Maintainability of denitrifying granular sludge in soft to marginally hard waters in an upflow sludge-blanket reactor

摘要

The maintainability of denitrifying granular sludge in a bench scale reactor treating soft groundwater with low nitrate (21 mg N 1~-1) was investigated. With influent alkalinity at 180 mg CaCO_3 1~-1, a calcium addition to a relatively low total hardness of 120 mg CaCO_3 1~-1 and an influent pH of 8.5, generation of mineral precipitation needed for production of a heavy granular sludge with good settling characteristics was achieved. Bed biomass concentration increased with increasing granule mineral content due to improved retention.