NITROGEN REMOVAL FROM PIGGERY WASTE BY NITRITE NITRIFICATION

Piggery farms discharge small amount of flow, but its nitrogen contents is relatively high with low COD/TKN ratio. Therefore, nitrite nitrification with piggery waste would be a short cut process for savings in oxygen for nitrification and carbon requirements for denitrification. A stable nitrite nitrification was achieved at room temperature with sufficient alkalinity addition. Nitrite process could save about 10 % of oxygen and 40 % of carbon requirements. Continuous process was more advantageous than cyclic process when influent COD/TKN ratio became smaller, since influent COD could be allocated more for denitrifiers than for heterotrophs. Basically, the applicable oxic organic and TKN loading rates were identical, respectively 0.7 kgCOD/m3/d and 0.24 kgTKN/m3/d for both processes, but the anoxic NOxN loading rates were different; respectively 0.5 kg NOxN/m3/d for continuous and 0.4 kg NOxN/m3/d for cyclic processes.