Impact Of Adding Micro-Powders On Formation And Characteristics Of Aerobic Granular Sludge

Compared with traditional activated sludge, aerobic granular sludge has good settling performance, high biomass, and strong ability to resist impact load etc. The formation and stability of aerobic granules is strictly limited by operating modes which hindered its full-scale application. This study puts forward that adding crystal micro-powder and sludge micro-powder with diameter from 50 to 200μm, induced and promoted aerobic granulation, and formed large size granules from sludge with rich filamentous bacteria.Three SBR with diameter of 10.5cm, height of 1.0m and effective volume of 4.0L were constructed in lab. Raw water for three reactors used sodium acetate as the main carbon source. Results showed that sludge achieved better aerobic granulation in the reactor added crystal micro-powder under the condition of high aeration rate (gas velocity was 1.2cm/s), and the granular sludge had compact structure and better settling performance. Under the condition of lower aeration rate (gas velocity was 0.6cm/s), sludge floc still dominated in the reactor without added micro-powder. However, granular sludge was observed in the reactor which added crystal micro-powder five times and 6g every other day, and the granule’s average diameter and SVI were 300μm and 63mL/g, respectively. Granular sludge also could be observed in the reactor added sludge micro-powder every four days and 7.6g each time, with the average diameter and SVI were 450μm and 51mL/g. When the sludge was full of filamentous bacteria at lower aeration rate (gas velocity was 0.42cm/s),the overhanging growth of filamentous bacteria disappeared and the granular sludge with the diameter from 1mm to 3mm eventually achieved by adding the crystal micro-powder two days and 6g every day.The micro-powder promoting aerobic sludge granulation is analyzed as follows. The micro-powder can be a crystal nucleus and induced lots of microorganism, the micro-powder also provides a appropriate friction shear force and helps control the growth of filamentous bacteria. With the micro-powder as the crystal nucleus, filamentous bacteria as a framework, EPS as a binder, interact with each other which overcome the adverse effects caused by low aeration and finally promote sludge granulation. This provides a feasible way and theoretical foundation for the application of aerobic granular sludge technology.