Constructed
Wastewater
Management
fofConflned
Animal Feeding
'^-'
'•
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Acknowledgments
Funding for this brochure was provided by the
Nutrient Enrichment Issue Committee of the Gulf of
Mexico Program (GMP). Dr. Douglas Lipka was the
acting director of the GMP. Co-chairs of the Nutrient
Enrichment Issue Committee were Lon Strong of the
Natural Resources Conservation Service (NRCS) and
Dugan Sabins of the Louisiana Department of
Environmental Quality. The United States
Environmental Protection Agency (EPA) provided
financial support for this project under the GMP. The
EPA project officer was Lloyd Wise.
A portion of this project was funded through an EPA
grant to the National Council of the Paper Industry
for Air and Stream Improvement (NCASI). Dr. Robert
Fisher was project manager. NCASI also provided
matching funds for additional work on the treatment
wetland technology. GH2M HILL was a contractor to
NCASI to complete this effort. Key participants at
CH2M HILL were Dr. Robert Knight, John Pries,
Robert Borer, Ronald Clarke, and Tara Boonstra.
A portion of this project was funded through the
Alabama Soil and Water Conservation Committee
(ASWCC). Stephen Cauthen was executive secretary.
Victor Payne of Payne Engineering was a contractor
to the ASWCC.
Funded by:
wEPA
U.S. Environmental Protection Agency
* Gulf of Mexico Program
Nutrient Enrichment Issue Committee
Published by:
CH2MHILL
Gainesville, Florida
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Constructed
Wetlands
and Animal
Wastewater
Management
Dairy, cattle, swine, and poultry producers can help
improve the quality of our streams, lakes, rivers, and
. estuaries by reducing the amount of pollutants
released with wastewater. To do so, producers need
practical and cost-effective ways to treat wastewater
before it leaves the farm. One of those treatment
options is a constructed wetland—a treatment system
that uses natural processes to improve water quality.
Constructed wetlands have been treating other kinds
of wastewaters for many years, and, as this brochure
demonstrates, they show promise for treating
wastewaters from confined animal feeding operations
as well. Designed to be an overview of how wetland
systems can be used to manage wastewater, this
brochure introduces the following topics: • : .
at wetland systems
are and how they work
»How wetland systems have
performed for existing
confined animal feeding
operations
Wow to incorporate a wetland
into a wastewater' ;
management system ,
What is involved in designing
and constructing a wetland
"system .
"Where to 'get more information
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It AppliedY/7 excess, the land
or water cannot handle the
nutrients and pathogens in
*
wastewatersfrom
aqtiacuttuce and other
confined animal feeding
operations. As a result, the
ecological balance Is
disrupted, and plants and
animals die.
Relationship between
Confined Animal Production
and Water Quality
After 30 years of trying to reduce water pollution, it is still a
major concern in North America. We have made progress with
reducing the amount of pollution discharged in pipes (called
point source pollution). Now we are paying more attention to
reducing pollution that enters water bodies through surface
runoff. This type of water pollution is called nonpoint source
pollution and is typically contributed by land-intensive
activities such as agriculture, forestry, and mining, and urban/
commercial development.
Agriculture has been identified as one of the major generators of
nonpoint source pollution. Eroded soils, farm chemicals, and
manure find their way into streams, lakes, rivers, and estuaries.
As a result, agricultural producers have been and will continue
to be asked to reduce the amount of pollution leaving the farm.
At the same time that producers are being asked to reduce
pollution, agricultural operations are becoming more
concentrated, making wastewater management an even 5
more important issue. .-••".-.""
Farmers and ranchers have already responded to concerns
about water quality by taking steps to reduce the amount of
pollution they generate and release into the environment. The
greatest progress has been in the control of soil erosion, which
has reduced the amount of solids entering water bodies.
For many confined animal feeding operations, the challenge is
to prevent manure from being discharged with the water. The
organic matter and nutrients in the manure are important
resources that need to be recycled to the land to maintain high
crop productivity. However, released into natural water bodies,.
the organic matter and nutrients promote algal growth and
deplete dissolved oxygen, leading to further problems.
to reduce pollution while maintaining or increasing
productivity, confined animal operators need practical ways to
either prevent wastewater from entering surface water and
groundwater or treat the water before it leaves the farm.
Operators want wastewater management systems that are
affordable, reliable, and practical to build and operate.
Today, various technologies are available to treat wastewater in
ways that use the natural chemical, physical, and biological
processes of the environment and that rely on nature's energies.
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One of these technologies is a constructed wetland system.
Constructed wetlands mimic the water purification properties of .
natural wetland systems. These constructed wetlands use the
same plants, soils, and microorganisms as natural wetlands to
remove contaminants, nutrients, and solids from the water.
Constructed wetlands have been used for years to treat
municipal wastewater, industrial wastewater, and stormwater.
More recently, they have been used in confined animal feeding
operations before discharge or land application of wastewater.
Results from existing constructed wetlands on farms suggest that
these systems can help in several ways. Constructed wetlands
can remove solids and nutrients from wastewater so that more
effluent can be land applied to a given area or discharged to
surface water. Constructed wetlands also help minimize odor
problems, reduce labor costs associated with hauling and
applying effluent, and provide aesthetic and wildlife benefits.
