initial filtration step, the
filtrate is usually recycled to the waste feed tank. During the main
filtration step, solids accumulate on the Tyvek® and form a filter
cake, while filtrate drains from the lower chamber to a filtrate
collection tank. When the pressure in the upper chamber reaches
a preset value (blowdown pressure), the waste feed valve closes
and the cake drying step begins. Pressurized air (typically, 35
psig) is fed into the upper chamber to further dry the cake. After
air breaks through the cake, drying continues for a preset time
(blowdown time). During this step, any remaining liquids are
forced through the Tyvek® and are recycled to the waste feed
tank. Immediately following the cake drying step, the upper
chamber is lifted, clean Tyvek® is drawn from a roll into the unit
for the next cycle, and the filter cake is discharged.
WASTE APPLICABILITY: The combined DuPont/Oberlin
microfiltration system has been applied to landfill leachate,
groundwater containing cyanide, wastewaters containing uranium,
and electroplating wastewaters containing heavy metals. The
technology is best suited for treating wastes with solid concentra-
tions less than 5,000 parts per million prior to pretreatment;
otherwise, cake capacity and handling become limiting factors.
DEMONSTRATION RESULTS: The DuPont/Oberlin microfittration
system was demonstrated at the Palmerton Zinc Superfund (PZS)
site in Palmerton, Pennsylvania, over a 4-week period in April
and May of 1990. During the demonstration, about 3,000 gallons
of groundwater contaminated primarily with zinc from the PZS
site were treated by the microfiltration system. The demonstra-
tion was carried out in four phases. Phases 1 and 2 involved
nine runs each, and Phases 3 and 4 involved two runs each.
Each run consisted of three cycles, as described above.
To evaluate the technology under different operating conditions,
chemical operating parameters (precipitation pH and filter aid
dose) and filter operating parameters (blowdown pressure and
blowdown time) were varied in Phases 1 and 2, respectively.
The precipitation pH was controlled by adding lime slurry to the
untreated groundwater in the precipitation tank. A filter aid,
ProFix, was added in-line prior to the microfiltration unit to
improve the filtering characteristics of the precipitated solids. The
filter operating parameters were set using the controls on the
microfiltration unit. The operating conditions were varied as fol-
lows: pH, 8 to 10; ProFix dose, 6 to 14 g/L; blowdown pressure,
30 to 45 psig; and blowdown time, 0.5 to 3 minutes. Phase 3
runs were performed at optimum conditions, based on the results
from Phases 1 and 2, to verify the reproducibility of the
microfiltration system's performance. Phase 4 runs were per-
formed to evaluate the reusability of the Tyvek® filter media.
Key findings from the technology demonstration are summarized
below:
• The DuPont/Oberlin microfiltration system achieved the follow-
ing: (1) zinc and total suspended solids (TSS) removal efficien-
cies ranged from 99.75 to 99.99 percent; and (2) the percent
solids in the filter cake ranged from 30.5 to 47.1 percent. At the
optimum conditions, shown in Table 1, the zinc and TSS
removal efficiencies were about 99.95 percent; and the filter
cake percent solids were about 41 percent.
• The treated groundwater (filtrate) met the applicable National
Pollutant Discharge Elimination System (NPDES) standards,
established for disposal into a local waterway, for metals and TSS
at the 95 percent confidence level. However, the filtrate did not
meet the NPDES standard for pH. The filtrate pH was typically
11.5, whereas the discharge standard is 6 to 9 pH units.
• The filter cake passed the paint filter liquid test (PFLT) in all runs.
Also, a composite filter cake sample from the demonstration runs
passed the extraction procedure (EP) toxicity and the toxicity
characteristic leaching procedure (TCLP) tests.
Printed on Recycled Paper
-------
&EPA
United States
Environmental Protection
Agency
EPA/540/M5-90/007
February 1991
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Membrane Microfiltration
E. I. DuPont de Nemours and Company, Inc.
Oberlin Filter Company
TECHNOLOGY DESCRIPTION: The DuPont/Oberlin
microfiltration technology is a physical separation process that
removes solid particles from liquid wastes. The process can filter
particles that are submicron or larger in diameter. Pretreatment,
such as chemical additions, will be required if dissolved contami-
nants are present in the liquid waste. The end microfiltration
products are filtered solids, called filter cake, and filtered liquids,
called filtrate.
