Research On Short-range Denitrification-Anammox Denitrification Process Based On The Embedment And Immobilization Technology Of Enteromorpha

As a new biological nitrogen removal process,Anammox(Anammox)has been widely paid attention by researchers because of its advantages such as one-step nitrogen removal,no additional organic carbon source,no need of aeration and less residual sludge.Anammox process will produce a certain amount of nitrate nitrogen,and the theoretical total nitrogen removal efficiency is only 80%.Facing increasingly stringent emission standards,the post-denitrification unit is generally still required.Therefore,in recent years,the partial denitrification-Anammox process has become a new research hotspot,but how to maintain enough biomass and maintain the advantages of functional bacteria has become the key to maintain the stable operation of this system.As a coastal city,Qingdao is affected by the"green tide"formed by Enteromorpha prolifera every year,causing serious ecological disasters.At the same time,Enteromorpha prolifera,as a macroalgae,has the potential to extract alginate and hemicellulose to prepare hydrogels.For example,using Enteromorpha prolifera as the material to prepare water treatment embedded bacteria will effectively solve the problem of the loss of functional bacteria and lack of biomass in coupling process when treating the offshore pollutants of Enteromorpha prolifera.Therefore,in this study,Enteromorpha prolifera was used as raw materials to prepare partial denitrification sludge and anammox sludge into hydrogel-embedded bacteria,to study the performance of Enteromorpha prolifera and polymer materials to prepare embedded bacteria,and combine with other Materials for comparative research.Partial denitrification sludge embedding bacteria were prepared,and their physicochemical properties,mass transfer performance and matrix kinetic properties were measured.The short-cut denitrification-embedded bacteria reactor was started,and the influencing factors and long-term operation stability of the reactor were studied.The partial denitrification and Anammox embedded bacteria reactor were coupled to study the relationship between the denitrification performance of the integrated process,the recovery strategy after instability and the change of bacterial community structure.The main conclusions are as follows:(1)Hydrogel particles were successfully prepared by using waterborne polyurethane(WPU),polyvinyl alcohol(PVA),sodium alginate(SA)and Entermorpha WPU as embedding materials,among which Entermorpha WPU embedding particles have better spatial structure and mechanical properties,The effective diffusion coefficient(DE)value of Enterommorpha WPU embedded granules was 1.2456×10-8 m2/s,and the higher DE value was conducive to substrate transfer and biological activity.The short-cut denitrification kinetics study of Enteroma-WPU embedded particles showed that the maximum reaction rate was 1.4405 d^-1 and the saturation constant was 27.14 mg·L^-1,which had good kinetic parameters and was suitable for long-term use in water treatment process.(2)After 90 days of acculturation and culture,the nitrate nitrogen(NO₂^--N)accumulation rate and nitrate nitrogen(NO₃^--N)removal rate reached 80.75%and 98.52%respectively.This study shows that the COD and NO₃^--N concentrations of different initial influent water are important factors affecting the NO₂^--N accumulation rate during the start-up stage of short-cut denitrification reactor.In,addtion,When C/N ratio(C/N)is 3,the system has better short-cut denitrification performance.In the subsequent 80 d continuous flow long-term operation experiment,the system's short-cut denitrification performance remained stable,the accumulation rate of NO₂^--N was maintained at about 68%,and the removal rate of NO₃^--N was close to 100%.At the same time,the embedded particles did not appear a large number of crushing phenomenon,showing good mechanical strength and swelling performance.The results showed that Enterommorpha-WPU embedded particles can be used in sewage treatment for a long time,and can effectively maintain the stable operation of the biomass system.(3)By changing the influent NH₄⁺-N,NO₃^--N and COD concentrations,the nitrogen removal performance of short-cut denitrification-Anammox embedded integration process under different pollution loads was investigated.The experimental results show that the integrated process with embedded bacteria as the main part can gradually adapt to the conditions of low,medium and high load,and maintain good denitrification performance,and the Anammox bacteria in the system has always maintained a high activity.The recovery experiment after system instability showed that the activity of Anammox was recovered first in the integrated process,and the system was transformed into an Anammox-dominated denitrification system.The high-throughput results showed that with the recovery of the denitrification performance of the system,the relative abundance of P.and C.aerobicus increased,and Candidatus?Brocadia was the typical Anammox bacteria detected by the system,and the abundance increased from 0.19%to 16.36%.Functional prediction analysis showed that the energy metabolic capacity of the anaerobic ammonium oxidation system was enhanced after recovery.