Constructed wetlands can be integrated into the farm in a way
that benefits the operator and neighbors.
fif/7 additionto
treating
wastewater,
wetland systems
can be attractive
additions to farming
operations.
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How Wetlands Work
Once considered worthless, wetlands are now recognized as one
of the most diverse and productive ecosystems in the world.
Wetlands dean water, produce food and fiber, provide wildlife
habitat, recharge the groundwater, reduce flooding, and offer
recreational opportunities.
Natural wetlands have received wastewater ever since people
began to live in towns and cities. Scientists soon realized that
natural wetlands were more than just a convenient disposal
site—the wetlands were actually cleaning the water. As a result,
researchers began to investigate using natural and constructed
wetlands purposely to improve water quality. Some of the
earliest investigations were in Europe, and since then treatment
wetlands throughout North America have been studied,
mostly for treating municipal and industrial wastewaters and
stormwater. Using wetlands specifically for improving water
quality has been studied for about 40 years. During the past 5 .to
10 years, this technology has been researched for treating waste-
water from confined animal feeding operations in particular.
Incoming
Wastewater
Transformation
and
Volatilization
(Carbon, Nitrogen)
Sedimentation
andSorption
(5-Day Biochemical
Oxygen Demand,
Total Suspended
Solids, Nitrogen,
Phosphorus)
Diffusion
(Nitrogen,
Phosphorus)
I. 1
Outgoing
Wastewater
-Wetland treatment systems use ',
natural processes and energies
to transform or trap pollutants.
All treatment wetlands, constructed or natural, have the same
general components of landform, water, soil, plants, microbes,
plant litter (also called organic matter or detritus), and fauna. As
a result of physical, biological, and chemical processes that take
place in a wetland environment, many pollutants in the water
flowing through the system are transformed or inactivated. The
low flow rate of the water'and the long time the water stays in
-------
the wetland (called residence time) result in the settling and
trapping of solids in the wastewater.
The plants provide a place for
microbes to attach. These microbes
take nutrients from the water to
grow. The processes by which
microbes transform and remove
pollutants from the water are
complex. With nitrogen, for
example, microbes ammonify
nitrogen (convert organic nitrogen
to ammonia, which is used by
plants as a. nutrient); nitrify
nitrogen (convert ammonia to
nitrite and nitrate, which is used by bacteria and some plants
for growth); and denitrify nitrogen (volatilize nitrogen, which
is lost to the atmosphere). As a result of these processes, excess
nitrogen is removed from the water.
Wetland plants also absorb nutrients, and like the microbes,
they convert the nutrients into a form that they use for growth.
As the process of uptake, transformation, and release of
nutrients in the wetland repeats itself, some of the nutrients in
the system are trapped in the soils or released into the air. The
result is water that is cleaner than when it entered the wetland.
Although some natural wetlands still receive highly treated
wastewater, more often constructed wetlands are being ^
designed and built to treat higher strength wastewaters.
Wetlands are constructed by excavating a shallow area,
installing water control structures, and planting wetland
vegetation. If the site has highly permeable soils, additional
excavation may be required so that an impervious, compacted
clay liner can be installed. In this case> the original soil is
placed over the liner to be the growth medium for plants. The
wetland vegetation is either planted manually or allowed to
grow naturally from seeds. Wastewater flows across the
bottom at a shallow depth, receiving treatment asit meanders
through the plant stems and litter.
Constructed
wetlands provide
multiple benefits,
including wildlife
support.
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^Although more than 68
animal wastewater
treatment wetlands exist in
North America, the study
focused on systems with
published information on
the wetland's design and
performance. The map
below shows the number
of systems found in each
state or province.
1-2 3-8 9-18 >19
Number of Welfare! Systems
Performance of Existing
Wetland Systems
Constructed wetlands have been improving water quality at
confined animal feeding operations for years. The study of
published information that led to this brochure was based on
accounts of farms using such systems throughout the United
States and Canada. In fact, despite skepticism that wetland
systems would work in cold climates, research has shown that
these systems function even under ice and snow.
A literature review identified information for 68 different
sites using constructed wetlands to treat wastewater from
confined animal feeding operations. Overall, the wetlands
reduced the concentration of wastewater constituents such as
5-day biochemical oxygen demand (BOD5), total suspended
solids (TSS), ammonium nitrogen (NH4-N), total'
nitrogen (TN), and total phosphorus (TP).
Table 1 shows the average treatment
performance.
Of the 68 sites identified, 46 were at
dairy and cattle feeding
".'" operations. The herd
: sizes ranged from 25
to 330, with an
average of 85 head.
Dairy wastewater often
included water from
milking barns and from
feeding/loafing yards with
varying characteristics. Cattle
feeding wastewaters typically
came from areas wher_e animals
were confined. Usually, dairy and
cattle wastewaters were pretreated or
diluted before being discharged to
constructed wetlands.
Swine operations accounted for 19 of the
wetland sites in the study. Swine wastes were collected using
flushwater from solid floor barns and paved lots, or they were
collected directly from slatted floors in farrowing or nursery
barns.-In many cases, the wastewater was pretreated in lagoons
and then discharged to a wetland system to further reduce
concentrations to a level that could be applied to the land.
