Study On Enhanced Nitrogen Removal By Short-range Nitrification And Denitrification By Tidal Biological Contact Oxidation

Since the promulgation of the "Thirteenth Five-Year Plan for Comprehensive Improvement of the National Rural Environment",the decentralized sewage treatment in the vast rural areas has attracted the attention of relevant departments,and the most critical of these is to seek reasonable treatment technologies and process improvements according to local conditions.At present,low C / N in rural areas limits the effect of nitrogen removal,so a nitrogen removal process that can save carbon sources is of great significance for the reduction of total nitrogen in the effluent;at the same time,high impact load,the lack of professionals,and the impact load and management of the treatment device Put forward higher requirements.Compared with complete denitrification,short-range denitrification can save 40% of the carbon source,and the biofilm method also has the advantages of high biofilm volume,strong impact load,and easy management.Therefore,the short-cut nitrification and denitrification process is applied to the tidal type in this study In the biological contact oxidation process,a new idea is provided for decentralized sewage to improve the efficiency of nitrogen removal.The experiment first carried out the start of the tidal biological contact oxidation tank,using sludge regeneration filler and polyurethane filler at the same time,the startup performance of the sludge regeneration filler was better than that of the polyurethane filler.The sludge regeneration filler took 29 days to start,and the ammonia nitrogen and COD removal rates finally stabilized at 90% and 95%,respectively;while the polyurethane filler took 43 days to start,the ammonia nitrogen and COD removal rates finally stabilized at 72% and 80%.Based on the sludge regeneration filler,the inundation time / vacancy time,the number of tides and the residence time were changed,the change of the denitrification effect of the contact oxidation tank effluent was analyzed,and the oxygenation law inside the biological contact oxidation tank was analyzed.Under the condition of 24 h residence time and 24 times of tides,the oxygenation effect is inversely proportional to the submerged vacancy ratio.The concentrations of ammonia nitrogen,COD,and effluent DO decrease as the submerged vacancy ratio decreases.The increase shows a trend of decreasing first and then increasing.The optimal submergence / vacancy ratio is 5,and the average total nitrogen concentration in the effluent is 18.4 mg / L,which meets the national standard Class B emission standard.Under the condition of residence time of 12 h and submerged vacancy ratio of 29,the oxygenation effect is proportional to the number of tides.The ammonia nitrogen and COD in the effluent decrease with the increase of the number of tides.Nitrogen concentration decreases first and then increases with the increase of the number of tides.The optimal operating condition is 18 tides per cycle.The average nitrite concentration in the effluent is 2.2 mg / L.It is 12.3mg / L,which meets the national standard Class A emission standard.According to the oxygenation law of the tidal biological contact oxidation tank,seek the optimal working conditions that are conducive to nitrite-type simultaneous nitrification and denitrification.After the realization,the activity change law is explored by two methods of activity test.The full nitrification biological contact oxidation reactor with a residence time of 24 h,after 48 cycles of 12 h low-oxygen operation,successfully achieved efficient nitrite-type simultaneous nitrification and denitrification,with an average effluent total nitrogen of 11.3mg / L,reaching the national standard level A emission standard,Denitrification rate increased by 38%.The specific oxygen consumption rates of the nitrous acid type SND starting process at 0d,30 d and 60 d were measured respectively.Under low-oxygen conditions,the oxygen absorption capacity of AOB bacteria was better than that of NOB bacteria.The min dropped to 0.15mgO2 / gVSS · min,the activity of NOB bacteria decreased by 78%,and the panning of NOB bacteria was successfully completed.