United States September
Environmental Protection 1983
Agency
830F83100
Figure 3 Wetland Costs vs. Distance
Capital Costs
Information on the construction cost for wetlands
treatment reveals that this alternative is competitive
with other treatment technologies available to
smaller communities. In Figure 3, the additional
capital cost to provide tertiary treatment for
secondary effluent utilizing wetlands is shown as a
percentage of the additional costs using other
treatment methods.
shown in Figure 4. The c;: /eel in Figure 4
reflect a transport distance of approximately 3 miles
and a land cost of approximate
Operation and Maintenance Costs
Operation and maintenance (O&M) costs for
wetlands systems are relatively low due to:
Low labor and energy requirement.
Use of natural treatment components.
Adaptability to use with inexpensive preapplication
treatment systems, such as primary treatment,
stabilization ponds, and aerated lagoons.
Creation of wildlife habitats can increase
recreational and educational opportunities.
Consistently meeting treatment objectives
requires conscientious management in the use of
wetlands as in other wastewater treatment
processes.
&EPA An Emerging
Technology
Wetlands
Treatment
A Practical
Approach
rigure 4 uapitai uosts
Table 3 Annual O&M Costs
In Table 3. actual O&M costs for two wetland
systems (one using natural wetlands and the
second using constructed wetlands) are shown.
Actual O&M costs for each system will vary due to
different labor rates, energy cost, monitoring
requirements, and other factors.
Summary
Wetlands can achieve high removal efficiencies
for biological oxygen demand, suspended solids.
and nitrogen.
Costs compare favorably to other treatment
systems due to:
Utilization o' 'and
Mini-
Lev.
Simplicity of Oi
For additional information contact:
EPA-OWPOIWH-5471
EPA Region 1
EPA Region 2
JY 10278
EPA Region 3
6th & V
EPA Region 4
EPA Region 5
EPA-RSKERL
EPA Region 6
i, Street
EPA Region 7
324 Ea'
EPA Region 8
1860 Lin-
EPA Region 9
A 94105
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Wetlands Treatment A Practical Approach
The Task Ahead
The increasing costs of treatment often place
greater financial pressure on smaller towns than on
their larger neighbors. Nevertheless, these
communities recognize their responsibility for
protecting the environment while providing
adequate wastewater treatment. Such communities
are searching for the most practical approach to
meeting their treatment needs while being receptive
to emerging technologies.
Wetlands treatment has fulfilled those needs with
cost-effective facilities in various locations around
the country. Wetlands treatment can also improve
the wildlife habitat features of "nutrient poor" natural
wetlands through the application of beneficial
nutrients in wastewater. The combination of
effective treatment with environmental benefits
offers a potentially attractive solution to wastewater
treatment needs.
Description
WETLANDS may be defined as land where water
is near or above the ground surface at such
frequency that plants adapted to saturation in their
root zone are normally present. Wetlands include
marshes, swamps, bogs and similar areas.
Wetland treatment is the process by which the
quality of water applied to a natural or constructed
wetland is improved. The improvement is achieved
through the interaction of the applied effluent waters
with the wetland's vegetation, micro-organisms, and
soils. A schematic of the wetlands treatment
process is shown in Figure 1
Wetlands treatment can utilize either naturally
occurring or constructed wetlands. One NATURAL
WETLAND system is located near Houghton Lake,
Michigan, where pretreated wastewater is
transported to a 500-acre state-owned peat marsh.
The system design includes an elevated wooden
walkway which supports irrigation pipelines and
allows access for operation and maintenance
without disturbing the wetland surface.
Figure 1 Wetlands Flow Schematic
Figure 2 Houghton Lake Wetlands System
Walkway and Gated Irrigation Pipeline
Figure 2 is a view of the Houghton Lake distribution
system. Operation records document that a high
level of treatment is achieved with minimal impact
on the marsh. Increased vegetation resulting from
the wetland treatment enhances the wildlife food
supply of this nutrient poor area so that, with time.
the productivity of this marsh tends to improve.
CONSTRUCTED WETLANDS can be developed
on suitable sites. Factors to be considered in site
selection are: existing topography, soil condition,
and the distance and elevation difference between
the potential site and the pretreatment facilities.
Constructed wetlands have shown the ability to
provide wastewater treatment while becoming a
haven for wildlife. Another beneficial feature is the
potential to accept higher application rates by
providing a less sensitive (more adaptable)
environment than natural wetlands.
In strip mine areas or other barren lands, the
irrigation of treated effluent could transform large
unproductive tracts into productive wetlands. In
regions that lack viable marsh habitat for wildlife,
the use of constructed wetlands could significantly
increase the wildlife population and provide new
educational opportunities for students and
naturalists.
Preapplication treatment is often required prior to
wetlands application. Techniques utilized may
include: screening for solids removal, biological
treatment for partial BOD removal, and/or
disinfection. Table 1 depicts several features to be
considered in the design of a wetland treatment
system.
Table 1 Wetlands Treatment System
Design 'Features
Table 2 Operating Wetland Systems
Table 2 lists a number of operational facilities which
are successfully utilizing wetlands treatment.
Potential Limitations
Evaluation of the use of wetlands for wastewater
treatment must consider the possible limitations as
well as the benefits of such systems. Possible
limitations include:
Wastewater Characteristics - Wetlands treatment
may not be suitable for treatment of wastewaters
containing high levels of pesticides, refractory
chemicals, or heavy metals.
Climate - In northern climates, treatment may be
limited by dormant vegetation and frozen
conditions. Therefore, seasonal treatment with the
wastewater held in holding ponds during the cold
weather period may be required to meet
treatment objectives.
Site Availability - The availability of a suitable
wetland site in the vicinity of the preapplication
treatment facilities is a critical factor. As shown in
Figure 3, the distance to the wetland site is a
major factor in determining the cost-effectiveness
of wetlands treatment.
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