Immobilization of ammonia-oxidizing bacteria by calcium alginate

Ammonia-oxidizing bacteria were immobilized by calcium alginate. The immobilization conditions and ammonia oxidation ability of the immobilized bacteria were investigated. The following immobilization conditions were found to be optimal: sodium alginate, 4.5%; calcium chloride, 2.0%; 2000 immobilized balls per 1000 immobilized medium; pH, 10; 110 r/min and temperature, 30 °C. The immobilized ammonia-oxidizing bacteria exhibited strong ammonia oxidation ability even after recycling for six times. The ammonia nitrogen removal rate of the immobilized ammonia-oxidizing bacteria reached 89.51% under the optimal immobilization conditions. When compared with non-immobilized ammonia-oxidizing bacteria, those immobilized by sodium alginate were superior with respect to preservation, recycle and ammonia oxidation ability.