Swine Production Facility Manure Management: Underfloor Flush - Lagoon Treatment

Prepared by:
James C. Barker, Professor and Extension Specialist
Biological and Agricultural Engineering
North Carolina State University
Raleigh, NC

Published by: North Carolina Cooperative Extension Service

Publication Number: EBAE 129-88

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 attention must be given to methods of manure management. Location, land use patterns, size of operation, labor resources, soil type, land availability, 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 buildings 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 in the planning stages both from a production and environmental standpoint for:

prevention of the direct discharge of manure or wastewater into surface waters or onto adjacent neighbors' land. Water pollution control laws declare that it is illegal to discharge untreated wastewater without a permit.
enhancement of the operational efficiency of the production unit. 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 fertilizer. 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 (Table 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 flushed 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. Underfloor 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 control programs are essential.

FLUSH SYSTEMS

Advantages

Flush systems which recycle lagoon liquid for frequent removal of feces and urine from underfloor collection gutters or pits offer opportunities for improved waste management. By avoiding prolonged storage of manure, less solids accumulate in the bottoms of collection pits. 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 odorous gases are exhausted from the pits to the surrounding building vicinity. Potential disease reservoirs in stored manure are removed. A reduction of corrosive gases decreases metallic equipment deterioration. Frequent daily loadings of flushed manure enhance lagoon performance. Capital costs of installing flush systems in new buildings are partially offset by a shallower underfloor collection pit.

Design Criteria

Flushing should be practiced under slotted floors or raised decks. A 24- inch depth is recommended between the slotted floor and the pit or gutter floor. Liquid volume, discharge rate and flush frequency determine the adequacy of cleaning. Flush tanks should have the capacity to release at least 1.5 gallons per 100 pounds of live animal weight per flush. Floors should be flushed at least 4-6 times per day. Discharge rates are governed by flush channel slope and width. The desired floor slope for most flush tank systems should be between 1-2%. Pit floors should be perfectly level from side to side and wide pits should be divided into individual channels no wider than 4-5 feet. Using these criteria flush tank discharge pipes or valves generally range from 6-10 inches in diameter per channel.

Flush Tanks

Valved or gated discharge tanks offer the ease of ground level reinforced concrete or concrete block construction adjacent to the end of the building. Commercial tanks are also available. Valves inside the tank are hinged aluminum or stainless steel flat plates seated against a PVC pipe connecting the tank to the building pit. Commercially available automated valve openers or fabricated water weighted mechanisms control the tank release cycles.

Recycle Pumps

Low-pressure, self-priming centrifugal or submersible pumps control the filling of flush tanks with lagoon liquid. Electric pumps must be well grounded to reduce salt buildup on the housing and impeller. Intakes may be screened by a 1-inch mesh wire fence or basket with a diameter at least 5 times the suction pipe diameter. The pump intake is generally an open-ended suction pipe floating about 18 inches beneath the liquid surface of the lagoon. The pump should be located as far 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 of 1.5 inches in diameter is used to transport lagoon liquid from the pump to the flush tanks.

Drains

The flushed waste must be collected and removed from the building so that flow is not restricted and solids are not redeposited. A narrow gutter 16 inches wide and at least 4 inches deep across the drain end of the pit floor directs waste to an exterior collection box which couples with a smooth-walled drainpipe at least 8 inches in diameter. The top of this drainpipe 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 about 25 feet beyond the top edge of the lagoon.

LAGOONS

Capacity

Unless a producer has adequate supplies of fresh water and is equipped to handle the additional water being added to the lagoon, recycling of lagoon liquid for flushing is recommended. Lagoons must be sized properly to achieve odor control and a water quality suitable for flushing. North Carolina recommendations currently 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 no overflow is 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 n eeded 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 good swine image helps sell the product. 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 Improving Your Image. PS&T Guide #17, N.C. Agricultural Extension Service, Raleigh, NC. 2 pp.

Table 1. SWINE ANAEROBIC LAGOON LIQUID FERTILIZER NUTRIENTS *

============================== ============================== ===============
Type of      Animal         Animal Unit      Total Anaerobic   Total Lagoon  
Production     Unit          Equivalent       Lagoon Liquid    Liquid to be  
Unit                        Live Weight           Capacity,      Irrigated,a 
                      ---------------------      ft3/animal      per animal  
                      initial final average   unit capacity       unit/year  
                                             --------------   -------------- 
                                             single 2-stage            acre- 
                         -------lbs--------  stage  1st+2nd   gallons inches 
-----------------------------------------------------------------------------
Weanling-to  per hd      10      50      30    60    45+ 15     191   .0070  
  Feeder   capacity                                                          
                                                                             
                                                                             
Feeder-to    per hd      50     220     135   270   200+ 70     927    .034  
  Finish   capacity                                                          
                                                                             
                                                                             
Farrow-toc      per                     433   650   435+215    3203     .12  
  Weanling   active                                                          
                sow                                                          
                                                                             
Farrow-toc      per                     522   783   523+260    3861     .14  
  Feeder     active                                                          
                sow                                                          
                                                                             
Farrow-toc      per                    1417  2834  2124+710   10481     .39  
  Finish     active                                                          
                sow                                                          
============================== ============================== ===============

Table 1. (continue..)

