Swine Production Facility Manure Management:
Pit Recharge- Lagoon Treatment
Prepared by:
James C. Barker, Professor and Extension Specialist
Biological and Agricultural Engineering
North Carolina State University
Published by: North Carolina Cooperative Extension
Service
Publication Number: EBAE-128-88
Last Electronic Revision: March 1996 (JWM)
Swine production operations, particularly
high-density large-volume units, must be
planned as a total system beginning with
site selection. With increasing emphasis
on a cleaner environment, more attenbon
must be given to methods of manure
management. Locabon, land use patterns,
size of operation, labor resources, soil
type, land availabilify, crop scheduling and
climate are factors entering into the
decision of which waste system is the
most efficient and environmentally
acceptable. The system that works best
for one operator with a particular set of
constraints may not necessarily be best for
another with different circumstances,
management capabilities, or farm
objectives.
PRODUCTION SYSTEM PLAN
Planning a group of builings and their
surroundings to present a wholesome image is
as important as planning for productive
efficiency. When the public sees a swine
farm, they see much more than buildings and
grounds. They see an attitude - an attitude
of pride in the business or an attitude of
indifference. They see an environmental
protector or an environmental polluter.
Farm operators who take pride in
maintaining the farmstead are generally
better managers than those who practice
poor housekeeping. Employees take more
pride in their jobs and work output improves
(Morris et al., 1973).
Production Effects from Manure
Production advantages are also likely to be
realized by proper in-house manure
management. Manure anaerobic
decomposition produces more than 40
different gases which may be detrimental to
animal health and productivity, unhealthy to
workers or offensive to neighbors. The
levels of ammonia and other gases in swine
housing has been closely associated with
ventilation and manure management.
Animal respiratory diseases such as rhinitis
and chronic pneumonia are aggravated by
the continuous breathing of ammonia.
Ammonia also causes a loss of appetite
resulting in slower gains. Hydrogen sulfide,
when rapidly released during agitation of
stored manure, is toxic and can kill in a
matter of seconds. Dried manure on floor
surfaces contributes to dusty conditions
inside a production facility which can also
damage an animal's respiratory structure.
Objectives:
Therefore, proper
consideration should be given to the manure
management system inthe planning stages
both from a production and environmental standpoint
for:
- previon of the direct dischorge of manwe or
wastewater into surface waters or onto adiacent
neighbors' hzed Water pollution control laws declare
that it is illegal to discharge untreated wastewater
without a permit.
- enhancement of the operational efficieny of the
prodin len) Advisory personnel must be familiar
with management and production needs and maintain
close communication with the pork producer.
- collection and utilization of manure and wastewater as
ferSlizer. The best way to reduce the costs of waste
handling is to recognize that regardless of the
collection, storage, or pretreatment process, the final
step in the overall system is land application.
- prevention of nuisance conditions. Nuisance is
defined as anything that interferes with the normal
use and enjoyment of property such as odors,
rodents, flies or mosquitoes.
PRODUCTION UNIT LOCATION
Site Selection
When planning new facilities or
significant expansion of older ones, avoid selecting sites
near residential developments, commercial enterprises,
recreational areas, or other prime areas for non-agricultural uses. A site may seem ideal with respect to
transportation, feed supply, accessibility or land
ownership, but may be inappropriate because of existing
or proposed development. When possible, locate
production facilities near the center of a tract of land
large enough to allow manure to be applied at
agronomic rates (lable 2). Pollution control and waste
treatment facilities should be located as remotely as
possible from areas of high environmental sensitivity
such as drainage ditches, streams or estuaries.
Buildings in flat, high water table areas should be built
on pads of earth fill excavated from the lagoon.
Elevating these buildings several feet above ground
routes surface drainage away from them and allows
manure to flow by gravity to the lagoon.
Wind Direction and Air Drainage
Refer to
wind direction probability diagrams available from most
technical agencies to locate facilities downwind of the
warm season prevailing winds. The strategic planting of
rows of trees or hedges serves both to shield the
production and waste management facilities from direct
sight and to reduce the wind speed across these facilities
allowing odorous gases more opportunity to rise
vertically and dissipate into the atmosphere.
Facility Management
An orderly system for
manure collection and storage or treatment reduces
potential pockets of odor production. All manured
surfaces on which animals are maintained should be as
clean and dry as possible. Dirty manure-covered
animals promote accelerated bacterial growth and
odorous gases which are quickly vaporized by animal
heat. Adequate ventilation is essential for gas and odor
reduction, moisture removal, and temperature control.
Underfioor ventilation aids in drying slotted floor
surfaces. Exhaust fans and shutters should regularly be
cleaned of dust. Building sidewall screens should
periodically be cleaned of debris such as dust, spider
webs and vines to allow maximum warm season cross
ventilation. All components of the total production and
waste treatment system should be operated and
maintained in good functional order. Accumulations of
solids and wastewater should be removed from these
systems expediently. Proper disposal of dead animals
and good fly and rodent contol programs are essential.
