| The slaughter-process wastewater is a kind of typical industrial wastewater of high COD, high nitrogen and high suspended substance. The wastewater contains complicated component and high concentrate organic, especially the urea, uric acid, protein, fat and carbohydrates in the organic matter can be converted further to ammonia nitrogen of high concentration by ammonification, which make it more difficult for the nitrogen removal. If discharged without proper treatment, it could seriously pollute the aquatic environment. In order to improve the nitrogen removal rate of biochemical treatment unit of slaughter-process wastewater after hydrolytic acidification, A/O contact oxidation process and SBR process were applied in advanced denitrification experiments, both widely used in practical engineering. The best operation condition and optimized improvement methods to realize efficient biological nitrogen removal were discussed and it was expected to provide guidance for engineering applications of the biological nitrogen removal process of slaughter-process wastewater.Under the premise of the success of biofilm in the inoculated biological contact oxidation reactor, these influence factors, such as, mixed liquor recycle ratios, anoxic denitrification HRT, aerobic nitrification HRT, DO, influent loading of ammonia nitrogen on denitrogenation were investigated and optimum condition parameters of A/O biological contact oxidation process to treat slaughter-process wastewater were established ultimately. It was showed the satisfying denitrogenation effect was achieved when the A/O biological contact oxidation process was used for slaughter-process wastewater treatment with the following parameters, aerobic nitrification HRT and anoxic denitrification HRT should not be less than 18 h and 8 h, mixed liquor recycle ratios can be set to 200%, DO in the aerobic tank in 2.5~3.5 mg/L and the ammonia nitrogen load should not be more than 0.109 kg/(m3·d). Every quality index of water reach the class I of second period level of water pollution discharge limits of Guangdong province(DB44/26-2001). In order to guarantee the effluent quality in the low temperature region not up to standard, the coagulation precipitate or other auxiliary measures should be added.The removal rate of effluent ammonia nitrogen was below 80% when conventional aerobic/anoxic SBR process treat the slaughter-process wastewater of high concentration. It’s considered that the unbalanced relation between carbon source and the basicity may cause ammonia nitrogen index to exceed emission standards frequently. To keep the balance between the two in the process of denitrification, multiple alternating aerobic/anoxic SBR process was created by adjusting the operation mode and working condition. By experiment it was concluded that: when the cycles for three times, the removal rate of ammonia nitrogen and COD reached 97% and 90%, respectively, realizing the discharge standard. This is an effective method to further improve the efficiency of denitrogenation of conventional SBR process.The comparison was made about pollutants removal efficiency, water treatment amounts and economic costs between the A/O biological contact oxidation process and alternating aerobic/anoxic SBR process. It is consider that improved SBR process is more suitable for slaughter-process wastewater of high concentration and actual production characteristics of current slaughtering industry of our country; However, the improved SBR process is a little stricter with the equipment performance and the control system. Though the process is superior to the A/O bio-contact oxidation process in the infrastructure, power consumption and maintenance, the advantage may be weakened with the increase of the amount of the wastewater treated. |
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