Nitrogen Removal Characteristics of Wastewater Containing High-Strength Ammonium by Biofilter

초록

Biofiltration for a wastewater containing high NH4-N and low BOD concintration was investigated to assess the nitrification characteristics and the configurational effects of nitrification, as well as the effects by wastewater circulation, on the nitrification performance. The treatment method applied included nitrification, denitrification, and re-aeration processes. Methanol was used as a hydrogen donor for denitrification. Nitrification was carried out at the circulation ratio of 2.7-4.6 to treated water flow rate. Consequently, it was found that the nitrification tended to become an nitrite type, with nitrite nitrogen constituting over 50% in the total oxidized nitrogen(NOx-N). The nitrification performance was found to be more favorable with a higher circulation ratio. It was also found that the ratio of NO2-N/NOx-N in the nitrificationfluid became higher with higher NH4-N at the inlet of the nitrification tank. As for denitrification, both NO2-N and NO3-N were able to be removed by charging methanol. It was speculated that residual NH4-N and NO2-N in the nitrification process caused inhibition on nitrite bacteria by free ammonia, formed during an inflow of highly concentrated NH4-N.