8
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For poultry and aquaculture farms, the study found published
information on constructed wetlands at one poultry site and two
aquaculture sites. Although the data in this brochure do not
cover all animal waste categories, they apply in general to
planning new wetland systems.
TABLE! .
Summary of Average Performance of Wetlands Treating
Wastewater fromConfined Animal Feeding Operations"
Average Concentration (mg/Lf
fastewater Constituent
5-Day biochemical oxygen demand (BODS)
Total suspended solids (TSS)
Ammonium nitrogen (NH4-N)
Total nitrogen (TN)
Total phosphorus (TP)
Inflow
263
585
122
254
24
Outflow
93
273
64
148
14
Average Reduction (%)
65
,53
' 48
42
42
* Data from the Livestock Wastewater Treatment Wetland Database (LWDB), which.includes wefland systems at dairy, cattle,
swine, poultry, and aquaculture sites (Knight et al. 1996). b Average concentration is based on a hydraulic loading rate of 1.9
inches per day (50,000 gallons per day per acre [gpd/ac]). Averages were calculated from data for 30 to 86 systems.
mg/L = milligrams per liter ' . ' . . ; '
Although percent reductions of 42 to 65 percent are impressive,
the average outflow concentrations in Table 1 are not low '
enough to allow discharge to surface water; instead, the effluent
is usually collected and land applied. However, by reducing
pollutant loadings to constructed wetlands by increasing
pretreatment or the wetland area^ effluent pollutant concentra- ,i - , :
tions would approach those typical of municipal treatment
wetiands summarized in Table 2. In some cases, the effluent •.'...;..-':., :- : : "-''"'•
may be suitable for discharge to surface waters.
TABLEZ •_ .......-.._. , - -. ,
Summary of Average Performaince of Wetlands Treating
Municipal Wastewater3 ' ;
Wastewater Constituent
BODS
TSS
Average Concentration (mg/L)f
Inflow Outflow Average Reduction (%)
NH4-N
TN
TP
30
46
4.9
9.0
3.8
8
14
2.2
4.3
1.6
74
70
54
53
57
" Data from the North American Treatment Wetland Database^ (NADB) (Knight et al. 1993). "Average
concentration is based on a hydraulic loading rate of 1.3 inches per day (34,000 gpd/ac):
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Pretreatment
K
I Wetland |
* Si
1
Irrigation =j
Stream •
m wetland system
can provide final
. polishing before.
the wastewateris
applied to the land .
or discharged to
surface waters.
Incorporating
a Constructed Wetland
into a Wastewater
Management System
Typically, producers use a variety of methods to manage
wastewater. Some of these methods are lagoons, ponds, storage
structures, compost areas, filters, and sediment basins. A con-
structed wetland offers another option for polishing wastewater
before it is recycled as flushwater, land applied, or ultimately
discharged. This section discusses the following important
considerations to evaluate whether a constructed wetland is
right for your operation:
*§ystem goals—hi what cases would a wetland system
be beneficial? A wetland can help decrease wastewater
pollutant levels, decrease odors, reduce the amount of land
needed for wastewater application, meet surface water
discharge regulations, and enhance the landscape.
• msi • - - -. -, ^ _. ,
tPretreatment—Does the wastewater need to be treated
before it goes to the wetland system? Nearly always,
. wastewater from confined animal feeding operations needs
to be pretreated. Otherwise, high pollutant concentrations
may overload the wetland system.
*Wastewater characteristics—What pollutants are in the
wastewater? Nitrogen, phosphorus, and organic, oxygen-
demanding substances (measured as BOD5) are the main
pollutants of concern. Information on these pollutants is
important to adequately size a constructed treatment
wetland and determine effluent concentrations.
rastewater volume—How much wastewater will be
discharged to the wetland? The calculation of wastewater '
volume is critical to designing a successful treatment
wetland. Dilution water is often needed to protect the
wetland vegetation from being harmed
by high strength wastes and from
dessication when water
volume is inadequate.
10
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Wetland System Goals
A wetland system can be helpful in the following situations:
When the wastewater is too high in nutrients to apply to the
land available. To minimize the risk of contaminating surface
and groundwater by applying too many nutrients, a producer
with limited land and high-nutrient wastewater must either
(1) convert to a crop that can handle higher nutrient loads or
(2)4find a way to reduce nutrient loads. A wetland system can
reduce total nutrient loads and therefore reduce the amount of
land needed at the application site. This, in turn, decreases the
amount of time spent hauling or irrigating and may allow the.
use of smaller and more cost-effective spreading equipment.
When you want to reduce odors at the land application site.
Odors can be a problem when wastewaters from confined
animal feeding operations are taken directly from a treatment or
storage unit and applied to the land. A wetland system reduces
odors, thereby minimizing the chance for nuisance complaints
during land application. . .
When you want to discharge wastewater to surface water, and
the effluent must meet^Natiohal Pollutant Discharge Elimination
System (NPDES) or more stringent local requirements. As part
of an overall wastewater system with adequate pretreatment, a
constructed wetland can further lowerxoncentratioris of BODS,-
TSS, fecal bacteria, and nitrogen.
When aesthetics and wildlife enhancement are important.