The DuPont/Oberlin microfiltration system is transportable and
requires little or no attention during operation. The system uses
Oberlin's automatic pressure filter and DuPont's special
spunbonded olefin style filter material called Tyvek® T-980. The
automatic pressure filter has two chambers—an upper chamber
that feeds liquid waste under pressure through the Tyvek® and a
lower chamber that collects the filtrate (Figure 1).
A typical microfiltration cycle consists of four steps: (1) initial
filtration, (2) main filtration and cake forming, (3) cake drying, and
(4) cake discharge. The process begins with liquid waste being
pumped usually from a waste feed tank into the upper chamber.
During the first minute of filtration, or the initial filtration step, the
filtrate is usually recycled to the waste feed tank. During the main
filtration step, solids accumulate on the Tyvek® and form a filter
cake, while filtrate drains from the lower chamber to a filtrate
collection tank. When the pressure in the upper chamber reaches
a preset value (blowdown pressure), the waste feed valve closes
and the cake drying step begins. Pressurized air (typically, 35
psig) is fed into the upper chamber to further dry the cake. After
air breaks through the cake, drying continues for a preset time
(blowdown time). During this step, any remaining liquids are
forced through the Tyvek® and are recycled to the waste feed
tank. Immediately following the cake drying step, the upper
chamber is lifted, clean Tyvek® is drawn from a roll into the unit
for the next cycle, and the filter cake is discharged.
WASTE APPLICABILITY: The combined DuPont/Oberlin
microfiltration system has been applied to landfill leachate,
groundwater containing cyanide, wastewaters containing uranium,
and electroplating wastewaters containing heavy metals. The
technology is best suited for treating wastes with solid concentra-
tions less than 5,000 parts per million prior to pretreatment;
otherwise, cake capacity and handling become limiting factors.
DEMONSTRATION RESULTS: The DuPont/pberlin microfiltration
system was demonstrated at the Palmerton Zinc Superfund (PZS)
site in Palmerton, Pennsylvania, over a 4-week period in April
and May of 1990. During the demonstration, about 3,000 gallons
of groundwater contaminated primarily with zinc from the PZS
site were treated by the microfiltration system. The demonstra-
tion was carried out in four phases. Phases 1 and 2 involved
nine runs each, and Phases 3 and 4 involved two runs each.
Each run consisted of three cycles, as described above.
To evaluate the technology under different operating conditions,
chemical operating parameters (precipitation pH and filter aid
dose) and filter operating parameters (blowdown pressure and
blowdown time) were varied in Phases 1 and 2, respectively.
The precipitation pH was controlled by adding lime slurry to the
untreated groundwater in the precipitation tank. A filter aid,
ProFix, was added in-line prior to the microfiltration unit to
improve the filtering characteristics of the precipitated solids. The
filter operating parameters were set using the controls on the
microfiltration unit. The operating conditions were varied as fol-
lows: pH, 8 to 10; ProFix dose, 6 to 14 g/L; blowdown pressure,
30 to 45 psig; and blowdown time, 0.5 to 3 minutes. Phase 3
runs were performed at optimum conditions, based on the results
from Phases 1 and 2, to verify the reproducibility of the
microfiltration system's performance. Phase 4 runs were per-
formed to evaluate the reusability of the Tyvek® filter media.
Key findings from the technology demonstration are summarized
below:
• The DuPont/Oberlin microfiltration system achieved the follow-
ing: (1) zinc and total suspended solids (TSS) removal efficien-
cies ranged from 99.75 to 99.99 percent; and (2) the percent
solids in the filter cake ranged from 30.5 to 47.1 percent. At the
optimum conditions, shown in Table 1, the zinc and TSS
removal efficiencies were about 99.95 percent; and the filter
cake percent solids were about 41 percent.
• The treated groundwater (filtrate) met the applicable National
Pollutant Discharge Elimination System (NPDES) standards,
established for disposal into a local waterway, for metals and TSS
at the 95 percent confidence level. However, the filtrate did not
meet the NPDES standard for pH. The filtrate pH was typically
11.5, whereas the discharge standard is 6 to 9 pH units.
• The filter cake passed the paint filter liquid test (PFLT) in all runs.
Also, a composite filter cake sample from the demonstration runs
passed the extraction procedure (EP) toxicrty and the toxicity
characteristic leaching procedure (TCLP) tests.
Printed on Recycled Paper
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