Enrichment of anaerobic ammonium oxidizing (Anammox) bacteria from OLAND and conventional sludge: Features and limitations

► A CSTR and an UFBR are proposed to cultivate Anammox bacteria. ► Anammox bacteria can be enriched from conventional active sludge. ► Biomass retention in sponges and controlled feed regime enhances Anammox growth. ► Anammox activity can stay hidden until the bacteria encounter suitable conditions. ► Under acceptable levels of organic load, Anammox can cooperate with denitrifiers.