vvEPA
United States Office of
Environmental Protection Research and Development
Agency Cincinnati, Ohio 45268
EPA/540/R-95/503a
August 1995
SITE Technology Capsule
ZenoGem™ Wastewater
Treatment Process
Abstract
The ZenoGem technology is a wastewater treatment
process designed to treat groundwater, landfill leachate,
industrial effluent, and soil washing effluent contaminated
with high concentrations of volatile organic compounds
(VOCs) and semivolatile organic compounds (SVOCs) that
cause elevated levels of biochemical oxygen demand
(BOD) and chemical oxygen demand (COD). The
technology uses an innovative combination of aerobic
biological treatment to remove biodegradable organic
compounds and ultrafiltration to separate residual
suspended solids from the treated effluent.
The ZenoGem technology was evaluated under EPA's
Superfund Innovative Technology Evaluation (SITE)
Program on about 30,000 gallons of contaminated
groundwater at the Nascolite Superfund Site in Millville,
New Jersey. The demonstration focused on the system's
ability to degrade methyl methacrylate (MMA) and reduce
COD from contaminated groundwater. Results for the
3-month demonstration indicate that MMA removal
efficiency averaged greater than 99.9 percent, and COD
removal efficiency averaged 97.9 percent. The treated
effluent was clear and odorless, and accepted for
discharge by the local publicly owned treatment works
(ROW).
The ZenoGem technology exhibited smooth and
unattended operation over the course of the
demonstration. The system is trailer-mounted, easily
transportable, and can be operational within 1 week, if
the necessary utilities are available. The ZenoGem
technology fulfills the nine criteria used for decision-
making in the Superfund Feasibility Study (FS) process,
as summarized in Table 1.
Introduction
In 1980, the U.S. Congress passed the Comprehensive
Environmental Response, Compensation, and Liability Act
(CERCLA), also known as Superfund, committed to
protecting human health and the environment from
uncontrolled hazardous waste sites. CERCLA was
amended by the Superfund Amendments and
Reauthorization Act (SARA) in 1986. These amendments
emphasize the long-term effectiveness and permanence
of remedies at Superfund sites. SARA mandates
implementing permanent solutions and using alternative
treatment technologies or resource recovery technologies,
to the maximum extent possible, to clean up hazardous
waste sites.
State and federal agencies, as well as private parties,
are now exploring a growing number of innovative
technologies for treating hazardous wastes. The sites on
the National Priorities List total more than 1,700 and
comprise a broad spectrum of physical, chemical, and
Printed on
Paper
SVPERFVND INNOVATIVE
TECHNOLOGY EVALUATION
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Table 1: Feasibility Study Evaluation Criteria for the ZenoGemTM Technology
CRITERION
1 Overall Protection of
Human Health and the
Environment
2 Compliance with Federal ARARs
Long-Term Effectiveness
and Permanence
4 Reduction of Toxicity,
Mobility, or Volume
Through Treatment
5 Short-Term Effectiveness
6 Implementability
7 Cost
8 Community Acceptance
9 State Acceptance
ZENOGEM™ TECHNOLOGY PERFORMANCE
Effectively degrades VOCs in groundwater into innocuous
products, eliminating contaminant exposure
Minimizes the mobility of contaminants in groundwater
Minimizes exposure to workers and the community from VOC
emissions
Operation of the system may require compliance with
location-specific ARARs
Emission controls may be required to ensure compliance with
air quality standards depending on chemical-, location-, and
action-specific ARARs
Compliance with RCRA treatment, storage, and land disposal
regulations for a hazardous waste
Effectively degrades VOCs in groundwater
Residuals consisting of spent carbon, sludge, and treated
effluent require disposal
The process is not a volume reduction technology, but
completely degrades the contaminants and reduces toxicity
Reduces long-term contaminant mobility by minimizing or
eliminating contaminants from the source
Presents minimal short-term risks to workers and community
from air releases during treatment
System components are contained inside an easily
transportable trailer
About 1,000 square feet of space is needed for trailer setup;
additional space may be needed for future expansion
Requires installing utilities, production wells, and influent feed
lines to the system
Capital costs for purchasing the ZenoGem™ equipment is
estimated to range from $90,000 to $160,000, and annual
operation and maintenance costs are estimated at $40,000 for
a unit similar to the system demonstrated
Public acceptance is likely due to (1) the lower risk presented
to the community, and (2) permanent contaminant removal
State acceptance is likely due to well-documented and widely
accepted processes used to remove contaminants from
groundwater
State regulatory agencies may require permits for system
operation, air emissions, and waste storage longer than 90
days.
