UASB Combined With A~2/O Process For Treatment Of Piggery Wastewater

Piggery wastewater is an important cause of agricultural non-point source pollution.Agricultural non-point source pollution has become a major environmental problem in China.There are two types of pollution components for piggery wastewater:one is the direct discharge of piggery wastewater,and the other is the digested piggery wastewater.The main difference between the two is the difference in composition.The former has high organic and nitrogen-phosphorus contents and is easy to biochemically treat,while the latter belongs to wastewater with low C/N ratio and is difficult to biochemically treat.Therefore,there are major differences in the processes and methods for selecting treatments.As the the digested piggery wastewater of piggery wastewater is produced in the anaerobic digestion process of the piggery wastewater,a continuous combination process should be used to treat the piggery wastewater.In this paper,UASB anaerobic reactor is used to treat raw water from piggery wastewater.The digested piggery wastewater is treated by A2/O process(anaerobic/anoxic/aerobic)treatment.The method combines the high organic matter removal capability of the UASB anaerobic reactor,and the A2/O process takes into account the characteristics of nitrogen and phosphorus removal.This not only addresses the high organic matter in the piggery wastewater,but also addresses the problem of high nitrogen and phosphorus in the digested piggery wastewater.Using UASB and A2/O process combination is the focus of this thesis.This project has produced a series of test devices,inoculated the activated sludge of the sewage treatment plant,and then completed the start-up of the reactor through a culture and acclimatization process.After the start of the reactor,the parameters of the test device are optimized to obtain the best operating conditions.Under the optimal working conditions,the conditions and environment of piggery wastewater treatment in the actual project were simulated,and a comparative study of the effects of conventional and inverted A2/O processes on anaerobic digestion was conducted;UASB and reversed A2/O combined process The effect of treatment of piggery wastewater was investigated;and the effects of anoxic/anaerobic/aerobic tank volume ratio on the nitrogen and phosphorus removal of low C/N ratio anaerobic digestion solution were investigated.After a series of experiments,the following conclusions were obtained:1.Comparing conventional and reverted A2/O processes to treat digested piggery wastewater with low C/N ratio,the inverted A2/O process has superior performance in removing COD,ammonia nitrogen,and TP from digested piggery wastewater superior,the removal rate increased by 8.2,10.9%and 27.3%,respectively,compared to the conventional A2/O process.Moreover,whether it is the conventional A2/O process or the reverted A2/O process,the anoxic bath is the main process that affects the organic removal and nitrogen removal of the system.2.The UASB-reverted A2/O combined process was used to treat the piggery wastewater.and the effluent was stable after continuous operation.The combined process combines the advantages of both the UASB reactor and the reversed A2/O process.It not only has a high removal rate for organics,but also achieves good nitrogen and phosphorus removal.Through UASB combined with inverted A2/O process,the cumulative removal rates of COD,ammonia nitrogen,and TP were 97.2,84.2,and 65.8%,respectively.The effluent of the sedimentation tanks after the operation was stable was lower than the pollutant discharge standard of livestock and poultry breeding industry.(GB18596-2001).For low C/N ratio digested piggery wastewater,the reverted A2/O process can overcome the inherent defects of the conventional A2/O process.The anoxic tank is located at the front of the anaerobic tank and the influent carbon source is preferentially satisfied.Nitrification and denitrification strengthen the system's ability to remove nitrogen.At the same time,because of the connection between the anaerobic tank and the aerobic tank,the alternating environment of anaerobic and aerobic causes the phosphorus-absorbing bacteria to have strong phosphorus absorption power and improve the efficiency of phosphorus removal in the system.3.Based on the three conditions set in the test,under the premise of the same total hydraulic retention time and operating conditions,the treatment effect of pollutants in anoxic/anaerobic/aerobic tank capacity ratios of 3:2:4 was obtained.Optimal,the removal efficiencies of COD,ammonia nitrogen,TN,and TP reached 88.75%,80.12%,65.33%,and 62.53%,respectively.In the reversed A2/O process,under the condition that sufficient nitrification is provided by the nitrification reaction in the aerobic section,the reflux ratio is the same,and the increase in the anoxic section tank capacity is beneficial to the improvement of the system's ability to denitrify denitrification,and it also helps to improve the system degradation efficiency of organic matter in sewage and the ability of denitrifying phosphorus removal.For the reversed A2/O process,the removal rate of TP in the wastewater by the system is greatly affected by the anaerobic section tank capacity.Increasing the anaerobic section pool capacity of the system and prolonging the residence time of the anaerobic section make the phosphorus-accumulating bacteria more fully released in the anaerobic section,which is more conducive to improving the system's fficiency of phosphorus removal.Therefore,using the UASB-reverted A2/O process to treat swine wastewater,the UASB anaerobic reactor has a higher removal rate of organic matter,and the reverted A2/O has better denitrification and phosphorus removal efficiency.The effluent can achieve pollution in the livestock and poultry breeding industry.Emission standards,the use of the joint process to treat piggery wastewater is completely feasible.Moreover,during the process of the process,there is no need to add chemical reagents and supplement carbon sources,reducing the cost,reflecting the application value of the process in the wastewater treatment of livestock and poultry farming.