Simulation of energy efficient biological wastewater treatment process in a circulation oxidation ditch

Summary

In the National Research Moscow State University of Civil Engineering comprehensive work is carried out in the field of simulating energy efficient wastewater treatment processes in circulation oxidation ditches. Notably, process flow schemes of removing nitrogen compounds from wastewater at low dissolved oxygen concentrations are considered. The study is aiming at the determination of optimal process modes of biomass activity under different conditions in the course of implementing experimental schemes. The summarized results of the second stage of the comprehensive study of energy efficient wastewater treatment in circulation oxidation ditches are presented: the efficiency dependency of simultaneous nitrification and denitrification at variable oxygen regimen has been determined, the mechanism of biomass adaptation and specific features of biomass bringing to the operating regime has been studied. The experimental plant model is described that provides for considering not only biochemical but also more detailed hydraulic specific features of the experimental process.

Key words

wastewater , biological treatment , nitrification , energy efficiency , denitrification , circulation oxidation ditch , easily oxidable organic substrate

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