DEVELOPMENT OF SIMPLE TREATMENT SYSTEM FOR A LARGE QUANTITY OF NITRATE-POLLUTED WASTEWATER

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The aim of this study was to establish the nitrogen removal system employing autotrophic thiobacillus denitrificans for wastewater of which C/N ratio was very low. Sulfur particle was used as an electron donor in a column. The following results were obtained.1)Inhibition by nitrite Nitrite, formed as an intermediate of denitrification reaction, is known to cause an inhibitory effect on denitrification itself. By the experiments under various conditions, the inhibition behavior was explained by the same kinetic model as a non-competitive inhibition model used in enzymatic reaction kinetics. An inhibition constant lowered(inhibition effect increased) with the decrease in pH, indicating that undissolved nitric acid might be the source of inhibition. The degree of inhibition against nitrite reduction was lower than that for nitrate reduction. The minimum nitric acid concentration that showed the influence on reduction rate in suspension system was lower than that in biofilm system. This in … More dicated the importance of pH control during operation.2)Continuous treatment of wastewater from acid-washing process of iron works The effect of heavy metals or fluoride involved in wastewater of ppm order was found to be negligible based on long-term runs with a column packed with limestone and sulfur particles. The performance of denitrification dropped gradually during operation in industrial wastewater, whereas it was almost constant in model wastewater of same nitrate concentration. This was suspected to be caused by the decrease of alkalinity in actual wastewater. By the analysis of limestone particles, iron, phosphate and sulfur compounds were observed to deposit on surface, which might cause the reduction of alkalinity supply3)Continuous treatment of the wastewater eluted from the landfill Nitrate involved in the wastewater from land fill was treated continuously employing a column packed with limestone and sulfur particles. A constant performance was obtained probably because the concentrations of both nitrate and organic carbon were low. The components of organic carbon compounds in wastewater were not clarified, but substantial inhibitory effect was not observed. Less