Theoretical total nitrogen removal efficiency and reactor volume ratio in oxic-anoxic-oxic system can be found by influent water quality in this study. The influent water quality items for calculation were ammonia, nitrite, nitrate, alkalinity, and COD which can affect nitrification and denitrification reaction. Total nitrogen removal efficiency depends on influent allocation ratio. The total nitrogen removal follows the equation of 1/(1+b). Optimal reactor volume ratio for maximum TN removal efficiency was expressed by those influent water quality and nitrification/denitrification rate constants. It was possible to expect optimal reactor volume ratio by the calculation with the standard deviation of ±14.2.

An experimental research was conducted in order to study the treatability of leachate and a combined wastewater of municipal landfill leachate and municipal sewage. The landfill leachate was that of Nanjido landfill site, and the municipal sewage was obtained from Chungnang municipal sewage treatment plant of Seoul. Several sets of bench-scale sequencing batch reactor(SBR) were used as experimental apparatus. Specially investigated items in this experiment were the removal efficiency of substrate and the influence of the hydraulic retention time(HRT). The experiment lasted for about 8 months. The result are as follows ; 1) The characteristics of leachate were pH 7.4∼8.1, BOD 280∼450 ㎎/1, COD 1300∼1350 ㎎/l, T-N 2021∼2110 ㎎/l, T-P 2.7∼3.2 ㎎/l, Cl- 3540∼4085 ㎎/l, and heavy metals are a very small amount. And the characteristics of sewage were pH 6.9∼7.3, BOD 78.4∼129.3 ㎎/l, COD 121.2∼305.0 ㎎/l, T-N 14.9∼36.4 ㎎/l, T-P 1.3∼5.9 ㎎/l. 2) The treatability of leachate alone was not treat well. So for the good treatment of leachate, it w;is necessary to deal with the pretreatment before biological treatment and a combined treatment of municipal sewage. 3) The various contents of the leachate were 5%, 10%, 30%, and 50%, and the removal efficiency of COD was 86.0%, 82.8%, 60.6%, and 31.7%. The maximum content of the leachate which could be successfully treated by SBR in the combined treatment eas 10% of that of sewage.