A constructed wetland can be an attractive addition to the
landscape while.providing excellent habitat for wildlife. These -
may be desirable features for the conservation-minded producer,
and for the producer who wants to enhance the image of the
confined animal feeding .operation in the eyes of neighbors.
Pretreatment
In most confined animal wastewater management
systems, the wastewater must be pretreated before land
application or discharge to other treatment units. The
use of wetland systems does not eliminate the need for
pretreatment. In fact> because of the high levelsLof
organic carbon, nitrogen, and solids in the,wastewater,
pretreatment is usually necessary. Otherwise, the
wetland system could be overloaded with oxygen-
demanding pollutants and solids that would cause ^
the wetland plants to die. - :...-.--"
incorporating a treatment
wetland into an overall
wastewater management.
system can significantly
reduce the amount of
pollutants leaving the farm.
Land
Application
ws diagram is just
one example of how
a wetland can fit into
a wastewater
'."-' management system.
11
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jis confined animal
operations become more
concentrated,
wastewater management
becomes even more
comprtcated and
important.
The following three pretreatment practices can be used before
discharging wastewater to a wetland for final polishing:
Sagoons are used to settle solids and phosphorus, convert
nitrogen and organic materials, temporarily store wastewater,
and dilute wastewater with rainfall. This is usually the recom-
mended pretreatment method. t
^Storage ponds are used to collect manure and miscellaneous
by-products for a specific storage period. Typically, discharge
from a storage pond passes through a treatment lagoon before
going to a constructed wetland.
• eSolids separators collect solids and pass the liquid portion of
the wastewater to another treatment or storage process. Solids
separators remove 40 to 60 percent of solids and a significant
fraction of the nutrients in wastewater. As with a storage pond,
discharge from solids separators typically pass through a
lagoon before going to a constructed wetland.
Wastewater Characteristics .
Before designing a wetland system, you should know the quanti-
ties of major pollutants in the wastewater. This information,
called pollutant load, is key to selecting the correct wetland size
so that the wetland removes, pollutants at the rates you expect.
Animal wastes are often classified according to moisture content
(solid, slurry, or liquid). Solid wastes consist of manure and
possibly bedding material such as straw or wood chips. Solid
and slurry wastes usually have very high nutrient concentrations
and are good soil amendments. However, these wastes, whether
fresh or stored, should not be applied directly to wetlands, or the
plants will die. •
Licjuid wastes consist of manure, flushwater, contaminated
rainfall, and other liquids and solids that come into contact with
the manure. In most cases, the amount of water added to the
system greatly exceeds the amount of manure. Liquid wastes are
typically collected and treated in a lagoon or storage pond before
being land applied.
The Agricultural Waste Management Field Handbook (USDANRCS
1992), the engineering standards of the American Society of
Agricultural Engineers (1985), "and other technical books and
publications provide information on average volumes of
manure (feces and urine) and average production rates of
certain pollutants produced by different types of livestock.
Average quantities and concentrations of nitrogen, phosphorus,
and BOD5 in manure are summarized in Tables 3 thrpugh*6.
12
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TABLE 3
Swine: Approximate Waste Quantities
" • * Grovfgrs Replacement
Unit" (40to22Qlbs) Gilts
Mass Ibs/d 63.4 32.8
Volume ff/d . 1.0 0.53
Nitrogen Ibs/d 0.42 0.24
^Phosphorus Ibs/d 0.16 0.08
,-BODs Ibs/d 2.08 1.08
a Units per 1,000 Ibs of animal weight. Source: USDANRCS 1992.
Ibs = pounds d = day • ft3 = cubic feet
TABLE 4
Dairy: Approximate Waste Quantities
§, /-;-; „-":/- "1 cow
'" ; 1"^A „ .JUnita JLactating Dry
Mass ' Ibs/d 80.00 82.00
Volume' fp/d 1.30 1.30
[Nitrogen Ibs/d 0.45 0.36
.Phosphorus Ibs/d 0.07 0.05
-BOD5 Ibs/d 1.60 1.20
Sows Cursing) 1
Gestation Lactation Boars (6 to 40 Ibs) j
27.2 60.0 20.5 . 106
0.44 0.96 . * 0.33 1.70
0.19 0.47 0.15 0.60
0.063 0.15 0.05 0.29 '.
0.83 2.00 0.65 3.40 [
i .
Heifer
85.00 '•"•:" . ' -- -'
1:30
0.31
0.04 •
1.30 ;-i'
* Units per 1,000 Ibs'of animal weight. Source: USDANRCS 1992! ' ":'~
Wastewater Volume
In addition to the waste quantities being generated (also called
pollutant load), you must identify the sources and amounts of
water being added to the wastes. This information yields the
total wastewater volume to be treated in the wetlandt system.
The major sources typically are flushwater to remove manure
from alleys and barns, water for cleaning milking and milk
processing facilities, rainfall runoff from roofs and open lots,
and direct rainfall on pretreatment facilities and the wetland.
