Options for Discharging Treated Water
from Pump and Treat Systems
TREATMENT
BUILDING
V
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Office of Solid Waste EPA 542-R-07-006
and Emergency Response (5203P) May 2007
www.cluin.org
www.epa.gov/superfund
Options for Discharging Treated Water
from Pump and Treat Systems
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DISCLAIMER
This document provides references to technologies and processes in use by outside parties and other
Federal Agencies. Mention of these technologies and processes does not imply endorsement for specific
purposes.
This fact sheet is not intended to be a detailed instruction manual. In addition, this fact sheet is not a
regulation; therefore, it does not impose legally binding requirements on EPA, States, or the regulated
community, and may not apply to a particular situation based upon the circumstances. The document
offers technical information to EPA, states and others who manage or regulate long-term ground water
remedies as part of any cleanup program. EPA and State personnel may use other approaches, activities
and considerations, either on their own or at the suggestion of interested parties. Interested parties are
free to raise questions and objections regarding this document and the appropriateness of using these
recommendations in a particular situation, and EPA will consider whether or not the recommendations are
appropriate in that situation. This fact sheet may be revised periodically without public notice. EPA
welcomes public comments on this document at any time and will consider those comments in any future
revision of this document.
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PREFACE
This fact sheet discusses potential options for discharging treated water from pump and treat (P&T)
systems. It is part of a series of fact sheets that the EPA Office of Superfund Remediation and
Technology Innovation (OSRTI) is preparing to assist the ground water remediation community to
effectively and efficiently design and operate long-term ground water remedies. This series is available at
www. cluin. org/optimization and consists of the following fact sheets, plus others that will be available in
the future.
• Elements for Effective Management of Operating Pump and Treat Systems
OSWER 9355.4-27FS-A, EPA 542-R-02-009, December 2002
• Cost-Effective Design of Pump and Treat Systems
OSWER 9283.1-20FS, EPA 542-R-05-008, April 2005
• Effective Contracting Approaches for Operating Pump and Treat Systems
OSWER 9283.1-21FS, EPA 542-R-05-009, April 2005
• O&MReport Template for Ground Water Remedies (with Emphasis on Pump and
Treat Systems)
OSWER 9283.1-22FS, EPA 542-R-05-010, April 2005
• Cost Comparison Framework for Use in Optimizing Ground Water Pump and Treat
Systems, EPA 542-R-07-005, May 2007
• Optimization Strategies for Long-Term Ground Water Remedies (with Particular
Emphasis on Pump and Treat Systems), EPA 542-R-07-007, May 2007
The ideas contained in this series of fact sheets are based on professional experience in designing,
operating, and optimizing long-term ground water remedies and on lessons learned from conducting
optimization evaluations called Remediation System Evaluations (RSEs) at sites with P&T systems.
RSEs have been conducted at Superfund-financed sites, Resource Conservation and Recovery Act
(RCRA) sites, and leaking underground storage tanks sites. Reports from RSEs conducted by EPA are
available at www.cluin.org/optimization.
The content of these fact sheets is relevant to almost any long-term ground water remedy, particularly
those that involve P&T. Therefore, these documents may serve as resources for managers, contractors, or
regulators of any P&T system, regardless of the regulatory program.
Access to a wider range of EPA documents is available at wjTO.duin.OTg.
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TABLE OF CONTENTS
A, INTRODUCTION,
,1
B, THE POTENTIAL VALUE OF TREATED
WATER 1
C, DISCHARGE TO SURFACE WATER 2
D, RETURN OF TREATED WATER TO THE
SUBSURFACE 4
E. DISCHARGE TO THE POTW OR OTHER ON-
SITE TREATMENT 9
F. REUSE OF TREATED WATER 10
G. SELECTING AN APPROPRIATE DISCHARGE
OPTION 12
H. REFERENCES 13
A. INTRODUCTION
Federal agencies have conducted optimization
evaluations at approximately 100 operating pump
and treat (P&T) systems since 2000 and have
successfully identified hundreds of potential
opportunities for improving effectiveness in
protecting human health, reducing operating costs,
and speeding progress toward site closure. Several
of the opportunities involve the consideration of
alternate options for discharging treated water.
This fact sheet presents information on available
options for the discharge of water that results from a
P&T remedy. The target audience for this fact sheet
includes environmental case managers from Federal
and State agencies, environmental program
managers from private organizations, and
environmental contractors involved in the design
and/or operation of P&T systems. Discharge
options are typically evaluated during the remedy
selection and system design phases of the remedy,
and discharge alternatives could also be evaluated
during routine optimization evaluations that are
performed while the remedy is operating.