PIT RECHARGE SYSTEMS
Advantages
The pit recharge concept is a
periodic draining of the pit contents by gravity to a
lagoon, then recharging the pit with new liquid.
Regular pit draining removes much of the manure
solids that would otherwise settle and remain in the
bottom of the pit. The regular liquefaction of settled
solids increases their likelihood of being removed at the
next pit draining. With less raw materials available
for bacterial digestion and gas production, a better in-house environment results in improved animal health
and performance and better working conditions. Fewer
odorous gases are exhausted from the pits to the
surrounding building vicinity. Potential disease
reservoirs resulting from prolonged pit storage are
removed. A reduction of corrosive gases decreases
metaDic equipment deterioration. Regular loadings of
manure also enhance lagoon performance.
Recycle Pump
Low-pressure, self-priming
centrifugal or submersible pumps with enough flow
capacity to recharge the largest building pit with 12
inches of liquid in 4 hours or less are recommended.
Electric pump housings must be well grounded to
reduce the buildup of salt deposits on the housing and
impeller. Intakes may be screened with a 1-inch wire
mesh fence or basket with a diameter at least 5 times
the suction pipe diameter. The pump intake is generaDy
an open-ended suction pipe floating approximately 18
inches beneath the liquid surface of the lagoon. The
pump should be located as remotely as possible from
the waste input. An underground PVC pipe large
enough to maintain a liquid flow velocity between 3-5
feet per second or a minimum diameter of 1.5 inches is
used to transport lagoon liquid from the pump to the
buildings.
Example A grower/finishing building pit has dimensions of 16 ft wide by 160 ft long.
Pit floor area = 16 ft x 160 ft = 2560 sq ft
Volume needed to add one foot liquid to pit = 2560 sq ft x 1 ft
= 2560 cubic ft x 7.5 gallons/cubic ft = 19,200 gallons
Pump capacity needed to add liquid volume in four (4) hours
= 19,200 gals / 4 hours / 60 min/hour = 80 gallons/minute
Minimum pressure head rating of pump = 50 ft
(This should be checked since actual total pzressure head ay need to be greater.)
Pump efficiencies vary from 45% to 65% (0.45 - 0.65)
Electric motor efficiencies vary fro 80% to 90% (0.80 - 0.90)
Approxioate motor horsepower = Pumping rate, gpm x Total pressure head, ft
--------------------------------------------
3960 x Puwp efficiency x Motor efficiency
= 80 gp x 50 ft
----------------------- = 2 hp
3960 x 0.55 x 0.90
Installation
A lateral pipe from the mainline is
installed into each pit wall preferably at a location
opposite the drain outlet. However, the location of this
recharge pipe is not critical since liquid addition to the
pit is the objective rather than higher velocity sweeping
action. The lateral can either be stubbed directly into
the pit wall with a conveniently located and protected
butterfly valve outside the building, or it can enter the
building wall near ceiling level and drop down to the pit
with an inside-the-building valve. The lateral diameter
should not be reduced between mainline and outlet.
Design Criteria
The lateral discharge point
should be located between the slotted floor and
maximum pit liquid level. The recharge system can be
managed sucessfully with a flat pit floor, although a
minimum slope of 1 inch in 20 feet is generally
recommended to overcome uneven concrete
construction. If the entire building is sloped, enough pit
depth must exist to cover the upper end of the pit floor
with at least 6 inches of liquid while enough storage
exists below the air plenum openings on the lower end.
Allow for an average depth of 12 inches of recharge
liquid and another 12 inches for waste accumulation
between pit drainings. The maximum pit liquid level
should be at least 4 inches below the air plenum
openings or 12 inches below the slats. Generally, a 32-inch pit depth is the minimum recommended between
the slotted floor and pit floor.
Drains
A narrow gutter 16 inches wide and a
minimum of 4 inches deep across the drain end of the
pit floor directs waste to an exterior collection box. This
box encloses a removable standpipe seated into a tee or
elbow connected to an underground drainpipe. An 8-inch diameter smooth-walled pipe is sufficient for
individual pit drainings or 10 inches to drain the entire
building. The bottom of the standpipe should be at
least 4 inches below the bottom of the cross collection
gutter so that water flow to the lagoon will not be
restricted. This drainpipe should have a minimum
grade of 1%, preferably 2%, extending approximately 25
feet beyond the top edge of the lagoon.
By draining and recharging a pit more frequently,
more manure solids will be removed, and gas
generation will be lessened. Research data indicates
that ammonia and hydrogen sulfide gas evolution begins
a significant increase after 5-8 days. Pits, therefore,
should be drained and recharged once per week.
