Questions and answers on common technologies for livestock manure treatment

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1. What is animal manure?　　 　

Manure, as the name implies, refers to wastes such as manure and sewage generated in the process of livestock and poultry breeding. Broadly speaking, manure includes manure, urine, litter, flushing water, animal carcasses, feed residues and odors produced in the process of livestock and poultry breeding; in a narrow sense, manure refers to livestock and poultry manure, urine excrement And its mixture with rinse water. In this article, manure takes its narrow connotation, and mainly introduces the treatment and utilization of manure and its washing water mixture. 　　

2. What are the main forms of manure? 　　

The form of manure is distinguished according to its solid and moisture content: intuitively, manure mainly exists in two different forms, solid and liquid; if you follow the solid content in manure, you can further subdivide its form. Solid, semi-solid, slurry and liquid, the solid content of these four forms are> 20%, 10%-20%, 5%-10%, <5%. Due to different types of livestock and poultry, different physiological and metabolic processes, the degree of dryness and wetness of excreted feces and the amount of urine are also different, so the state of feces during excretion is also different. There is not necessarily a clear dividing line between adjacent forms of manure, such as manure slurry and semi-solid. 　　

When the manure is affected by the external environment and the solid content or moisture content in it changes, it may change from one form to another. In addition, animal species, feeding rations, type and quantity of bedding Other factors may affect the form of manure. 　　　

3. What factors affect the excretion of livestock and poultry manure and urine? 　　

Due to individual differences between different livestock and poultry, their defecation volume is very different. For example, the daily defecation volume of adult cattle is 20 to 35 kg, while the daily defecation volume of laying hens is only 0.14 kg to 0.16. kg. Even if the same kind of livestock and poultry are different in sex, age, weight, growth stage and the nature of the diet they are fed, the amount of animal defecation will be different. Studies have shown that there is a significant positive correlation between the amount of feces in sheep and the amount of feed intake and body weight. The amount of feces in rams of the same breed is greater than that of ewes. 　　

The urine output of livestock and poultry is affected by factors such as breed, age, production type, feed, service status, season and external temperature. Any change in factors will change the animal's urine output. Poultry has a small amount of urine. Adult chickens urinate between 60 ml and 180 ml a day and night. Because avian urine is excreted in the cloaca and feces, it is generally not measured separately. For the same individual, the amount of urine in an animal mainly depends on the amount of water ingested and discharged by other means. When the dietary protein or salt content is high, the amount of drinking water increases, and the urine output increases at the same time; When the temperature is high and the amount of activity is high, the amount of water discharged from the lungs or the skin increases, resulting in a decrease in urine output; certain pathological reasons can often cause significant changes in urine output. 　　　　

4. What are the main sources of aquaculture wastewater? 　　　　 　

Sewage from farms mainly comes from the washing water of livestock and poultry houses, dripping drinking water, cooling water, and domestic sewage from farms. The amount of water used for washing depends on the manure removal process, and the amount of washing water used by different manure removal processes is very different, so the amount of farming wastewater is also very different. For pig farms, if the fermented bed pig production process is adopted, the flushing water in the production process is very small, or even no water is used for flushing, so the amount of farming sewage is very little or no; but if the water flushing process is used, the livestock All the excretion of poultry is collected by washing with water. The amount of washing water is large and the amount of sewage is also large. The dripping drinking water mainly comes from the drinking fountain or the connection of the drinking system. If the drinking fountain is not closed tightly or the connection of the drinking system is damaged or loose due to quality problems, there will be continuous dripping. In addition, the installation height of the drinking fountain is not suitable for animals. There will also be dripping during the drinking process, and the dripping drinking water will also be mixed with manure. 　　

5. Why is manure removal important?　

In modern livestock and poultry farms, especially large-scale farms, livestock and poultry are raised in livestock and poultry houses, and their production, reproduction and other life activities are completed in the livestock and poultry houses. The manure produced by their life metabolism The urine is also excreted into the livestock and poultry houses. If the excrement and urine excreted by the livestock and poultry are not cleaned out in time, the fecal and urine waste will be degraded to a certain extent under the action of microorganisms, and harmful gases such as ammonia and hydrogen sulfide will be volatilized. These harmful gases accumulate in the livestock and poultry houses, leading to the deterioration of the air environment in the livestock and poultry houses. The livestock and poultry will feel uncomfortable, and their growth and reproduction performance will be affected. In severe cases, they may even cause disease and death. 　　　

Not only that, livestock and poultry manure also contains a variety of microorganisms, including pathogenic microorganisms. If the manure with pathogenic microorganisms stays in the livestock and poultry house for a long time, the spread of pathogenic microorganisms may occur. It can be seen that manure removal is an important part of the livestock and poultry breeding process, which not only helps to keep the environment in the livestock and poultry house clean, but also helps to reduce the occurrence of diseases. Therefore, appropriate cleaning methods should be adopted in the process of livestock and poultry breeding, and the manure in the livestock and poultry houses should be cleaned out in time to facilitate the later harmless treatment. 　　　