This fact sheet begins with a discussion regarding
the potential value of treated water, followed by
detailed descriptions of the following discharge
options:
discharge to surface water
return of treated water to the subsurface
• discharge to a publicly owned treatment
works (POTW) or other existing treatment
plant
reuse of treated water
The term operation and maintenance (O&M) is used
throughout this document to describe the activities
involved in operating and maintaining a P&T
system. For the purpose of this document, "O&M"
does not refer to any specific period of time or
regulatory status associated with the remedy. For
example, the Superfund program generally refers to
the first 10 years of a Fund-lead P&T system as
Long-Term Response Action (LTRA), and the
subsequent period as "O&M". However, in this
document both of those time periods are considered
to be types of O&M. Also, this document discusses
issues regarding permitting for various discharge
options. It should be noted that for Superfund sites
"permit equivalency" is generally established in lieu
of an actual permit.
B. THE POTENTIAL VALUE OF TREATED
WATER
Significant quantities of water may be treated by a
treatment plant associated with a ground water P&T
remedy. For instance, each 100 gallons per minute
(gpm) of remedy pumping would translate to
144,000 gallons per day, or more than 52 million
gallons per year. Assuming a typical household
might utilize 146,000 gallons per year (AWWARF,
2005), the water passing through one treatment plant
at a rate of 100 gpm would be the equivalent to the
amount of water consumed by approximately 360
households.
It is important to consider the value of the treated
water when evaluating discharge options. In some
cases, where ground water resources are limited, it
may be important to return treated water to the
subsurface so that adequate water levels are
maintained, or to use the treated water directly for
water supply. In other cases, significant costs
savings and avoided energy use may be realized by
reusing the treated water in place of other water
supplies. Examples might include use of treated
1
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water for irrigating crops or as cooling water within
a factory. In addition, treated water can be utilized
to create or augment wetland habitats.
The following sections provide details regarding
various options for discharge of treated water. In
each case, a section called "Sustainability
Considerations" is included to highlight how the
specific discharge option relates to the value of the
treated water as a potential resource.
C. DISCHARGE TO SURFACE WATER
Exhibit 1
General description
Under the National Pollution Discharge Elimination
System (NPDES), treated water may potentially be
discharged directly to a nearby surface water body or
indirectly to surface water through a storm sewer.
Figure 1 schematically illustrates this discharge
option, and more information is discussed below.
General advantages and disadvantages of this
discharge option are provided in Exhibit 1.
Figure 1
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TREATMENT PU
System Design, Permitting, and Project Planning
EPA is authorized to implement the NPDES
program (and associated permitting) but has
authorized several States to implement all or part of
the NPDES program in their own State. Information
regarding the NPDES program can be found at the
following website:
For most ground water P&T systems, the NPDES
permit includes effluent limits, monitoring and
Discharge to Surface Water;
Advantages and Disadvantages
Potential Advantages
Discharge is typically not subject to a flow-
based fee, but some storm sewer systems
may charge a fee.
Potential Disadvantages
Discharge standards are based on ambient
water quality and may be comparable or
more stringent than drinking water standards.
Reporting may be more rigorous than for
other discharge options. Environmental
toxicity testing may be needed.
Removal of natural constituents in ground
water may required to discharge water.
Access to a nearby surface water body or
storm sewer is needed.
Public may have negative perception of
discharging treated water from a
contaminated site to surface water.
reporting requirements, and site-specific conditions.
The permits are obtained by filing a standard
application with EPA or the authorized State.
The site-specific discharge limits are developed by
EPA or the authorized State by considering
standards based on available treatment technologies,
water quality, and whole effluent toxicity (WET).
Limits are typically derived for the following types
of pollutants (in addition to WET):
toxic pollutants (including the contaminants
of concern)
conventional pollutants (e.g., total
suspended solids, pH, oil and grease, etc.)
non-conventional pollutants (e.g., chlorine
and ammonia)
Limits on temperature, dissolved oxygen, and flow
rate may also be considered to address concerns
regarding aquatic life and erosion control. The large
variety of pollutants considered means that treatment
criteria may be established for many constituents
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that are not actually contaminants of concern at the
site. As a result, discharge to surface water may
require treatment of more constituents than would be
required for other discharge options. Exhibit 2
provides a list of constituents that typically have a
surface water discharge limit and would be relatively
expensive to treat as part of a typical P&T system,
yet may not be a contaminant of concern at many
sites. If these constituents are in the extracted water
at concentrations above discharge standards,
additional treatment may be required. It is common
for the site team to evaluate the life-cycle costs of
such additional treatment and to compare these costs
with the costs for other discharge options.
Discharge of treated water to surface water may
change the surface water body from gaining (i.e.,
ground water discharges to the surface water body)
to losing (i.e., surface water discharges to ground
water). This change in system hydraulics could have
a negative or positive effect on the ability of the
P&T system to control contaminant migration. If
the discharge from surface water to ground water
occurs within or upgradient of the plume, it may
cause the plume to spread or require a higher
extraction rate to provide plume capture. However,
if the discharge occurs downgradient, it may help
prevent plume migration.
