Abstract: The fly ash was acid or alkali modified with 1mol/L hydrochloric acid and 1mol/L NaOH solution. The modified and non-modified fly ash were added into the SBR reactor for simulating the treatment of ammonia nitrogen wastewater. The bacteria in the reactor were taken from the activated sludge of a biochemical pool in a sewage treatment plant. The concentration of the influent NH⁺₄-N was increased gradually. Then， the concentration of NH⁺₄-N in the effluent of the reactor， the sludge concentration and the abundance of the dominant bacteria were all measured. The experimental results show that after the reactors has run for 40 days with an influent NH⁺₄-N concentration of 861.1mg/L， the removal rate of NH⁺₄-N of R3 reactor(adding acid-base modified fly ash)， R2 reactor(adding unmodified fly ash) and R1 reactor(without adding fly ash) are 100%， 98.76% and 91.87%， respectively. If the concentration of sludge in the three reactors is indirectly characterized by protein concentration， the concentration of protein in the R3 reactor， R2 reactor and R1 reactor are 829.08mg/L， 789.37mg/L and 154.2mg/L， respectively. In addition， the high throughput sequencing results show that the abundance of nitrifying bacteria and nitrifying bacteria in R3 reactor is higher than that in R1 and R2 reactor.

Key words: fly ash, acid and alkali modification, ammonia wastewater, reactor