Study On Culture Of Aerobic Granular Sludge And The Influencing Factors On The Treatment Of High Ammonium Nitrogen Wastewater

In recent years,with the increasing of economic development and the living standards of people,China is facing the lack of water resources and water pollution intensified the situation,so it is necessary to take appropriate measures to control the impact and harm of water environment.Nitrogen is one of the causes of water eutrophication,to remove the nitrogen in water efficiently and low-cost has become one of the main objectives of China sewage treatment.The traditional biological denitrification process has the disadvantages of poor handling efficiency and lower running efficiency,so research and development the new and efficient denitrification process is of great significance to improve the water pollution problem.Aerobic granular sludge(AGS)technology has many advantages,such as stronger impact load,better sludge settling performance and the reactor area is small,which has overcame some problems of the traditional process,so it has a good application prospects.In this study,the removal efficiency of pollutants and the dynamic changes of extracellular polymer(EPS)content in AGS were studied with high ammonium nitrogen wastewater.The effects of dissolved oxygen concentration,temperature and C/N ratio factors on the pollutants removal efficiency of aerobic granular sludge were detected.The mature AGS were formed in the SBR reactor by 90 days of culture.The sludge color was dark brown and the shape was spherical or ellipsoidal.The sludge concentration(MLSS)was stabilized gradually,and the sludge sedimentation index(SVI)decreased from 114 ml/g to 50 ml/g,the sedimentation performance was higher.In the process of culture,the removal efficiency of COD and ammonium nitrogen was 90.87% and 98.19%,respectively,the content of EPS increased with the gradual formation of granular sludge,The total concentration of EPS(in terms of the sum of protein(PN)and polysaccharide(PS))increased from 58.04 mg/g MLSS to 100.24 mg/g MLSS.Temperature and C/N ratio had a greater effect on the removal of pollutants,when the temperature decreased from 20? to 10?,COD removal rate decreased from 90.47% to 72.80% while the ammonium nitrogen removal rate decreased from 98.87% to 82.85%,EPS showed a tendency of decreased at first and then increased.When the C/N ratios were 1: 1,3: 1,5: 1,COD removal rate was about 92%,the removal rate of ammonium nitrogen decreased from 90.38% to 54.78%,and the removal rate of total nitrogen increased from 32.78% to 57.84%.Dissolved oxygen concentration had little effect on the removal of COD and ammonium nitrogen,but had a great effect on the removal efficiency of total nitrogen.When the dissolved oxygen was 6~8,4~6 and 2~4 mg/L,the removal rate of COD and ammonium nitrogen were 88% and 96%,respectively.When the dissolved oxygen concentration is 2~4 mg/L,the total nitrogen removal rate was the best,which reached 40%.The effect of dissolved oxygen concentration on EPS content and composition was not significant,but it affected the ntegrity of granular sludge,the concentration of PN were 80.5,80.6 and 77.2 mg/g,respectively,and the PS were 23.7,24.2 and 23.4 mg/g,respectively.With the decrease of dissolved oxygen concentration,the proportion of sludge with particle size less than 0.5 mm was 64.7%,65.65% and 72.01%,respectively.High-throughput sequencing results showed that AGS was rich in microbes,the proportion of Proteobacteria in the category was the highest,the next one was Bacteroidetes.Granular sludge contained a variety of microbial with simultaneous nitrification and denitrification capacity,such as Nitrosomonas and Comamonadaceae_unclassified,and Thauera,Paracocccus,Enterobacter and Xanthomonadaceae_unclassified with denitrification ability.Among the main microbial species,Xanthomonadaceae_unclassified had almost 0% while the dissolved oxygen concentration bigger than 4 mg/L and presented 5.06% at a low dissolved oxygen concentration..