ARAR -Applicable or relevant and appropriate requirements
RCRA -Resource Conservation and Recovery Act
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environmental conditions requiring varying types of
remediation. The U.S. Environmental Protection Agency
(EPA) has focused on policy, technical, and informational
issues related to exploring and applying new remediation
technologies applicable to Superfund sites, One such
initiative is EPA's SITE Program, which was established
to accelerate development, demonstration, and use of
innovative technologies for site cleanups. EPA SITE
Technology Capsules summarize the latest information
available on selected innovative treatment and site
remediation technologies and related issues. These
Technology Capsules are designed to help EPA remedial
project managers, EPA on-scene coordinators,
contractors, and other site cleanup managers understand
the type of data and site characteristics needed to
effectively evaluate a technology's applicability for cleaning
up Superfund sites. Additional details regarding the
technology demonstrations are presented in Innovative
Technology Evaluation Reports.
This Technology Capsule provides information on the
ZenoGem technology developed by Zenon Environmental
Systems, Inc. The technology is a wastewater treatment
process designed to treat groundwater, landfill leachate,
industrial effluent, and soil washing effluent contaminated
with VOCs and SVOCs. The ZenoGem technology was
evaluated under the SITE Program from September 1994
through November 1994 at the Nascolite site in Millville,
New Jersey. Information in this Technology Capsule
emphasizes specific site characteristics and results of
the SITE field demonstration at the Nascolite site.
Technology Description
The ZenoGem technology integrates aerobic biological
treatment with membrane-based ultrafiltration. This
innovative system uses ultrafiltration to separate residual
suspended solids from biologically treated effluent. Zenon
claims that the process reduces VOCs and SVOCs in
wastewater to below regulatory limits, improves effluent
quality, reduces sludge production, resists contaminant
shock-loading, and reduces the size of the bioreactor by
maintaining a long sludge retention time.
The major components of the ZenoGem system are an
influent holding-equalization tank, a biological reactor
(bioreactor), an ultrafiltration module, an air blower, a pH
buffer tank, a nutrient solution tank, optional off-gas carbon
filters, optional permeate carbon filters, and feed, process,
and metering pumps (Figure 1). The system components
are computer-controlled and equipped with alarm indicators
to notify the operator of mechanical and operational
problems. The entire system, except for the main air
blower and optional activated carbon filters, is mounted
inside an 8-foot by 48-foot ZenoSite trailer. The air blower
is mounted below the trailer for noise control purposes.
The ZenoSite trailer is also equipped with a laboratory
that enables field personnel to conduct tests to evaluate
system performance.
Following equalization, treatment begins by continuously
pumping wastewater into a 1,000-gallon polyethylene
stirred-tank bioreactor that contains an acclimated
microbial culture maintained under aerobic conditions.
The aerobic, suspended-growth environment is
maintained by diffused aeration, which continuously
mixes the bioreactor's contents, known as mixed liquor.
The mixed liquor is retained in the bioreactor for sufficient
time to allow the microorganisms to metabolize the
biodegradable organic contaminants into innocuous
end-products and intermediate by-products.
The mixed liquor is continuously pumped from the
bioreactor into a pressure-driven ultrafiltration module.
