Characteristics of anaerobic granular sludge in EGSB reactor treating traditional Chinese medicine wastewater

The characteristics of granular sludge in the EGSB reactor treating TCM wastewater were analyzed in terms of particle size distribution (PSD), integrity coefficient (IC), metal content and extracellular polymeric substances (EPS) of granular sludge. When COD concentration was 2000-5000 mg·L^-1, hydraulic residence time (HRT) was 12 h, temperature was 30℃, the peak of PSD was in the range of 500-1000 μm, IC value was less than 20, and the contents of total EPS, protein, polysaccharide in granular sludge were 85.59, 63.67 and 21.92 mg·(g VSS)^-1, respectively. At this stage, flocculation of granular sludge was good, and its mechanical strength was high. When HRT was reduced to 6 h, IC value increased to 30.03, and the ratio of protein and polysaccharide increased to 6.86.However, the concentration of polysaccharide in granular sludge decreased to 18.11 mg·(g VSS)^-1. When temperature decreased to 20℃, the peak of PSD was in the range of 250-750 μm and IC value was 32.11.The concentrations of Ca²⁺, Mg²⁺ and Mn²⁺ were only 20.78, 4.79 and 0.94 mg·L^-1, respectively. At the same time, the contents of total EPS, protein, polysaccharide in granular sludge were 69.04, 58.87 and 10.17 mg·(g VSS)^-1, respectively. During this period, granular sludge was washed out from the EGSB reactor and COD removal efficiency decreased.