Exhibit 2
Discharge to Surface Water:
Potential for Parameters that are not
"Constituents of Concern" to Impact Costs
In some cases, parameters that are not considered to
be constituents of concern at a site may nevertheless
have a concentration limit associated with a permit for
discharge to surface water. Examples might include
the following parameters:
* iron
• manganese
• arsenic
• other metals (e.g., copper, nickel)
• pH
* ammonia
• nitrate and/or nitrite
• phosphate
In such cases, additional treatment costs may be
incurred simply to meet the surface water discharge
requirements for these parameters. As a result, other
discharge options that do not have similar limits for
these parameters may be more cost-effective.
The distance and terrain from the P&T system to the
discharge point can also affect the practicability of
discharge to surface water. The following
parameters are generally favored when selecting this
(and other) discharge options:
a short distance between the P&T system
and the discharge point
minimal infrastructure between the P&T
system and the discharge point
• a discharge point that is lower in elevation
than the P&T system (allows for gravity
discharge rather than forced pumping)
Sampling, reporting, and other ongoing costs
generally play a minor role in determining if
discharge to surface water is the most appropriate
discharge option. The sampling and reporting,
which is typically conducted on a monthly basis, is
similar to that for other discharge options. In
addition, there is usually no ongoing usage fee for
discharge to surface water. However, such fees can
be substantial when present. For example, discharge
to the Thea Foss Waterway in Tacoma, Washington,
is one example of where such a fee has been applied
(U.S. EPA 2001). In that case, a fee of
approximately $5,000 per month was applied to the
50 gpm of treated water discharged to the storm
sewer, which increased the annual costs of the
remedy by approximately $60,000 per year.
Sustainability Considerations
If the treated water is discharged to surface water in
a manner that precludes the further beneficial use of
that water, such as discharge to a creek that
ultimately empties into the ocean, then the value of
that treated water as a potential resource may be lost.
In some cases, however, the treated water is
discharged into a receiving body that serves as a
reservoir such that the treated water will eventually
be used for drinking water, irrigation, industrial
purposes, or some other beneficial use. In these
cases, the treated water displaces the use of water
from other sources, and therefore helps conserve
water as a natural resource.
Treated water can also be used to help restore or
replace habitat that was previously lost due to
contamination or that is lost due to other aspects of
an environmental remedy. The reliable flow of
treated water from a P&T system can be used to
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Example 1
Discharge to Surface Water at a Rural Site
The site is a former chemical manufacturing facility
in a rural setting. Some of the key site conditions
relevant to selecting a discharge option are as follows:
The site is not located near urban
infrastructure that would allow for discharge
to a storm sewer or POTW.
Reuse of treated water for industry or
agriculture is not viable.
Due to remedy pumping, seeps that formed a
small tributary to a nearby creek may no
longer flow, effectively destroying a small
riparian habitat.
There is limited area on site to return water
to the subsurface without adversely affecting
plume capture.
With the exception of the presence of
contaminants of concern, the extracted water
meets typical criteria for discharging to
surface water.
Selected Discharge Option
The site team opted to discharge treated water to the
area where the seeps historically discharged. The
discharge location has been designed to minimize
erosion associated with a point discharge. Therefore,
this discharge option will replace the riparian habitat
that would otherwise be destroyed by pumping.
Ongoing costs associated with this discharge option
consist of routine sampling of the effluent in
association with an NPDES permit and regular filing
of a discharge monitoring report.
establish flow in a creek or wetlands or to augment
flow in a stream. In these cases, the treated water
does not necessarily displace the use of other water
or conserve water as a natural resource, but it does
provide additional value through the created habitat.
Site teams can incorporate sustainable
environmental practices by considering the fate of
the treated water when screening discharge to
surface water as a discharge option. Example 1
illustrates the use of surface water as an appropriate
discharge location for a P&T system because it
provides a cost-effective means of discharging
treated water while creating a small riparian habitat
that was displaced during other aspects of the
environmental remedy.
D. RETURN OF TREATED WATER TO THE
SUBSURFACE
General description
Treated water can be returned to the subsurface
through infiltration basins, infiltration galleries, or
injection wells, as follows:
An infiltration basin allows treated water to
seep through the ground surface in a
controlled area.
• An infiltration gallery includes a subsurface
network of perforated pipes in trenches that
return the treated water below the surface
but above the water table.
An injection well returns the treated water to
the saturated zone in either a water table
aquifer or a deeper confined aquifer.
These approaches are schematically illustrated on
Figure 2. Advantages and disadvantages for this
discharge option are summarized Exhibit 3.
System Design, Permitting, and Project Planning
The return of treated water to the subsurface
generally requires a permit authorized by the State.
It may also require a permit under the Underground
Injection Control (UIC) Program, which regulates
the injection of fluids into the subsurface through an
injection structure where the depth is greater than the
largest surface dimension or through a subsurface
fluid distribution system. These structures typically
include injection wells, shafts, dug holes, and
infiltration galleries but would not include shallow
infiltration basins. The injection structures covered
by the UIC Program are divided into five classes,
and Class V applies to the reinjection of treated
ground water.
