Biological denitrification of high concentration nitrate waste

A process for removing nitrate ions from an aqueous waste stream having a nitrate concentration in excess of one kilogram nitrate per cubic meter, comprising the steps of:

• incubating under anaerobic conditions a culture of mixed denitrifying bacteria in the presence of a solution comprising at least 750 grams of nitrate per cubic meter and a biologically effective amount of a first carbon source to produce a culture of incubated mixed denitrifying bacteria;
• mixing said waste stream with a second source of carbon to form an influent solution;
• passing said influent solution vertically upward through a packed concially shaped column having as a packing material a support for denitrifying bacteria and having said incubated mixed denitrifying bacteria attached thereto;
• said conically shaped column having an upper diameter larger than its lower diameter;
• allowing said influent solution to contact said packing whereby said nitrate ions and said carbon source are converted to carbon dioxide and elemental nitrogen by the incubated denitrifying bacteria;
• and
• separating said elemental nitrogen from the influent solution.