Characteristics and Stability of Aerobic Granules Treating Domestic Sewage

A granular sludge sequencing batch reactor (GSBR) was applied to treat domestic sewage, so as to investigate the characteristics and stability of granular sludge associated with real wastewater. During stable running period, high sludge concentration and low SVI were maintained in reactor, accompanying with good pollutant removal performances. Moreover, sludge size distribution examination showed that granular sludge was the dominant form in the reactor during this operation phase, especially under high organic loading, granules with the diameter over 1.25 mm accounted for around half of the total MLSS. In comparison, flocculent sludge grew faster during the low load running period, weakening the stability of system. In addition, characteristics comparison of granules at different size categories showed that settling velocity, wet density and microbial activity of sludge increased with the increase of granule size, but SVI and moisture content decreased, in accordance with the feature of aerobic granules, such as high activity, high settling property and low moisture content.