Preparation Of A New Slow-release Filler And Its Application In Biological Nitrogen Removal System

With the progress and development of society,domestic sewage and industrial waste water are constantly discharged into natural water bodies,resulting in excessive nitrogen pollutants in water bodies,which not only have a negative impact on the stability of aquatic ecosystem,but also cause the aggravation of global water shortage.Therefore,it is urgent to study the new technology of wastewater denitrification.Biological treatment of domestic wastewater with low carbon to nitrogen ratio often leads to poor denitrification efficiency due to insufficient carbon sources,and adding carbon sources is an effective method to solve this problem,among which plant slow-release carbon sources have great research value and application prospect.Therefore,in this paper,Arundo/Bamboo was used as raw materials to prepare new slow-release carbon source fillers with different alkalinity and immersion time.Through static release tests and characterization methods,their carbon release performance and physical and chemical properties were grasped,and new slow-release fillers applied in A~2/O anoxic tank were screened.Through the operation test of A~2/O reactor,the influence of the new type of slow-release carbon source filler on the denitrification of biological treatment low carbon nitrogen ratio domestic sewage was understood,and the theoretical basis for the practical application of the new type of slow-release carbon source filler was provided.The main conclusions of this paper are as follows:(1)Compared with the raw material,the alkali-modified Arundo/Bamboo has better carbon release capacity.Meanwhile,the Arundo is selected as the raw material to be modified under the conditions of alkalinity 6%and soaking time 6 h,under which conditions the new slow-release filler obtained has the best carbon release performance,and can be used as a carbon source filler for biological nitrogen removal research.Under the modified conditions of 6%alkalinity and soaking time for 6 h,the static release of COD of Arundo is the largest,with an average daily release of 1.31mg/g,which is higher than that of bamboo,which is 1.22 mg/g static release of COD obtained under the modified conditions of 0.5%alkalinity and soaking time of 12 h.(2)Alkali modification improved the physical and chemical properties of the surface of Arundo/Bamboo,enhanced the carbon release capacity of the material,and the increase of surface roughness created a more suitable attachment condition for microorganisms,which was helpful to improve the biological nitrogen removal efficiency.Alkali modification also promoted the decomposition of lignin,in which the lignin content on the surface of Arundo and Bamboo decreased by 7.2 g/100g and 5.6g/100g respectively.(3)The denitrification efficiency of the A~2/O reactor was significantly improved by the new slow-release filler.The average TN removal rate reached 66.7%,which was 14.0%higher than that of the control group without adding any carbon source in the anoxic pool,and 6.9%higher than that of the reactor with adding raw material Arundo carbon source.This conclusion was mainly related to the high carbon release performance of the new slow-release filler.(4)Alkali modification treatment can promote the growth of biofilm denitrification microorganisms.The number of dominant microorganisms on the surface of the new slow-release filler increased,mainly including Actinobacteria(10.53%),Proteobacteria(20.05%),Chlorocurved(12.29%),Bacteroidetes(19.34%)and Firmicutes(16.72%).The new slow-release fillers had the largest number of dominant bacteria related to nitrogen removal,including Proteobacteria,Chlorocurved,Bacteroidetes and Firmicutes,and their proportion was the highest,accounting for68.40%.The denitrification gene copy number on the surface of modified Arundo was the highest,which was 2.38×10~9 Copies/g.(5)Under HRT=8 h,11 h and 14 h,the average TN removal rates of the three A~2/O reactors are 58.6%,56.4%and 48.3%,respectively.The TN removal rates of the two reactors are similar when HRT=8 h and 11 h,and the denitrification efficiency of the reactor is significantly reduced under HRT=14 h.Therefore,Considering the engineering economy and denitrification efficiency,the optimum HRT is 8 h.In conclusion,as a new type of slow-release filler,alkaline modified Arundo has excellent carbon release ability.Adding it to the anoxic section of A~2/O process can significantly improve the biological nitrogen removal efficiency,which has an important research and application prospect.