United States
                       Environmental Protection
                       Agency
 Office of Water
 Washington, D.C.
EPA 832-F-00-023
September 2000
                       Waste water
                       Technology  Fact Sheet
                       Wetlands:  Subsurface  Flow
DESCRIPTION

Wetland systems are typically described in terms of
the position of the water surface and/or the type of
vegetation grown. Most natural wetlands are free
water surface systems where the water surface is
exposed to the atmosphere; these include bogs
(primary  vegetation  mosses),  swamps  (primary
vegetation trees), and marshes (primary vegetation
grasses and emergent macrophytes). A subsurface
flow (SF) wetland is  specifically designed for the
treatment or polishing of some type of wastewater
and are typically constructed as a bed or channel
containing appropriate media. An example of a SF
wetland is shown in Figure 1. Coarse rock, gravel,
sand and other soils have all been used, but a gravel
medium is most common in the U.S. and Europe.
The medium is typically planted with the same types
of emergent vegetation present in marshes, and the
water surface is designed to remain below the top
surface of the medium. The main advantages of this
subsurface water level are prevention of mosquitoes
and odors, and  elimination of the risk of public
contact with the partially treated wastewater.  In
contrast, the water surface in natural marshes and
free water surface (FWS) constructed wetlands is
exposed to the atmosphere with the attendant risk of
mosquitoes and public access.

The water quality improvements in natural wetlands
had been  observed by scientists and engineers for
many years and this led to the development of
constructed wetlands  as an attempt to replicate the
water quality and the habitat benefits of the natural
wetland in a constructed ecosystem.   Physical,
chemical,  and biochemical reactions all contribute to
water  quality  improvement  in  these wetland
  Optional Inlet
  Manifold Warm
   Climates f|
                   Vegetation
  Inlet Zone
  2" to 3"
  Gravel
    Inlet Manifold
    Cold Climates
                          Water
                Treatment Zone   Surface
                V," to 1V," Gravel
         Outlet Zone
          2" to 3"
          Gravel
      Outlet
      Manifold
         Membrane Line or
         Impermeable Soils
Source: Adapted from drawing by S.C. Reed, 2000.

     FIGURE 1  SUBSURFACE FLOW
                WETLAND

systems. The biological reactions are believed due
to the activity of microorganisms attached to the
available submerged substrate surfaces. In the case
of  FWS  wetlands  these  substrates  are  the
submerged portion of the living plants, the plant
litter, and the benthic soil layer.  In SF wetlands the
available submerged substrate  includes the plant
roots growing in the media, and the surfaces of the
media themselves. Since the media surface area in
a SF wetland can far exceed the available substrate
in a FWS wetland, the microbial reaction rates in a
SF wetland can be higher than a FWS wetland for
most contaminants. As a result, a SF wetland can
be smaller than the FWS type for the same flow rate
and most effluent water quality  goals.

The design goals for SF constructed wetlands are
typically an exclusive commitment to treatment
functions because wildlife  habitat and  public
recreational opportunities are  more limited than
FWS wetlands. The size of these systems ranges

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from small on-site units designed to treat septic tank
effluents to a 1.5x107 liters per day (4 MOD) system
in Louisiana treating municipal wastewater.  There
are approximately 100 systems in the U.S. treating
municipal wastewater, with the majority of these
treating less than 3.8x103 nrVday (1 MOD). Most of
the municipal systems are preceded by facultative or
aerated treatment ponds.  There are approximately
1,000 small scale on-site type systems in the U.S.
treating  waste  waters  from individual  homes,
schools,  apartment   complexes,   commercial
establishments,   parks,   and  other  recreational
facilities.  The  flow from these smaller  systems
ranges from  a  few hundred  gallons  per  day to
151,400 liters per day (40,000 gallons per day),
with septic tanks being the dominant  preliminary
treatment provided.   SF wetlands are  not now
typically selected for larger flow municipal systems.
The higher cost of the rock or gravel media makes
a large SF  wetland uneconomical  compared to a
FWS wetland in spite of the smaller SF wetland area
required. Cost comparisons have shown that at flow
rates above 227,100 liters per day (60,000 gallons
per day) it will usually be cheaper to construct a
FWS   wetland   system.    However,  there  are
exceptions  where  public access, mosquito,  or
wildlife issues justify selection of a SF wetland. One
recent example is a SF wetland designed to treat the
runoff from  the Edmonton Airport  in Alberta,
Canada. The snow melt runoff is contaminated with
glycol de-icing fluid  and a SF  wetland treating
1,264,190 liters per day (334,000 gallons per day)
was selected to minimize habitat values and bird
problems adjacent to the airport runways.

