Effect Of Key Inhibitors On The Performance And Microbial Community Of Treating Simulated Monosodium Glutamate Wastewater By UASB

Monosodium glutamate wastewater is a typical amino acid wastewater containing high concentration of ammonia nitrogen and sulfate.High concentration of ammonia nitrogen and sulfate will lead to decrease of the effect and energy recovery rate of anaerobic biological treatment of high concentration organic wastewater.However,the inhibitory properties and mechanism of ammonia nitrogen and sulfate on anaerobic biological treatment of monosodium glutamate wastewater are still unclear.In this paper,two groups of up-flow anaerobic sludge bed(UASB)reactors for treating simulated sodium glutamate wastewater were studied.The UASB reactor was operated continuously for 210 and 320 days under different ammonia nitrogen(0-4000 mg N/L)and sulfate(0-1000 mg SO42-/L)inhibition conditions.The long-term performance and microbial community structure of UASB reactor were studied under the influence of key inhibitors.The main results are as follows:(1)The concentration of free ammonia in UASB reactor increased with the increase of influent ammonia nitrogen concentration.When the influent ammonia nitrogen eoncentration was 2000 mg/L,it began to show obvious inhibition.When the concentration of influent ammonia nitrogen increased to 4000 mg/L,the concentration of free ammonia in the reactor reached 354.63±39.06 mg/L,the average removal rate of COD decreased to 49.35±2.30%and the methane content decreased to about 60%,which was close to the semi-inhibition state.Compared with the initial conditions,the microbial community structure of granular sludge changed significantly in the semi-inhibitory state,and the diversity and richness of bacteria decreased after the inhibition,while Archaea increased slightly.Firmicutes,Synergistets and Proeobacteria were the main bacteria at the end of the inhibition stage,accounting for about 88%of the total;Methanosaeta was the main Archaea genus,accounting for 47.7%.(2)When the influent sulfate concentration increased from 0 mg/L to 667 mg/L,the overall performance of UASB remained stable.The highest COD removal rate was 94.43±0.27%and the lowest COD removal rate was 83.41 ± 1.08%.The gas production performance was good,and the accumulation of volatile fatty acids did not occur.When the concentration of sulphate in influent reached 1000 mg/L,51.95 ± 4.42%COD was utilized by methanogens.Compared with the results of high throughput sequencing,after inhibition,the diversity and richness of bacteria and archaea decreased.Firmicutes,Synergistetes,Proteobacteria,Bacteroidetes,Chloroflexi and Thermotogae were the main phylum,accounting for about 81%of the total.The dominant Archaea(Methanosaeta)accounted for 80.12%.In conclusion,for anaerobic biological treatment of simulated sodium glutamate wastewater,when the concentration of influent ammonia nitrogen is higher than 2000 mg/L,the performance of UASB reactor is obviously inhibited,while the inhibition of influent sulfate concentration to 1000 mg/L is still relatively weak;due to the long-term inhibition of ammonia nitrogen and sulfate,the microbial community structure of granular sludge will be significantly changed.