Nitrogen Conversion Characteristics of ANAMMOX Sludge for Long-term Preservation

Since inoculated sludge with ANAMMOX could efficiently reduce the startup time of the ANAMMOX reactor, it is important to develop a cost-effective technology for preservation. In the present study, the flocculent ANAMMOX sludge was preserved under either -20 degrees C, 5 degrees C, natural environment or 30 degrees C for 15d, 30d, 45d, 150d and 365d, respectively. The preserved ANAMMOX sludge under all these conditions displayed different levels of nitrification. Specifically, freezing conditions (-20 degrees C) led to a loss of ANAMMOX activity, whereas ANAMMOX activity was the highest in natural environment, which showed a positive linear relationship with the relative amount of substrates. Moreover, a short-term anoxic (<= 45d) preservation in a dark yet natural environment (0 similar to 15 degrees C) is a highly economical and effective approach.