Have you caught the key points about sewage treatment in pig farming?

As the world's largest pig farming country, China holds a pivotal position in the economic development of modern pig farming. But at the same time, the pollution problem caused by sewage treatment is also quite challenging.

Taking a 10000 head pig farm as an example, its daily fecal and urine wastewater can reach 100-150t. The difficulty of purifying these fecal pollutants in sewage treatment technology can be imagined. However, after sewage treatment, it still needs to meet national discharge standards for a long time, which requires a large amount of investment and high operating costs, which increases the cost of sewage treatment in the pig breeding process.

In recent years, many economically developed provinces in China have been carrying out large-scale sewage treatment and renovation of pig farms, and many pig farms have been forced to demolish. Some areas have begun to strictly divide prohibited and restricted breeding areas, indicating that the control of sewage treatment in pig farms will be one of the necessary ways for future pig farms to seek development opportunities.

1、 Harm of Wastewater from Pig Farms

The discharge of fecal pollutants from farms without sewage treatment can cause serious pollution of surface water, groundwater, soil, and ambient air. The fecal sewage without sewage treatment contains a large number of pollutants that are brushed into rivers, lakes and reservoirs, consuming dissolved oxygen in the water body, making the water body black and smelly, causing water pollution.

A large amount of nutrients in fecal wastewater cause eutrophication of the water body, and discharge into rivers gradually causes the death of aquatic organisms sensitive to organic pollution. In severe cases, it can lead to the loss of function in fish ponds and rivers.

The long-term infiltration of aquaculture wastewater into the ground increases the concentration of nitrate or nitrite nitrogen in the groundwater, reduces the content of dissolved oxygen in the groundwater, increases toxic components, and leads to the deterioration of water quality, seriously endangering the quality of surrounding domestic water. Even harming crops, causing growth obstruction or death. The consequences of on-site discharge without sewage treatment cannot be underestimated.

2、 Sewage treatment ideas for pig farm farming

The sewage discharged from pig farms without sewage treatment belongs to organic sewage, which has the best anaerobic fermentation effect. However, after sewage treatment, it has not yet reached the optimal standard and cannot be directly discharged. Moderate use in farmland and fish ponds is an excellent nutrient solution. Therefore, the sewage treatment of pig farms must be considered from a combination of biology and ecology, which is the most economical and effective way for the mutual promotion and development of the breeding industry.

At present, the sewage treatment methods for large-scale pig farm manure at home and abroad mainly include comprehensive utilization and treatment of up to standard discharge. Comprehensive utilization is a sustainable development path that involves the multi-level utilization of biomass energy, creating a harmonious coexistence between ecological agriculture and the environment. After reaching the standard for sewage treatment, it can be discharged into many areas that can be utilized, such as fish ponds, farmland, or orchards, within the allowable daily discharge concentration range, in order to minimize the degree of environmental pollution.

3、 Pretreatment methods for pig farm wastewater

The use of pre-treatment methods can reduce the load of sewage pollutants in subsequent sewage treatment steps, while preventing large solids or debris from entering the subsequent sewage treatment process, causing congestion or damage to sewage treatment equipment.

For the large particle components in fecal wastewater, pig farms can use solid-liquid separation technologies such as sedimentation, filtration, and centrifugation to achieve pre-treatment before sewage treatment. Common grids, sedimentation tanks, and screens in sewage treatment all belong to this category.

4、 Main technologies for wastewater treatment in aquaculture industry

Artificial anaerobic treatment method

The sewage treatment method based on increasing sludge concentration and improving the mixing effect of sewage and sludge is developed through a series of high load reactors for sewage treatment. The characteristics of anaerobic treatment are small land occupation, low energy demand, and the ability to produce biogas. The treatment process does not require oxygen and has a high potential for organic matter loading, which can degrade some parts that cannot be degraded by aerobic microorganisms.

After anaerobic treatment, sewage can be returned to the field as liquid organic fertilizer under available land conditions. However, the discharge volume is often large, and transportation and application are not very convenient. Generally, it is advisable to undergo multi-stage aerobic treatment to meet the sewage treatment discharge standards.

Artificial aerobic treatment method

Using microorganisms to decompose organics under aerobic conditions, and at the same time synthesize their own cells (activated sludge), the organics in sewage can be biodegraded, and finally be completely oxidized to simple inorganic compound substances. The oxidation ditch, SBR, and A/O belong to the improved activated sludge method. Generally, it is not possible to use primary aerobic methods to treat pig farm wastewater to meet the standards, and multi-level series connection must be carried out, such as using acidification and tertiary contact oxidation processes for pig farm wastewater treatment.

Anaerobic aerobic treatment method

Pig farm wastewater is an organic wastewater that is difficult to treat in sewage treatment technology. Due to its large displacement, low temperature, mixed solid and liquid content, high organic content, rich nitrogen and phosphorus content, and difficulty in removal, the anaerobic method has a high BOD load, while the aerobic method has a low BOD load. During the anaerobic process of sewage treatment, the water still has a foul odor after treatment, and all indicators cannot meet the national sewage treatment discharge standards.

Generally speaking, a combination of multiple treatment methods is required, and further aerobic treatment (such as oxidation ponds) is often used as the secondary purification of anaerobic treatment. This is also a good sewage treatment method for treating high concentration organic matter, and is also a sewage treatment method used in many large-scale pig farms.

After sewage treatment, the water can basically meet the national discharge standards. Finally, it is generally discharged into the fish pond. On the one hand, the fish pond can further oxidize the pond, and at the same time, the algal reaeration can improve the dissolved oxygen content, while promoting the growth of phytoplankton, zooplankton and fish, forming nitrogen, phosphorus algae fish biological chain, and reducing nitrogen and phosphorus environmental pollution.

Based on the above analysis, as long as the removal of COD, ammonia nitrogen, phosphorus, SS and other substances in sewage is effectively reduced, it can save a lot of time and economic investment for the subsequent series of sewage treatment processes.

As a systematic engineering project, wastewater treatment in the aquaculture industry needs to follow ecological principles, combined with the use of microbial wastewater treatment bacteria and other methods to form a systematic water quality purification biological chain. By comprehensively utilizing technology and environmental protection products, it can achieve the recycling of pig farm water after reaching the standard, effectively improve the breeding environment, and reduce the threat to the surrounding environment.