The ultrafiltration module consists of eight 1 -inch diameter
tubes connected in series and contained in a 12-foot by
4-inch-diameter polyvinyl chloride housing (Figure 2). The
tubes support the ultrafiltration membrane, which filters
some of the dissolved contaminants and all suspended
solids from the mixed liquor. The cut-off threshold size
above which organic compounds are retained by the
membrane is called the molecular weight cut-off. This
cut-off ranges between 0.003 to 0.1 microns, and depends
on the membrane type.
The continuous flow of mixed liquor primarily consisting
of suspended solids are drawn toward the membrane's
surface, forming a gel layer. Particles from the gel layer
are detached by the cross-flow water movement,
maintaining a gel layer equilibrium on the membrane's
non-clogging surface. The detached particles and
unfiltered fraction of the mixed liquor (called concentrate)
are continuously recycled to the bioreactor to maintain a
desired microorganism concentration and to further
degrade higher molecular weight organic compounds. The
filtered effluent (called permeate) flows through activated
carbon filters to remove any nonbiodegradable and trace
organic compounds before final treated effluent is
discharged.
The final treated effluent may be injected into the aquifer,
disposed of at a POTW, reused on site, or discharged
directly to surface water under an appropriate National
Pollutant Discharge Elimination System (NPDES) permit.
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WASTE WATER
INFLUENT
HOLDING/
EQUALIZATION
TANK
NUTRIENT
SOLUTION
TANK
METERING
PUMP
AIR
VENT
OFF-GAS
CARBON
FILTER
ft
V
ED
MP
1
L
CONCEN
t 1
i
1 rr
1 T
(A
c
^ METERING
PUMP
pH BUFFER
TANK
A 1 R
PROCESS
PUMP
ULTRAFILTRATION
MODULE
TREATED
EFFLUENT ,-
CARBON
FILTER
4-
TREATED
EFFLUENT
HOLDING
TANK
Figure 1: The ZenoGem ™ technology as demonstrated
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-inch diameter tubes
Ultrafiltration Membrane
Polyvinyl chloride housing
Permeate
outlet port
Biologically
treated effluent
inlet port
Concentrate
outlet port
Figure 2: Cross-Section of the Ultrafiltration Module
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Technology Applicability
In general, the ZenoGem technology is applicable for
the treatment of elevated concentrations of VOCs and
SVOCs that cause elevated levels of BOD and COD in
contaminated groundwater. Zenon claims that the process
can also be readily adapted to treat other contaminated
wastewater, such as landfill leachate, industrial effluent,
and soil washing effluent.
In addition to the potential different treatment applications,
the ZenoGem technology provides advantages in terms
of effluent quality and disposal costs. The ultrafiltration
system removes suspended solids from the effluent,
yielding a clear product. The ultrafiltration system also
reduces the volume of waste sludge for disposal. This
advantage may be important when the need to minimize
residual waste is a critical disposal issue.
Technology Limitations
Elevated oil and grease concentrations, inorganic
suspended solids, and heavy metals may reduce the
ZenoGem treatment efficiency. Elevated oil and grease
concentrations and oil containing biocides can inhibit or
prevent microbial activity. Unemulsified oil and grease
concentrations may also foul the ultrafiltration membrane
surface, reducing the amount of permeate discharge from
the module.
Inorganic suspended solids that are not biologically
degraded will accumulate in the mixed liquor and increase
the amount of sludge for disposal. Suspended solids can
also limit the process pumps' efficiency to recirculate the
concentrate and could foul the ultrafiltration membrane.
In addition, heavy metal concentrations can be toxic to
microorganisms, reducing biological growth enough to
discontinue treatment.
Depending on wastewater characteristics, pretreatment
can be incorporated into a treatment train to prevent these
problems. Pretreatment options include sedimentation,
flotation, chemical precipitation, and microfiltration. Zenon
manufactures pretreatment systems for any necessary
application.
Site Requirements
The ZenoSite trailer requires a 12-foot by 60-foot area to
support a maximum operating weight of 45,000 pounds.
