Research On The Stability And The Activities Of Extended Idle Conditions Of Aerobic Granules

Microbial immobilization is a process of cell-to-cell interaction, or cell-to-carrier surface attachment. Aerobic granules have some advantages over conventional bioflocs, such as excellent settleability, high biomass retention and resistance to inhibitory and toxic compounds and so on. It is believed that aerobic granulation would be a novel and promising biotechnology for handling industrial and municipal wastewater. However, it appears from previous research that the stability of aerobic granules is poorer than that of anaerobic granules. It can be anticipated that the poor stability of aerobic granules would limit its application in wastewater treatment practice.This study investigated the feasibility of improving the stability of nitrifying granules through selecting slow-growing nitrifying bacteria by stepwise increasing substrate N/COD ratios. The strategy was involving stepwise increases in ammonium-nitrogen concentration in the influent. The stability, physical characteristic and the ability to remove nutrient substrate et al. were all investigated between the nitrifying granules and heterotrophy granules (the main population in the aerobic granules was heterotrophy bacteria). The research on the activities of extended idle conditions of aerobic granules was also included. Conclusions were as followed:1. Better stability and settleability, higher biomass concentrations, nitrifying granules can be developed by stepwise increasing substrate N/COD ratios. The nitrifying granules were dense when the heterotrophy granules disaggregated on day 160. The value of sludge volume index (SVI) was below 20 ml/g and the mean granules size was about 1.2 mm.2. In this period, the role of extracellular polymeric substances (EPS) in the granulation process was mainly investigated and found that the Polysaccharide played a key role in this process.3. The total nitrogen (TN) removal was greatly increased and could reach 68 % without any dissolved oxygen (DO) controlling. Besides DO, the granules size was also a dominant factor to influence denitrification. In this experiment, the optimum granules size for denitrification was about 2.5 mm.4. The performance of physical characteristics, respirometric activities in aerobic granules and the simultaneous nitrification and denitrification (SND) of a 3-month anaerobic...