Study On Technological Process And Kinetics In The Biological Nitrogen Removal Of Slaughter-Process Wastewater

The pollution of NH3-N has become the primary problem of the water pollution in China, while the slaughter-process wastewater is the main source of NH3-N pollution. To deal with the difficulties of nitrogen removal in the course of producing slaughter-process waste water, the author investigated and analyzed the biological process of slaughter-process wastewater, did the simulating experiments on ABR anaerobic ammoniation \SBR nitrogen removal (nitration and denitrification), identified nitrobacteria, and researched the reaction kinetics and the mechanism of process of biological nitrogen removal systematically and deeply, and then validated the application of the research achievements.The spot investigations and analyses indicate that the slaughter-process wastewater is a kind of organic water full of organic nitrogen (carbamide, uric acid, protein etc.) , the NH3-N concentration of which exists a certain variety law in the whole biological process. Especially the concentration of anaerobic NH3-N will increase greatly(net increase 70%¹50%), obviously most of the designs of nitration and denitrification based on the influent NH3-N index are wrong, which is one of the significant reasons why the NH₃—N is hard to meet the standards. Lack of a set of effective technological nitrogen removal conditions to guide the process of slaughter-process wastewater is another point.The experimental result of anaerobic ammoniation shows, the most appropriate hydraulic retention time is between six and eight hours, the longer the HRT , the higher the rate of NH3-N net increase. And the higher peak value, the later the appearing moment. The experimental result proves that the rate of net increase is just between 90 % and 196 % after ammoniation. The phenomenon of anaerobic ammonia oxidation will happen apparently during the latter period of anaerobic ammoniation, which cause the decreasing range of NH3-N is between 8%-14%. The process of ammoniation will happen in the anaerobic or aerobic condition. The period of anaerobic ammoniation is longer and NH3-N peak value is higher(the rate of net increase may reach 196%)with thoroughly ammoniation. In comparison, the period of aerobic ammoniation is shorter and NH3-N peak value is lower (the rate of net increase can reach 33 % only) . As for the wastewater containing organic nitrogen, thebest approach of ammoniation should be anaerobic ammoniation. In the process of anaerobic ammoniation, NO3" is always in the rather lower level , and meanwhile NO2" can never be found.The experiments of SBR nitrification and denitrification shows, at the aim of nitrogen and carbon removal, the best operating conditions of slaughter-process wastewater are: water enter-aeration (8h) ->anaerobic mix (lh, adding carbon) -> aeration again (0.5h) -?deposition (lh) -> drainage (leave it) .The best DO concentration=2mg/l, and the best sludge concentration MLSS=3500mg/l. The best carbon source is methyl alcohol or wastewater. During the course of nitrification, NO2" is always in the rather low level. Companion with nitration reaction, NO3" is increasing gradually till the denitrification reaches. But beyond the limitation of the period or NO3" < 15mg/L, the decreasing rate is extremely low. So the discharge standards of wastewater should include the indexes of total nitrogen or Keyes nitrogen indexes besides NH3-N. There is the obvious phenomenon of aerobic denitrification, which causes the loss of 24% total nitrogen.The mechanism research shows the NH3-N removal process of slaughter-process wastewater is mainly composed of ammoniation, nitrification and denitrification. The three steps need microorganisms to involve in, so the characteristics of the steps depend on that of the microorganisms. In the process of nitrification, alkalinity should be testified and be added whenever necessary. In addition, organic carbon source should be added in the course of denitrification. The author have isolated fifteen strains of nitrobacteria (nitrobacilus and nitrococcus) , and the nitrobacteria plays a percentage of 6.2 in the total amount of the activated sludge.The phenomenon of anaerobic ammonia oxidation is found in the experiment, because there exist anaerobic ammonia oxidation bacteria in the reactor, which can regard NO3" or NO2" as electron acceptor, gaining energy from oxidation of NH3-N. Therefore, the anaerobic ammonia oxidation phenomenon comes into occurrence. So, the existence of NO3" and NO2" is essential for the occurrence of anaerobic ammonia oxidation, the other one is in the anaerobic condition. By analyzing, the paper proposes that anaerobic ammonia oxidation process has no advantages comparing with the traditional one. In the experiment, the efficiency of anaerobic ammonia oxidation is rather low (only 8 — 14 % ) because of the...