A denitrification process was examined by using Entrapped-Mixed-Microbial Cells Immobilization (EMMCI) process. The mixed microbes were entrapped into a polymeric cellulose triacetate. The reactor was operated over one year with feed concentration ranging from 50 to 850 mg NO3-N/l. The hydraulic retention times (HRT) were also varied from 1.8 to 11.3 hours. Complete denitrification was obtained at an HRT of 2.6 to 11.3 hours. At an HRT of 1.8 hours, the maximum nitrate-N loading rate of 591.6 g/m3 ·h (based on carriers volume) was achieved with an 88.3% denitrification efficiency. Under high range of NaHCO3 concentrations from 10 to 20 g/l, the denitrification efficiency above 96% could be obtained. This EMMCI process has showed very promising results in respect to nitrate removal. It can be considered as an alternative approach tor direct treatment of nitrate-rich water or in a combination with an ion exchange process with an intent to eliminate the high nitrate concentration from the spent regenerant.

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