pollution from feaces of livestock and poultry2

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pollution from feaces of livestock and poultry2

2 pollution to the atmosphere

The organisms contained in livestock manure and urine can be roughly divided into carbohydrates and nitrogen-containing compounds, which decompose different substances under aerobic or anaerobic conditions. Carbohydrates decompose under aerobic conditions to release heat, most of which is decomposed into carbon dioxide and water. Under anaerobic conditions, the chemical reaction is incomplete and can be decomposed into methane, organic acids and various alcohols. These substances are slightly odorous. And sour taste makes people feel unpleasant. The nitrogen-containing compound is mainly a protein, which can be decomposed into an amino acid under the action of an enzyme. The amino acid can continue to decompose under aerobic conditions, and the final product is a nitrate; under anaerobic conditions, it can be decomposed into ammonia, sulfuric acid, vinyl alcohol. , malodorous gases such as dimethyl sulfide, hydrogen sulfide, methylamine and trimethylamine, have their own unique odors such as rotten onion odor, spoiled egg odor and fish odor. These gases not only endanger the growth and development of livestock and poultry but also harm Human health, exacerbating air pollution. In general, the odor concentration emitted is proportional to the phosphate and nitrogen content of the manure. The phosphate content in poultry manure is relatively high, and the pig manure is higher than the cow manure. Therefore, the harmful smell of the cattle farm is less than that of the pig farm. There are fewer chicken farms. Volatile gases and other pollutants can travel far when there is wind, but as the distance increases, the concentration and amount of pollutants will decrease significantly. Among the malodorous substances, ammonia and hydrogen sulfide are the most affected to human and animal health. When the content of hydrogen sulfide is high, it may cause dizziness, nausea and chronic poisoning symptoms; in the long-term environment with high ammonia content, people may cause tears in the eyes and blind eyes in severe cases. Due to CH 4 and
N H 3 contributes a lot to global warming and acid rain, so in recent years, these two gases in livestock manure have been studied more. CH 4, CO 2 and N 2O are the main gases of the global warming effect. According to the study, the contribution of CH 4 to global warming is about 15%. Among the 15% contribution rate, the breeding industry has CH 4 The largest amount of emissions. According to the test, the CH 4 per pig year is 0. 768 kg / head · year, CO 2 is 0. 714 kg / head / year, N 2O is 0. 002 kg / head / year, global livestock manure CH 4 The annual emissions are 80-130 T/year. In 1990, the total amount of CH 4 emissions from animal waste in China was 1. 249 T g, accounting for about 5% of the CH 4 emissions of livestock and poultry in the world. According to American scholar Natalie A nderson et al. (2003), livestock waste is the largest source of ammonia. In 1995, ammonia produced by US livestock waste was approximately 3 × 109 kg. The amount of ammonia produced from livestock manure depends on a number of parameters, so the influencing factors of emissions are difficult to predict. Recently, studies have been conducted in Europe to measure the emission rate of ammonia in livestock and poultry manure. N H 3 volatilizes into the atmosphere, increasing the nitrogen content in the atmosphere, and in severe cases, it constitutes acid rain and harms crops.