The trailer also requires 14-feet of overhead clearance.
About 1,000 square feet are necessary to operate and
unload equipment. Once the trailer is set up, the system
can be operational within 1 week, if all necessary utilities,
production wells, feed lines, and supplies are available.
According to Zenon, the system can also be constructed
in a 40-foot International Standard Organization (ISO)
shipping container or mounted on a modular skid. The
40-foot ISO container can be modified to provide shelter,
where the skid-mounted unit needs to be housed inside a
building.
Potable water must be available for personnel
decontamination, performing laboratory analytical
procedures, and for bioreactor cooling. For bioreactor
cooling, the water supply must be capable of providing 60
pounds per square inch (psi) pressure and a flow rate of
30 gallons per minute (gpm). If potable water is
unavailable, arrangements must be made to deliver, store,
and pump water. In addition, about 200 gallons of potable
water are required for equipment washing and
decontamination. The electrical requirements of the
ZenoSite trailer are a three-phase, 460-volt power supply
that is located within 15 feet of the trailer. If an electrical
source is unavailable on site, a trailer-mounted generator
can supply electricity to the system.
Support facilities include an area for optional untreated
and treated groundwater storage tanks, and a drum staging
area for generated wastes. Additionally, a building or shed
is useful to protect supplies. Other installation and
monitoring requirements include security fencing and
access roads for equipment transport.
Process Residuals
The primary residual generated by the ZenoGem
technology is waste sludge, which consists of
microorganisms and unfiltered wastewater from the
bioreactor. Zenon can reduce the volume of waste sludge
by continuously recirculating the contents through the
ultrafiltration module. This procedure dewaters and
concentrates the sludge, yielding a smaller volume for
disposal. During the SITE demonstration, the ultrafiltration
system reduced the volume of sludge in the bioreactor
from 700 gallons to 400 gallons in about 4 hours. Waste
sludge can be stored in 55-gallon drums for off-site transport
and disposal. The waste sludge may be subject to RCRA
or state regulations as a hazardous waste depending on
influent metals concentrations.
Secondary waste streams generated by the ZenoGem
technology include proprietary membrane cleaning solution,
spent carbon filters, and decontamination water. During
the SITE demonstration, Zenon generated about 100
gallons of membrane cleaning solution, which was treated
in the bioreactor. Spent carbon used for VOC removal in
the permeate and off-gas streams may be disposed of or
regenerated. Decontamination water may be stored in
55-gallon drums for off-site disposal.
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Table 2: MMA and COD Results from the ZenoGamT Demonstration
Influent
Number of
Weeks Samples
1-6 39
7-6 17
Nov. 8 1994C 3
9-10° 13
1-6 38
7-8 15
Nov. 8 1994C 3
9-10* 13
mg/L Milligrams per
NA Not analyzed
NC Not calculated
MMA
Concentration*
(mg/L)
2,000
2,200
7,100
8,100
COD
Concentration'
(ms/L)
4,900
5,500
18,200
19,900
liter
Average
Flow Ratd
(gpd)
420
450
480"
140
Average
Flow Rate*
(gpd)
420
450
480"
140
Permeate
MMA
Concentration' Percent
(mg/L) Reduction
1 .00 >99.9
< 0.02 >99.9
< 0.02 >99.9
0.02 <99.9
COD
Concentration* Percent
(mg/L) Reduction
500 89.7
900 83.6
1,200 93.6
1,100 95.0
a Average values for weeks noted
b 11 samples collected
c Organic shock-loading
d Flow rate maintained for 4 hours
e Maintained volumetric loading
f 7 samples collected
Effluent
MMA
Concentration*
(mg/L)
NA
0.03"
< 0.02
0.02
COD
Concentration*
(mg/L)
NA
72.0'
430
365'
Percent
Reduction
NC
>99.9
>99.9
>99.9
Percent
Reduction
NC
98.7
97.6
98.2
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Economic Analysis
A number of factors affect the estimated costs of treating
groundwater with the ZenoGem treatment system. The
factors affecting capital equipment costs and annual
operation and maintenance costs are highly variable and
depend on site-specific factors, including (1) system size,
(2) influent characteristics, (3) process rate, and (4) target
cleanup concentration. The cost of time-dependent
factors such as labor, and consumables and supplies
varies directly with treatment time.
