There are very little data to evaluate the extent to which animal wastes are a significant nonpoint source of pollution in the Cayuga watershed. Animal waste (manure) includes the fecal and urinary wastes of livestock and poultry; process water (such as from a milking parlor); and the feed, bedding, litter, and soil with which they become intermixed. The following pollutants may be contained in manure and associated bedding materials and could be transported by runoff water and process wastewater from confined animal facilities:
Fish kills may result from runoff, wastewater, or manure entering surface waters, due to ammonia or dissolved oxygen depletion. The decomposition of organic materials can deplete dissolved oxygen supplies in water, resulting in anoxic or anaerobic conditions.
Solids deposited in waterbodies can accelerate eutrophication through the release of nutrients over extended periods of time. Because of the high nutrient and salt content of manure and runoff from manure-covered areas, contamination of ground water can be a problem if storage structures are not built to minimize seepage.
Animal diseases can be transmitted to humans through contact with animal feces. Runoff from fields receiving manure will contain extremely high numbers of bacteria if the manure has not been incorporated or the bacteria have not been subject to stress. Beach closure can result from high fecal coliform counts.
The method, timing, and rate of manure application are significant factors in determining the likelihood that water quality contamination will result. Manure is generally more likely to be transported in runoff when applied to the soil surface than when incorporated into the soil. Spreading manure on frozen ground or snow can result in high concentrations of nutrients being transported from the field during rainfall or snowmelt, especially when the snowmelt or rainfall events occur soon after spreading (Robillard and Walter, 1986).
When application rates of manure for crop production are based on crop N needs, the P and K rates normally exceed plant requirements (Westerman et al., 1985). The soil generally has the capacity to adsorb phosphorus leached from manure applied on land. As previously noted, however, nitrates are easily leached through soil into groundwater or to return flows, and phosphorus can be transported by eroded soil.
Management and structural improvements to young stock raising and manure handling facilities may be required to reduce the risk that pathogenic protozoa (Cryptosporidia and Giardia) might reach surface waters. According to NYSDEC, the first barrier for reducing pathogen risk from farming activities is proper calf and heifer management. Maintaining healthy calves may minimize the occurrence of pathogens on farms. Additional practices to reduce contamination with these pathogens include: preventing runoff from animal housing and exercise areas, handling manure from young stock separately, treating or storing manure, and carefully selecting land application areas to avoid hydrologically sensitive areas.
Conditions that cause a rapid die-off of bacteria are low soil moisture, low pH, high temperatures, and direct solar radiation. Manure storage generally promotes die-off, although pathogens can remain dormant at certain temperatures. Composting the wastes can be quite effective in decreasing the number of pathogens.
Methods to Control Nonpoint Source Pollution from Animal Wastes
USDA and EPA have collaborated on a series of BMPs for manure handling. The following guidance is adapted from the March 1999 joint publication "Unified National Strategy for Animal Feeding Operations".
Manure needs to be handled and stored properly to prevent water pollution from animal feeding operations (AFOs). Manure and wastewater handling and storage practices should also consider odor and other environmental and public health problems. Handling and storage considerations should include:
Divert clean water - Siting and management practices should divert clean water from contact with feedlots and holding pens, animal manure, or manure storage systems. Clean water can include rainfall falling on roofs of facilities, runoff from adjacent lands, or other sources.
Prevent leakage - Construction and maintenance of buildings, collection systems, conveyance systems, and permanent and temporary storage facilities should prevent leakage of organic matter, nutrients, and pathogens to ground or surface water.
Provide adequate storage - Liquid manure storage systems should safely store the quantity and contents of animal manure and wastewater produced, contaminated runoff from the facility, and rainfall. Dry manure, such as that produced in certain poultry and beef operations, should be stored in production buildings or storage facilities, or otherwise stored in such a way so as to prevent polluted runoff. Location of manure storage systems should consider proximity to water bodies, floodplains, and other environmentally sensitive areas.
Manure treatments - Manure should be handled and treated to reduce the loss of nutrients to the atmosphere during storage, to make the material a more stable fertilizer when land-applied or to reduce pathogens, vector attraction and odors, as appropriate.
Management of dead animals - Dead animals should be disposed of in a way that does not adversely affect ground or surface water or create public health concerns. Composting, rendering, and other practices are common methods used to dispose of dead animals.
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CLW IO 2004