Start-up And Stable Operation Of The Pilot-scale Aerobic Granular Sludge Reactor

Aerobic granular sludge?AGS?has become one of the hot research technologies for wastewater biological treatment due to its many advantages.However,AGS technology still has some defects,such as:long startup time,unclear mechanism of stability decline during AGS storage,harsh conditions of autotrophic nitrifying granular sludge formation and long incubation time,which limits the development and application of this technology.Therefore,the research on related issues has important practical significance and engineering value.?1?Heterotrophic granular sludge was cultivated in the pilot SBR by selective pressure and controlled sludge age strategy to investigate the effect of particle size control on AGS stability and maintenance.Inoculation of the sediment in the artificial lake of the campus starts the pilot SBR,and the septic tank sewage was used as the influent.By gradually reducing the sedimentation time,the mature AGS was cultured after 40 days,the color was bright yellow,and the MLSSwas stable at 4.44⁴.97 g/L.EPS and SOUR were between 42.08⁵6.39 mg/g MLSS and 25.87³8.41 mg O₂/g MLSS h,respectively.The granulation rate was maintained above 90%,and the average particle size was maintained at 1.96².36 mm.The removal efficiency of the pollutants in the reactor was gradually improved and stabilized,and the COD and TP removal rates were all maintained above 90%.However,due to the lack of carbon source in the denitrification stage,the total nitrogen removal rate was low?40%to 50%?.After successful domestication,the effects of different ultrasonic power on the stability of different particle size AGS,the effect of different sludge concentrations of 2³ mm particle size AGS on the ultrasonic effect and the AGS activity of different particle sizes were investigated.The results showed that 2³ mm particles size AGS has the highest stability.After screening for 500 mL of the mud-water mixture every two days after granulation for 44 days,artificially increasing the ratio of AGS in the reactor of 2 to 3 mm,the stability of the system was improved.?2?Explored the mechanism of AGS stability decline and post-storage activation during dry storage.After the heterotrophic AGS was placed in an agar block for storage for 30 days,the activity recovery of AGS was successfully achieved within 11 days.During storage,the AGS remained yellowish and structurally intact,but the appearance was rough.Loss of moisture and particulate quality during storage was accompanied by irritating odors.The activity was recovered by the actual wastewater,and the AGS after the activity recovery was yellow and dense.The proportion of organic elements in the activation phase increases,but the proportion of most inorganic elements decreased.The physical and chemical properties of the sludge were good.The EPS remained between 42.99⁴9.56 mg/g MLSS,and the SOUR remained between 50.49⁵4.37mg/O ₂·g MLSS h.The removal rates of COD and TP in the reactor were 93.23%and 93.33%,respectively.The effluent ammonia nitrogen and nitrite were all below 5 mg/L,and the nitrate and total nitrogen were 4.77³8.34 mg/L and 43.16⁴6.92 mg/L,respectively.However,due to the lack of denitrifying carbon source,the nitrate was accumulated in a large amount,and the denitrification efficiency was less than 50%.?3?The large amount of heterotrophic granular sludge cultured in the previous period was inoculated with sludge to explore the feasibility of heterotrophic granular sludge to autotrophic granular sludge.The inorganic carbon source was used as the substrate to realize the conversion of autotrophic nitrifying granular sludge in 65 days and stable operation for 205 days.During the domestication process,the sludge always maintained good physical and chemical properties:the color changed from bright yellow to reddish brown,the EPS was stable at 19.12⁴7.80 mg/g MLSS,the MLSS was 4.5 g/L,and the granulation rate was always maintained at 90%.Decreased,but autotrophic bacteria activity was enhanced.The removal rate of ammonia nitrogen in the reactor first increased and then decreased.The concentration of nitrite in the effluent continued to decrease,and the concentration of nitrate increased.The NAR remained above 90%for the first100 days,and then decreased to zero.The abundance of domesticated autotrophic nitrifying granular sludge increased,but the diversity decreased.The autotrophic denitrifying bacteria represented by AOB bacteria?Nitrosomonas?,NOB bacteria?Nitrobacter?,Comamonas,and Acidovorax accounted for up to 35.67%,which replaced the dominant flora dominated by the original heterotrophic bacteria.