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Manure can be managed by regulating large or small animal facilities. Confined animal facilities can be used to house or grow animals, for processing and storage of a product, and for manure and runoff storage areas and silage storage areas (EPA, 1993). Large animal facilities contribute to nonpoint pollution to the Gulf of Mexico via facility wastewater and runoff. Facility wastewater is water discharged in the operation of an animal facility due to washing, watering, and cooling the animals, plus washing out the pens (EPA, 1993). Large animal facility management focuses on surface water problems, but also aims to protect the groundwater from seepage of nutrients by incorporating plastic, or earthen liners in the bottom of the runoff or manure storage structure. Smaller animal facilities create similar problems to that of their larger counterparts, but on a smaller scale. Therefore, creating a need for different management schemes. These forms of nonpoint pollution are due to poor storing and spreading practices of manure (Ervin,1998). Runoff, volatilization, and leaching losses of plant nutrients in stored animal manure may be very high, which results in only a fraction of the original nutrients remaining to be applied to the field. Management schemes will greatly reduce the volume of runoff, facility wastewater, and manure reaching a body of water. These results would greatly increase water quality. Several best management practices can be implemented in order to reduce the loss of nutrients from manure in both large and small-scale situations.
For large animal facilities the EPA (1993) suggests the following management practices:
1. Dikes: creation of an earthen embankment to protect the land against overflow or to regulate water (i.e. creation of wetlands).
2. Diversions: a channel constructed across the slope that will stabilize the watershed by reducing erosion, thus reducing sediments and related pollutants entering the surface waters.
3. Waste storage pond: reduces direct delivery of polluted water to surface water.
4. Waste treatment lagoon: an earthen impoundment used to allow denitrification to decrease the nitrogen content in surface runoff that contains animal waste.
5. Grassed waterway: a natural or constructed channel established in suitable vegetation that filters some of the sediment delivered to the waterway.
6. Terrace: an earthen embankment, a channel, or combination of both that trap sediment and reduce the sediment and associated pollutant content in the runoof water which improves surface water quality.
For small animal facilities the EPA (1993) suggests these management practices:
1. Waste storage pond (same as above)
2. Filter strip: a strip or area of vegetation for removing sediment, organic matter, and other contaminants from runoff and wastewater.
3. Sediment basin: basin designed to collect sediment and other debris from water that is passed downstream.
4. Constructed wetland: wetland with rooted emergent hydrophytes to treat agricultural wastewater.
5. Composting facility: created for the biological stabilization of waste organic material by producing a humus-like material that can be used as fertilizer.