Study On Short-Cut Nitrification And Denitrification By Intermittent Aeration SBR And Its Application To The Treatment Of Wastewater Containing Aniline

Aniline is widely used in printing and dyeing,pharmaceutical,pesticide,rubber and other industries,and its demand and production are increasing year by year,while it is more difficult to degrade and more harmful to human body,and the emission is strictly required.In this study,the short-cut nitrification and denitrification process was used to treat low concentration aniline wastewater,saving energy and carbon source for denitrification.The start-up and stable operation of the short-cut nitrification and denitrification process and its treatment of aniline wastewater were studied respectively,and the main findings were as follows.Short-cut nitrification was successfully achieved in the start-up phase of short-cut nitrification by controlling the aeration rate of 40 m L/min,influent C/N of 4,influent ammonia nitrogen of 50 mg/L,and influent p H of 7.5 in a sequencing batch activated sludge reactor(SBR).The average ammonia nitrogen removal rate of the system was93.36 % and the average nitrite accumulation rate was 73.04 %.In order to achieve simultaneous denitrification based on short-cut nitrification,the stable operation of the intermittent aeration short-cut nitrification and denitrification process was investigated by controlling the reaction stage of the SBR reactor to operate with intermittent aeration and studying the effects of aeration quantity,water distribution C/N and initial p H on the short-cut nitrification and denitrification process.Oxygen is crucial to the control of short-cut nitrification,and the ammonia and nitrogen removal effect was improved when the aeration rate was increased from 40 m L/min to80 m L/min.However,to ensure the short-cut nitrification effect,it was considered that aerobic aeration for 20 min/anoxic mixing for 20 min operation with an aeration rate of60 m L/min was beneficial to the short-cut nitrification and denitrification effect of the short-cut nitrification and denitrification process.Organic matter influenced the denitrification effect.The total nitrogen removal rate of the system increased gradually when C/N was increased from 0 to 6.When C/N was 6,the denitrification reaction was the most complete and the total nitrogen removal effect was the highest.A suitable p H provides a suitable growth environment for microorganisms in the system on the one hand,and on the other hand,it can increase the free ammonia concentration(FA)in the system and inhibit the activity of nitrite oxidizing bacteria(NOB).The p H of water distribution was increased from 8.1 to 8.3,and the initial FA reached more than 1 mg/L,which inhibited the activity of NOB,and the nitrate concentration in the system effluent was reduced and the nitrite accumulation rate was increased.With the controlled aeration rate of 60 m L/min,influent C/N of 6,and the p H of 8.3 of 100 mg/L of the lagoon water,the stable operation of short-cut nitrification and denitrification was achieved with intermittent aeration operation and initial FA inhibition,and the average removal rate of ammonia nitrogen was 98.79 %,nitrite accumulation rate was 95.23 %and total nitrogen removal rate was 87.03 %.The results were good and had some impact resistance.The microbial community structure during the stable operation of SBR was found that the proportions of Nitrosomonas spp.(AOB)and Nitrosospirillum spp.(NOB)were 0.11 % and 52.25 % respectively before and after the realization of SBR,and the proportions of Nitrosospirillum spp.(NOB)were 5.6 % and 0.44 % respectively,and the AOB was enriched and the NOB proportion was greatly reduced,thus achieving the stable operation of SBR.Under the stable operation of SBR short-cut nitrification and denitrification,aniline was added to the feed water at 5 mg/L,20 mg/L,and 30 mg/L to study the effect of aniline removal in the system.The addition of aniline caused a decrease in the ammonia removal rate of the system,but after a period of recovery the ammonia removal rate increased to different degrees.After 8 days of recovery,the ammonia removal rate of the reactor with aniline concentration of 20 mg/L recovered to more than 99 %,and the ammonia removal rate did not decrease after adding the same concentration of aniline to the feed water,and the average nitrite accumulation rate was87.06 % and COD removal rate was 84.41 %.However,it was difficult to recover the decrease in ammonia removal rate of the system when the influent aniline concentration reached 30 mg/L.The SBR system was effective in removing aniline at all three influent aniline concentrations,and the effluent aniline concentration was below 1 mg/L.The SBR short-cut nitrification and denitrification system treated coke wastewater containing 20 mg/L aniline,and the ammonia nitrogen removal rate was 94.55 %,nitrite accumulation rate was 94.76 %,total nitrogen removal rate was 90.50 %,and the aniline effluent concentration was 0.44 mg/L,and the removal rate was 95.01 %.The removal rate was 95.01 %,and the treatment effect was good.It was found that the proportion of Nitrosomonas(AOB)was still higher than that of Nitrospirae(NOB)after the addition of aniline,and AOB was still in the dominant position in the genus Nitrosomonas,and the SBR system was still in the short-cut nitrification and denitrification operation.The SBR system was still in short-cut nitrification and denitrification operation.After adding 20 mg/L aniline,the proportion of Thauera spp.and unclassified＿Bacteroidetes spp.unclassified＿Anaerolineaceae spp.increased,and these spp.were able to degrade the refractory organic matter,and it was inferred that they might be the spp.involved in the degradation of aniline.