Water use varies considerably from one operation to another,
depending on such factors as type of buildings, method of
flushing, and type of management. Flow rates for flushing and
washdown can be estimated on the basis of titxe size of the flush
tanks and the number of flushes or the flow rate of pumps and
hours pumped per day. Rainfall runoff can be estimated on the
basis of the area of roofs and open lots, the monthly or annual -
volumes of rainfall, and.runoff curves. .- •-•"'.:.-
13
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In general, you can estimate the volume of flushwater used in
swine and poultry facilities by calculating approximately
2 gallons per minute (gpm) of water per 100 pounds (Ibs) of
animal weight for the flushing period. For cattle and dairy
facilities, use 40 to 50 gallons per cow per day to predict flushing
' requirements for freestall alleys (Overcash et al. 1983). Tipping
buckets, siphon tanks, and drop side tanks have capacities
ranging from 250 to 1,000 gallons. The frequency of daily
flushing will determine the total volume of flushwater used.
TABLE 5
Beef: Approximate Waste Quantities
HwiHHWHHBBBBsssiiasflfe -^^^^^-—-j^,^
Mass
Volume
Nitrogen
Phosphorus
BODS
BMft/flH'
Ibs/d
gpd
* . , •" ,
Ibs/d
Ibs/d
Ibs/d
Diet
59,10
7.1
0.31
0.11
1.36
Diet
51.20
6.1
•' , „ J ;;' ' ''"i '
0.30
0.094
1.36
mm^ to 750 ID
58.20
.,. , ^
•':•" ;«!!' ,:;.:', ' «•;;: ;;,, ;!«',." :• , , '.•;;. ' '• '
0.30
' "o:ib '
1.30
[
>sj Cow
63.00
"" 7.5. :
i. 'V:, •;/; •! !";>;' .','". ",»"'' ' ,: ,'•«, t'1
'0.33-
' '•' 0.12
1.20
• Units per 1,000 Ibs of animal weight. Source: USDA NRCS 1992.
TABLE6 ............ • .........
Poultry: Approximate Waste Quantities"
Mass
Volume
Nitrogen
Phosphorus
BODC
Ibs/d
ft3/d
Ibs/d
Ibs/d
Ibs/d
S0.5
0.93
0.83
0.31
3.70
1 Waste from most poultry facilities is handled as dry material. Waste frorn laying
hens is often handled in liquid form; thus, waste characteristics for only the layers are,
shown in this table.b Units per 1,00,0 Ibs .of animal weight. Source: USDA NRCS 1992.
14
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Wetland Design and
Construction Considerations
Choosing a Site
In addition to meeting technical requirements, the wetland
must be conveniently located and fit into the overall operation.
To pick a suitable location, keep the following items in mind:
Kfurisdictional wetlands—A treatment wetland cannot be
located in any part of a natural wetland as defined by
applicable regulations (called a jurisdictional wetland).
A professional opinion from the U.S. Army Corps of
Engineers, NRCS, or other professional certified in wetland
delineation is essential.
Eploodplains—The site should hot be in an area that floods
moire frequently than once in 100 years. State regulations •
may be more stringent. - "
*" 8S33I . ...".V: -. - -" --- ••• "-
iloils—The soils at the site should contain a relatively high
fraction of day to prevent wastewater from seeping into
groundwater. Soils; classified as clay, sandy loam, and sandy
day are preferred. Sandy soils should be avoided unless a
compacted day layer can be added or adequate pretreatment
is provided. The soils evaluation also should determine the
: "depth to bedrock. Shallow soils can cause problems during
construction and seepage during operation.
topography—The lay of the land is important, with level or
nearly .level slopes desired. All wetland cells should be level
from side-to-side. If the land has considerable slope in the
lengthwise direction, it may be necessary to install several
terraced ceUs m series, wHch wiU add to tiie cost of construc-
tion, the overall size, and the maintenance and management
requkements.
Hand area—-The wetland surface area will be based on
treatment goals and should be as large as is practical.
Additional land area will be needed for the embankments.
Surface and groundwater—The proximity of the system to
nearby streams and to shallow groundwater should be
evaluated for possible impacts.
Your NRCS office and other
information sources listed at
the end of this brochure provide
detailed information on the
design and construction of .
wetland systems. In the
meantime, this section
introduces the following topics:
loosing a site
izing a wetland
Engineering a wetland
electing wetland plants
roviding wildlife habitat
anaging water
15
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i. J/fe densely planted
wetlandireats
wastewater before it
Is land applied.
Sizing a Wetland
You're probably wondering, "How big will a wetland have to be
to get the results I need?" Information on designing wetlands
for animal wastewater is still being developed, and as a result
no clear consensus exists on sizing systems. The simplest
method for estimating the size of a constructed wetland is based
on the following:
, iiln estimate of the amounts of
pollutants produced by the animals
iiF^T
-All estimate of pollutant reduction in
pretreatment
LA prescribed areal mass loading in
pounds of pollutant per acre of
wetland per day
To help estimate how many acres you might need
for a wetland, a rule-of-thumb method and two
examples are provided below.
Step 1: Set goals for the
wetland system
according to
requirements for final
disposal of the
wastewater.
Assume you can dispose of
1,000 Ibs of nitrogen per year
(2.7 Ibs/d) on 5 acres of
irrigated pasture.
Assume you can discharge to surface water
if the wastewater has less than 30 parts per
million (ppm) of BOD5 at least 80 percent of
the time.
Step 2: Determine the
pollutant load and
wastewater volume.
