Bioaugmentation of sidestream nitrifying-denitrifying phosphorus-accumulating granules in a low-SRT activated sludge system at low temperature.

Sidestream granular activated sludge grown on anaerobic digester dewatering centrate was bioaugmented and selectively retained to enable high nitrification performance of a 2.5-day aerobic SRT non-nitrifying flocculent activated sludge system at 12 °C. Sidestream-grown granules performed enhanced biological phosphorus removal (EBPR) and short-cut nitrogen removal via nitrite.

Comparison of different aerobic granular sludge types for activated sludge nitrification bioaugmentation potential.

Three types of nitrifying granules were grown on media simulating anaerobic digestion dewatering reject water and compared for their potential to increase nitrification capacity when added to mainstream flocculent activated sludge treatment. An advantage of nitrification bioaugmentation with sidestream granules instead of flocculent biomass is that the granules can be selectively maintained at longer retention times than flocs and thus provide higher nitrification capacity from bioaugmentation. The three granule types and feeding conditions were: nitrifying granules with aerobic feeding, nitrifying-denitrifying granules with anoxic feeding, and nitrifying-denitrifying/phosphate-accumulating (NDN-PAO) granules with anaerobic feeding.

Bioaugmentation with Nitrifying Granules in Low-SRT Flocculent Activated Sludge at Low Temperature.

  Nitrifying granules were grown in a sidestream reactor fed municipal anaerobic digestion centrate and added in an initial slug dose and subsequent smaller daily doses to a non-nitrifying mainstream activated sludge system at 12 °C and 2.5-day aerobic solids retention time (SRT) to increase its nitrification capacity. Effluent NH3-N concentrations less than 1 mg/L were achieved with bioaugmentation, and nitrification was immediately lost when granules were removed after 30 days of bioaugmentation.