INCREASES IN REMOVAL OF PHOSPHORUS COMPOUNDS DURING BIOLOGICAL TREATMENT OF URBAN WASTEWATER IN CONSTRUCTIONS WITHOUT ZONING

Abstract

Indicators of biological treatment of urban wastewater from the compounds of nutrients (nitrogen and phosphorus) during processing in aeration tanks (aerotanks) without zoning of the traditional scheme «primary clarifier aerotank secondary settling tank» were studied. Research was carried out at the existing wastewater treatment plants of Kharkov and in laboratory experiments. It was established that the concentration of nutrients in the incoming wastewater to the treatment plant exceeds the admissible concentration. Treatment processes in the studied plants include ammonification and nitrification, while the denitrification process does not occur. The concentration of mineral nitrogen compounds in the effluent, as a rule, does not exceed the regulatory limits at Kharkov’s biological wastewater treatment plant. The concentration of phosphate in wastewater after the secondary settling tank exceeds the regulatory limits for these facilities. It was found that after settling in the secondary settling tank the phosphate concentration in the wastewater increases, on average, by 110%. For the inhibition of water phosphatizing in the secondary settling tank nitrates were used and an inhibition constant process was installed using 25 mg. l –1 nitrate. To prevent pollution of wastewater by phosphates in the secondary settling tank during the regulatory 2 hour settling period, the nitrate concentrations in wastewater have to be above 35 mg. l–1.