The effect of the operation of secondary settling tanks on the efficiency of biological removal of nitrogen through the example of Kuryanovskie wastewater treatment facilities

Summary

«Mosvodokanal» JSC conducted an industrial-scale experiment with the secondary settling tanks of the new section of the Kuryanovskie wastewater treatment facilities in Moscow in order to determine the effect of the operation of settling tanks on the efficiency of biological removal of nitrites. With an increase in the level of sludge stand in the secondary settling tanks, conditions arise in the sludge layer at the bottom of the settler for the anaerobic processes that cause the lysis of activated sludge cells. Under these conditions, a sufficient amount of organic matter is generated in the sludge layer, both residual, occluded on sludge flocks, and formed during the lysis of part of the cells, so that in the presence of nitrates, the process of incomplete denitrification starts with the formation of nitrites. The occurrence of anaerobic processes in the bottom sludge layer in the secondary settling tanks is also affected by the oxygen concentration in the mixed liquor entering the secondary settling tanks. The process parameters of the operation of the facilities that prevent a decrease in the quality of effluent are determined: regulating the operation of secondary settling tanks depending on the load and residence time of the sludge dry matter that prevents the sludge from long staying in the bottom layer, as well as maintaining a high oxygen concentration at the end part of the aeration tanks.

Key words

wastewater , biological treatment , sludge disposal truck , secondary settling tank , activated sludge , nitrite nitrogen