SF wetlands typically include one or more shallow
basins or channels with a barrier to prevent seepage
to sensitive groundwaters. The type of barrier will
depend on  local  conditions.   In  some  cases
compaction of the local soils will serve adequately,
in other cases clay  has  been imported or plastic
membrane   (PVC   or   HDPE)  liners   used.
Appropriate inlet and outlet structures are employed
to insure uniform distribution and collection of the
applied wastewater. A perforated manifold pipe is
most  commonly used  in the smaller systems. The
depth of the media in these SF wetlands has ranged
from 0.3 to 0.9 meters (1 to 3 feet) with 0.6 meters
(2 feet) being most common.  The size of the media
in use in the U.S.  ranges from fine gravel (>0.6
centimeters  or > 0.25  in.)  to large crushed rock
(>15.2 centimeters or  >6 in.); A combination of
sizes from 1.3 centimeters to 3.8 centimeters (0.5 to
1.5 inches)  are most typically used. This gravel
medium should be clean, hard, durable stone capable
of retaining  it's shape and the permeability of the
wetland bed over the long term.

The most commonly used emergent vegetation in
SF wetlands include cattail (Typha spp.), bulrush
(Scirpus spp.), and reeds (Phragmites spp.).  In
Europe, Phragmites are the preferred plants for
these systems. Phragmites have several advantages
since it is a  fast growing hardy plant and is not a
food source for animals or birds. However, in some
parts of the U.S.  the  use  of Phragmites is not
permitted because it is an aggressive plant and there
are concerns that it might infest natural wetlands. In
these cases cattails or bulrush can be used. In areas
where muskrat or nutria are found, experience has
shown  that these animals, using the plants for food
and nesting material, can completely destroy a stand
of cattails or bulrush  planted  in a constructed
wetland.  Many  of the smaller  on-site  systems
serving  individual  homes  use  water  tolerant
decorative plants. The vegetation on a SF wetland
bed is not a major factor in nutrient removal by the
system and  does not require harvesting.  In cold
climates, the accumulating plant litter on top of the
gravel bed provides useful thermal insulation during
the winter months.  The submerged plant roots do
provide substrate for microbial processes and since
most emergent macrophytes can transmit oxygen
from the leaves  to their roots there are aerobic
microsites on the rhizome and root surfaces. The
remainder of the  submerged environment in the SF
wetland tends to be devoid of oxygen. This general
lack  of  available  oxygen limits  the  biological
removal of ammonia nitrogen (NH3/NH4  - N) via
nitrification in these SF wetlands, but the system is
still  very effective for removal  of BOD, TSS,
metals, and  some priority pollutant organics since
their treatment can occur under  either  aerobic or
anoxic  conditions.  Nitrate removal via biological
denitrification can also be very effective since the
necessary anoxic conditions are always present and
sufficient carbon sources are usually available.

The  limited availability of oxygen  in these SF
systems reduces the capability for ammonia removal

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via biological nitrification.  As  a  result,  a long
detention  time in a very large wetland  area is
required to produce low levels of effluent nitrogen
with typical municipal wastewater influents unless
some system modification  is  adopted.   These
modifications have included installation of aeration
tubing at the bottom of the bed  for mechanical
aeration,  the use  of an integrated gravel trickling
filter for nitrification of the wastewater ammonia,
and vertical flow wetland beds. These vertical flow
beds usually contain gravel or coarse sand  and are
loaded intermittently   at the top  surface.   The
intermittent  application  and  vertical  drainage
restores aerobic conditions in the bed permitting
aerobic reactions to proceed  rapidly. Cyclic filling
and draining of a horizontal flow system  has been
successfully demonstrated at the 130,000  gallons
per day SF wetland system  in Minoa,  NY.  The
reaction rates for BOD5 and ammonia removal
during these cyclic operations were double the rates
observed  during  normal  continuously  saturated
flow.