Use Tables 3 through 6 to
estimate the pollutant
load in pounds per day
on the basis of your herd
Or flock si/e. Estimate the
wastetvater volume, ui'."
gallons per dayt
|i i ii i *it:"
!-"'''l;l
Assume you have 100 confined dairy
cows and they weigh about 1,200 Ibs
eacfil Calculate the estimated mass of
nitrogen (pollutant load) excreted by
these cattle. "'
nitrogen load =
x 100 cows x 1,200 Ibs/cow
Assume you have 500 finishing hogs and
they weigh about 180 Ibs each. Calculate
the, ejfimate^.massd JODS (pollutant
loacf) excreted By fhese swine. , .
'=WIsl ' '
!! :;i!i!iw^^^ ;ii|i:i..!iiiii!;iii!!iiii'iirti!ii!!!lli!iiiiii!iii!!iiKiiii'!ijf!1'!llii!ii!:
'Assume 40 gpd per head is used for
|, ]' |i|!'|!'|!|"ii' ||i|i!!ii
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Step 3: Estimate
pollutant reductions
during pretreatment.
NRCS can provide
information on the
efficiency of
pretreatment options.
Assume that lagoon pretreatment will
reduce nitrogen concentrations by 80
percent, leaving 20 percent that will
need treatment and disposal.
nitrogen load = 54 Ibs/d x 0.20
= 10.8 Ibs/d
•(•• v-
Example 2 - Surface Discharge
I-,,-,..;,!^,--..-,.~ „...„.-,-...,. ,..-,. ,,--... r... .,-, :- ...... .- . ,^f. ,
Assume that lagoon pretreatment will reduce
BOD5 concentrations by 90 percent, leaving
10 percent that will need treatment and
disposal.
BOD5 load = 187 Ibs/d x 0.10
= 18.7 Ibs/d
Step 4: Estimate the
pollutant loading rate.
Calculate the concentration of nitrogen
at the wetland outlet that is appropriate
for irrigation.
nitrogen concentration at outlet
= 2.7 Ibs/d
4,000 gpd
= 81 pprn
FrornTable 7, this concentration can be
achieved, at a nitrogen loading rate of
about 26 JbsMd,,
x 119,841 ppm/lbs/gallon
Assume a BOD5 concentration of 30 ppm at
the wetland outlet. From Table 7, this
concentration can be achieved at a BOD5
wetland loading rate of about 9 Ibs/ac/d.
Step 5: Estimate the
wetland area
necessary to achieve
the target pollutant
loads required by the
disposal method.
Calculate the wetland area needed to
treat a load of 10.8 Ibs/d of nitrogen at a
loading rate of 26 Ibs/ac/d.
wetland area
= 10.8 Ibs/d
26 Ibs/ac/d
= 0.42 ac or 18,100 square feet (ft2)
Calculate the wetland area needed to treat
a load of 18.7 Ibs/d of BOD5 at a loading
rate of 9 Ibs/ac/d. •
wetland area
= 18.7 Ibs/d
9 Ibs/ac/d
= 2.1acor90,€00ft2
TABLE?. .\ ' - '-• . • • ; .... ... '_. " -"" " •-- ' :
Estimated Pollutant Loadings to Achieve Desired Wetland Outflow Concentrations3
z "£" 'jpg s
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Engineering a Wetland
Length-to-Width
Cells can be nearly any shape that fits site
requirements. Treatment performance is
best when flow is evenly distributed from
one end of the cell to the other. Length-to-
width ratios for individual wetland cells
range from 1:1 to 10:1.
Gate
Valves { ,-•
From L
Pretreatment
Marsh Vegetation
Number of Cells
Multiple wetland cells make operation and mainte-
nance easier because cells can be shut down, cleaned
out, or replanted as necessary without disrupting the
entire system. Multiple cells should be parallel to
each other. For larger wetland systems, cells can be
arranged in parallel sets of cells in series. Preliminary
cells should be smaller and more accessible so that
they can be routinely cleaned'of accumulated solids.
Agridrain
3:1 Embankments
Embankments and Liners
Embankments must be constructed
using appropriate design and compaction
techniques. Embankments should be 1.5
to 2 feet above the highest expected water
depth to contain severe rainfall and to
accommodate sediment accumulation in
the wetland over time. Dikes should have
side slopes that can be maintained by
tractor-mounted mowers. Bottoms of
wetland cells should consist of a com-
pacted day layer or liner covered by
about 12 inches of native topsoil to
serve as a rooting bed for plants.
Deep Zones
Water Depth
In most constructed wetlands,
the water is about 1 foot deep or
less.. Water control structures
should be designed with stop
logs, gates, or moveable weirs
so that the water level can be
adjusted between 0.1 to 1.5 feet.
Deep Zones •
Deeper zones (3 to 6 feet below grade) can be added to
the wetland to collect solids, to better mix the water,
and to provide wildlife habitat. Deep zones should be
perpendicular to the flow direction so that the water
flow will not short-circuit the intended pathway.
Relatively narrow inlet and outlet deep zones can
help maintain even flow distribution.
18
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Selecting Wetland Plants
Treatment wetlands need densely growing plants. With nutri-
ents and shallow water, plants grow well in wetlands and
provide a carbon source and attachment area for the microbes'
that help treat the water. Plants do not need to be harvested as
long as embankments are high enough, but plants do need to be
nurtured when first established and then observed for stress.
