OBSERVATIONS ON THE KINETICS OF NITRIFICATION UNDER INHIBITING CONDITIONS CAUSED BY INDUSTRIAL WASTE-WATER COMPOUNDS

Within the next few years nitrogen removal will be obligatory for both municipal and industrial wastewater treatment plants in Austria. Duri ng the operation of pilot plants, severe inhibition of the nitrificati on process has been observed in several cases. Further investigations have been carried out at two biochemical factories at. temperatures in the range of 22 to 32 +/-C, in one case at two pilot plants, in the o ther case at a full-scale plant, in order to estimate kinetic paramete rs of nitrifying biomass under the particular inhibiting conditions of these wastewaters. In both cases competitive inhibition occurred duri ng the start-up period for about two months. The ammonia nitrogen half -saturation coefficient for autotrophic biomass was in the range of 10 mg/l. In one case also maximum autotrophic specific growth rate varie d in a wide range. It could be proved that the compounds of this waste water have an inhibiting but no toxic effect on Nitrosomonas. The effl uent ammonia concentration can be kept within the limits in case of co mpetitive as well as non-competitive inhibition up to about 60% by inc reased minimum SRT. In case of severe non-competitive inhibition it is not possible to achieve feasible biological nitrification. In any cas e the inhibiting compounds should be located and removed from the wast ewater.