the ph value was not beneficial for the growth of the bacteria the concentration of the dissolved oxygen in the culture solution was 0 6 mg l when the concentration of the dissolved oxygen is lower than 0 6 mg l the growth of the nitrifying bacteria was slow and too high the concentration of the dissolved oxygen resulted in surplus the bacteria solution after cultivation was then centrifuged at the rotational speed of 2000 rpm for 15 min and the bacteria were separated to prepare a concentrated bacterial suspension 0 8 percent by weight of glycine and 2 0 percent by weight of glycerin were mixed according to a weight ratio of glycine to glycerin of 1 2 to prepare a protecting agent and the protecting agent was then added to the concentrated bacterial suspension in which an addition of the protecting agent was 2 2 folds of the concentrated bacterial suspension the resulting mixture was uniformly loaded on sterilized calcium alginate as a carrier by dry spraying to yield the denitrifying bacterial agent in which a water content of the carrier was controlled equal to or less than 12 percent by weight the yielded bacterial agent was sealed for storage the culture solution comprised 20 parts by weight of ch 3 coona 22 parts by weight of na 2 co 3 12 parts by weight of nh 4 cl 0 05 parts by weight of feso 4 3 parts by weight of mgso 4 7h 2 o and 380 parts by weight of a phosphate buffer the phosphate buffer was prepared by k 2 hpo 3 and kh 2 po 4 in a weight ratio.