Cattails are common in many natural and constructed wetlands
throughout North America. These plants have long (up to 12
feet high), tape-like leaves that grow from a thick dump at the
sediment level. Cattails grow from a fleshy rhizome and spread
vegetatively by rhizome or from seed germinated in muddy •
ground. Cattails freeze back after the first hard frost, but they
usually maintain upright, dead leaves and stems during the
winter. Cattail marshes have been able to significantly reduce
pollutants even under ice in northern climates.
Several species of bulrushes are also commonly used in con-
structed wetlands. Softstem and hardstem bulrush are tall
plants with hundreds of cylindrical, pointed leaves per square
yard. Masses of brown seeds dangle from the tip of each leaf,
providing good food for a variety of wildlife. Like cattails,
bulrushes spread vegetatively by rhizomes or from seed. During
winter, bulrushes may or may not brown, and they remain
standing throughout the season.
Many other plant species can be established in constructed
treatment wetlands. Each species has slightly different prefer-
ences for water depth and water quality, and each species has -'-:•
specific benefits for wildlife. However, for water treatment
performance, the species of plant is not very important. For that
reason, a wetland owner should focus attention on establishing
a dense population of cattail or bulrush throughout most of the
wetland, and then add as many other plant species as possible.
Other common species are arrowhead (Sagittariaspp.) and
softrush (Juncus spp.),, shrubs such as alder (Alnus,spp.)/ and
trees such as willow (Salix spp.), cottonwood (Populus spp.),
and cypress'(Taxodium spp.).
"^Cattails, bulrush, and
flowering plants such
as marsh mallow
thrive in constructed
treatment wetlands,. *
19
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Constructed wetlands can be
designed to enhance the landscape
for both humans and wildlife.
Providing Wildlife Habitat
Constructed wetlands attract a variety of wildlife. Animals
include amphibians (frogs), reptiles (turtles and snakes), mam-
mals (wild rodents, muskrats, and nutria), and birds (herons,
egrets, rails, sparrows, ducks, shorebirds, coots, blackbirds, and
hawks). Fish may also find a home in constructed wetlands that
are not overly enriched by nutrients in animal wastes. You can
encourage wildlife use in constructed wetlands by following
several general principles:
fT3
-Create a wetland with habitat diversity by
providing both deep and shallow areas and
by planting a variety of plants in distinct
zones. The deep water areas (deeper than
4 feet) should occupy 30 to 50 percent of the
wetland, and shallow areas (less than 1.5 feet
deep) should occupy the remaining 50 to 70
percent. Include deep water areas within the
shallow vegetated marsh zones but not
adjacent to the outlet deep zone. Increase the
length of edges between marsh and open
water areas and include islands in deep water
areas to provide safe areas for wildlife to rest
and nest.
-Pretreat the wastewater as much as practical
and reduce pollutant loadings to the wet-
land. To enhance wildlife use, pollutant
loadings at the wetland inlet should be less
than 10 to 20 Ibs/ac/d for BODS and TSS and
less than 3 to 5 Ibs/ac/d for TN.
^Provide other features to attract and support
wildlife around the constructed wetlands.
Plant wildlife food and cover crops on dikes
and surrounding upland fields; install bird
houses, nesting boxes, and roosting structures
such as tree snags; and fence and protect the
area from disturbance by humans, livestock,
and domestic pets.
20
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Managing Water
, Although wetland systems transform and remove pollutants,
they do not magically dispose of water. The evapotranspiration
(water evaporation and plant transpiration) of a constructed
wetland is about the same as a pond or lake of the same size. In
warmer regions with low summer rainfall, the volume of water
in a wetland decreases between the' inlet and outlet as a result of
high evapotranspiration. In areas that are cooler or have high
rainfall, the volume of water stays the same or increases between
the wetland inlet and outlet. ,,
The fate of the treated water at the wetland outlet must be
determined when the wetland is designed. Various options are
available: / •
!Ise the water to irrigate crop areas.
%se the water for recycling as flushwater.
^Discharge to a surface water such as a stream, river, or lake
(NPDES permit required), -.;... ' ;
Create additional wetland and aquatic habitat on the farm.
A monthly water budget helps account for all water (wastewaterV
and freshwater) entering and leaving the system from all sources
on a monthly basis. The water budget allows the planner to
determine (1) if enough water will be available for plants during
dry seasons, (2) if storage will be needed to contain all sources of
water during dormant or cold seasons, and (3) how water must
be managed throughout all seasons.
During initial planning, determine if water will be available to
the wetland during startup and all seasons thereafter. In some
cases, water may need to be stored in the temporary storage unit
of the pretreatrnent system so that enough water is available for
the wetland year-round.
If wetland effluent will be collected rather than discharged, the
size of the downstream storage pond must be determined. The
storage pond must be sized to manage the irrigation component,
•and pumping^ requirements for irrigation and recycling as
flushwater must be considered. A storage pond, pumps, and
piping may be needed to transport the effluent to the appropriate
irrigation system, whether center-pivot, big-gun, or flood.
®?&nce this wastewater leaves
the barn, it is stored in a
lagoon and then discharged 1o
a constructed wetland. The
treated wastewater, is •
ultimately land applied.
