DENITRIFICATION KINETICS IN AN ACTIVATED-SLUDGE SYSTEM

For all water bodies especially for sea, lakes, and ground waters it i s very important that nutrient pollution is the least possible (minima l). From municipal and industrial waste waters where considerable amou nt of nutrients is expected it is possible to remove nutrients with bi ological treatment. The first step is usually aerobic activated sludge treatment and the second step is combined anaerobic-anoxic-aerobic st ep in different combinations. A very effective process for nitrogen re moval is anoxic activated sludge system. It is very important that in the first aerobic step complete nitrification is achieved. In our labo ratory denitrification kinetics was studied. The objective of this stu dy was determination of denitrification velocity and attendance of dif ferent parallel phenomena such as nitrite, disappearance of nitrate an d nitrite, sulphide formation, etc. Denitrification process was studie d in two systems, in closed system (such as in dosed reactors for deni trification) and in open systems (such as in open denitrification tank s). We found out that denitrification rate in dosed systems was from a bout 8 to 52 mg/l.h and was dependent on activated sludge type, sludge concentration, and temperature of the system. In open system (such as in an anoxic aeration tank) the rate of denitrification was lower tha n in closed system; it was from 4 to 15 mg/l.h dependent on activated sludge type, sludge concentration, and temperature of the system. Expe riments were carried out in the range of temperature from 20 degrees t o 30 degrees C.