The U.S. EPA (U.S. EPA 2005a) notes that over 30
States have primacy for the UIC Program (i.e., have
authorization to administer the UIC Program), and
these States have generally incorporated the UIC
Program into a broader program for reinjection. For
example, New Jersey has primacy for the UIC
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Figure 2
TO
Program and uses a Ground Water Discharge
NJPDES permit for discharges to ground water.
This permit includes the UIC Program components.
For the remaining States, EPA has or shares primacy
with each State. In such cases, a permit may be
needed from the State for a discharge to ground
water, and if a Class V UIC structure is used, a UIC
permit from EPA would likely apply. For example,
EPA implements the UIC program in New York,
and two permits would apply for discharge to
ground water. One permit is under the New York
SPDES program, and the other is under the EPA
UIC program. More information on the UIC
Program can be found at the following website:
http://www.cpa.gov/safcwatcr/uic/indcx.litml
The permits associated with the above-mentioned
programs (such as the New Jersey Ground Water
Discharge Permit) regulate the construction of the
reinjection structure and the monitoring of the
treated water that is injected. If reinjection occurs
immediately adjacent to a receiving surface water
body, the reinjection may also fall under the NPDES
program, which as described in the previous section
may be implemented by either the U.S. EPA or the
State.
The following factors are involved in selecting
return of treated water to the subsurface as a
discharge option:
• constructability
maintenance
role in the ground water remedy
• discharge limits and monitoring
requirements
Each of these factors is discussed in more detail
below.
Constructability
It is important that the subsurface materials be able
to accept the flow rate of water that is being
discharged. Infiltration basins and galleries are
typically limited to areas that meet all of the
following criteria:
• There is sufficient space to accommodate
the discharge flow rate.
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The vadose zone is sufficiently permeable to
allow water to percolate to the water table.
There is a water table aquifer to receive the
water.
• There is sufficient distance between the
bottom of the injection point and the water
table.
If any of these criteria are not met, then an
infiltration basin or gallery is likely not an
appropriate discharge option. Exhibit 4 notes some
of the design criteria for infiltration basins
associated with stormwater applications that can be
used as a rule of thumb.
Injection wells require less space than infiltration
basins or galleries. In addition, injection wells can
return water to deeper aquifers that may more
readily accept the discharged water.
The quality of the discharged water and the
geochemistry of the receiving ground water also
play a large role in determining whether or not
return of treated water to the subsurface is an
appropriate discharge option. Treated water with
high solids or metals, such as iron or manganese, can
clog an infiltration basin or gallery and increase
maintenance requirements. Similarly, microbial
activity and/or precipitation of iron, manganese,
calcium, or other metals can clog (or foul) an
injection well. Fouling of injection wells may occur
much more frequently than fouling of extraction
wells because the treated water may have higher
dissolved oxygen concentrations from aeration
during treatment, and this dissolved oxygen can
foster the microbial activity and/or the metals
precipitation. Potential for fouling can be assessed
based on quality of the discharged water and the
geochemistry of the receiving ground water.
Maintenance
Unlike other discharge options, such as discharge to
surface water or to a POTW, returning the treated
water to the subsurface typically involves routine
maintenance. The degree of maintenance depends
on the rate of fouling. Maintenance may involve
removal of sediments, precipitated metals, and other
fine solids that clog the basin and reduce infiltration.
For infiltration galleries, high pressure jetting may
be helpful in removing fines from the perforated
piping. However, over time, the gravel and sand
Exhibit 3
Return of Treated Water to the Subsurface:
Advantages and Disadvantages
Potential Advantages
« Discharge standards are typically similar to
drinking water standards, but for some
constituents, such as ammonia, standards
may be more relaxed than those for
discharging to surface water.
• Unlike discharge to surface water, there
generally are not requirements to remove
some natural ground water constituents prior
to returning treated water to the subsurface.
• Returning treated water to the subsurface can
be used to augment hydraulic containment or
flush a contaminant source. These potential
benefits should be considered in the
extraction system design.
• Return of treated water to the subsurface
helps conserve ground water as a natural
resource, which is particularly beneficial in
areas where ground water serves as a sole
source for drinking water or where
dewatering is a concern.
Potential Disadvantages
* Reinjection into the plume may compromise
plume capture by spreading the plume.
Additional hydrogeological analysis (perhaps
including modeling) may be necessary in
designing such an approach.
• Reinj ection wells and infiltration structures
may need more maintenance than other
discharge options, especially due to solids or
biological fouling.
• There is potential to discharge contaminants
that are present at the site, currently unknown
to the site team, and not readily treated by the
employed treatment technologies. Recent
examples might include sites with
perchlorate and 1,4-dioxane. This could
result in dispersing a contaminant plume and
increasing the cost of cleanup.
surrounding the perforated pipe may need to be
replaced. For injection wells, chemical treatments or
well redevelopment might be appropriate but are
quite expensive if they are conducted frequently.
