Effect of Temperature Elevation from 55°C to 65°C on the Performance of a Thermophilic UASB Reactor and Characteristics of Methanogenic Granular Sludge

Abstract

A thermophilic (55°C) upflow anaerobic sludge blanket (UASB) reactor was operated by feeding a wastewater containing sucrose at a fixed total organic carbon (TOC) loading rate of 18 kg TOC m−3 d−1 for a period of 3 years. After this operation period, the reactor temperature was shifted from 55°C to 65°C to investigate the effect of this temperature elevation both on reactor performance and on the characteristics of thermophilic granular sludge. A sharp increase in the effluent TOC occurred after the temperature shift, leading to a deterioration of TOC removal from 90% to 65%. Methane production from the reactor gradually increased from 100 to 130 l d−1 during the first 40 days of 65°C operation, and then drastically decreased to 40–50 l d−1. This process failure was attributed to the disintegration of the granular sludge during 65°C operation. Microbial characteristics of the granular sludge were evaluated before and after the temperature shift. The acetate-utilizing and propionate-utilizing methanogenic ...