Aerobic granular sludge treatment of piggery wastewater: solution to the problem of non-filamentous bulking and analysis of microbial community structure in practical application.

Abstract

Abstract In this study, actual piggery wastewater was treated by aerobic granular sludge (AGS) in a sequencing batch reactor (SBR) and verified its treatment capacity. At the same time, the non-filamentous bulking was controlled through a series of measures. The results showed that on the 13th day of operation, the AGS was formed with a particle size of 611.4 µm. The highest removal rates of ammonia nitrogen (NH4+-N), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP) by the AGS were 99%, 99%, 90%, and 96%, respectively. After 32 days of reactor operation, an overgrowth of zoogloea led to increased polysaccharides (PS) secretion from the extracellular polymeric substances (EPS), resulting in a non-filamentous bulking. Adjusting the carbon source concentration to change the organic loading rate (OLR) in SBR, which increased from 4 kg COD m3·d− 1 to 16 kg COD m3·d− 1, then decreased to 5.6 kg COD m3·d− 1, this value is considered suitable for the long-term growth of AGS. During this period, the non-filamentous bulking was solved by reducing water temperature, increasing hydraulic shear force and selective pressure, and manual screening. Finally, the sludge bulking was reduced on the 60th day. The experimental results indicated that the sludge bulking has little effect on the removal of COD by AGS, but has a significant impact on the nitrogen and phosphorus removal effect. In the process of sludge granulation, species diversity, and microbial biomass in the sludge decreased, especially before and after controlling sludge bulking, and dominant microbial species changed significantly.