The U.S. Army Corps of Engineers Engineering
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Pamphlet 1110-1-27 titled Operation and
Maintenance of Extraction and Injection Wells
at HTRWSites (USAGE 2000) documents
Exhibit 4
Common Design Considerations for
Infiltration Basins
The following are common criteria for properly
locating and designing infiltration basins. The criteria
are generally developed for the purpose of infiltrating
stormwater, but many of the criteria apply to returning
treated water to the subsurface.
* Allow sufficient distance between the bottom
of the infiltration basin and the seasonal high
water table (2 feet to approximately 10 feet,
depending on local regulations).
* Select an area with a minimum soil
infiltration rate of 0.5 inches per hour. The
clay content should be less than 20% and
clay/silt content should be less than 40% to
provide adequate infiltration.
• Allow vegetation growth within basin to
promote infiltration.
• Avoid construction of infiltration basins on
slopes that are greater than 10%.
• Avoid sediment loading to the infiltration
basin to reduce the potential for clogging.
« Design basin area using the infiltration rate
and the anticipated flow rate. The area of the
basin times the infiltration rate should be
greater than or equal to the anticipated flow
rate.
« Avoid ponding to foster vegetation growth,
minimize anaerobic conditions, and prevent
mosquitoes.
The above information has been collected from review
of selected best management practice handbooks,
including those from California and New Jersey.
• California Stormwater BMP Handbook,
California Stormwater Quality Association,
TC-11, January 2003
• New Jersey Stormwater Best Management
Practices Manual, Chapter 9.5: Standard for
Infiltration Basins, February 2004
common practices for maintaining and rehabilitating
injection wells.
A treatment plant can be designed or enhanced to
remove metals or other constituents that add
significantly to fouling; however, this enhanced
treatment might be more expensive to construct and
operate than maintaining an infiltration basin,
infiltration gallery, or reinjection well. It is often
helpful to consider the life-cycle costs of the various
options, which includes consideration of annual
O&M costs, rather than focusing on the option with
the lowest upfront cost.
Role in the Ground Water Remedy
The return of treated water to the subsurface can
play an important role in the performance of a
ground water remedy. The returned water can be
designed to positively impact the ground water
remedy in the following ways:
Contaminant flushing can be enhanced by
returning treated water upgradient of the
plume and extraction system, or in a zone
where contamination is present in the
unsaturated zone.
• Degradation of remaining contamination in
the subsurface can be enhanced through the
addition of oxygen and/or nutrients to the
returned water.
Hydraulic containment of impacted ground
water can be enhanced by returning treated
water to the subsurface and creating a
hydraulic divide, particularly downgradient
of the extraction wells.
Negative impacts that might be caused by
ground water extraction, such as reduced
ground water discharge to wetlands or
dewatering of water supply well screens, can
potentially be mitigated by returning the
treated water to the subsurface.
Evaluation of these impacts may include analysis
with ground water modeling.
Return of treated water to the subsurface can also
have a negative impact on the ground water remedy
in the following ways:
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Frequent fouling of the infiltration or
injection structures can result in frequent
system shutdowns.
• Returning treated water into the plume can
result in spreading of the plume and could
compromise plume capture.
Returning treated water in close proximity to
the extraction wells can result in the
extraction of treated water rather than
contaminated water, which can compromise
plume capture and/or slow progress toward
aquifer restoration.
Discharge Limits and Monitoring Requirements
The discharge limits associated with return of treated
water to the subsurface are determined by each State
under its own ground water protection program.
Typically, the limits for contaminants of concern are
equal to the cleanup standards for those
contaminants. If the discharge limits are less
stringent, it is generally advisable to treat the water
to the cleanup standard so that the treated water does
not serve as a continuing "source" of ground water
contamination. Because ground water does not
support aquatic life like surface water, the discharge
limits for some constituents that are not
contaminants of concern in ground water may be
much higher than the discharge limits for surface
water. If returning treated water to the subsurface
will prevent costly treatment of these non-
contaminant constituents, then it may be more cost-
effective compared to discharge to surface water.
Sustain ability Considerations
Discharge of treated water to the subsurface may
effectively store the treated water as ground water
that can be used at a later time. If the treated water
is returned to a usable aquifer with similar quality to
that of the treated water, then the extracted and
treated water has been conserved as a resource.
However, if water is extracted from a deep aquifer of
high quality (other than the contamination that will
be removed by treatment) but is returned to a
shallow aquifer of low quality, then the extracted
and treated ground water has not been conserved as
a resource.
Discharging the treated water to the subsurface to
enhance the performance of the ground water
remedy may represent a sustainable environmental
practice because it offsets the energy and expense of
using an alternative to provide the same effect. For
example, injecting the treated water upgradient of
the plume to enhance contaminant flushing could
shorten the duration of P&T operation and reduce
overall amount of energy consumed or water
extracted. Injecting treated water downgradient of
the extraction wells may reduce the flow rate
required for capture, which may reduce energy costs
associated with pumping and/or treatment.
