Improvement of biological removal of nitrogen and phosphorus compounds from wastewater under the conditions of cascade denitrification

Summary

In view of ever toughening requirements to wastewater treatment the optimization and intensification of wastewater treatment facilities operation become priority areas. The flow process scheme of wastewater biological treatment at the Minsk Wastewater Treatment Plant is represented by traditional aeration tanks and aeration tanks with organized cascade denitrification scheme. The main component of this scheme is the lack of inner recycle and possibility of dispersed inflow of clarified wastewater over the aeration tank zones. This provides for the presence of easily oxidizable organic substances in every anoxic zone. In view of building-up of pollutants in incoming wastewater and toughening the requirements to their removal the intensification of the biological stage has been an important aspect of the treatment facilities operation. The research objective was the scheme of cascade denitrification at the operating treatment facilities for the optimization of which different options of clarified wastewater distribution over the aeration tank zones were used. Wastewater entering the cascade denitrification is characterized by insufficient quantity of organic substances because a significant amount of industrial wastes. To increase the amount of organic substances it was decided to take out of service the primary settling tank and to reduce the frequency of sludge removal. The chosen optimal distribution of clarified wastewater over the aeration tank zones and increase of organic loading the efficiency of phosphate removal increased from 60 to 70%; and that of nitrogen removal – from 61 to 67%.

Key words

wastewater , biological treatment , nitrification , activated sludge , nutrients removal , cascade denitrification