REMOVAL OF NITRATE FROM INDUSTRIAL WASTEWATERS IN A PILOT-PLANT BY NITRATE-TOLERANT KLEBSIELLA-OXYTOCA CECT-4460 AND ARTHROBACTER-GLOBIFORMIS CECT-4500

Two strains, a gram-negative bacterium Klebsiella oxytoca CECT 4460 an d a gram-positive, mycelium-forming bacterium Arthrobacter globiformis CECT 4500, tolerant to up to 1 M nitrate, were isolated from the grou nds of a munitions factory. Under strict aerobic conditions and with a ppropriate C-sources, growth of these bacteria took place when the nit rate concentration in the medium was below 150 mM. Optimal growth cond itions regarding the culture medium composition for the biological rem oval of nitrate were established in batch cultures. Then, the system w as scaled up to a 40-L pilot plant and operated under continuous condi tions in a factory with direct waste streams from dinitroethylene glyc ol production after appropriate dilution with nontreated groundwaters. The level of nitrate in the effluent was below 0.5% of the initial N- load. Nitrite and ammonium were undetectable and the level of the C-so urce in the effluent was below 50 mg per L. On the basis of these resu lts, we conclude that the system worked on site satisfactorily. (C) 19 98 John Wiley & Sons, Inc.