NITRITE REMOVAL BY A FIXED CULTURE IN A SUBMERGED GRANULAR BIOFILTER

The present investigation was carried out in the aim of developing a new fixed-culture nitrification-denitrification scheme short-circuiting the production of nitrate ion. The analysis of the behaviour of a submerged biofilter is reported for the development of a denitritation process. The results obtained show that the denitritation reaction takes place in the submerged biofilter according to apparently zero-order kinetics with a maximum nitrite removal rate of 2.1 kg NO2--N m(-3) of liquid phase . d(-1), corresponding to a maximum volumic loading of 1.1 kg NO2--N m(-3) of reactor . d(-1). The critical volumic loading applied (above which the denitritation yield fell) was 0.8 kg NO2--N m(-3) of reactor . d(-1). The carbon requirement in the form of acetate was estimated for denitritation as 0.84 kg soluble TOC . kg(-1)NO(2)(-)-N eliminated. Biological sludge was produced at a rate of 0.69 kg dry solids . kg(-1)NO(2)(-)-N removed. Finally, it was shown that the denitrifying microorganisms adapted very well to a sudden input of nitrate into the denitritation biofilter.