Example 2 provides an example of returning treated
water to the subsurface as an appropriate discharge
Example 2
Returning Treated Water to the Subsurface
to Enhance Remedy Effectiveness
A site with a chlorinated solvent plume has
trichloroethene (TCE) contamination. Some of the
key site conditions relevant to selecting a discharge
option are as follows:
Contaminants of concern (i.e., TCE and
associated breakdown products) are easily
removed using air stripping or GAC.
Iron concentrations in the extracted water
are approximately 1 mg/L, which is not
enough to foul the treatment system if it is
properly maintained and cleaned. This
concentration meets the criteria for
discharging to the subsurface but does not
meet the criteria for discharging to surface
water.
Reuse of treated water is not a viable
option, and the flow rate is too high for
discharging to the POTW.
Bag filters placed after an air stripper can
provide solids removal for reasonable
protection of an infiltration gallery, if used.
Selected Discharge Option
The site team opted to discharge treated water to the
subsurface to avoid the need to add metals removal
to the treatment system in order to meet surface
water discharge standards. Although this option
will involve regular cleaning of the air stripper and
periodic maintenance of an infiltration gallery,
those costs are lower than operating and
maintaining a treatment system with metals
removal.
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option for a P&T system because treatment system
O&M is substantially reduced relative to other
discharge options.
E. DISCHARGE TO THE POTW OR OTHER
ON-SITE TREATMENT
General description
With this option, extracted water is discharged to a
publicly-owned treatment works (POTW) through
the sanitary sewer line or to a facility's on-site
wastewater treatment plant that can provide
appropriate treatment. In some cases, discharge can
occur with no other treatment needed, and in other
cases, pre-treatment may be required to meet the
POTW requirements of certain compounds. More
information on this discharge option is discussed
below, primarily in the context of discharging to a
POTW, and general advantages and disadvantages
of this discharge option are provided in Exhibit 5.
System Design, Permitting, and Project Planning
Discharge to a POTW is typically negotiated with
the local municipality, which issues a permit
governing the discharge. Because a POTW is a
treatment plant, it generally accepts water with much
higher concentrations of organic compounds than
would apply at other discharge locations. However,
discharges that would interrupt operation or pass
through the POTW without adequate treatment are
prohibited. In September 2005, EPA provided a
revised rule on pre-treatment for discharging to a
POTW in a document titled Streamlining the
General Pretreatment Regulations for Existing and
New Sources of Pollution (U.S. EPA 2005b).
Regulations generally stipulate that discharges from
some industrial facilities (such as metal finishing)
receive pretreatment prior to discharge to a POTW.
Ground water remediation systems are not such
facilities; however, some ground water remediation
systems address such sites, and, therefore, the
POTW may use this as a basis for requiring
pretreatment. Although this may be appropriate at
some sites, at others, it may result in additional
expense with little environmental benefit.
The typical discharge limit for total toxic organics
(TTO) to a POTW is 2.13 mg/L. At many (but not
all) sites, this is higher than the combined influent
from the extraction wells, making it possible to
implement a "pump and discharge" remedy rather
than a P&T remedy. Certain chemicals, such as
acetone, 2-butanone (MEK), and 4-methyl-2-
pentanone (MIBK), are not included in the
calculation of TTO. These compounds, which are
all classified as ketones, are difficult to treat with
common economical ground water treatment
technologies such as air stripping and carbon
adsorption. However, they are readily treated by the
biological processes used in a POTW. Discharge of
these chemicals to the POTW is typically limited to
those quantities that will not result in vapors that are
harmful to workers. Therefore, for a site where the
contaminants are TCE and acetone, it may be most
Exhibit 5
Discharge to the POTW or
Other On-Site Treatment;
Advantages and Disadvantages
Potential Advantages
This option often has less stringent discharge
standards and monitoring requirements,
especially for organics. Generally,
municipalities use a discharge limit of 2.13
mg/L for total toxic organics, which is a
higher concentration than the influent to
many P&T systems.
Ketones and ammonia, which are difficult to
treat with P&T systems, are easily treated by
POTWs.
The POTW provides a secondary treatment
for some constituents to prevent (except in
extreme cases) damage to surface water
receptors.
Potential Disadvantages
If the POTW is near capacity, it may not
accept treated ground water discharge.
In certain areas where ground water is the
sole source of drinking water, return of
treated water to the subsurface may be
necessary.
The POTW may be reluctant to accept water
that has certain constituents or is relatively
"clean" compared to typical sewer water.
Discharge to a POTW becomes quite costly
for high flow rates relative to other options.
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cost-effective to treat the TCE with air stripping and
discharge the water to the POTW. Acetone is not
removed by air stripping but is effectively treated at
the POTW.
The practicality of discharge to a POTW or on-site
treatment plant is typically limited by the following:
• There may be current or future limitations of
the POTW or on-site treatment plant to
accept additional flow.
