Factors affecting nitrogen removal by nitritation/denitritation.

Nitrogen removal from wastewater with high nitrogen concentration and low COD/N ratio via nitrite is advantageous. The specific character of the sludge liquor enables the application of such a method. The factors affecting process efficiency were studied. From the factors followed pH, NH4+/NH3 and NO2-/HNO2 concentration and distribution seem to be most important, using sequencing batch reactor technology and treating wastewater with high NH4+ concentration (above 1 g/l). The efficient oxidation of N-NH4+ to nitrite was achieved at a minimal nitrate production. Primary sludge was used as an internal source of substrate for the denitritation because of the organic substrate deficiency of the sludge liquor. The denitritation can be controlled by dosing of the primary sludge and can be complete. There are two operational alternatives of sludge liquor pretreatment: without pH control--lower operational costs and N-removal up to 65% and with pH control--higher operational costs and N-removal close to complete.