LAGOON SYSTEMS for LIVESTOCK WASTE TREATMENT
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MP-1341 LAGOON SYSTEMS for LIVESTOCK WASTE TREATMENT y TEXAS AGRICULTURAL EXTENSION SERVICE, THE TEXAS A&M UNIVERSITY SYSTEM, Daniel C. Pfannstiel, Director, College Station, Texas BLANK PAGE IN ORIGINAL Lagoon Systems for Livestock Waste Treatment John M. Sweeten and C. Wayne Keese* Lagoon systems provide a means of treatment and (3) The need for periodic sludge removal; storage of livestock manure prior to terminal disposal (4) Possible groundwater pollution; on land. Properly designed and operated, lagoons can (5) Formation of mosquito habitat; and reduce organic matter 75 to 95 percent and reduce nitrogen 40 to 80 percent through ammonia volatiliza- (6) The need for terminal disposal of effluent. tion. In addition, lagoons can provide ample storage Most of these disadvantages can be avoided or of manure and wastewater to meet no-discharge re- minimized through proper design and management of quirements of state and federal water pollution con- the lagoons. trol agencies and to fit cropping and labor cycles of the In the warm climate of Texas, lagoon systems are livestock feeding operation. preferable to storage pit/tank wagon systems when The recommendations presented in this bulletin any of the following conditions exist: apply only to lagoons used to treat liquid manure and (1) Insufficient cropland is available for full utiliza- wastewater from confinement feeding operations tion of manure as fertilizer; through the creation of carefully controlled, steady (2) Large volumes of water are routinely used for state conditions. These recommendations do not manure removal; or apply to feedlot runoff holding ponds which are some- (3) Liquid manure storage pits would create odor times improperly called "lagoons." nuisance or fly breeding places. Lagoon systems are also preferable to direct slurry irrigation if land area available is inadequate for di- ADVANTAGES AND DISADVANTAGES rect disposal. Advantages of lagoon systems for treatment and On the other hand, lagoons are not recommended storage of livestock waste include: for a site that has a porous subsoil or a high water (1) Compatibility with modern hydraulic cleaning table, since groundwater pollution problems could re- methods; sult. Lagoons are not advised where the operator wants to (and is able to) realize maximum fertilizer (2) Low cost construction; value from the manure. Lagoons also are not recom- (3) Minimum operating costs; mended where minimum distances to property lines (4) Low labor requirement; and and residences cannot be maintained. (5) Reduction or elimination of fly problems. However, some of the disadvantages of lagoon sys- tems are: APPLICABLE REGULATIONS (1) Appreciable loss of manure fertilizer value; Where groundwater quality may be impaired, the (2) Offensive odor and flies if improperly designed Texas Department of Water Resources (formerly Texas and managed; Water Quality Board) requires that a soil permeability X * Extension agricultural engineer-animal waste management; and not exceed 1.0 10"' cm/sec (1.24 in/yr). It is neces- project leader in agricultural engineering and Extension agri- sary to select a site with an impervious subsoil, or to in- cultural engineer, The Texas A&M University System. stall a 6- to 12-inch compacted clay layer to ensure that 3 seepage does not exceed this very low rate. The Texas means of treatment because of the large surface area Department of Water Resources also requires live- required for oxygen transfer. Aerobic lagoons must stock and poultry operations to provide at least 30-day have about two times as much volume and four times storage capacity for all manure and wastewater. For as much surface area as anaerobic lagoons. The large lagoon systems, however, this requirement has little size may also cause difficulty in sludge removal, em- practical consequence, because much larger storage bankment maintenance and control of aquatic plants. capacity is inherent in lagoons properly designed for Aerobic lagoons are well suited for secondary treat- treatment of livestock wastes. ment and storage of effluent from anaerobic lagoons. The Texas Air Control Board requires that new or Mechanically aerated lagoons combine the odor expanding confined animal feeding facilities obtain a control advantages of aerobic lagoons with the rela- construction and operating permit any time new con- tively small size requirement of anaerobic lagoons. struction would provide for more than 1,000 livestock They are sometimes used to control odors in sensitive or poultry of any type or size. Therefore, the location locations, or for nitrogen removal where land disposal and design of lagoons must be approved before a areas are severely limited. However, use of floating permit will be issued for new or modified operations. surface aerators to provide oxygen is much more ex- The Texas Department of Health Resources and pensive than normal lagoon operation. For floating the local milk inspection unit must approve waste