The phosphorus removal mechanisms available in all
types of constructed wetlands  also require long
detention times to produce low effluent levels of
phosphorus with typical municipal wastewater. If
significant  phosphorus  removal  is a  project
requirement then a FWS wetland will probably be
the most cost effective type of constructed wetland.
Phosphorus removal is also possible with final
chemical addition and mixing prior to a final deep
settling pond.

The   minimal  acceptable  level  of  preliminary
treatment  prior to a  SF  wetland  system  is the
equivalent  of primary treatment.   This  can be
accomplished with septic tanks or Imhoff tanks for
smaller  systems  or  deep ponds  with a short
detention time for larger systems.  The majority of
existing SF wetland systems treating  municipal
waste waters are preceded by either facultative or
aerated ponds. Such ponds are not necessarily the
preferred type of preliminary treatment. At most of
these existing systems the SF wetland was selected
to improve the water quality of the pond effluent.
Since the  SF wetland can provide very effective
removal for both BOD5 and TSS, there is no need to
provide for  high levels of removal  of these
constituents in preliminary treatments.
The SF wetland does not provide the same level of
habitat value as the FWS wetland because the water
in the system is not exposed and accessible to birds
and animals. However, wildlife will still be present,
primarily in the form of nesting animals, birds, and
reptiles.  If provision of more  significant habitat
values is a project goal it can be accomplished with
deep ponds interspersed between the  SF wetland
cells.  The first pond in such a system would be
located  after  the point where water quality is
approaching at least the  secondary level

APPLICABILITY

SF wetland  systems are best suited  for  small to
moderate sized applications (< 227,100 liters/day or
<60,000  gallons per day) and  at larger systems
where the risk of public contact, mosquitoes, or
potential odors are  major concerns. Their use for
on-site systems provides a high quality effluent for
in-ground disposal, and in some States  a significant
reduction in the final disposal field area is allowed.
SF wetlands will reliably remove BOD, COD, and
TSS, and with sufficiently long detention times can
also produce low levels of nitrogen and  phosphorus.
Metals are removed effectively and about a one log
reduction in  fecal coliforms can be  expected in
systems designed to produce secondary or advanced
secondary effluents.

ADVANTAGES AND  DISADVANTAGES

Some advantages and disadvantages of subsurface
flow wetlands are listed  below.

Advantages

       SF wetlands provide effective treatment in a
       passive manner  and minimize mechanical
       equipment, energy, and skilled  operator
       attention.

•      SF  wetlands  can  be  less  expensive to
       construct and are usually less expensive to
       operate and maintain  as compared  to
       mechanical treatment processes designed to
       produce the same effluent quality.

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       Year-round   operation   for  secondary
       treatment is possible in all but the coldest
       climates.

       Year-round  operation  for  advanced  or
       tertiary treatment is possible in warm  to
       moderately  temperate climates. The SF
       wetland  configuration   provides   more
       thermal protection than the FWS wetland
       type.

       SF wetland systems produce no residual
       biosolids  or sludges requiring  subsequent
       treatment and disposal.

       The SF wetland is very effective and reliable
       for removal of BOD, COD, TSS, metals,
       and some persistant organics in municipal
       wastewaters.  The removal of nitrogen and
       phosphorus to low levels is also possible but
       requires a much longer detention time.

       Mosquitoes and similar insect  vectors are
       not a problem with SF wetlands as long as
       the  system is  properly  operated  and a
       subsurface water level maintained. The risk
       of contact  by   children  and pets  with
       partially   treated  wastewater  is   also
       eliminated.
Disadvantages
       A SF wetland will require a large land area
       compared  to  conventional  mechanical
       treatment processes.