One-time capital costs for a single pilot-scale unit were
estimated to be $90,000 for the modular skid, $118,000
for the 40-foot ISO container, and $160,000 for the
ZenoSite trailer unit. Annual operation and maintenance
costs for the first year were estimated to be $40,000.
Based on the estimates for the 40-foot ISO contained
unit, the total operating cost for 1 year is estimated to be
$158,000. Following treatment, the unit can be
decontaminated, allowing the equipment to retain some
residual value. These costs are based on the following:
The site is a Superfund site located in New Jersey.
Suitable site access roads are available.
Overhead utility supply lines, such as electricity
and telephone lines, are available on site.
No pretreatment, such as oil separation, solids
removal, or pH adjustment of the influent
groundwater, is necessary.
The treatment system operates automatically
without the constant attention of an operator.
Necessary consumables and supplies include
treatment chemicals, activated carbon, personal
protective equipment, and sampling equipment.
The total annual electrical energy consumption
is estimated to be 80,000 kilowatt hours (kWh) of
electricity at $0.09 per kWh.
Annual equipment costs, excluding labor, are
estimated to be about 3 percent of the capital
equipment costs.
One trained operator spends 3 hours per week
performing routine equipment monitoring and
sampling activities.
One treated and one untreated groundwater
sample will be collected monthly from the system
and analyzed for pH, VOC, SVOC, and COD;
quality assurance samples will also be collected.
Contaminated groundwater will be treated to below
maximum contaminant levels and injected into
the ground.
A detailed breakdown of the costs for operating the
ZenoGem system is presented in the Innovative
Technology Evaluation Report (ITER). The ITER will also
include a scenario for a full-scale system treating landfill
leachate over a 10-year period.
Technology Status
Since the development of the ZenoGem technology in
1987, Zenon has performed pilot tests for government and
private clients on several different types of wastewater,
including oily wastewater, metal finishing wastes, cleaning
solutions containing detergents, alcohol-based cleaning
solutions, landfill leachate, aqueous paint-stripping wastes,
and de-icing fluids. Information is available on two
demonstrations conducted in Canada and the United
States. At the Canadian Department of National Defense
fire fighting school, the ZenoGem biological unit was
demonstrated on wastewater containing burned and
unburned fuel residue. The system successfully
demonstrated the biodegradation of aqueous foam
formulation compounds and simultaneous removal of oil
and grease, petroleum hydrocarbons, and suspended
solids. The system was also demonstrated at the Army
Material Command Watervliet Arsenal, where the
ultrafiltration module treated oily wastewater. Results
indicated that the ultrafiltration module reduced waste
disposal by 70 percent at a significant cost savings. Full-
scale systems are in operation at design capacities of
150 gpm in North America and Europe.
Disclaimer
Data presented in this Technology Capsule were reviewed
by the PRC SITE QA Manager. When the draft ITER and
TER are submitted, the EPA National Risk Management
Research Laboratory QA office will conduct a data review
to verify compliance with project QA requirements.
10
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Sources of Further Information
For further information, contact:
U.S. EPA Project Manager:
Daniel Sullivan
U.S. Environmental Protection Agency (MS-106)
2890 Woodbridge Avenue
Edison, NJ 08837-3679
908-321-6677
FAX: 908-906-6990
Technology Developer:
F.A. (Tony) Tonelli
Zenon Environmental Systems, Inc.:
845 Harrington Court
Burlington, Ontario, Canada L7N 3P3
905-639-6320
FAX: 905-639-1812
11
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United States
Environmental Protection Agency
National Risk Management
Research Laboratory (G-72)
Cincinnati, OH 45268
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