Biological reduction of nitrate wastewater using a fluidized-bed bioreactor

CIM Bulletin, Vol. 73, No. 819, 1980

W.W. PUT, C.W. HANCHER and B.D. RATION, Oak Rjdge National Laboratory, Chemical Technology Division, Oak Ridge, Tennessee

There are a number of nitrate-containing wastewater sources, as concentrated as 30 wt% NO3- and as large as 2000 m3/day, in the nuclear fuel cycle. The biological reduction of nitrate in wastewater to gaseous nitrogen, accompanied by the oxidation of a nutrient carbon source to gaseous carbon dioxide, is an ecologically sound and cost-effective method of nitrate waste disposal.These nitrate-containing wastewater sources can be successfully biologically denitrified to meet discharge standards in the range of 10 to 20 g N(NO3-)/m3 by the use of a fluidized-bed bioreactor. The denitriflcation bacteria are a mixed culture derived from garden soil; the major strain is Pseudomonas. In the fluidized-bed bioreactor, the bacteria are allowed to attach to 0.25- to 0.50-mm-diam. coal fluidization particles, which are then fluidized by the upward flow of influent wastewater. Maintaining the bacteria-to-coal weight ratio at approximately 1:10 results in a bioreactor bacteria loading of greater than 20,000 g/m3.This paper describes the results of a biodenitrification R&D program based on the use of fluidized bioreactors capable of operating at nitrate levels of up to 7000 g/m3 and achieving denitrification rates as high as 80 g N(NO3-) per day per litre of empty bioreactor volume.
Keywords: Hydrometallurgy, Biological reduction, Reduction, Nitrate wastewater, Bioreactors, Fluidized-bed bioreactors, Denitrification, Effluent treatment.