• Constituents in the discharge may not meet
the criteria of the POTW or the on-site
treatment plant requirements for
pretreatment.
• The distance and terrain between the P&T
system and a connection point to the POTW
or on-site treatment plant may be too far to
be cost-effective.
• For discharging to the POTW, the unit cost
associated with the discharge, which is
typically based on the flow rate, may be too
high to be cost-effective.
Each of these factors is site-specific, but one item of
note is the discharge fee, which can be a substantial
component of annual operating costs for a P&T
system that discharges to a POTW. Costs for
discharging treated water to a POTW typically range
from $0.003 per gallon to $0.03 per gallon (2007
dollars). For a P&T system with a flow rate of 10
gpm and a POTW cost of $0.03 per gallon (i.e., $3
per 100 gallons), this translates to an annual cost of
over $150,000 per year. In some cases, the fee may
be worth paying if certain aspects of treatment
(construction and/or O&M) can be avoided.
Therefore, a site team should compare the life-cycle
costs of discharge to the POTW with life-cycle costs
for other alternatives. Generally, due to cost, the
POTW option will compare less favorably with
other options as the flow rate increases.
Sustain ability Considerations
Discharge to a POTW generally does not conserve
the extracted ground water as a resource. The water
discharged to the POTW is treated and then typically
discharged to surface water. However, by using a
POTW (or on-site treatment plant) as a component
of the P&T treatment process, unnecessary or
redundant treatment components can be eliminated.
Example 3
An Optimization Evaluation
Recommendation to Discharge to a POTW
A P&T system, installed over 10 years ago, treats a
variety of organic compounds, including ketones,
using a bioreactor at flow rate of approximately 8
gpm. The organic contaminant concentrations are
relatively dilute (e.g., approximately 1 mg/L).
Treated water is discharged to marine surface water.
An optimization evaluation suggested a change in the
discharge option from surface water to the POTW,
citing the following reasons:
Maintenance and solids handling of the
current treatment system requires a full-time
operator at a cost of $120,000 per year.
Partially due to its age, the current treatment
system is down more than 20% of the time.
At a flow rate of 8 gpm and a POTW
discharge rate of $0.01 per gallon, discharge
to the POTW would be approximately
$42,000 per year.
By discharging to the POTW, operation of
the treatment system can be discontinued
and maintenance costs decreased to $40,000
per year, representing a cost savings of
approximately $38,000 per year.
There would be no net loss in the potential
use of the treated water by discharging it to
the POTW because water from the current
treatment system is discharged to marine
surface water without reuse.
Example 3 illustrates an optimization evaluation
recommendation to change the discharge option
from surface water to a POTW to reduce annual
costs without sacrificing remedy effectiveness.
F. REUSE OF TREATED WATER
General description
With this option, the treated water is used directly
for another application, such as process water for an
industrial facility, water for irrigation, creation or
enhancement of wetlands, or in some cases, as a
potable water supply (see Figure 3). More
information on this discharge option is discussed
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below, and general advantages and disadvantages of
this discharge option are provided in Exhibit 6.
Figure 3
Exhibit 6
System Design, Permitting, and Project Planning
The primary applications for reuse of treated water
are as follows:
process or cooling water for industry
• irrigation water
• creation or enhancement of wetlands
drinking water
Availability of this option is typically determined by
the distance and terrain between the P&T system and
the specific location for reuse.
The following are some of the factors that apply
when considering treated water for industrial process
or cooling water:
• The discharge will now be part of plant
operations and can have an effect on plant
output. Wastewater and air discharge
permits may need to be modified if the
treated water is used as process water.
• Aspects of treated water unassociated with
environmental cleanup, such as hardness,
pH, or total solids, may be an important
factor in using the treated water as process
water. The treatment requirements for using
the treated water as process water may be
more stringent than treatment requirements
for other discharge options, as follows:
Reuse of Treated Water:
AdYantages and Disadvantages
Potential Advantages
Reuse of treated water reduces or eliminates
the need for a facility or organization to use
water from other sources, thereby conserving
water as a natural resource and potentially
reducing utility costs.
Reuse can be cost-effective relative to other
discharge options at some sites.
Reuse may be viewed positively by the
community if water is a scarce natural
resource.
Potential Disadvantages
For use in irrigation, drinking water supply,
or wetlands creation/enhancement, specific
Federal and State regulations may be
applicable, or relevant and appropriate.
Additional testing or monitoring relative to
other discharge options may be needed.
Additional system conservatism (e.g., an
additional GAC vessel) may be needed
compared to treatment systems without direct
discharge to human receptors.
Reusing water in industrial processes may
involve additional treatment relative to
discharging the water elsewhere. Reused
water should be treated to meet the facility
standards and any downstream discharge
standards. Treating to facility standards may
be more costly than discharging to another
location and using public water at the
facility.
Facilities may operate on a part-time basis,
and the P&T system may need to operate
continuously. If continuous extraction with
batch treatment during facility hours is not
available, reuse may not be feasible.
