Breeding wastewater treatment process

1. Solid-liquid separation

No matter what system or comprehensive measures are used to treat the wastewater from livestock and poultry farms, solid-liquid separation must be carried out first. The content of suspended matter is very high, up to 160000mg/L, and the corresponding organic matter content is also high. Through solid-liquid separation, the pollutant load of the liquid part can be greatly reduced; secondly, through solid-liquid separation, larger solid matter can be prevented. Enter the follow-up processing link to prevent equipment from being blocked and damaged. In addition, solid-liquid separation before anaerobic digestion treatment can also increase the reliability of anaerobic digestion operation, reduce the size of anaerobic reactor and the required residence time, reduce facility investment and improve COD removal efficiency. Solid-liquid separation technology generally includes: screening, centrifugation, filtration, flotation, sedimentation, precipitation, flocculation and other processes. At present, my country has mature solid-liquid separation technology and corresponding equipment, and its equipment types mainly include screen type, horizontal centrifuge, filter press, hydrocyclone, rotary cone screen and centrifugal disc separator, etc. . Mature agents include polyaluminum chloride, polyacrylamide, activated carbon and other water treatment agents.

2. Anaerobic treatment

Because the aquaculture wastewater belongs to the "three high" wastewater with high organic matter concentration, high N, P content and high number of harmful microorganisms. Therefore, anaerobic technology has become an indispensable key technology in the treatment of livestock and poultry farm manure. For the high-concentration organic wastewater in farms, the anaerobic digestion process can effectively remove a large amount of soluble organic matter at a low operating cost. The COD removal rate can reach 85% to 90%, and it can kill infectious bacteria. Conducive to the epidemic prevention of farms. If the aquaculture wastewater after solid-liquid separation is directly treated by aerobic process, although the one-time investment can save 20%, but due to the large power consumption, the power flow consumption is 10 times that of anaerobic treatment, so long-term operation The cost will bring a heavy economic burden to the farm.

There are many anaerobic processes currently used to treat farm manure, among which the more commonly used ones are: anaerobic filter (AF), upflow anaerobic sludge bed (UASB), composite anaerobic reactor (UASB+AF) , secondary anaerobic digestion and upflow sludge bed reactor (USR), etc. In recent years, anaerobic digestion or biogas fermentation technology has been widely used in farm waste treatment. By the end of 2002, my country had more than 2,000 large and medium-sized biogas projects for livestock and poultry farms, making it one of the countries with the largest number of biogas installations. one. Although there are many examples of failed biogas projects in my country, and the success rate of project construction is only 85%, this technology can be regarded as a way to solve the problem of livestock and poultry manure. An effective technical solution for the harmless and resource utilization of sewage. Livestock manure and farm wastewater are valuable resources. After anaerobic digestion treatment, it can be harmless, and biogas and organic fertilizer can also be recovered. Therefore, the construction of biogas projects will be a wise move for small and medium farms.

3. Aerobic treatment

Aerobic treatment refers to a process that uses aerobic microorganisms to treat aquaculture wastewater. Aerobic biological treatment can be divided into two categories: natural aerobic treatment and artificial aerobic treatment. Natural aerobic biological treatment is a method of purifying wastewater by using microorganisms in natural water and soil, also known as natural biological treatment, mainly including water purification and soil purification. The former mainly includes oxidation ponds (aerobic ponds, facultative ponds, anaerobic ponds) and breeding ponds, etc.; the latter mainly includes land treatment (slow infiltration, rapid method filtration, overland flow) and constructed wetlands. The natural biological treatment method not only has low infrastructure costs and less power consumption, but also has a higher removal rate for biodegradable organic matter, nutrients such as nitrogen and phosphorus, and bacteria than conventional secondary treatment, and some of them can achieve the effect of tertiary treatment. In addition, under certain conditions, this method can realize the utilization of sewage resources when combined with sewage irrigation. The disadvantages of this method are mainly that it occupies a large area and the treatment effect is easily affected by the seasons. However, if the scale of the farm is small and there are abandoned ditches and tidal flats available nearby, this method should be selected as much as possible to save investment and treatment costs. Artificial aerobic biological treatment is a wastewater treatment method that artificially strengthens oxygen supply to improve the activity of aerobic microorganisms. The methods mainly include activated sludge method, biological filter, biological turntable, biological contact oxidation method, sequencing batch activated sludge method (SBR), anaerobic/aerobic (A/O) and oxidation ditch method, etc. As far as the treatment effect is concerned, the treatment effect of the contact oxidation method and the biological turntable is better than that of the activated sludge method. Although the treatment effect of the biological filter is also very good, it is prone to filter blockage. Oxidation ditch, SBR and A/O processes are all improved activated sludge processes. Oxidation ditch has good effluent quality, less sludge, and can also denitrify sewage, but the BOD load of the treatment is small, the area is large, and the operating cost is high. The SBR method has a high degree of automation control and can treat sewage

Advanced processing, but its disadvantage is that the BOD load is small, and the one-time investment is also large. A/O body is an activated sludge treatment process with dual functions of removing BOD and denitrification. Although the investment is relatively large, the water treated by this method is easy to discharge up to the standard. Therefore, the A/O method can be selected for those farms with large scale of farming, large amount of wastewater and strong economic capacity, and aerobic treatment processes such as contact oxidation and biological turntable for medium-scale farms.