Effect of Aerobic/Phosphorus Granules on Start-up of Partial Nitrification Granular Sludge

Abstract

The different effects of additional aerobic granules (AGs) and phosphorus removal granules (PRGs) on the start-up and stable operation of partial nitrification granular sludge (PNGS) were compared at room temperature(22-28℃). The results showed that in the first stage (days 0-22), partial nitrification was accomplished on day 19 for the three reactors (R1, R2, and R3). In the second stage (days 23-56), 20% AGs and 20% PRGs were added to R2 and R3 to induce PNGS. The start-up of the granules of the three reactors was successfully achieved. The mean particle sizes of R1, R2, and R3 reached 412 μm at day 76, 468 μm at day 42, and 400 μm at day 56. In the third stage (days 57-108), because the influent ammonia load increased from 0.4 kg·(m3·d)-1 to 0.5 kg·(m3·d)-1 and the COD load increased from 0.2 kg·(m3·d)-1 to 0.5 kg·(m3·d)-1, the mean particle sizes of R1 and R2 increased significantly. The average particle sizes of R1 and R2 reached 689 μm and 893 μm by the end of the operation (day 108), but sludge expansion occurred in R3. The inoculation of either AGs or PRGs could quickly achieve granulation, but the PNGS inoculated with the AGs could adapt to higher C/N and be more tolerable to shock loads and long-term stable operation.