Simulation des Nitratabbaus im Grundwasser

Ten reaction vessels containing 1 m³ were used as the experimental arrangement. They were filled with coarse sand or fine gravel and installed 60 cm below the floor. The pore volume (water saturation) was 227… 260 l. Anaerobic conditions were established by the addition of 6 g glucose at storage. The reactors were given tap water with 50 and 200 mg/l NO from KNO₃ in such a way that a volumetric rate of flow of 0.2, 0.4 and 0.8 l/d was created. The volumetric rates of flow corresponded to the natural recharge of groundwater, the recharge of groundwater under the conditions of irrigation and the conditions of an intensive wastewater ground treatment. In the effluent from the reaction vessels the nitrate concentration was determined every month. It was stationary from the 7th to the 55th month after the beginning of the experiment. The experiments are evaluated by means of a model which takes into account the diffusion, convection and kinetics of the nitrate degradation according to Michaelis-Menten. A simple method for solving homogeneous non-linear differential equations of the second order is proposed. The experimental and model results show a good agreement and prove the very slow nitrate degradation in the groundwater with k_M = 210 mg/l, v_max = 1.5 mg/l · d or k₁ = 0.005 d^?1.