aerators, the aeration requirement for odor control is management practices for dairies. Dairymen should 1 horsepower per 750 to 1,000 square feet of lagoon check with local milk inspectors when planning a la- surface. goon system. LAGOON DESIGN AND OPERATION Design and operating criteria for primary or first- TYPES AND CHARACTERISTICS stage anaerobic lagoons are described in this section. OF LAGOONS A typical layout and cross-section of an anaerobic or facultative lagoon, are shown in Figures 1 and 2. Livestock waste lagoons act as digestion vessels in Location which three types of bacteria — aerobic, anaerobic and/or facultative — decompose the manure organic Anaerobic lagoons should be located near the matter. Aerobic bacteria require dissolved oxygen to source of livestock waste, yet as far from inhabited survive. Anaerobic bacteria cannot survive in free dwellings as practical (500 feet suggested minimum). oxygen. Facultative bacteria can grow with or without They should be at least 100 feet from wells used for free oxygen in the liquid waste material. human water supply or from milking parlors. Prevail- Anaerobic lagoons are the most common type ing summer winds should carry odors away from used for livestock waste treatment. This type of la- nearby residences. Natural or constructed visual bar- goon can handle relatively high loading rates of or- riers around the lagoon can minimize possible com- ganic wastes. However, anaerobic decomposition of plaints from neighbors. Lagoons should not be con- livestock waste can result in the production of more structed in natural drainage paths or gulleys. Runoff than 40 different types of odorous gases. Odors can be from open-lot surfaces or outside drainage areas controlled to reasonable levels with proper design and should be diverted around the lagoon(s) to minimize operation. The lagoon volume and dimensions should storage capacity requirements and to avoid upsetting be carefully selected. Relatively constant operating the bio-chemical balance needed for proper digestion. conditions for anaerobic decomposition should be provided by maintaining the proper water level and Water Supply discharging manure into the lagoon daily. The water supply must be adequate to maintain In aerobic lagoons, algae generate oxygen through full water depth in the anaerobic lagoon. Stock tanks photosynthesis, which takes place where sunlight are often used as a temporary source of supplemental penetrates the water (upper 4 to 5 feet). Oxygen diffu- dilution water. In West Texas where high evaporation sion also occurs across the surface of the water. Thus, depletes lagoon water and leads to salt buildup, a a maximum water depth of 5 feet is recommended. dependable water supply is essential for proper la- Aerobic bacteria decompose waste more rapidly and goon operation. completely than anaerobic bacteria, and produce little To minimize hydrogen sulfide emissions, water or no odor. However, a naturally aerobic livestock entering the lagoon should contain less than 100 parts waste lagoon is generally impractical as the sole per million (ppm) sulfate. 4 Fig. 1. Typical layout of combined anaerobic and aerobic lagoon system using combination of excavated pits and embankments. LIQUID LEVEL NATURAL^ MINIMUM l'-0" / 2' BELOW TOP GROUND ) LIQUID LEVEL HIGH LEVEE OF LEVEE r p\p£ a TEE h 2' BELOW TOP OF LEVEE MIN 8' TOP WIDTH --GROUND LINE EXCAVATED SLOPES 3 HORIZONTAL TO I VERTICAL OR STEEPER FILL SLOPES TO BE 3:1 OR FLATTER TO PERMIT MOWING PRIMARY LAGOON SECTION "A-A' SECONDARY LAGOON (ANAEROBIQ (AEROBIC) LEVEE OR DIVERSION \ / \ / 4 MIN, / DIMENSIONS • J VARIABLE VARIABLDIMENSIONE S y PER SYSTEM 1 _i PER / / SYSTEM x \ LEVEE OR DIVERSION/ - \ NOTE' LAGOON SYSTEM TO BE ENCLOSEO BY FENCE. LONG LAGOON MAY REQUIRE TWO OR MORE INFLOW a j NOT TO SCALE DISCHARGE PIPES FOR ADEQUATE MIXING. Fig. 2. Typical layout of combined anaerobic and aerobic lagoon system using excavated pits. Capacity and Loading Rates mendations in Table 2, the actual dimensions of the The liquid volume of anaerobic lagoons should be lagoon can be computed. Various combinations of based on the amount of volatile (or biode grade able) lengths, widths and depths are given in Tables 3, 4 solids produced from the livestock facility (Figure 3). and 5. Select the volume in the right-hand column of Volatile solids account for 80 to 85 percent of the total Tables 3, 4 and 5, and then read the dimensions solids in swine, beef, sheep and dairy cattle manure. (lengths and widths) at the top of the excavation, at In poultry manure, only 70 percent of the total solids the water line and at the bottom needed to provide are volatile. Daily volatile solids (VS) production rates the lagoon volume determined from Table 2. The di- and other livestock waste characteristics are shown in mensions and volumes shown in the tables are based Table 1. on the use of 2:1 side slopes. In Texas, livestock producers should provide Primary anaerobic lagoons should have a liquid 1,000 cubic feet of liquid volume for every 3 to 10 depth of at least 8 feet.