FACTORS AFFECTING NITRITE BUILDUP IN SUBMERGED FILTER SYSTEM

The accumulation Of the nitrification intermediate, nitrite, is undesi rable because of its toxicity to fish. The elevated nitrite concentrat ion in waste-water-treatment processes significantly increases the amo unt of chlorine required for disinfection. Consequently, environmental and operational factors of hydraulic and ammonium loading rates as we ll as pH and alkalinity were evaluated for their effects on the accumu lation of nitrite in a fixed-film submerged filter system. Elevated ni trite levels were observed at higher hydraulic (5 L/d.cm2) and ammoniu m loading rates (0.7 kg N/d.m2), pH = 8.8 and low alkalinity/ammonium ratio (6 mg CaCO3/mg NH4+-N). Addition of 2.5-5 mg N/L hydroxylamine, an intermediate in the ammonium oxidation to nitrite, also significant ly enhanced the accumulation of nitrite concentration. The inhibitory effect of hydroxylamine on Nitrobacter was irreversible.