Impact Of Static Pressure On Performance Of Nitrite-dependent Anaerobic Methane Oxidation Process And Its Functional Mechanism

Recently,Sewage biological denitrification plays an important role in sewage treatment.However,Sewage biological denitrification has been a significant man-made source of greenhouse gas(GHG)emission because of the serious GHG(CH4 and N2O)emission during denitrification.Nitrite-dependent anaerobic methane oxidation(n-damo)is a promising wastewater treatment process,which could use nitrite as the electron accepter and methane as the electron donor.It can conduct sewage biological denitrification while realizing the resource utilization of methane.N-damo process is considered to be energy efficient since it is needless to supply organic carbon source or oxygen,leading to a conspicuous saving of operational cost.However,the application and promotion of n-damo process for wastewater treatment suffered from limitation of its long doubling time,harsh requirement of environmental conditions and low reaction rates.Based on this,this study aimed to improve the methane availability during n-damo process by improving static pressure and immobilization with actived carbon,and further investigate the nitrite removal performance and its mechanism of n-damo under certain static pressure.The main conclusions are as follows:(1)Static pressure is a vital factor affecting n-damo process,increase in static pressure could optimize the living environment of n-damo bacteria,then facilitate the growth of n-damo bacteria and n-damo process.Under high static pressure,the nitrite removal rate improved 11.68%and the potential n-damo specific activity improved 146.62%.When NO2--N concentration in influent reached 120 mg/L,inhibition was detected in reactor under ASP while it was didn't detected under HSP.This indicated that increase in static pressure could facilitate n-damo process and increase the tolerance of n-damo bacteria to nitrite.(2)The sludge size and specific surface area under HSP were about 2-fold than that under ASP,which was beneficial to anaerobic environment inner sludge flocs and substrate transfer.In addition,intracellular organic matter and cell membrane altered with the increase of static pressure,this improved the methane availability and then improved n-damo performance.As a result,the abundance of n-damo bacteria in reactor under HSP reached 2.91 ×1011 copies/g,much higher than reported abundance.Besides,n-damo bacteria obtained more plenty of diversity under HSP,indicaing increase in static pressure could optimize n-damo living environment and improve the growth of n-damo bacteria.(3)Immobilization with actived carbon could achieve effective retention of biomass.The maximum methane adsorption capacity of IBAC improved more than ten-fold than sludge,which accelerate the methane transfer between liquid phase and gaseous phase.The result manifests that immobilization with activated carbon could optimize methane adsorption and methane transfer,then increase methane availability.Therefore,the nitrite removal rate of IBAC improved 49.64%and the n-damo specific activity improved 49.28%.(4)It played a synergistic improvement on n-damo process when combined staitic pressure and immobilization with activated carbon,and further improved nitrite removal performance and n-damo specific activity,which improved by 95.83%and 106.09%,respectively.The proportion of n-damo bacteria to total in IBAC-HSP were 82.47%,indicating combining static pressure and immobilization with activated carbon could further promote the growth of n-damo bacteria and n-damo process.