LAGOONS
Capacity Unless a producer has adequate supplies
of fresh water and is equipped to handle the additional
water being added to a lagoon, recycling of lagoon
liquid is recommended. Lagoons must be sized
properly to achieve odor control and a water quality
suitable for recharging. Current North Carolina
recommendations are 2 cubic feet of liquid volume per
pound of live animal weight for a single anaerobic
lagoon. Table 1 gives equivalent volumes per head
capacity for finishing units or per sow for farrow-to-feeder and farrow- to-finish units. A two-stage lagoon
would have 1.5 cubic feet of volume per pound live
weight in the first stage and another 0.5 cubic feet in the
second stage. The tendency to expand production
capacity adding more manure to an existing lagoon
without expanding lagoon treatment capacity should be
avoided.
Location
It is suggested that a lagoon be located at
least 1000 feet from any residence or inhabited dwelling
not owned by the producer. Separation distances should
be evaluated on a case-by-case basis. Aggravating
factors such as potential for development downwind
might increase the separation while mitigating factors
such as wooded buffers might decrease the distance.
Lagoons should be located on soils of low permeability
or soils which seal through biological action or
sedimentation to avoid groundwater contamination.
Startup
New lagoons should be filled at least half
full with water before manure loading begins to nurture
bacteria establishment. When possible, manure loading
of a new lagoon should begin in the spring to permit a
stable bacterial population to develop during the warm
season. Under no circumstances should dead animals,
molded feed, plastic gloves, long-stemmed vegetation,
or other foreign material be allowed to enter a lagoon.
Maintain strict vegetation, rodent and varmint control
around lagoon edges.
Management
Lagoons usually fill to capacity
within 2-3 years of startup due to the added waste
volume and a rainfall excess over evaporation. North
Carolina has an annual moisture surplus ranging from 8
inches in the Coastal Plain to 18 inches in the
Mountains. While the lagoon is progressing through
the filling process, some seepage might be occurring.
When the interior soil surfaces have biologically sealed
and the lagoon is full, liquid overflow will occur unless
the operator is in a position to land apply the excess
liquid. Since nooverflowis permitted, excess liquids
will need to be applied to grassland, cropland, or
woodland at rates within the soil infiltration capacity
and the fertilizer requirement of the vegetation.
Sampling and analysis of the lagoon liquid is suggested
to determine its nutrient content. Table 1 provides
information on average annual lagoon liquid
accumulation rates and estimated available nutrient
contents. Table 2 estimates application rates and
minimum land areas needed for lagoon liquid
application for various cropping schemes.
Lagoons should be pumped down during the
warmer growing seasons such that adequate wastewater
storage is available during the wetter, colder season.
Always maintain at least two-thirds of the liquid volume
in a lagoon to allow continuous bacterial digestion of
the incoming wastes. If a high groundwater table exists,
do not lower the lagoon liquid level below the seasonal
water table. Irrigation is the most cost-effective method
of applying lagoon liquid to land. Irrigate on days with
low humidity and when breezes are blowing away from
neighboring residences. Also irrigate in the mornings
and early in the week when odors are apt to be least
offensive.
SUMMARY
After weighing the important points of
alternative manure management systems, a producer
must decide which system appears best, then commit to
providing the attention and management necessary to
make the system function. No waste system will take
care of itself. The appearance of buildings and grounds
on swine farms constantly generates images of the
product, good or bad. A qpod swgnc una~ helps seU thc
prodd Portraying an attitude of success is contagious
- to employees, to neighbors, to consumers and to the
general public (Morris et al., 1973).
REFERENCE
Morris, T.B., W.C. Mills,Jr., and D.G. Harwood. 1973.
Profit From ImprovingYour Image. PS&T Guide
#17, N.C. AgriculturalExtension Service, Raleigh,
NC. 2 pp.
Table 1. SWINE ANAEROBIC LAGOON LIQUID FERTILIZER NUTRIENTS *
===================================================================================================================================
Type of Animal Animal Unit Total Anaerobic Total Lagoon Plant Total Plant Available Nutrients(b)
Production Unit Equivalent Lagoon Liquid Liquid to be Nutrient Nutrients --------------------------
Unit Live Weight Cspacity, Irrigated,(a) Irrigated Soil Incorp.