==================================== ============================== ==
Type of      Animal     Plant   Total      Plant Available Nutrientsb 
Production     Unit  Nutrient Nutrients  ---------------------------- 
Unit                                       Irrigated     Soil Incorp. 
                                         -------------  ------------- 
                                              #/animal       #/animal 
                                 lbs/    lbs/     unit  lbs/     unit 
                                 acre    acre capacity  acre capacity 
                                 inch    inch    /year  inch    /year 
--------------------------------------------------------------------- 
Weanling-to  per hd      N        136      68     .48      96     .67 
  Feeder   capacity      P2O5      53      37     .26      40     .28 
                         K2O      133      93     .66     100     .70 
                                                                      
Feeder-to    per hd      N        136      68     2.3      96     3.3 
  Finish   capacity      P2O5      53      37     1.3      40     1.4 
                         K2O      133      93     3.2     100     3.4 
                                                                      
Farrow-toc      per      N         91      45     5.4      64     7.5 
  Weanling   active      P2O5      35      25     2.9      26     3.1 
                sow      K2O       89      62     7.3      67     7.9 
                                                                      
Farrow-toc      per      N         91      45     6.5      64     9.1 
  Feeder     active      P2O5      35      25     3.5      26     3.8 
                sow      K2O       89      62     8.8      67     9.5 
                                                                      
Farrow-toc      per      N        136      68      26      96      37 
  Finish     active      P2O5      53      37      14      40      15 
                sow      K2O      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

a Estimated total lagoon liquid includes total liquid manure plus average annual rainfall surplus incidental to lagoon surface; does not account for seepage.

b Irrigated: sprinkler irrigated liquid uncovered for 1 month or longer. Soil incorporated: sprinkler irrigated liquid plowed or disked into soil within 2 days.

c 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 LIQUID *

=============================================================================
Type of      Animal    Rate-          Lagoon Liquid Application Ratea        
Production    Unit   Limiting  --------------------------------------------  
Unit                 Nutrient  ----Grain---    ---Grazed Pasture--- Hayland  
                               Cereal  Corn    Fescue  ---Tifton44 Bermuda-  
                                               ----range--- control          
                               -----------------irrigated @----------------  
                # N/ac/yr =     100     150     200     275     325     400  
             # P2O5/ac/yr =      50      60      75      75      85     100  
              # K2O/ac/yr =      80     100     100     225     260     300  
-----------------------------------------------------------------------------
                                ----------------inches/year----------------  
Weanling-to   per hd   N        1.5     2.2     2.9     4.0     4.8     5.9  
  Feeder    capacity   P2O5     1.3     1.6     2.0     2.0     2.3     2.7  
                       K2O      .86     1.1     1.1     2.4     2.8     3.2  
                                                                             
Feeder-to     per hd   N        1.5     2.2     2.9     4.0     4.8     5.9  
  Finish    capacity   P2O5     1.3     1.6     2.0     2.0     2.3     2.7  
                       K2O      .86     1.1     1.1     2.4     2.8     3.2  
                                                                             
Farrow-to        per   N        2.2     3.3     4.4     6.1     7.2     8.8  
  Weanling    active   P2O5     2.0     2.4     3.0     3.0     3.4     4.0  
                 sow   K2O      1.3     1.6     1.6     3.6     4.2     4.8  
                                                                             
Farrow-to        per   N        2.2     3.3     4.4     6.1     7.2     8.8  
  Feeder      active   P2O5     2.0     2.4     3.0     3.0     3.4     4.0  
                 sow   K2O      1.3     1.6     1.6     3.6     4.2     4.8  
                                                                             
Farrow-to        per   N        1.5     2.2     2.9     4.0     4.8     5.9  
  Finish      active   P2O5     1.3     1.6     2.0     2.0     2.3     2.7  
                 sow   K2O      .86     1.1     1.1     2.4     2.8     3.2  
============================== ============================== ===============

Table 2. (continues..)

===========================================================
Type of          Minimum Land Area for Liquid Applicationa 
Production    ---------------------------------------------
Unit          -----Grain---    ---Grazed Pasture--- Hayland
              Cereal   Corn    Fescue  ---Tifton44 Bermuda-
                               ----range--- control        
              ------------------irrigated @----------------
                100     150     200     275     325     400
                 50      60      75      75      85     100
                 80     100     100     225     260     300
-----------------------------------------------------------
              ----------acres/animal unit capacity---------
Weanling-to   .0048   .0032   .0024   .0017   .0015   .0012
  Feeder      .0052   .0043   .0035   .0035   .0031   .0026
              .0082   .0066   .0066   .0029   .0025   .0022
                                                           
Feeder-to      .023    .015    .012   .0085   .0072   .0058
  Finish       .025    .021    .017    .017    .015    .013
               .040    .032    .032    .014    .012    .011
                                                           
Farrow-to      .054    .036    .027    .019    .016    .013
  Weanling     .058    .049    .039    .039    .034    .029
               .092    .073    .073    .033    .028    .024
                                                           
Farrow-to      .065    .043    .032    .023    .020    .016
  Feeder       .070    .059    .047    .047    .041    .035
                .11    .088    .088    .039    .034    .029
                                                           
Farrow-to       .26     .18     .13    .096    .081    .066
  Finish        .29     .24     .19     .19     .17     .14
                .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 P2O5 soil immobilization unaccounted for.

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EBAE 129-88