Effect Of Organic Loading On Characteristics Of Short-cut Nitrification Granular Sludge

Compared with traditional nitrification-denitrification processes,some new denitriding processes such as ANAMMOX has attracted much attention due to their features of saving carbon source,low energy consumption and low sludge yield.These new processes all require the efficient accumulation of nitrite as the premise.However,the characteristics of ammonia oxidizing bacteria（AOB）,such as slow growth,low cell yield and sensitivity to environmental changes,make it difficult to accumulate nitrite in practical operation,and restrict the promotion of new denitrification processes.Granular sludge as microbial,on the other hand,since the special biofilm condense and becomes,has good microbial intercept performance,for enrichment of nitrifying bacteria of slow growth is of great significance,structure is compact and granular sludge stability,strong ability to resist impact load,good settling performance,so the nitrosation granular sludge technology is expected to solve the dilemma facing new technology of denitrification.In the current research on the cultivation of nitrifying granular sludge,the method of self-mixing inorganic wastewater is mostly adopted.However,there are more organic pollutants in actual domestic sewage,and the impact of organic matter is more common.Therefore,it is of great significance to study the influence of organic matter and organic load on nitrifying granular sludge.This study on the basis of cultivating ah granular sludge digestion,from the perspective of macro and micro combined with physical and chemical properties of granular sludge,and shortcut nitrification denitrification performance properties,microbial community structure of organic load to study the influence of nitrosation granular sludge,and explores the nitrosation granular sludge performance under the conditions of different particle size differences,the main research achievements were as follows:（1）The flocculent sludge was inoculated,and the laboratory wastewater was prepared by increasing the drainage ratio,shortening the reaction period,increasing the influent substrate concentration and gradually shortening the precipitation time.The stable nitrification effect was successfully achieved after 30 days of operation,and the flocculent sludge was successfully granulated after 50 days of operation.At the end of operation,the proportion of granular sludge with particle size greater than 1mm reached 40%.Granular sludge is reddish brown;The accumulation rate of nitrite in effluent was stable at about 90%.The high hydraulic selective pressure caused by low settling time is the key factor for rapid granulation,while low dissolved oxygen and high FA concentration are the important conditions for nitrite accumulation and stability.（2）The hydraulic retention time of SBR was the same,and the influent organic loads of the three groups were 0.6,1.2 and 2.4 kg·m^-3·d^-1,respectively.With the increase of organic load,the granular sludge gradually changes from brick red to earth yellow.Under medium and high load,the particles grow rapidly.The higher the loading,the larger the particle size,and the long-term operation under high load will cause the particle disintegration.The increase of organic load promoted the increase of EPS content,and mainly affected the content of protein in EPS,but had little effect on polysaccharide.When operating under medium and low load,the system has excellent ammonia nitrogen removal performance,but high load will obviously inhibit the nitrogen removal capacity of granular sludge.At the end of operation,the nitrite accumulation rates of the three groups of reactors were 84%,87%and 93%,respectively,but the effluent nitrite concentration gradually decreased with the increase of organic load,which were 125.31,106.63 and 75.35mg·L^-1,respectively.The nitrate concentration also decreased successively,which were as follows:The results showed that high organic load inhibited AOB and NOB activity in granular sludge system,and inhibited NOB activity more strongly.（3）Three groups of granular sludge with particle size ranging from 0.5 mm to 1.0mm and 1.0 to1.6mm,1.6 to-2.0 mm were studied.With the increase of particle size,the granular sludge’s wet density and settling velocity increase.and the larger particle size has better settling performance.However,the larger the particle size,the higher the instability coefficient,the lower the integrity coefficient;The EPS concentration of sludge increases with the increase of particle size.The activity of particles in the range of 0.5～1.0mm recovered slowly,but the removal effect of ammonia nitrogen was the best.The average nitrite accumulation rates of the three reactors were 84.78%,86.55%and 86.52%,respectively.The nitrate concentration in the effluent of 0.5-1.0mm and 1.0-1.6mm particles was kept at a high level,but the nitrate concentration in the effluent of R1 was higher,resulting in a low overall accumulation rate.Both nitrite and nitrate nitrogen in R3 effluent are lower.In general,the granular sludge with the particle size range of 1.0-1.6mm has the best short-cut nitrification performance,which can not only maintain a high level of NO2--N,but also maintain a high accumulation rate.