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 the microbial population. Complete removal of nitrate (100 mg l^-1) was readily achieved, without accumulation of nitrite. The treated water contained low dissolved organic carbon (4-10 mg l^-1). The cellulose-dependent denitrification process was sensitive to changes in temperature: nitrate removal rates at 14°C were approximately one third of the rates observed at 32°C. Pretreatment of newspaper with diluted NaOH or diluted HCl, or by autoclave did not improve the efficiency of the process. A time-dependent decay in denitrification rate was noticeable after several months of operation. The reasons for this phenomenon, which may be due to weakened adhesion of the bacteria to the substrate, are under investigation.