----------- cub. ft/animal per animal --------- ------------
initial final average unit capacity unit/year #/animal #/animal
-------------- ------------- lbs/ lbs/ unit lbs/ unit
single 2-stage acre- acre acre capacity acre capacity
----lbs------ stage 1st+2nd gallons inches inch inch /year inch /year
-----------------------------------------------------------------------------------------------------------------------------------
Weanling-to per hd 10 50 30 60 45+ 15 191 .007 N 136 68 .48 96 .67
Feeder capacity P205 53 37 .26 40 .28
K20 133 93 .66 100 .70
Feeder-to per hd 50 220 135 270 200+ 70 927 .034 N 136 68 2.3 96 3.3
Finish capacity P205 53 37 1.3 40 1.4
K20 133 93 3.2 100 3.4
Farrow-to(c)per 433 650 435 +215 3203 .12 N 91 45 5.4 64 7.5
Weanling active P205 35 25 2.9 26 3.1
sow K20 89 62 7.3 67 7.9
Farrow-to(c)per 522 783 523 +260 3861 .14 N 91 45 6.5 64 9.1
Feeder active P205 35 25 3.5 26 3.8
sow K20 89 62 8.8 67 9.5
Farrow-to(c)per 1417 2834 2124 +710 10481 .39 N 136 68 26 96 37
Finish active P205 53 37 14 40 15
sow K20 133 93 36 100 39
===================================================================================================================================
* References: Depts of Biological & Agricultural Engineering, Animal Science, North Carolina State University; Jan 1990
Agronomic Division, North Carolina Department of Agriculture
- Estimated total lagoon liquid includes total liquid manure plus average annual rainfall surplus incidental to lagoon
surface; does not account for seepage.
- Irrigated: sprinkler irrigated liquid uncovered for 1 month or longer.
Soil incorporated: sprinkler irrigated liquid plowed or disked into soil within 2 days.
- Assumes 400-lb sow and boar on limited feed, 3-wk old weanling, 50-lb feeder pig, 220-lb market hog and 20 pigs/sow/yr
Table 2. LAND APPLICATION OF SWINE ANAEROBIC LAGOON LIOUID *
==========================================================================================================================
Type of Animal Rate- Lagoon Liquid Application Rate(a) Minimum Land Area for Liquid Application(a)
Production Unit Limiting ----------------------------------------- --------------------------------------------
Unit Nutrient ----Grain---- --Grazed Pasture-- Hayland ---Grain--- --Grazed Pasture- Hayland
Cereal Corn Fescue -Tifton44 Bermuda Cereal Corn Fescue --Tifton44 Bermuda-
---range-- control
------------irrigated @--------------------
# N/ac/yr = 100 150 200 275 325 400 100 150 200 275 325 400
# P205/ac/yr = 50 60 75 75 85 100 50 60 75 75 85 100
# K20/ac/yr = 80 100 100 225 260 300 80 100 100 225 260 300
--------------------------------------------------------------------------------------------------------------------------
--------------inches/year---------------- --------acres/animal unit capacity---------
Weanling-to per hd N 1.5 2.2 2.9 4.0 4.8 5.9 .0048 0032 .0024 .0017 .0015 .0012
Feeder capacity P205 1.3 1.6 2.0 2.0 2.3 2.7 .0052 0043 .0035 .0035 .0031 .0026
K20 .86 1.1 1.1 2.4 2.8 3.2 .0082 0066 .0066 .0029 .0025 .0022
Feeder-to per hd N 1.5 2.2 2.9 4.0 4.8 5.9 .023 .01 .012 .0085 .0072 .0058
Finish capacity P205 1.3 1.6 2.0 2.0 2.3 2.7 .025 .021 .017 .017 .015 .013
K20 .86 1.1 1.1 2.4 2.8 3.2 .040 .032 .032 .014 .012 .011
Farrow-to per N 2.2 3.3 4.4 6.1 7.2 8.8 .054 .036 .027 .019 .016 .013
Weanling active P205 2.0 2.4 3.0 3.0 3.4 4.0 .058 .049 .039 .039 .034 .029
sow K20 1.3 1.6 1.6 3.6 4.2 4.8 .092 .073 .073 .033 .028 .024
Farrow-to per N 2.2 3.3 4.4 6.1 7.2 8.8 .065 .043 .032 .023 .020 .016
Feeder active P205 2.0 2.4 3.0 3.0 3.4 4.0 .070 .059 .047 .047 .041 .035
sow K20 1.3 1.6 1.6 3.6 4.2 4.8 .11 .088 .088 .039 .034 .029
Farrow-to per N 1.5 2.2 2.9 4.0 4.8 5.9 .26 .18 .13 .096 .081 .066
Finish active P205 1.3 1.6 2.0 2.0 2.3 2.7 .29 .24 .19 .19 .17 .14
sow K20 .86 1.1 1.1 2.4 2.8 3.2 .45 .36 .36 .16 .14 .12
==========================================================================================================================
(*) References: Depts of Biological & Agricultural Engineering, Soil Science, Crop Sci.; North Carolina St. Univ; Jan 1990
North Carolina Agricultural Chemicals Manual
Potash Institute of North America
(a) N leaching and denitrification and P205 soil immobilization unaccounted for.
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people
regardless of race, color, national origin, sex, age, or disability. North
Carolina State University, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.
EBAE-128-88