A backup discharge point should be available
in case the needs of the facility change.
Contaminants that are undetected using
current analytical techniques or contaminants
that are present as tentatively identified
compounds (TICs) may not be removed by
treatment, causing a potential risk to end
users of the water.
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- The quantity and continuity of the
treated water may differ from that
required for industrial operations.
- The P&T system flow rate may be lower
than the process water needs.
- The maintenance schedule and
downtime for the P&T system may
make the treated water an unreliable
source for process water.
- The P&T system may have a higher
flow rate or may operate at times when
process water is not needed.
Each of the above scenarios may complicate the use
of treated water as process or cooling water, but
many of them can be overcome by having a backup
or supplementary source of process water, or a
backup or supplementary discharge option.
With respect to potential use of treated water for
irrigation, wetlands creation/enhancement, or water
supply, public perception may play a significant
role. For these applications, it is appropriate to
obtain community acceptance prior to making
substantial investments in the design and
construction of the discharge process. Additional
failsafes or redundancies that might not be
appropriate for other discharge options may also be
required. In addition, it is advisable to sample for a
wider range of parameters to ensure that additional
chemicals are not passing through the treatment
system at unacceptable levels.
Sustain ability Considerations
The direct reuse of treated water displaces the use of
other water, and, therefore, conserves water as a
natural resource. Additional energy would also not
be used in obtaining water from another source, such
as a production well. With the creation or
enhancement of wetlands, anew ecological resource
is provided.
Example 4 provides an example of using discharge
of treated water for irrigation. In the scenario
described in the example, reuse for irrigation is an
appropriate discharge option for a P&T system
because it is cost-effective and displaces the use of
other water resources.
Example 4
Use of Treated Water for Irrigation
A P&T system, located in a desert environment,
treats approximately 100 gpm of ground water
impacted with low levels of VOCs. Some of the
key site conditions relevant to selecting a discharge
option are as follows:
A surface water discharge point or storm
sewer is not located near the site, and
discharging to the POTW is prohibitively
costly due to the flow rate.
Returning ground water to the subsurface
is a possibility.
The site is located near a public golf course
that needs frequent irrigation.
The water table is over 200 feet below
ground surface, which makes the
electricity for pumping water a significant
cost for the P&T system and for the
neighboring golf course.
The treatment technologies are predictable
and reliable. The system is designed to
treat to "non-detect" levels. Redundancies
and failsafes are included to avoid
exceedances.
Selected Discharge Option
The site team selected two interchangeable
discharge locations. The primary discharge location
is to return the treated water to the subsurface, but
when irrigation at the golf course is needed, the
treated water is preferentially diverted to the golf
course irrigation system. These discharge options
preserve the value of the treated water by using it
for irrigation or returning it to the subsurface. In
addition, by using the treated water directly for
irrigation, electricity and several thousand dollars
per year in electricity costs are saved by avoiding
the cost of pumping water for irrigation.
G. SELECTING AN APPROPRIATE
DISCHARGE OPTION
Selecting an appropriate discharge option involves
the use of experienced professionals evaluating
several criteria, including those mentioned in this
fact sheet. This fact sheet provides important
considerations, but cannot provide a comprehensive
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framework for selecting a discharge location,
particularly given important site-specific factors that
include contaminants of concern, hydrogeology,
treatment components, infrastructure, and
regulations.
H. REFERENCES
American Water Works Association Research
Foundation (AWWARF), Residential End Uses of
Water Report, 2005
California Stormwater BMP Handbook, California
Storm water Quality Association, TC-1 1, January
2003
New Jersey Stormwater Best Management Practices
Manual, Chapter 9. 5: Standard for Infiltration
Basins, February 2004
< httpi//www jijstormwatcr .grg/binp_manual2_Jitm >
U.S. EPA (2001) Remediation System Evaluation,
Comm. Bay/South Tacoma Channel, Well 12A
Superfund Site EPA 542-R-02-008q, December
2001
< http://www.cluin.org/optimization >
U.S. EPA (2005a) Underground Injection Control
(UIC) Program
3aj^
U.S. EPA (2005b) Streamlining the General
Pretreatment Regulations for Existing and New
Sources of Pollution: Final Rule, September 27,
2005
< http://www.epa.gov/npdes >
USAGE (2000) Operation and Maintenance of
Extraction and Injection Wells at HTRW Sites,
Engineering Pamphlet 1 1 10-1-27, 27 January 2000
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NOTICE:
This document may be downloaded from EPA's Clean Up Information (CLUIN) System at http:7/www.cluin.org.
Hard copy versions are available free of charge from the National Service Center for Environmental Publications
(NSCEP) at the following address:
U.S. EPANSCEP
P.O. Box 42419
Cincinnati, OH 45242-2419
Phone: (800) 490-9198
Fax: (301) 604-3408
nscep@bps-lmit.com
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t
United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
EPA 542-R-07-006
May 2007
www.cluin.org
www.epa.gov/superfund
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