BIOLOGICAL DENITRIFICATION OF DRINKING-WATER USING NEWSPAPER

Microbial denitrification of drinking water was studied in laboratory columns packed with shredded newspapers. Newspaper served as the sole carbon and energy substrate as well as the only physical support for t he microbial population. Complete removal of nitrate (100 mg 1(-1)) wa s readily achieved, without accumulation of nitrite. The treated water contained low dissolved organic carbon (4-10 mg 1(-1)). The cellulose -dependent denitrification process was sensitive to changes in tempera ture: nitrate removal rates at 14 degrees C were approximately one thi rd of the rates observed at 32 degrees C. Pretreatment of newspaper wi th diluted NaOH or diluted HCL, or by autoclave did not improve the ef ficiency of the process. A time-dependent decay in denitrification rat e was noticeable after several months of operation. The reasons for th is phenomenon, which may be due to weakened adhesion of the bacteria t o the substrate, are under investigation.