COMPLETE OXIDATION OF HIGH CONCENTRATION OF AMMONIA BY RETAINING INCOMPATIBLE NITRIFICATION ACTIVITIES IN THREE-VESSEL SYSTEM

A three-vessel system (3-V system) that has three equal-volume compartments was used for oxidizing inorganic synthetic wastewater containing 500 mg-l−1 NH4-N. This system was inoculated with polyethylene glycol granular activated sludge. Inorganic synthetic wastewater was supplied to the first vessel at the granular loading rate of 15 g-N.(l-granule)−1d−1 (volumetric loading rate of 3.0-g N l−1d−1), which is 5.0 g-N (l-granule)−1 d−1 (volumetric loading rate of 1.0 g-N l−1d−1) overall, respectively. About half of the NH4-N supplied was oxidized in the first compartment and the remaining half was oxidized in the second compartment. Nitrite oxidation was not significantly detected in the first two compartments, but that solely occurred at high levels in the third compartment. The results suggest that these nitrification processes may be incompatible, resulting in a series of sequential reactions in the 3-V system. It was hypothesized that different nitrifying populations came to predominate in each compartment by partitioning the vessel. It was reproducibly observed that about half of the NH4-N supplied to a single-vessel system at the granular loading rate at 5.0 g-N(l-granule)−1d−1 remained unoxidized. Thus, complete ammonia oxidation was first achieved and ammonia- and nitrite-oxidizing populations can be segregated by the 3-V system.