       The removal of BOD, COD, and nitrogen in
       SF  wetlands  are  continuously renewable
       processes.  The phosphorus,  metals, and
       some  persistent organics removed in the
       system are bound in the wetland sediments
       and accumulate over time.

       In  cold  climates the  low winter water
       temperatures reduce the rate of removal for
       BOD,  NH3,  and  NO3.   An  increased
       detention time can  compensate for these
       reduced rates but the increased wetland size
       in extremely cold climates may not be cost
       effective or technically possible.
•      Most  of the  water contained in the SF
       wetland  is  anoxic and  this  limits  the
       potential for nitrification of wastewater
       ammonia. Increasing the wetland size and
       detention time will compensate, but this may
       not be cost effective. Alternative methods
       for nitrification in  combination with a SF
       wetland have been successful.  SF wetlands
       cannot be designed for complete removal of
       organic  compounds, TSS,  nitrogen, and
       coliforms. The natural ecological cycles in
       these  wetlands   produce  "background"
       concentrations of these substances in the
       system effluent.

       SF wetland systems can typically remove
       fecal coliforms by at least one log. This is
       not always  sufficient to meet  discharge
       limits in all locations and post disinfection
       may be required. UV disinfection has been
       successfully  used  in   a  number   of
       applications.

       Although SF wetlands can be smaller than
       FWS  wetlands for the removal of most
       constituents, the high cost of the gravel
       media in the SF wetland can result in higher
       construction costs for SF systems larger
       than about 227,100 liters per day (60,000
       gallons per day).

DESIGN CRITERIA

Published models for the design of SF wetland
systems have been available since the late 1980's.
More recent efforts in the mid to late  1990's have
produced three text books containing design models
for SF wetlands (Reed, et al 1995, Kadlec & Knight
1996, Crites & Tchobanoglous, 1998). In all three
cases, the models are based on first order plug flow
kinetics, but results do not always agree due to the
author's  developmental  choices  and  because the
same databases  were not used for derivation of the
models. The Water Environment Federation (WEF)
presents a comparison of the three approaches in
their Manual of Practice on Natural Systems (WEF,
2000)  as  does  the US  EPA design manual on
wetland systems (EPA, 2000). The designer of a SF
wetland system  should consult these references and
select the method best suited for the project under

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consideration.  A preliminary estimate of the land
area required for a SF wetland can be obtained from
Table 1 of typical areal loading rates. These values
can also  be used to check  the results  from the
previously cited references.

The SF wetland size is determined by the pollutant
which requires the largest land area for it's removal.
This is the bottom surface area of the wetland cells
and, for that area to be 100 percent effective, the
wastewater flow must be uniformly distributed over
the entire surface. This is possible with constructed
wetlands by careful grading of the bottom surface
and use of appropriate inlet and outlet structures.
The total treatment area should  be divided into at
least two cells  for all  but the  smallest systems.
Larger systems should have at  least two parallel
trains of cells to provide flexibility for management
and maintenance.

These wetland systems are living ecosystems  and
the life  and death cycles of the biota produce
residuals  which can  be  measured as BOD, TSS,
nitrogen, phosphorus and fecal coliforms.  As a
result, regardless of the size of the wetland or the
characteristics of the influent, in these systems there
will always be a residual background concentration
of these  materials.  Table  2  summarizes these
background concentrations.

It  is necessary for the  designer to determine the
water temperature  in  the wetland because  the
removal of BOD, and the various nitrogen forms are
temperature dependent. The water temperature in
                        large systems with a long URT  (>10 days)  will
                        approach the average air temperature except during
                        subfreezing weather in the winter. Methods for
                        estimating the water temperature for wetlands with
                        a  shorter URT (<10 days) can be found in the
                        published references mentioned previously.

