DENITRIFICATION OF CONCENTRATED INDUSTRIAL WASTE-WATER - MICROORGANISM SELECTION AND KINETIC-STUDIES

This study was carried out to find a bacterial system to allow a compl ete denitrification of an industrial wastewater. The average nitrate c oncentration was 600 mM NO3 (about 37 g NO3 l), and there was no nitri te. The carbon substrate used wits the acetic acid. Batch and continuo us cultures were chosen as culture modes in stirred anaerobic reactors . The bacteria were selected from the microorganisms in the ponds of t he industrial plant where the wastewater was stored, using a selective denitrifying bacteria medium. Two strains were selected (Pseudomonas cepacia, and Staphylococcus hominis). Complete denitrification was pos sible, even with a high nitrate concentration. A batch culture on conc entrated medium showed that the microorganisms could tolerate high nit rate concentrations. The specific growth rates were 0.08 and 0.06 h(-1 ) respectively for the strain S1 and S2. The first strain (Pseudomonas cepacia) appeared to reduce the nitrates to nitrites stage (with a ra tio of 44%), and into gaseous nitrogen. The second strain (Staphylococ cus hominis) changed the nitrites into gaseous nitrogen. The continuou s experiment showed that development and denitrification with the two strains successfully processed the industrial wastewater under continu ous conditions. This experiment confirmed the kinetic parameters deter mined in the batch experiment (mu(max) below 0.1 h(-1)).