Studies On Nitrogen Removal Characters Of Aerobic Granular Sludge Under The Same Volume Loading

In recent years, aerobic granular sludge, as a new biological wastewater treatment technology, has been given much attention. It is featured by high biomass, excellent settling ability and so on,and its application in nitrogen removal is important in the research. This research focused on the characteristics of nitrogen removal of aerobic granular sludge. The cultivation process and nitrogen removal process were investigated, in order to provide reference for industrial application in the future.The research consists of two parts. The first was the cultivation of aerobic granular sludge, which investigated the effect of Ca²⁺ on the formation of aerobic granular sludge. The influent concentrations of CaCl₂ were 60mg/L(A) and 0mg/L(B) in two SBRs, respectively. The results showed that Ca²⁺ had no significant effect on the granulation but the stability and maturity of aerobic granules were seriously affected. In the first 30th day, the average particle size of aerobic granular sludge in two reactors were both 0.26mm, while the granular sludge in reactor B was irregular and filamentous bacteria existed. In the 82th day, aerobic granular sludge in reactor A had smooth edge, compact structure, and regular shape. The SVI, MLSS, average particle size and MLVSS/MLSS were 50mL/g, 4500mg/L, 0.76mm and 0.4, respectively. Furthermore, NH₃^-N removal efficiency was perfect, and the removal rate could reach 99%. However in reactor B, no Ca²⁺ was added, the granules could not successfully grow up, and too much filamentous bacteria was in the sludge, leading to failure of cultivation finally.The second part of the research focused on nitrogen removal characters of aerobic granular sludge under the same volume loading and the nitrogen removal process was analyzed. The operating cycle of reactor A and reactor B was 6h and 12h, respectively. In equal volume loading, reactor B had high and stable average ammonia nitrogen removal rate than reactor A. When the loading increased to 2.10 kgCOD/(m3·d), the average ammonia nitrogen removal rate of two reactors were both decreased. When the volume loadings were 1.05, 1.31, 1.57, 2.10 kgCOD/ (m³·d), the average ammonia nitrogen removal rates of reactor A and B were 85.3%, 77.5%, 88.6%, 62.4%and 89.4%, 90.0%, 88.8%, 62.3%, respectively. The effluent NO3--N and NO2--N concentrations of reactor A were more stable than that of reactor B. There was no significant accumulation of NO3--N and NO2--N during the operating process, indicted that simultaneous nitrification and denitrification was achieved with aerobic granular sludge. The rates of SND in reactor A, B were 93.57%, 84.71%, 78.62%, 94.26% and 95.74%, 90.82%, 86.29%, 96.18% under four volume loadings, respectively. The efficiencies of SND in two reactors were 3.77, 3.69, 5.30, 4.98 mgN/(L·h) and 4.09, 4.73, 5.69, 5.26 mgN/(L·h) under four volume loadings, respectively. The rate and efficiency of SND in reactor B were higher than that in reactor A. The rate and efficiency of SND in two reactors showed a similar trend as the loading increased.