[Effect of Ozone Dosage on Sludge Settleability and Biological Nutrient Removal in SBR System].

The effect of ozone dosage on sludge settleability and biological nutrient removal performance in a sequencing batch reactor was investigated by inoculating the bulking sludge with the SVI of 280 mL·g-1 from a wastewater treatment plant in winter. The filamentous mycelium was interrupted, and the SVI was decreased to 125 mL·g-1 after ozone dosage with a low concentration of 0.085 g·g-1(O3/MLSS) for 20 days, which indicated the disappearance of the sludge bulking. The performance of nitrification and phosphorus removal efficiency was not affected obviously. However, the sludge settleability deteriorated with a high dosage of ozone, and the phosphorus removal efficiency was decreased to around 60%. Further study showed that PS/PN had a positive correlation with SVI with the correlation coefficient of 0.9381, which can be used to characterize sludge settleability. A low ozone dosage not only interrupted the filamentous mycelium, but it also affected the content and composition of the EPS, which led to improved settleability.

[In-situ Phosphorus Removal Activity and Impact of the Organic Matter Concentration on Denitrifying Phosphorus Removal in Sludge Aggregates].

In this work, the redox potential, dissolved oxygen, and phosphate microelectrodes were used to quantitatively study the in-situ activity of dephosphorization bacteria and the impact of the organic matter concentration on denitrifying phosphorus removal in sludge aggregates in a sequencing batch reactor. The results showed that the maximum net volume release rate of phosphorus was 3.29 mg·(cm3·h)-1 in the initial anaerobic sludge aggregates, which was approximately 3 times the maximum net volume uptake rate of phosphorus at the initial anoxic stage. The release rate of phosphorus clearly decreased at the final anaerobic stage, and the maximum net volume release rate of phosphorus was only half of that at the initial anaerobic stage. At the final anoxic stage, the maximum net volume uptake rate of phosphorus decreased to 0.14 mg·(cm3·h)-1, and the phenomenon of secondary phosphorus release occurred in the deep area below 1800 µm. When the concentration of COD decreased from 350 mg·L-1 to 250 mg·L-1 and 150 mg·L-1, the maximum net volume release rate of phosphorus of dephosphorization bacteria decreased from 3.27 mg·(cm3·h)-1 to 2.44 mg·(cm3·h)-1 and 2.01 mg·(cm3·h)-1, respectively, and the rapid uptake area of phosphorus narrowed to the surface of the sludge aggregates.