Long-term Operation Performance Of Anaerobic Biological Treatment Of Monosodium Glutamate Wastewater And Its Methane Production

Recently,energy self-sufficiency as a feasible concept for wastewater treatment systems is widely accepted in both China and the rest of the world,which spurs the rapid development of energy recovery technology from wastewater utilities.As a cost-effective and environmental friendly technology,anaerobic biological treatment becomes increasingly attractive as its characteristics of high organic loading rate,less sludge yield,good resistance for shock loadings and energy recovery.Monosodium glutamate wastewater(MGW)is a typical organic wastewater with characteristics of high-concentration,complex in composition,which also has a large annual discharge amount(about 4.4×107 t/yr in China)and is lacking of cost-effective treatment technologies.In this study,an upflow anaerobic sludge blanket(UASB)was employed to investigate the long treatment performance with methane production potential of synthetic MGW.Meanwhile,we investigated the effects of organic load(OLR)and hydraulic retention time(HRT)on its performance,the characteristics of granular sludge,microbial community structure and its evolution in the system as well as the degradation pathway of monosodium glutamate in the anaerobic system.The main research contents and results are as follows.(1)Mixed seeding culture including an anaerobic suspended sludge from a sewage treatment plant with an anaerobic granular sludge from starch wastewater treatment plant was used for the UASB startup.The operation conditions were kept stable at pH of 7.0±0.1,reaction temperature of 35±1 ? and HRT of 48 h,while the influent COD concentration of the synthetic MGW was increased from 1000 to 4000 mg/L during the startup stage.On day 83,COD removal efficiency increased to 95.0%with a methane yield of 0.52 m3/m3 d,while no detection of VFA accumulation.(2)After successful startup by increasing the influent concentration,the UASB was operated under various OLRs of 4?6?8?12?16?24 kgCOD/m3 d,respectively,while a stable HRT of 24 h and other operating conditions were kept unchanged.Results showed that the corresponding COD removal efficiencies were 92.3%,95.4%,97.9%,91.1%,84.7%and 66.0%,the methane production rates were 0.90,1.70,2.19,3.03,3.72 and 4.20 m3/m3 d as well as the methane recovery efficiencies were 71.4%,84.5%,83.6%,78.04%,77.4%and 74.4%,respectively.At the stage of the highest COD removal efficiency(OLR 8 kgCOD/m3·d),the settling velocity and the VSS/TSS ratio of the granular sludge were 79.6 m/h and 60.8%,respectively.The corresponding specific methanogenic activities(SMA)were:acetic acid 0.085>butyric acid 0.074>valeric acid 0.013>glutamic acid 0.070>methanol 0.033>H2+CO2 0.030>propionic acid 0.008 gCOD CH,/(gVSS·d).Through high-throughput sequencing analysis of the granular sludge samples from the stage of OLR of 24 kgCOD/m3·d,the abundances of acetoclastic methanogens Methanosarcina and Methanosaeta were 35.11%and 14.37%,respectively.(3)When maintained the influent COD concentration of 2000 mg/L and other operating conditions unchanged,the MSW treatment and its methane production performances were investigated under various HRTs of 24,12,6,4.5,3 and 2 h,respectively.Results showed that the corresponding COD removal efficiencies were 94.5%,95.0%,95.5%,97.8%,78.8%and 67%,the corresponding methane production rates were 0.57,1.05,2.01,2.82,3.23,3.66 m3/m3·d,and the corresponding methane recovery efficiencies were 79.0%,80.1%,83.3%,82.9%,75.3%,and 63.8%,respectively.The highest COD removal efficiency was obtained at HRT of 4.5 h,in which the settling velocity and the VSS/TSS ratio of the granular sludge were 70 m/h and 66.6%,respectively.The corresponding SMA were:acetic acid 0.159>glutamic acid 0.131>butyric acid 0.102>H2+CO2 0.046>valeric acid 0.008>methanol 0.004 =propionic acid 0.004 gCODCH4/(gVSS·d).Through high-throughput sequencing analysis of the granular sludge samples from the last operation stage,the abundance of Methanosaeta was up to 77.05%.Therefore,the degradation pathway of monosodium glutamate by the anaerobic microbial would be glutamic acid ? butyric acid ?acetic acid ?methane.Using anaerobic biological treatment of monosodium glutamate wastewater,a large amount of organic pollutants were removed,and organic nitrogen was converted to ammonia nitrogen,which laid a good foundation for further processing.And produce a lot of methane gas,with good economic effects.It lays a theoretical and practical foundation for the treatment of monosodium glutamate wastewater.