                        It is also necessary to consider the hydraulic aspects
                        of system  design  because  there is  significant
                        frictional resistance to flow through the wetland
                        caused by the presence of the gravel media and the
                        plant roots  and other detritus. The major impact of
                        this flow resistance is on the configuration selected
                        for the wetland cell.  The longer the flow path the
                        higher  the  resistance  will be.  To  avoid these
                        hydraulic problems an aspect ratio (L:W) of 4:1 or
                        less is recommended.   Darcy's law  is generally
                        accepted as the model for the flow of water through
                        SF wetlands and descriptive information can again
                        be  found in the  published references mentioned
                        previously. The flow of water through the wetland
                        cell depends on the hydraulic gradient in the cell and
                        on the hydraulic conductivity (ks), size, and porosity
                        (n) of the  media used.  Table 3  presents typical
                        characteristics for potential  SF  wetland media.
                        These values can be used for a preliminary estimate
                        and for design of very  small systems.  For large
                        scale systems the proposed media should be tested
                        to determine these values.
   TABLE 1  TYPICAL AREAL LOADING RATES FOR SF CONSTRUCTED WETLANDS
 Constituent
  Typical Influent
Concentration mg/L
  Target Effluent
Concentration mg/L
 Note: Wetland water temperature » 20°C.
Mass Loading Rate
     Ib/ac/d*
Hydraulic Load (in./d)
BOD
TSS
NH3/NH4 as N
NO3 as N
TN
TP
3 to 12**
30to175
30to150
2 to 35
2 to 10
2 to 40
1 to 10

10 to 30
10 to 30
1 to 10
1 to 10
1 to 10
0.5 to 3

60 to 140
40 to 150
1 to 10
3 to 12
3 to 11
1 to 4

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      TABLE 2 "BACKGROUND" SF
      WETLAND CONCENTRATIONS
Constituent
BOD5
TSS
TN
NH3/NH4 as N
NO3 as N
TP
Fecal Coliforms
Units
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
MPN/100ml
Concentration
Range
1 to 10
1 to 6
1 to 3
less than 0.1
less than 0.1
less than 0.2
50 to 500
 Source:  Reed et al., 1995 and U.S. EPA, 1993.

PERFORMANCE

A lightly loaded SF wetland  can achieve the
"background" effluent levels given in Table 2.  In
the general  case, the SF constructed wetland is
typically  designed to produce a specified effluent
quality and Table 1  can be used for a preliminary
estimate  of the size of the  wetland necessary to
produce the desired effluent quality.  The design
models in the referenced publications will provide a
more precise estimate of treatment area required.
Table 4 summarizes actual performance data for 14
SF wetland systems included in  a US  EPA
Technology Assessment (EPA, 1993).
                        In theory, the performance of a SF wetland system
                        can be influenced by hydrological factors. High
                        evapotranspiration (ET) rates may increase effluent
                        concentrations, but this also increases the HRT in
                        the  wetland.  High  precipitation rates dilute the
                        pollutant concentrations but also shorten the HRT
                        in the wetland.   In  most temperate  areas with a
                        moderate climate these influences are not critical for
                        performance. These hydrological aspects need only
                        be  considered for  extreme  values of ET  and
                        precipitation.

                        OPERATION AND MAINTENANCE

                        The routine operation and maintenance (O&M)
                        requirements for  SF  wetlands are similar to those
                        for facultative lagoons, and include hydraulic and
                        water depth control, inlet/outlet structure cleaning,
                        grass  mowing  on  berms,  inspection  of berm
                        integrity, wetland vegetation management,  and
                        routine monitoring.

                        The water depth in the wetland may need periodic
                        adjustment  on a  seasonal basis or in response to
                        increased resistance over a very long term from the
                        accumulating detritus in the media  pore  spaces.
                        Mosquito control should not be required for a SF
                        wetland system  as  long as  the water level is
                        maintained  below the top  of the media surface.
                        Vegetation management in these SF wetlands does
                        not include a routine harvest  and removal of the
           TABLE 3  TYPICAL MEDIA CHARACTERISTICS FOR SF WETLANDS
        Media Type
Effective Size D
     (mm)*
                                       10
Porosity, n (%)
        * mmx 0.03937 = inches
        ** ft3/ft2/d x 0.3047 = m3/m2/d, or x 7.48 = gal/ft2/d
        Source:  Reed et al., 1995.
Hydraulic Conductivity ks
       (ft3/ft2/d)*
Coarse Sand
Gravelly Sand
Fine Gravel
Medium Gravel
Coarse Rock
2
8
16
32
128
28 to 32
30 to 35
35 to 38
36 to 40
38 to 45
300 to 3,000
1,600 to 16,000
3,000 to 32,000
32,000 to 160,000
16x104to82x 104