3 pollution of water bodies

In some areas, high-density animal-cultured manure becomes a serious problem when crops do not require additional nutrients. In addition to nutrients, livestock and poultry manure also contains various pollution indicators such as biological oxygen demand, chemical oxygen demand, group suspension, ammonia nitrogen, phosphorus and coliform bacteria. Livestock and poultry manure is mainly used in the soil, and the soil usually has good ability to absorb, store and slowly release nutrients. However, the continuous use of excess nutrients, the soil's storage capacity is rapidly weakened, and nutrients are finding new ways to enter rivers and lakes. In addition, livestock manure can also enter the water body by infiltration or direct discharge of wastewater, and gradually infiltrate underground pollution of surface water and groundwater. When the total amount of manure discharged into a body of water exceeds the ability of the body to naturally purify, it changes the physical, chemical properties and biome composition of the body of water, degrades the water quality, and affects the original use, not only polluting the water quality of the river, but also Draining well water, causing harm to human and animal health. Studies have shown that groundwater pollution is extremely difficult to recover, and it takes 300 years to recover under natural conditions, resulting in longer-lasting pollution. The N in manure is mainly in the form of ammonia nitrogen and organic nitrogen, and these forms easily lose or erode surface water. Naturally, the total ammonia nitrogen in most surface waters exceeds the standard of about 0.2 mg / L. It will poison fish. The toxicity of ammonia nitrogen changes with the acidity and water temperature of water. Under high temperature alkaline water conditions, The toxicity condition of the fish is 0.1 m/L. If there is sufficient oxygen, the ammonia nitrogen can be converted into nitrate nitrogen, which is dissolved in water and penetrates into the groundwater through the soil. Studies have shown that with the application of manure, the NO 3 - N contaminants in the groundwater in the area will increase, and the amount of nitrate infiltrated into the groundwater will be a function of the applied manure. The highest standard for nitrogen is 10 mg/L. At the same time, too much N in the water will cause eutrophication of water bodies, promote algae to grow wild, compete for sunlight, space and oxygen, threaten the survival of fish and shellfish, limit the supply of oxygen in aquatic organisms and microbial activities, and endanger the aquaculture industry; Affecting the ecological environment along the coast also affects water use and consumption. If a person drinks N-type N water for a long time or a large amount, it may induce cancer; newborn infants under 6 months of age may suffer from methemoglobin. Studies have shown that in the deep summer and autumn, the land use rate of livestock manure is likely to be a key factor in the pollution of water source N. In the manure of livestock and poultry, P is usually transferred to the surface water area with the loss of rainwater or through soil erosion. According to research, P is an important element leading to eutrophication of water bodies. P Entering the water body causes algae and aquatic weeds to grow abnormally. The dissolved oxygen in the water drops, causing fish pollution or death. Excess phosphorus is a limiting factor for eutrophication in most inland rivers or reservoirs. The US Environmental Protection Agency (U SEPA) recommends that water that is discharged from a point source into a lake or reservoir P does not exceed 0.05 m g/L, and is not directly discharged into the lake or reservoir water by a point source. P does not exceed 0.1 mg/L. The organic matter in livestock manure is 50 to 250 times higher than the normal municipal sewage. The discharge of wastewater from livestock and poultry farming in Guangzhou is only about 1.25% of the domestic sewage, but the COD cr emissions are domestic sewage. 1.5 times. The organic matter is mainly lost to the water body through rainwater. The organic matter enters the water body, causing the water body to change color and blacken, accelerating the accumulation of sediment. The nutrients decomposed by organic matter may cause a large amount of algae and weeds to grow wildly; the oxidation of organic matter can quickly consume oxygen in the water, causing Some aquatic organisms die, such as in aquaculture environments, often resulting in fish death due to the rapid depletion of oxygen. In addition, the irrigation of paddy fields with livestock manure with high organic matter content makes it easy to make the seedlings steep and fall, and the rice is late or mature. When used in fish ponds or infused into rivers, it will cause low-level plants (such as algae) to multiply and threaten fish. Growing. Livestock and poultry manure contains a large number of pathogenic microorganisms and parasite eggs originating from the intestines of animals. It is reported that the sewage discharged from livestock farms contains an average of 330,000 E. coli and 690,000 Escherichia coli per 1 mL; The sewage contains up to 190 ascaris eggs and more than 100 eggs of the genus. The entry of these pathogenic microorganisms and parasite eggs into the water body will increase the number of pathogens in the water body, increase the amount of bacteria and bacteria, and cause the proliferation and pollution of pathogenic bacteria and parasites, leading to the spread and prevalence of water-borne infectious diseases. Especially in the case of zoonosis, it will cause an epidemic and bring catastrophic harm to people and animals. When studying bacteria in groundwater that received irrigation water, it was found that filtration of the soil substrate significantly reduced the amount of E. coli in the feces, which could survive for several weeks in water sediments. In addition, the potential contamination of water in the feces of livestock and poultry can not be ignored. In several rivers in the Chesapeake Bay Basin of the United States, growth hormone hormones related to livestock manure return to the field were detected.
And estrogen.

4 Conclusion

Environmental pollution of livestock and poultry manure has become a sustainable development of animal husbandry
One of the main problems faced, China’s current livestock and poultry breeding environment
The new trend of pollution is that pollution spreads from the city to the countryside, from the point source
In the face of face-to-face, rural non-point source pollution has become increasingly serious and has threatened a wide range.
Ecological security in large rural areas. It is foreseeable that the study of livestock manure pollution
In the future, it will mainly develop in the direction of combining pollution mechanism and governance.