Effects of Wastewater Composition on Stability of UASB

Abstract

Three types of wastewater based on acetate, sucrose, and ice cream were used to investigate the long‐term effect of wastewater composition on the stability of the upflow anaerobic sludge blanket (UASB) process using laboratory‐scale reactors. Experimental results revealed that variations in the carbon source in the wastewater caused gradual changes in both the physical structures and the bacterial distribution of the seeding granular sludge, which resulted in disintegration or floatation of the granular sludge under certain conditions. The rate of such changes was found to be relatively slow, and depended on the sludge‐loading rate. A semiquantitative mathematical model on the ecological characteristics of the granular sludge was developed and was able to explain the experimental results. The study suggests that the failure of the UASB process under certain circumstance was primarily due to the limitation in the ecological structure of the granular sludge.