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UDC 628.35:661.5

Gogina Elena, Gul’shin I. A.

Nitrogen removal in a circulation oxidation ditch model
under the conditions of lowered concentration of organics in wastewater

Summary

The summarized results of the third stage of an integrated study of energy efficient processes of wastewater treatment in circulation oxidation ditches are presented. The experiment was carried out in a laboratory model of a circulation oxidation ditch with horizontal directional flow of mixed liquor. The impact of low concentration of dissolved oxygen in the bioreactor volume (at 0.5 mg/l level) and low concentration of organic pollutants in the incoming model wastewater on the treatment efficiency and biomass stabi­lity was studied. The highest efficiency of total nitrogen removal was reached at the specific organics load on activated sludge (BOD) R = 0.07 g/(g∙day), average dissolved oxygen concentration 0.5 mg/l and 7.5 hours aeration time. At that the concentration of ammonium nitrogen in the effluent was about 0.6 mg/l; the concentration of nitrate nitrogen was 9.6 mg/l. The operation of the bioreactor at lowered dissolved oxygen concentrations resulted in partial biomass bulking. The sedimentation properties of activated sludge changed; however stayed at satisfactory level.

Key words

wastewater , nitrification , energy efficiency , activated sludge , denitrification , circulation oxidation ditch , biological removal of nitrogen

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