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       TABLE 4 SUMMARY OF PERFORMANCE FOR 14 SF WETLAND SYSTEMS*
     Constituent
  Mean Influent mg/L
    Mean Effluent mg/L
     BOD5
     TSS
     TKN as N
     NH3/NH4 as N
     NO3 as N
     TN
     TP

     Fecal Conforms (#/100ml)
     28** (5-51)***
      60(23-118)
       15(5-22)
       5(1-10)
       9(1-18)
       20 (9-48)
        4 (2-6)
270,000(1,200-1,380,000)
        8** (1-15)***
        10  (3-23)
          9(2-18)
          5(2-10)
         3(0.1-13)
          9(7-12)
         2 (0.2-3)
57,000(10-330,000)
     *  Mean detention time 3 d (range 1 to 5 d).
     ** Mean value.
     *** Range of values.
     Source:  U.S. EPA, 1993.

harvested material.  Plant  uptake  of pollutants
represents a relatively minor pathway so harvest and
removal  on  a routine  basis does  not provide a
significant   treatment  benefit.     Removal  of
accumulated  litter  is unnecessary, and  in  cold
climates it serves  as thermal insulation to prevent
freezing  in  the   wetland  bed.     Vegetation
management may also require wildlife management,
depending on the type of vegetation selected for the
system, and the position of the water. Animals such
as nutria and  muskrats  have  been known to
consume  all  of  the  emergent  vegetation  in
constructed wetlands. These animals should not be
attracted to a SF wetland as long as the water level
is properly  maintained.  Routine  water  quality
monitoring will be required for  all SF systems with
an NPDES permit, and the permit will specify the
pollutants and frequency.  Sampling for NPDES
monitoring  is usually  limited to  the untreated
wastewater and the final system effluent.  Since the
wetland component is usually  preceded by some
form   of preliminary  treatment,  the  NPDES
monitoring program does not  document wetland
influent characteristics.  It is recommended, in all
but the smallest systems that periodic samples of the
wetland  influent   be  obtained  and  tested  for
operational purposes in addition to the  NPDES
requirements. This will allow the operator a better
understanding of wetland performance and provide
a basis for adjustments if necessary.
            COSTS

            The major items included in the capital costs for SF
            wetlands are similar to many of those required for
            lagoon systems. These include  land costs,  site
            investigation, site clearing, earthwork, liner, gravel
            media, plants, inlet and outlet structures, fencing,
            miscellaneous piping,  etc.,  engineering,  legal,
            contingencies ,  and contractor's  overhead and
            profit.  The gravel media and the liner can be the
            most expensive items from this list. In the Gulf
            States where clay soils often eliminate the need for
            a liner the  cost of imported gravel  can  often
            represent 50 percent of the construction costs. In
            other locations where local gravel is available but a
            membrane liner  is required the liner costs   can
            approach 40 percent of the construction costs. In
            many  cases compaction of the in-situ native soils
            provides  a  sufficient barrier  for groundwater
            contamination.   Table  5  provides  a summary of
            capital and O & M costs for a hypothetical 378,500
            liters/day (100,000 gallons per day)  SF constructed
            wetland,  required to achieve a 2 mg/L ammonia
            concentration in the effluent.   Other calculation
            assumptions are as follows: influent NH3= 25 mg/L,
            water temperature 20°C (68°F), media depth = 0.6
            meters (2 ft), porosity = 0.4, treatment area =1.3
            hectares (3.2 ac), land cost=$12,355/hectare ($5,000/ac).

