NITRIFICATION OF NH4-N POLLUTED SEA-WATER BY IMMOBILIZED ACCLIMATED MARINE NITRIFYING SLUDGE (AMNS)

Acclimated marine nitrifying sludge (AMNS) prepared from activated slu dge obtained from a night soil treatment plant equipped with a sea wat er dilution system for controlling the reactor's temperature was succe ssfully immobilized using a polyvinyl alcohol (PVA) freezing method. A bout 2 weeks of recovery culture was required before continuous treatm ent could be carried but. Transmittance electron microscopic observati ons of sliced immobilized AMNS pellets indicated that bacteria with an intracytoplasmic membrane dominated the AMNS colony. Continuous nitri fication experiments of NH4-N containing synthetic sea water were carr ied out in a 1.2 l bioreactor containing 57.2 g (wet weight) of immobi lized AMNS pellets. The NH4-N removal rate reached a saturation level above an NH4-N loading rate of 1.5 mg-NH4-N/g-pellet/d. The maximum al lowable NH4-N loading rate necessary to obtain 90% NH4-N removal was f ound to be 1.0 mg-NH4-N/g-pellet/d, It was possible to store the immob ilized AMNS pellets in a refrigerator for at least 1 week without loss of nitrifying capability. Inorganic carbon source was shown to be a l imiting factor in the continuous nitrification experiments. The maximu m allowable NH4-N loading rate needed to obtain 90% NH4-N removal incr eased to 2.0 mg-NH4-N/g-pellet/d through supplementation of an inorgan ic carbon (IC) source to the influent synthetic sea water.