Abstract
Basic studies were carried out to improve the nitrogen removal efficiency in the treatment of swine feces by experimental installation of an aerated lagoon for the prevention of eutrophication in a water basin for public use. Experiments were conducted to examine the effects of the decrease in speed of ORP, Oxygen uptake rate (OUR), TOC added, MLSS, and nitrate nitrogen upon denitrification rate and nitrogen removal efficiency. In all of them, the batch experimental method was performed. The detention time used was 5 days. The gentle mixing time for denitrification was 5 hours. The following results were obtained. 1. The higher the TOC added, the more rapid decrease in speed of ORP. The effect of the MLSS on the decrease in speed of ORP, however, was smaller than that of the TOC added. 2. The OUR per gram of MLSS was nearly constant when the TOC added was above 150mg/l. On the other hand, there was a positive correlation between the MLSS and the OUR per unit capacity, liter, of the aeration tank. 3. There was a positive correlation between the denitrification rate and the OUR per liter of the aeration tank, the nitrogen concentration, or the MLSS. 4. Having a gentle stirring of more than 2 hours, 80-85% of nitrogen was removed efficiency under conditions where the concentration of MLSS, nitrate nitrogen and the TOC added was 5, 000-6, 000, 18-22 and 440-600mg/l, respectively. In conclusion, it seemed possible to apply the biological denitrification process to the aerated lagoon. At the same time, it was clarified that swine feces used as waste samples were available as a source of organic carbon for the denitrification. Under the basic conditions mentioned above, a further long-term experiment was to be performed on denitrification by appling the aerated lagoon operated in a semi-batch style.