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  TABLE 5 CAPITAL AND O&M COSTS FOR 100,000 GALLONS PER DAY SF WETLAND
Item
Land Cost
Site Investigation
Site Clearing
Earthwork
Liner
Gravel Media**
Plants
Planting
Inlets/Outlets
Subtotal
Engineering, legal, etc.
Total Capital Cost
O&M Costs, $/yr
Native Soil Liner
$16,000
3,600
6,600
33,000
0
142,100
5,000
6,600
16,600
$229,500
$133,000
$362,500
$6,000/yr
Cost $*
Plastic Membrane Liner
16,000
3,600
6,600
33,000
66,000
142,100
5,000
6,600
16,600
$295,500
$171,200
$466,700
$6,000/yr
 * June 1999 costs, ENR CCI = 6039
 **12,000 cy of 0.75 in. gravel


  TABLE 6  COST COMPARISON SF WETLAND AND CONVENTIONAL WASTEWATER
                                     TREATMENT

Cost Item

Capital Cost
O &M Cost
Total Present Worth Costs*
Cost per 1000 gallons treated**


Wetland
$466,700
$6,000/yr
$530,300
$0.73
Process

SBR
$1,104,500
$106,600/yr
$2,233,400
$3.06
*Present worth factor 10.594 based on 20 years at 7 percent interest (June 1999 costs, ENR CCI = 6039).
**Daily flow rate for 365 d/yr, for 20 yr, divided by 1000 gallons

Source: WEF, 2000.
Table 6  compares the life cycle  costs  for this    REFERENCES
wetland to the cost for a conventional treatment
system designed for the same flow and effluent    Other Related Fact Sheets
water quality.  The  conventional process  is a
sequencing batch reactor (SBR).                   Free Water Surface Wetlands
                                              EPA 832-F-00-024
                                              September, 2000

                                              Other  EPA Fact  Sheets can be found  at the
                                              following web address:
                                              http://www.epa.gov/owmitnet/mtbfact.htm

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1.     Crites, R.W.,  G.  Tchobanoglous (1998)
      Small  and  Decentralized  Wastewater
      Management Systems,  McGraw Hill Co.,
      New York, New York.

2.     Kadlec, R.H., R.  Knight (l996)Treatment
      Wetlands,  Lewis  Publishers, Boca Raton,
      Florida.

3.     Reed, S.C., R.W. Crites, E.J. Middlebrooks
      (1995)  Natural   Systems  for   Waste
      Management and Treatment - Second
      Edition, McGraw Hill Co, New York, New
      York.

4.     U.S.  EPA (1999) Free  Water Surface
      Wetlands for  Wastewater  Treatment: A
      Technology Assessment, US EPA, OWM,
      Washington, DC.  (in press.)

5.     U.S.  EPA   (2000)  Design  Manual
      Constructed  Wetlands  for   Municipal
      Wastewater Treatment, US EPA  CERI,
      Cincinnati,  Ohio (in press.)

6.     US.   EPA  (1993)    Subsurface  Flow
      Constructed  Wetlands for  Wastewater
      Treatment A Technology Assessment, EPA
      832-R-93-008,   US  EPA  OWM,
      Washington, DC.

7.     Water Environment   Federation  (2000)
      Natural Systems for Wastewater Treatment,
      MOP FD-16, WEF, Alexandria, Virginia (in
      press.)

ADDITIONAL INFORMATION

Southwest Wetlands Group
Mr Michael Ogden
901 W. San Mateo, Suite M,
Santa Fe, NM 87505

City of Mandeville
Mr Joe Mistich, Public Works Director
3101 E. Causway Approach
Mandeville, LA 70448-3592
TVA
Mr James Watson
311 Broad Street, HB 25 27OC - C
Chattanooga, TN 37402-2801

EMC Group, Inc.
Mr Charles King
PO Box 22503
Jackson, MS 39205

Village of Minoa WWTP
Mr Steve Giarrusso
213 Osborne Street
Minoa, NY 13116

The mention of trade names or commercial products
does not constitute endorsement or recommendation
for use by  the U.S. Environmental Protection
Agency.
         For more information contact:

         Municipal Technology Branch
         U.S. EPA
         Mail Code 4204
         1200 Pennsylvania Avenue, NW
         Washington, D.C., 20460
                                                         »MTB
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                                                        MUNICIPAL  TECHNOLOGY BRANCH

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