Mathematical modeling on the nitrogen removal inside the membrane-aerated biofilm dominated by ammonia-oxidizing archaea (AOA): Effects of temperature, aeration pressure and COD/N ratio
MeiLi, Chunyu Du, Jun Liu, Xiao Quan, Meichao Lan, Baoan Li
Chemical Engineering Research Center, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, PR China.
One-dimensional multispecies model on membrane-aerated biofilm (MAB) containing ammonia-oxidizing archaea (AOA), nitrite-oxidizing bacteria (NOB) and heterotrophic bacteria (HB), the initial fraction of which were 55%, 15% and 30%, respectively, was successfully developed and simulated by AQUASIM 2.1 to comprehend effects of temperature, aeration pressure and influent COD/N ratio on the nitrogen removal performance for the wastewater treatment of low-leveled ammonia nitrogen (5 gN/m3). Results indicated that it’s applicable to decrease the aeration pressure for inhibiting the NOB activity and maintaining the total nitrogen (TN) removal efficiency under higher temperatures. Microbial distribution inside the MAB revealed that through moderately increasing the COD/N ratio at 293 K and the aeration pressure of 0.1 atm, the oxygen competition among AOA, NOB and aerobic HB could be better balanced with TN removal efficiency improved, demonstrating the feasibility of simultaneous nitrification and denitrification via nitrite. It’s been evaluated that with increased aeration pressures, higher TN removal efficiency could be achieved through the short-cut denitrification by improving the COD/N ratio to enhance the outperformance of aerobic HB over NOB for oxygen while substantially maintaining the AOA activity. And the denitrification process could be better performed in the biofilm adjacent to the bulk liquid by anaerobic HB utilizing soluble organics from the hydrolysis of slowly-degradable particulates to reduce the nitrite. The simulation results would be of great importance for the design, operation and optimization of AOA-dominating MAB applied in the nitrogen removal from micro-polluted wastewater.
Keywords: Ammonia-oxidizing archaea, Denitrification, Membrane aeration biofilm, Mathematical modeling, AQUASIM.