engleski

Nitrogen removal from ammonium-rich wastewater using adapted activated sludge with selected nitrificants and denitrificants

Nitrogen removal from wastewater from the Ihan pig farm was studied. The wastewater contains nitrogen concentrations up to 2000 mg/l, mainly in the form of ammonium nitrogen. For the treatment process an adapted activated sludge with a mixed culture of several bacterial strains, capable of autotrophic and heterotrophic nitrification and denitrification, was used. Laboratory level tests yielded the basic parameters needed to conduct pilot plant experiments. Pilot plant experiments were performed as a discontinuous and a semi-continuous process. The whole process was carried out with increasing initial N-NH_4 concentrations from 50 to 1200 mg/l. Nitrification rates increased with increasing initial N-NH_4 concentrations and with continuous operation at the same initial concentration. The experiment was stable over the whole time of operation, including the highest N-NH_4 concentrations. pH influenced nitrification rates. The optimal pH was from 6.8 to 8.5, with peak activity at approximately 7.2. The type of pH correction agent partly influenced the nitrification rates; better results were achieved using Na_2CO_3 compared to NaOH. Nitrification in laboratory tests was found to be heterotrophic and autotrophic, while on pilot plant scale it was mainly autotrophic since no significant COD reduction could be observed.

activated sludge; denitrification; mixed culture; nitrification; nitrogen removal; pig slurry

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