Nitrogen Removal By Coupling Of Nitrifying Granular Sludge And Denitrifying Granular Sludge

The physicochemical method is usually the preferred technology for inorganic wastewater treatment,but there are problems such as high operating costs.Although the operation cost of biochemical method is relatively low,it is also difficult to achieve efficient nitrogen removal of inorganic wastewater.The biggest difficulty is that the lack of carbon source required for denitrification leads to very limited total nitrogen removal capacity.Granular sludge has become one of the hot research technologies in wastewater biological treatment because of its many advantages.Among them,autotrophic nitrified granular sludge?ANGS?has good nitrification ability,denitrifying granular sludge?DGS?can achieve efficient nitrogen removal,and the coupling of the two can achieve efficient nitrogen removal of inorganic high ammonia nitrogen wastewater.However,the formation conditions of ANGS are harsh,and the requirement of DGS on the carbon-to-nitrogen ratio of influent is high,resulting in a lack of systematic understanding on how to achieve the efficient coupling of the two.Therefore,in order to achieve high-efficiency denitrification of inorganic high-ammonia nitrogen wastewater,ANGS and DGS were cultivated separately to explore the coupling denitrification effect of the two,providing theoretical guidance for the treatment of inorganic high-ammonia nitrogen wastewater.The main research content includes three parts:?1?Using heterotrophic AGS as a carrier,ANGS was quickly domesticated by the strategy of gradually reducing the influent COD and adding exogenous nitrifying bacteria.ANGS with an average particle size of 2.46 mm was successfully cultivated within 36 days.It had stable physical and chemical properties and the ability to remove pollutants.Even increasing the ammonia nitrogen load?0.56-1.28 kg/?m³?d??in the influent has little effect on it.The nitrite accumulation rate?NAR?always remained above 50%,indicating that ANGS has good nitrosation performance.The structure of bacteria and archaea in granular sludge was analyzed by using Miseq high-throughput sequencing platform.The results showed that the dominant genus was ammonia oxidizing bacteria?AOB?,whose relative abundance reached 49.9%,and the relative abundance of the relative abundance of 1.52%ammonia oxidizing archaea?AOA?and nitrite oxidizing bacteria?NOB?was found.It was 8.26%.This showed that the relative abundance of AOB was higher than NOB,which was the key to maintaining short-cut nitrification in the reactor.After dry storage of ANGS by embedding in agar,it was found that the storage had a certain effect on the physical and chemical properties,nitrification performance and flora structure of ANGS.?2?The response surface method was used to determine the operating conditions of ANGS denitrification to remove TIN.The response surface method and the Box-Behnken Design?BBD?method were used to design experiments to study the effect of each factor variable on the removal of TIN from ANGS,and the factors of each variable were optimized.The results showed that the order of significant impact of TIN removal was the concentration of external carbon source?COD concentration?>sludge concentration>reaction time>stirring rate.For 2.86 h,320 mg/L,202r/min,6000 mg/L.?3?ANGS with an average particle size of 1.60 mm was inoculated to cultivate denitrifying granular sludge?DGS?,and the ANGS system with the DGS system?addition of porous sponge filler R₂ and control group R₃?was coupled to remove TIN.After 50 days of cultivation,the denitrification system gradually stabilized,the average particle size of DGS was about 0.35-0.45mm.The removal rate of TIN by the process combination system was as high as 98.5%.Adding bio-filler R₂ to the TIN removal performance was more stable,using less carbon source.The denitrification rate and matrix degradation kinetic parameters of DGS in R₂ were measured.The results showed that the increase of carbon source significantly promoted its denitrification rate.A short-range denitrification-based microbial denitrification system formed in R₂.It has strong affinity and uptake ability to the matrix.Nitrosomonas?36.61%?,Ferruginibacter?12.77%?,and Aridibacter?4.35%?were the dominant bacteria in the nitration segment R₁ by high-throughput sequencing.Nitrosomonas is the most common genus in AOB.The dominant bacteria in denitrifying R₂ are Tepidisphaera?18.05%?,Thaauera?10.71%?,Aquimonas?5.98%?,Nitrosomonas?4.35%?,Aridibacter?3.98%?,and Rhodobacter?2.79%?,which abundance of bacteria with denitrification function was 21.17%.The advantages of R₃ are Aquimonas?16.89%?,Tepidisphaera?15.19%?,Thauera?10.54%?,Nitrosomonas?6.22%?,Ferruginibacter?5.45%?and Aridibacter?3.34%?,which abundance of bacteria with denitrification function was 17.27%.