Effective Biological Treatment of Tannery Wastewater from Nitrogen Compounds

Even after using physico-chemical and biological methods, tannery wastewater still contains a large amount of nitrogen compounds, which reaches 90 mg/dm3. The ingress of such wastewater into natural reservoirs leads to eutrophication. The goal is to determine the efficiency of nitrogen compounds removal during sequential wastewater treatment in anaerobic, anoxic and aerobic bioreactors with immobilized microorganisms. For the study, wastewater from a tannery, collected after cleaning in aeration tanks, was used. Model solutions with a concentration of 18.4 - 90 mg/ dm3 were obtained by dilution. 5 sequential bioreactors were used - anaerobic (2 stages), anoxic (2 stages) and aerobic (1 stage) with a capacity of 125 ml/h. Microorganisms were immobilized in each bioreactor on artificial carrier. The effects of organic nitrogen removal in anaerobic bioreactors were 58-66%, anoxic 51-70%, aerobic 57, 5%. A decrease in the concentration of nitrogen compounds occurs as a result of the formation of N2, NH3 gases and the use of nitrogen by microorganisms for biomass growth. It is proposed that sequential treatment of tannery wastewater in anaerobic, anoxic, and aerobic conditions with immobilized microorganisms made it possible to obtain a high degree of nitrogen removal. The method does not require chemical materials and is ecological.