21
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In low rainfall areas, the wetland can be sized so that water is
disposed of through evapotranspiration. Evaporative systems
require larger areas for a given wastewater flow.
Water management includes the installation of the right pipes
and fittings and maintenance of water control structures so'that
pipes and valves remain undogged and proper wafer levels are
maintained. Ideally, water control structures will be designed to
be self-operating most of the time.
Most states do not encourage or allow wastewater from
confined animal feeding operations to be discharged to surface
water. State water quality regulators will determine if the
wetland effluent can be permitted for discharge under'NPDES,
state, or water conservation district requirements. If a permitted
discharge is allowed, the owner must be fully aware of
monitoring requirements and the costs of obtaining and
maintaining such permits. In that case, conservative design
and operation are critical to eliminate the potential for
environmental harm.
.Constructed wetlands are operated and maintained by
controlling the water's quality, quantity, depth, and flow rate.
Flexible water control structures allow the wetland owner to
manage the system with minimal effort and to easily respond ,
to changing conditions. Results from regular monitoring should
guide wefland operation. This monitoring includes general
observations of water control structures and plant health, as
well as periodic sampling of parameters such as BOD5, TSS,
nitrogen, and phosphorus. '
Constructed wetlands are
especially useful at swine
facffities that use large
amounts offlushwater.
22
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Information Sources
Additional information concerning pollution management,
the importance of wetland and aquatic habitats, and wetland
design is available. Some of these Sources are listed below. Be
sure to ask your local NRCS or agricultural extension service
representative what you can do to improve the quality of our
water bodies.
American Society of Agricultural Engineers
> (ASAE). ASAE Standards. St. Joseph, MI:
- ASAE: 1985. ..
' CH2M HILL and Payne Engineering.
Constructed Wetlands for Livestock Wastewater
Management: Literature Review, Database, and .. .
Research Synthesis. Stennis Space Center, MS:
Gulf of Mexico Program, Nutrient Enrich-
ment Committee. 1997. ' -» ••
Kadlec, R.H. and R.L. Knight. Treatment i
Wetlands. Boca Raton, FL: CRC Press/Lewis.,'
Publishers. 1996.. " : ,
DuBowy, P.J. and R.P. Reaves, eds. .
Constructed Wetlands for Animal Waste
Management. Proceedings of a Workshop.
West LaFayette, IN: Purdue University, ' •
1994 / ,-"-• '_ • : - • :
- ' s? • . . '
DuBowy, P.J., ed. Proceedings of the Second
National Workshop on Constructed Wetlands
for Animal Waste Management. College
Station, TX: Texas A&M University. 1997.
Knight, R.L., R.W Ruble, R.H. Kadlec, and
S.C Reed. Wetlands for Wastewater
Treatment Performance Database. G.A. ,
Moshiri, ed. Constructed Wetlands for Water .
Quality Improvement. Boca Raton, FL: Lewis
. Publishers. 1993. „
•*' -
Overcash, M.R., F.J. Humenik, and J.R.
Miner. Livestock Waste Management,
Volume II. Boca Raton, FL: CRC Press. 1983..
Payne Engineering and CH2M HILL.
Constructed Wetlands for Animal Waste
Treatment. Montgomery, AL: Alabama Soil
and Water Conservation Committee. 1997.
U.S. Environmental Protection Agency
(EPA). Constructed Wetlands for Wastewater '
Treatment and Wildlife Habitat: 17 Case Studies.
EPA832-R-93-005. September 1993.
U.S. Department of Agriculture (USDA)
Natural Resources Conservation Service
(NRCS). Agricultural Waste Management Field
Handbook. Washington, D.C.: NRCS. 1992. .
Publications are
available that offer
specific and detailed
'guidance on •
constructing a
wet/and.
23
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Gulf of Mexico Program
Nutrient Enrichment Issue Committee
Building 1103, Room 202
Stennis Space Center, MS 39529-6000
Office (601) 688-3726
The Gulf of Mexico Program (GMP) was established in
1988 to improve the ecological and economic health of
the Gulf of Mexico region. The GMP is funded by the
United States Environmental Protection Agency (EPA)
and public and private organizations.
The Nutrient Enrichment Issue Committee of the GMP
is interested in ways to reduce the nutrient loads of the
rivers and estuaries of the Gulf of Mexico region.
Confined animal feeding operations directly and
indirectly contribute nutrients to the area's water
bodies. Realizing that farms play an important role in
• maintaining the area's environmental health, the
Committee funded a project to review the potential of
constructed wetlands to remove nutrients from
wastewaters before they leave the farm. The purpose of
the project was to document the ability of existing
constructed treatment wetlands for removing nutrients
from wastewaters in a way that was both practical and
cost-effective. This brochure is one part of that project.
Funded by:
EPA
U.S. Environmental Protection Agency
Gulf of Mexico Program
Published by:
CH2IVIHILL
3011 S.W. Williston Road
Gainesville, Florida 32608-3928
Additional copies of this brochure may be obtained from
The Gulf of Mexico Program Public Information Center
Building 1200, Room 103
Stennis Space Center, MS 39529
(601)688-7940
Printed on Recycled Paper
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