The Effect Of Volumetric Loading And Organic Matter On The Denitrification Efficiency Of Anaerobic Ammonia Oxidation Biofilm Reactor

The anaerobic ammonia oxidation does not require exogenous carbon sources,and the ammonia only needs to be partially oxidized to nitrite,which saves the requirements of aeration in traditional nitrification-denitrification or complete nitrification and operating cost.The combination of the partial nitrification-anammox has great potential to become an important component of new mainstream biological nitrogen removal systems.The aims of this study were to investigates the effect of different volumetric loading conditions and the presence of organic matter on the denitrification efficiency of anaerobic ammonia oxidation biofilm reactor,and provides a theoretical exploration for the wider engineering application.The main findings has been made as follows:（1）Under the operating conditions of hydraulic retention time（HRT）of 6 h and volumetric loads of 0.88,1.32,1.76,2.20,and 2.64 kg/（m~3·d）,respectively,the anaerobic ammonia oxidation was highly efficient in nitrogen removal in the first two stages;in the last three stages,the anaerobic ammonia oxidation nitrogen removal rate decreased continuously,the lowest total nitrogen removal rate was 65.73%when volumetric load increase to 2.64 kg/（m~3·d）.In terms of nitrogen removal efficiency,the best efficiency was achieved at a volumetric load of 2.20 kg/（m~3·d）..The removal rates of NH₄⁺-N and NO₂^--N in the anaerobic ammonia oxidation biofilm reactor were inconsistent at 70.56%and 56.06%,respectively,under the same volume loading conditions when HRT was extended to 10 h,and the accumulated concentration of NO₃^--N in the system was reduced.HRT extension may lead to an increase in dissolved microbial products and extracellular polymers,which produced organic matter and the concentration decreased along the reactor.The anaerobic ammonia oxidation denitrification rate decreased continuously under the operating conditions of HRT of 10h and volumetric loads of 1.10,1.30 and 1.48 kg/（m~3·d）,respectively;the lowest denitrification rate was 50.65%during the period of volume loading of 1.48 kg/（m~3·d）.By increasing the influent substrate concentration to increase the volumetric load,the efficiency of nitrogen removal at HRT=6h is better than that at HRT=10 h.The suitable hydraulic retention time is an important condition for the anaerobic ammonia oxidation system to achieve high load nitrogen removal.For investigating the feasibility of anaerobic ammonia oxidation biofilm reactors for the treatment of low ammonia nitrogen domestic wastewater in the presence of organic matter,the main findings were as follows:Under the operating conditions of HRT of 6 h and a volumetric load of 0.18 kg/（m~3·d）,the total nitrogen removal rate was 57.74%when 20 mg/L organic matter was added,which was close to56.43%when no organic matter was added;the total nitrogen removal rate was 66.10%when 40mg/L organic matter was added;the total nitrogen removal rate increased to 70.80%when 60 mg/L organic matter was added.70.80%.Under the experimental conditions,with the increase of organic matter concentration,denitrification reaction occurred in the system and the denitrification effect became better.The concentration of dissolved oxygen and p H in effluent can meet the conditions of denitrification by anammox and denitrification.In the upper layer of the reactor,Proteobacteria accounted for a large proportion of each sample,followed by Bacteroidetes,Chloroflexi,and Planctomycetes.In the lower layer of the reactor,Planctomycetes was the absolute dominant phylum,followed by Proteobacteria,Bacteroidetes,and Chloroflexi.It was found that the anaerobic ammonia oxidation activity reached a maximum of 6.23 mg N/（g MLVSS·h）,nitrate denitrification activity was 1.21 mg N/（g MLVSS·h）and nitrite denitrification activity was zero when 40 mg/L organic matter was added,and the system The maximum removal rate of total nitrogen in the system was85.36%.Under the suitable organic matter concentration,an efficient denitrification system with anaerobic ammonia oxidation as the main reaction and heterotrophic denitrification could be achieved.