Effect of ferrous iron on the settling properties of granular sludge in a UASB reactor

Abstract

The effect of ferrous ion addition on the settling properties of the granules in an upflow anaerobic sludge blanket (UASB) reactor was investigated. A UASB reactor (35ºC; pH=7) was operated for 3 months at a 20-h hydraulic retention time ( d-1 . After steady state conditions were achieved, the settling properties of granular sludge from the anaerobic sludge bed reactor were determined by using a novel upflow velocity test. From the results, it was concluded that iron promoted granulation. The U10% (10% of sludge washed out by applying upflow velocity U10%) was increased from 0,23 m.h -1 to 13,21 m.h -1 , while U30% from 0,87 m.h -1 to 29,11 m.h -1 and U60% from 6,63 m.h -1 to 49,82 m.h -1 .