6. How to choose the method of manure removal? 　　　　

Currently, the main methods of manure removal in the process of livestock and poultry breeding include dry manure removal, water flushing manure removal and blister manure removal methods. The selection of manure removal methods should follow the following principles: 　　

First of all, the method of manure removal should be cross-referenced with the post-treatment process of manure. Manure removal is only one link in the manure management process. It must be connected with other links in the manure management process to form a complete management system in order to achieve effective management of manure. In other words, the subsequent manure treatment technology can be determined according to the selected manure removal method; and the matching manure removal method can also be determined according to the selected manure treatment technology. For example, if a pig farm intends to adopt a biogas project to treat manure, the best choice for the pig farm’s manure removal method is blister manure removal; similarly, if a pig farm adopts blister manure removal method, the post-treatment of manure is determined Discharge treatment to meet the standards is not appropriate, because the concentration of organic matter in the manure of the blister manure is very high. Purification of such manure obviously requires a high price, and the gain is not worth the loss. 　　

Secondly, the choice of manure removal method should also consider various factors such as livestock and poultry species, breeding methods, labor costs, and economic conditions of the farm. Due to different types of livestock and poultry, their biological habits and production processes are different, which also affects the choice of manure removal methods. For example, laying hens are mainly raised in stacked cages. Because the urine of the chickens is excreted in the cloaca and feces, the production process Almost only solid feces are produced in the feces, so dry feces removal method is adopted. 　　　

7. What is dry excrement? 　　　　

Dry manure cleaning is a method of manure cleaning that uses manual or mechanical methods to collect all or most of the solid manure from the floor of the livestock and poultry house, and wash the residual manure on the ground with a small amount of water to separate the solid and liquid waste. 　　

The main purpose of the dry manure removal process is to prevent the mixing of solid manure with urine and sewage as much as possible. The specific method is that once the manure is produced, the dry manure is collected, cleaned and transported by machinery or manually, and the urine and washing water are removed from the The sewer flows out and is treated separately. 　　

The advantages of dry manure removal include: less water for flushing, reducing water consumption; low organic matter content in sewage, which is conducive to simplifying sewage post-treatment processes and equipment, reducing sewage post-treatment costs; maintaining the nutrients of solid manure, Improving the efficiency of organic fertilizer is beneficial to the resource utilization of manure fertilizer; it can effectively remove the manure and urine in the livestock and poultry houses, and maintain the environmental sanitation of the livestock and poultry houses. 　　

The dry manure removal process is divided into two types: manual manure removal and mechanical manure removal.　 　

 8. What is artificial manure removal?　

Artificial manure removal is one of the dry manure removal methods. The manure removal method manually removes the solid manure on the ground of the livestock and poultry house. Manual manure removal can be done with simple equipment such as cleaning tools and hand-push trucks. . Most of the solid manure in the livestock and poultry house is manually cleaned and sent to the manure storage facility for temporary storage; the residual manure on the ground is washed with a small amount of water, and the sewage is discharged into the manure storage tank outside the house through the manure ditch. The advantages of this method of manure removal are that it does not require electricity, requires less one-time investment, and can also be used for separation of manure and urine; the disadvantage is that the labor is large and the production efficiency is low. 　　　 　　

9. What is mechanical manure removal? 　　

Mechanical manure removal is also one of the dry manure removal methods. The manure removal method uses special mechanical equipment instead of manual cleaning to remove the solid manure on the floor of the livestock and poultry house. The mechanical equipment directly transports the collected solid manure outside the livestock and poultry house. , Or directly transported to the manure storage facility; the residual manure on the ground is also washed with a small amount of water, and the sewage is discharged into the manure storage tank outside the house through the manure ditch. 　　　

The advantages of mechanical manure removal are quick and convenient, saving labor, and improving work efficiency; compared with manual manure removal, it will not cause fecal pollution in the walkway in the house. The disadvantage is that the one-time investment is large, and it also costs a certain amount of operation and maintenance costs; the working parts are covered with feces, which is difficult to maintain; the manure cleaner is noisy when it is working, which is not conducive to the growth of livestock and poultry; in addition, domestically produced manure removal equipment There are still some deficiencies in the reliability of use, and the failure rate is high. Although there are still certain problems in the current use of manure removal equipment, with the advancement of animal husbandry machinery engineering technology, the performance of manure removal equipment will continue to improve, and mechanical manure removal is also an inevitable trend in the development of modern large-scale breeding. 　　

10. What is the role of solid-liquid separation?　　 　　

Solid-liquid separation is the pretreatment process of manure, which uses physical or chemical methods and equipment to separate solids and liquids in manure. This method can separate suspended solids, long fibers, weeds, etc. in manure, and usually reduces the chemical oxygen demand in manure by 14% to 16%. 　　

After solid-liquid separation, the solid part is easy to transport, dry, make organic fertilizer or be used as cow bedding material; the liquid part is not only easy to transport and store, but also because of the low organic content in the liquid part, it is also convenient for follow-up deal with. The current solid-liquid separation mainly uses methods such as chemical sedimentation, mechanical screening, screw extrusion, and decanter centrifugal dehydration.