Operational Characteristics And Process Optimization Of Methane-producing Reactor With High Ammonia Nitrogen Anaerobic Digestion

Anaerobic digestion is an effective way to treat organic waste and obtain clean energy.Due to the high protein,urea and other components in some anaerobic digestion raw materials,a large amount of ammonia nitrogen will be produced during the reaction and high ammonia concentration may inactivate methanogens and affect methane production.Granular sludge and activated sludge are two common inoculants in anaerobic digestion.There is currently a lack of comprehensive understanding on the structural characteristics of granular sludge and activated sludge under high ammonia nitrogen conditions.First,the anaerobic methanogenic properties and ammonia nitrogen resistance of granular sludge and activated sludge were investigated.The results showed that when the ammonia nitrogen concentration exceeded 3 g NH4+-N/L,the methane production decreased by nearly 35%in the activated sludge reactor.However,when the ammonia nitrogen concentration exceeded 5 g NH4+-N/L,the methane production decreased by nearly 35%in the granular sludge reactor.In addition,the concentration of TVFA in the granular sludge reactor with high ammonia nitrogen was 32-82%lower than that in the activated sludge reactor.With the increase of ammonia nitrogen concentration,the concentration of lactic acid in the granular sludge reactor gradually increased from 26 mg/L to 1580 mg/L.High ammonia nitrogen led to a decrease in the concentration of extracellular polymeric substances(EPS)in the granular sludge and an increase in the Zeta potential.High-throughput sequencing of the granular sludge reactors showed that the relative abundance of aceticlastic methanogens decreased.The relative abundance of Bacillus was increased by about two times,and Lactobacillus was the main genus in Bacillus,which was the main contributor to the production of lactic acid.Secondly,it was investigated to reduce the methane production inhibition of activated sludge under high ammonia nitrogen by adding trace elements and fillers.The results showed that the degree of recovery on methane production in the reactors with magnet powder and Ca2+ were higher,methane production were 94 mL/d and 93 mL/d,respectively,with the increase of 20.5%and 19.2%.The addition of magnet powder and Ca2+could effectively reduce the Zeta potential of activated sludge under high ammonia nitrogen.High-throughput sequencing results indicated that the addition of magnet powder and Ca2+ could enhance microbial species abundance and community diversity.The predominant bacterial population of the reactora adding magnet powder and Ca2+ were Methanosaeta and Methanobacterium.Finally,the investigation was carried out to reduce the inhibition of methane production by granular ammonia under high ammonia nitrogen by adding trace elements and fillers.The results showed that the degree of recovery on methane production in the reactors with magnet powder and Ca2+were higher,methane production were 106 and 104 mL/d,respectively,with the increase of 27.7%and 23.8%.The addition of Ca2+and magnet powder could increase the concentration of extracellular polymer substances,effectively reduce the Zeta potential of granular sludge under high ammonia nitrogen,reduce the electrostatic repulsion between microorganisms,and contribute to the maintenance of particle morphology and structure.High-throughput sequencing results indicated that the addition of Ca2+and magnet powder could enhance the abundance and community diversity of microbial species,and increase the relative abundance of aceticlastic methanogens.